Category Archives: cameras

Sony PXW-Z150 Review (with picture settings).

DSC06751-e1470742966440 Sony PXW-Z150 Review (with picture settings).
The Sony PXW-Z150 4K camcorder.

Although it’s been on the market for a while now I have not yet had a chance to write a proper review of the PXW-Z150. I’ve played with it a few times and I’ve felt it offers good value (approx £3k/$4K). As it’s starting to gain some traction amongst corporate producers and those looking for a straight forward 4K camera with lot’s of bang for the buck I though it’s time to share my thoughts.

Cameras like the Z150 are often overlooked these days as they don’t have the “cool” factor that comes with the large sensor Super 35mm cameras that are all the rage, cameras like the PXW-FS5 or FS7.

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Left side of the PXW-Z150

But not everyone wants shallow depth of field all of the time. In addition many people want zoom lenses that can zoom in to get a tight shot and zoom back out smoothly without a focus shift. If you add portability and ease of use into the mix then there is no Super 35mm camera that offers all of these. Want a big par focal zoom range – the lens gets big, heavy and very expensive.

This is where a one piece camera with a fixed zoom lens comes into it’s own. For a fraction of the the price of any of the 10 times or more par-focal S35m zoom lenses you can get a fully functioning camcorder. The PXW-Z150 has a 12x optical zoom that can be boosted up to 24x in HD (more on that later).

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Right side of the PXW-Z150

So lets take a closer look at the Z150.

From the outside the PXW-Z150 resembles many other handycam style cameras and is almost identical to the HXR-NX100. But this is from the PXW product line, I’m lead to believe that stands for “Professional XAVC Writer”. So this means it will have the XAVC codec. It’s also an XDCAM camcorder and in this case that means it also includes the MPEG2 HD codec. In addition in case you haven’t spotted it there is also a big “4K” symbol on the side.

CODECS AND RECORD FORMATS

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The PXW-Z150’s lens hood with built in shutter style lens cap.

So the camera can record UHD (3840 x 2160, the 4K standard for TV) at up to 30fps using Sony’s XAVC-L codec. This is the long GoP version of XAVC and comes in 60 and 100Mb/s versions in the Z150.  It is worth considering that this codec does require a pretty good computer to work with it in post production, ideally a minimum of a 4 core i7 processor with 16GB of main ram plus a good NVIDIA or AMD graphics card with 2GB of dedicated video ram. In UHD XAVC-L is limited to 8 bit 4:2:0, this still produces a great looking image but is not considered good enough for main stream UHD broadcast.

The image below is a UHD frame grab from the Z150. Click on the image to see larger versions including the full 3840×2160 image. The grab is a jpeg so may have some compression artefacts not in the original frame.

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UHD frame grab from the PXW-Z150. Click on the image to see a larger version or to view the full UHD frame.

If you are not shooting in UHD then you have lots of options. Again we have XAVC-L now at 25, 35 and 50Mb/s and up to 60fp. 35Mb/s and 50Mb/s XAVC-L is normally considered broadcast quality at 25/30fps. In HD XAVC-L is 10 bit 4:2:2.

As well as XAVC-L you also have two more 8 bit HD codecs, MPEG2HD and AVCHD. There are two versions of MPEG2HD, the regular HD version which is 4:2:0 at 35Mb/s as found in the older EX1 and EX3 camcorders as well as the 50Mb/s HD422 4:2:2 broadcast quality version as found in the PMW-200 and most of Sony broadcast camcorders. These older MPEG2 “XDCAM” codecs are still incredibly popular and accepted almost everywhere for broadcast HD. They are really easy to use and even though they are 8 bit still give great looking pictures. Finally if you just need something compact there is AVCHD, although frankly why you would want to use AVCHD when you have so many better options available I’m not sure. Perhaps those running older or consumer based edit software will benefit from the inclusion of AVCHD.

RECORDING MEDIA.

In order to be able to record all the different formats available you must use SDXC cards. These are readily available and low cost. Please remember though that SD cards are consumer media. It is normally very reliable (probably more reliable than tape used to be) but card failures can occur and a duff card could result in the loss of everything on the card. Fortunately Sony have considered this and the camera features two card slots.

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The PXW-Z150 has two slots for SDXC cards.

The two card slots can be configured in a number of ways. To record long events you can use relay record where once the first card is full the camera will automatically switch to the second card. For security you can use simultaneous record where you record to both slots at the same time. This means you are creating an instant backup, so the failure of a single card should not be a drama. As a further option you can control the recording function of each card slot separately. You can use the record button on the hand grip to control one slot and the record button on the carry handle to control the other to give 2 independent recordings.

A further recording function is the ability to record a proxy file alongside the main recording. The proxy file can be used in a number of ways. One way is to provide an easier to handle 720p HD file for use as an edit proxy when shooting in UHD. Another is as a small compact file that can be uploaded to the internet via the cameras built in ftp  function, perhaps for a breaking news story or remote editing and preview. As this is a proper video camera there are none of the overheating problems or limited record time issues that effect many DSLR type cameras.

One word of advice: Buy your cards from a reputable source. There is a lot of fake media out there that is almost indistinguishable from the real thing. The fake cards are often unreliable, so do make sure you only buy good quality genuine media from one of the main brands such as Transcend, Lexar, SanDisk etc.

1″ TYPE SENSOR.

The sensor that feeds all these different codecs is a “1 inch type” Exmor RS back illuminated CMOS sensor with 14.2 million effective pixels. What does all that mean?

“1 Inch Type” means the sensor size is bigger than the sensor on a 2/3″ broadcast camera but smaller than APS-C, Micro 4/3rds or Super 35mm (see this for more info on imperial type sensor sizes). So the depth of field will be deeper (more in focus) than a camera like Sony’s PXW-FS5 with it’s Super 35mm sensor, but shallower than most typical 2/3″ ENG broadcast shoulder cameras and other traditional handycams with 1/2″ or 1/3″ sensors.

Exmor RS is Sony’s latest generation of back illuminated sensor technology that gives better low light performance with small pixels compared to traditional front illuminated sensors. In addition RS stands for “Rear Stacked”. The stacking technology allows for a faster sensor readout among other things and this significantly reduces image skew and rolling shutter artefacts compared to the previous generation of these sensors. The faster readout also means that every pixel is used when shooting at up to 120 fps in HD using the cameras super slow motion function (note that this is 120fps interlace XAVC-L), so less aliasing and moire.

While RS does not eliminate rolling shutter artefacts from what I can see the Z150 offers a big improvement over cameras like the PXW-X70 and the A7S. You have to pan very fast before rolling shutter becomes a problem and in normal use skew and jello should not cause any significant problems.

12X OPTICAL ZOOM LENS.

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PXW-Z150’s 12x “G” series optical zoom lens.

Light is fed to the sensor by a 12x optical zoom lens. On the side of the camera there is a big and bold “18X“. That’s there because this camera also has Sony’s clever “Clear Image Zoom” technology. In the past if you mentioned a digital zoom it used to make people cringe as it normally meant a drop in picture quality. But Clear Image Zoom really is very clever.

First of all remember that in HD you have a UHD sensor, so you can crop into this by 2 times with virtually no loss in image quality anyway. So in HD you have an additional 2x zoom on top of the optical zoom giving a combined total of 24x. In UHD the camera uses a database of textures to determine the best way to process the image. This allows for a virtually transparent extra 1.5x electronic zoom on top of the optical one. This gives you the 18x zoom range indicated on the camera body. In use, the clear image zoom function works seamlessly with the optical zoom. So as you zoom in or out the electronic zoom takes over where the optical one finishes.

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PXW-Z100 full Wide.
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PXW-Z100 12 x optical zoom (click on image to see higher resolution versions)
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PXW-Z150 Full 18x zoom, 12x optical plus clear image zoom (click on the image to view higher resolution versions).

There is the very slightest of bumps in the zoom at the changeover point from optical to digital which I don’t think most audiences would spot. After shooting so much recently with Super 35mm cameras I really had forgotten just how much quicker it can be to shoot with a good par-focal zoom with a high zoom ratio (par focal – focus remains constant through the zoom range). The lens is reasonably wide at the equivalent of 29mm  going all the way optically to a 348mm in full frame 35mm terms. The only downside really to the zoom is that the widest aperture ramps from f2.8 to f4.5 as you zoom in. This is one of the penalties you pay for having a larger sensor.

Another slight peculiarity of the aperture is that the minimum is f11. Most lenses go down to f16 or smaller, but this is limited to f11. I suspect this may be to prevent something called diffraction limiting. When light travels though a very small aperture it can become slightly defocussed. When you have very small pixels (like when you cram 4K’s worth of pixels onto a smallish sensor) this slight defocussing has a big impact and can lead to soft and blurry looking pictures. I suspect that Sony may be limiting the smallest aperture to f11 to prevent this and help ensure sharp pictures at all times. If you have too much light then don’t worry as you have a 4 way ND filter system where you can choose between clear, 1/4, 1/16th and 1/64 ND.

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The zoom rocker.

The lens has three control rings. One for aperture, one for zoom and one for focus. Unfortunately none of these have any markings as they are all electronic controls with no direct connection to the mechanics of the lens. Fortunately though the lens is quite responsive. The iris ring works well with almost no lag. The zoom ring is the weakest link as you can turn the zoom ring faster than the lens can zoom and this can result in some lag as you wait for the zoom to catch up. The zoom speed range is pretty good, using the rocker on the hand grip you can go from a very slow creeping zoom to a respectable 2.5 seconds (approx)  from fully wide to 12x.

DSC06740-300x200 Sony PXW-Z150 Review (with picture settings).
There are 3 control rings on the PXW-Z150’s zoom lens.

The focus ring is big and chunky, easy to find and easy to grip. While you can’t crash focus with it the manual focus, it is nice and responsive and doesn’t exhibit any nasty overshoots or other surprises. So manual focussing is nice and easy.  This is assisted by a good viewfinder peaking and a focus magnification system  that helps you determine the sharpest parts of the image with ease. One observation though is that if you leave the peaking on the default “White” setting it can make some scenes appear over exposed as white sparkles appear across areas of fine detail. For this reason I normally use the Red or Blue peaking colors.

INPUT AND OUTPUT CONNECTIONS

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The PXW-Z150’s built in stereo microphone.

For audio there is a built in stereo mic on the front of the handle that is adequate for background and ambient sound recording. You then have the usual 2x XLR connectors with switchable phantom power on the front of the hand grip plus Sony’s MI Shoe on the top. Using the MI Shoe you can connect Sony’s UWP-D radio microphones directly to the camera via a low cost mounting adapter (SMAD-P3) eliminating the need for wires or batteries in the microphone receiver. It’s a very neat system.

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Video output options on the PXW-Z150

To output your pictures you have an HDSDI connector on the rear of the camera for HD plus an HDMI port that can deliver UHD.  There is also a legacy standard definition composite video output, this is one of the few Sony professional cameras to still have this built in. There is of course also a headphone socket on the rear panel of the camera just above the DC in socket.

POWER AND BUILD QUALITY.

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The PXW-Z150 runs off NPF-F type batteries.

The PXW-Z150 runs off readily available and incredibly common  Sony NP-F series batteries. It’s a low power camera so a single battery lasts for ages. I got about 3.5 hours from one of the smaller F770 batteries. An F970 would give at least half a working day, so two of those is all that most people would need.

Build Quality:

When I first picked the camera up it felt good. Like most modern cameras it’s constructed from a mix of plastics and alloy. The plastics appear to be of good quality and it seems to be well constructed. Perhaps not quite as high quality as the PXW-FS5 or FS7 but this is a much cheaper camera.

DSC06738-e1470743903861 Sony PXW-Z150 Review (with picture settings).
Audio switches and controls on the PXW-Z150

Buttons and switches:

There are very few switches on this camera. Just the on/off switch and switches for the audio inputs. But there are plenty of buttons including 6 user assignable buttons. For exposure control you have push buttons that select the gain, white balance and shutter settings and work in conjunction with a small up/down rocker button on the front left of the body. The rocker is used to scroll though the selections available for each of these. In practice this works quite well except that once you select one of these functions, lets say the gain, it remains selected and the rocker switch active unless you press a different function. If you press gain again to try to deselect it, gain will switch to auto and you have to press it again to go back to manual. It’s a minor thing but did result in me ending up accidentally going to auto gain or shutter when I didn’t mean to. I’m sure if you were to use the camera regularly you would soon get used to this.

Iris(aperture) is switched between auto and manual via a dedicated button as is focus. Autofocus works surprisingly well even in low light. It’s not fast but hunting is minimal once it’s focussed and it was able to track moving objects quite well.

While a one inch sensor is bigger than 2/3″ or 1/2″ it’s still significantly smaller than the Super 35mm sensors that are all the range. The Z150 has a lot of pixels squeezed onto quite a small space, so don’t expect amazing low light performance, it’s not that kind of camera. However it’s low light performance is very good for this class of compact all-in-one UHD/4K camera. For all but the most critical applications you can add 12dB of gain without any major dramas to boost the low light performance. +24dB isn’t horrendous if you really have to push the camera and the top limit of +33dB is impressive but rather noisy. In low light the lens works best when it’s wide and at f2.8. Zoom in and it drops down to f4.5 and that does drop your brightness by over a stop or the equivalent of a little over 6dB of gain (1 f-stop = 6dB = Double/half the ISO).

So picture quality… that’s a pretty important factor.

Single small sensor cameras have come a long way in recent years and the Z150 is no exception. The picture quality is pretty good for a budget camera. The smallish sensor with it’s tightly packed and very small pixels does impose some limitations on just how good it can be, especially in dynamic range and sensitivity but it does produce a nice picture for what it is.

Colours are vibrant, noise levels are low and dynamic range perfectly useable. I estimate about 10 stops of dynamic range so it’s not in the same league as the super 35mm cameras, but respectable none the less. Noise levels are low enough that you can afford to slightly under expose the camera and tweak the pictures a little in post production if you need to. This can be useful if you notice the camera is struggling with bright highlights.  I used the cameras built in Histogram to help judge exposure and found that if I had bright highlights such as the bright clouds in the sky as seen in the frame grabs here, that the best results were achieved when ensuring the highlights were below the grey 100% line on the histogram. If you expose the highlights all the way to the far right of the histogram (109%) the highlight areas are flattened by the cameras knee and they can look a bit odd. I felt  it was best to expose just a little lower as this gives better looking highlights (about half to one stop). If using auto exposure, including a -0.5 to -1 EV offset to the auto exposure (in the camera menu) has the same effect. Chromatic aberration is very low, probably being hidden by in camera processing. and the sharpening/detail correction well balanced. The PXW-Z150 creates good looking images for a single smaller chip sensor out of the box.

But as well as the standard look the camera does include 6 picture profiles which can be found towards the bottom of the camera menu. Each profile gives a quite different look.

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PXW-Z150 Picture Profile 1 (standard camera settings)
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PXW-Z150 Picture Profile 1 (standard camera settings)
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PXW-Z150 Picture Profile 2, DSLR Look.
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PXW-Z150 Picture Profile 2, DSLR look.
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PXW-Z150 Picture Profile 3 Rec-709 with Pro Color.
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PXW-Z150 Picture Profile 3, Rec-709 with Pro Color.
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PXW-Z150 Picture Profile 4, Rec709.
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PXW-Z150 Picture Profile 4, Rec709.
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PXW-Z150, Picture Profile 5, Cinematone 1, Negative Film.
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PXW-Z150, Picture Profile 5, Cinematone 1, Negative Film.
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PXW-Z150, Picture Profile 6, Cinematone 2, Print Film.
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PXW-Z150, Picture Profile 6, Cinematone 2, Print Film.

As you can see each of these looks is quite different (The Z150 also has several different scene settings that can be used for shooting in full auto under differing lighting conditions, these change the way the camera works out the auto exposure levels).

The dynamic range is no different in each profile. PP2, the DSLR look adds contrast by crushing the mid range and blacks, it’s also highly saturated to give stronger colors, particularly reds. The red flower in the frame grab was not that red.

Picture Profile 3 mixes Rec709 gamma with Sony’s “Pro” color matrix. I like the Pro color settings as it gives true to life colors and it grades quite well if you want to make tweaks in post production.

Picture Profile 4 is Rec709 (ITU709) gamma and color. To me the colors are not as accurate as they could be. The flower looks a little too “electric” compared to the real life color.

The Cinematone Gammas in picture profiles 5 and 6 flatten the image a little and bring up the shadows. This can help a little if you wish to tweak or adjust the images in post production. The Cinematone gammas are not the same as the Cinegammas found in the higher dynamic range cameras like the FS5 or A7.

Personally I did not like the colors associated with the Cinematone color settings. But one of the great things about the Picture Profiles is you can mix and match the various gamma curves and color matrix settings to create your own looks and styles. The “Pro” color matrix offers some very accurate colors and I quite like the look that you get when you combine Cinematone 2 gamma with the Pro color matrix. If you find the colors a little flat you can boost the saturation level a bit, I found that setting the saturation to +15 gave a great look straight from the camera. Don’t be afraid to go into the Picture Profile settings and experiment with different combinations of Gamma curve and Color matrix. Just don’t turn up the Saturation too high, I would not recommend going above +20.

DSC06743-300x200 Sony PXW-Z150 Review (with picture settings).
The Z150’s only menu controls are on the top of the handle.

One small annoyance I found with the PXW-Z150 was that the only menu button is up on the top of the hand grip. As I like to fiddle around with the Picture Profile settings I did find it a little awkward to access the menu controls on the very top of the camera, especially if it was at shoulder height or above on a tripod. You can’t see them up there!

Like most modern cameras the PXW-Z150 has a full set of WiFi features including the ability to transfer files wirelessly via ftp to a remote server, to stream live or control the camera from a tablet or mobile phone. A future firmware update will add Sony’s QoS (Quality Of Service) streaming error correction that promises much improved image quality over poor network connections when streaming to a Sony QoS server. To remotely control the camera you need to install Content Browser Mobile on your Android or iOS device.

SUPER SLOW MOTION

One more trick that the PXW-Z150 has is the ability to shoot continuously at up to 120fps (100fps when the camera is set to 50i area). The image is full HD but more highly compressed than the regular HD recordings, plus it’s interlaced, not progressive. In addition the inevitable faster shutter speeds mean that you do need plenty of light to get the very best results. I could definitely see a small drop in image quality when shooting at 100 or 120 fps, but the footage is perfectly useable and it is great to be able to slow down motion by 4 or 5 times. You do need to be a little careful if using the interlaced footage within a progressive production as very fast moving objects that travel through the frame may exhibit the combing artefact common in regular interlace material when show progressively. To get the full 5x slow down the camera needs to be set to 60i area to allow the selection of 120fps.

Summary:

The PXW-Z150 is a compact jack of all trades camera that’s easy to work with, has a great zoom range and delivers a respectable looking image. The largeish 1″ sensor gives a greater degree of control over the depth of field than you will have with a camera with a 1/2″ or 1/3″ sensor. But it’s isn’t going to give you that super shallow film look unless you are using longer focal lengths.

I think the Z150 will find a home in many corporate and industrial production applications. The ability to shoot in 4K gives the flexibility to crop int the image to re-frame shots for HD productions. And the price is good too, you get a lot of camera for the money.

Webinar Recordings.

In case you missed the webinars I presented yesterday here are recordings of the 2 afternoon sessions. The first one on HDR, what is it and what does it mean for you. The second is a question and answers session on Sony’s large sensor cameras, from the FS5 to the F55. There were quite a few a6300 and A7s questions thrown in there too!

Hopefully I will be able to find a sponsor that will be able to make these a regular event.

 

How much technology does a modern cinematographer need to know?

This post might be a little controversial, I am often told “you don’t need to know the technical stuff to be a cinematographer” or “I don’t need to know about log and gamma, I just want to shoot”.

I would argue that unless you are working closely with a good DIT a modern DP/Cinematographer really does need to understand many of the technical aspects of the equipment being used, in particular the settings that alter the way the camera captures the images. Not just things like “set it to gamma x for bright scenes” but why you would want to do that.

Now I’m not saying that you have to be a full blown electronics engineer, but if you really want to capture the best possible images it really is very important that you truly understand what the camera is doing. It’s also a huge help to understand how your footage will behave in post production. Any craftsman should understand the correct way to use his tools and not only know how to use them but how they work.

Part of the understanding of how your chosen camera behaves comes from testing and experimentation. Shooting test clips across a range of exposures, trying different gamma or log curves and then taking the footage into post production and seeing how it behaves.

Film cinematographers will shoot tests with different film stocks before a large production under the kinds of lighting conditions that will be encountered during the film. Then the film would be processed in different ways to find the best match to the look the cinematographer is trying to achieve. Digital cinematographers should be doing the same and importantly understanding what the end results are telling them.

Most of the great painters didn’t just pick up a paint brush and slap paint on a canvas. Many artists from  Da Vinci to Turner studied chemistry so they could develop new paints and painting techniques. DaVinci was a pioneer of oil painting, Turner used to make his own paints from base pigments and chemicals and patented some of the unique colors he created.

This doesn’t take anything away from the traditional skills of lighting and composition etc, those are just as important as ever and always will be. But modern electronic cameras are sophisticated devices that need to be used correctly to get the best out of them.  I believe that you need to understand the way your camera responds to light. Understands it’s limitations, understand it’s strengths and learn how to use those strengths and avoid the weaknesses.

And that’s a really important consideration. Today the majority of the cameras on the market are capable of making great images…… Provided you know how to get the best from them. One may be stronger in low light, one may be better in bright light. It may be that one camera will suit one job or one scene better than another. You need to learn about these differences and understanding the underlying technologies will help you figure out which cameras may be candidates for your next project.

It’s not just the camera tech that’s important to understand but also how to manage the footage all the way from the camera to delivery. While you don’t need to be an expert colorist, it certainly helps if you know the process, just as film cameramen know about color timing and film processing. A trend that is growing in the US is high end cinematographers that also grade.

This has come about because in the days of film the cinematographer could determine the look of the finished production through a combination of lighting, the choice of film stock and how it was to be processed. Today a cinematographer may have much less control  over the final image as it passes through the post production and grading process. Often the final look is determined by the colorist as much as the cinematographer. By also becoming colorists and staying with their material all the way through post production, cinematographers can retain control of the final look of the production.

As HDR (High Dynamic Range) delivery becomes more important along with the need to deliver SDR content at the same time, a good understanding of the differences between and limitations of both systems will be needed as you may need to alter the way you expose to suit one or the other.

So, there is lots that you need to know about the technology used in todays world of digital cinematography. Where there is a big enough budget DIT’s (Digital Imaging Technicians) can help cinematographers with guidance on camera setups, gamma, color science, LUT’s and workflows. But at the low budget end of the market, as a cinematographer you need at the very least a firm grasp of how a modern camera works, how to correctly mange the dat it produces (you would be amazed how many people get this wrong). Finally how the material handles in post production, if you really want to get the best from it.

It isn’t simple, it isn’t always easy, it takes time and effort. But it’s incredibly rewarding when it all comes together and results in beautiful images.

If you disagree or have your own take on this please post a comment. I’d love to hear other views.

Caution with new type 128GB XQD cards in the PMW-F5 and F55 (maybe others too).

xqd-new Caution with new type 128GB XQD cards in the PMW-F5 and F55 (maybe others too).
New, faster G series XQD cards that may be causing problems in some cameras.

UPDATE – IT IS NOW CONFIRMED THAT THE NEW 440MB/s CARDS WILL NOT WORK UNDER V7 OR EARLIER FIRMWARE. A FIX WILL BE INCLUDED IN VERSION 8.

There have been some comments on an older thread about problems with the very latest slightly faster Sony G series 128GB XQD cards with Sony’s F5 and F55 cameras (thanks Justin and Richard).

Many people, including myself use XQD cards with the Sony QDA-EX1 adapter in the PMW-F5 and PMW-F55 as well as other SxS cameras. Up to now I’ve never heard of any real problems, basically they work pretty much the same as SxS cards.

Very recently Sony released a new very slightly faster XQD cards. The old cards have a maximum write speed of 350MB/s while the new cards have a max write speed of 440MB/s. You can see in the image above of one of the new cards that both the read and write speeds are shown on the front of the card. The old (good) cards only show a single speed (400MB/s).

From what I have been able to gather so far the old 128GB G series cards work just fine, but a few people are reporting that the new faster 128GB ones do not. Problems include being unable to format the cards in the camera or unable to write anything to the cards.

If you have any experience of this issue, good or bad, with the new 64GB or 128GB 440MB/s cards please let me know by adding a comment.

 

Training Videos for the PXW-FS5 and PXW-FS7

Just a reminder that the full sets of traing films for the PXW-FS5 and the PXW-FS7 are available for viewing for free on YouTube.

The FS7 videos can be found by following this playlist link.

There are 10 videos taking you from basic setup all the way through scene files, cine EI and the effects shooting modes.

There are currently 2 PXW-FS5 videos.

The first on picture profiles and picture settings is here.

The second on the advanced shooting modes is here.

I am currently working on a further video on using the FS5’s raw output and this should be available in the next couple of weeks.

Don’t forget if you have any questions I have my Webinar day coming next week.

 

Free Webinar Day – July 26th 2016.

4K – It’s not the be-all and end-all.

I often hear people talking about future proofing content or providing the best they can for their clients when talking about 4K. Comments such as “You’d be crazy not shoot shoot 4K for a professional production”. While on the whole I am a believer in shooting in 4K, I think you also need to qualify this by saying you need to shoot good 4K.

As always you must remember that bigger isn’t always better. Resolution is only one part of the image quality equation. Just take a look at how Arri’s cameras, the Alexa etc, continue to be incredibly popular for high end production even those these are in effect only HD/2K cameras.

Great images are a combination of many factors and frankly resolution comes some way down the list in my opinion. Just look at how DVD has managed to hang on for so long, feature films on DVD still look OK even though the resolution is very low. Contrast and dynamic range are more important, good color is vital and low noise and artefact levels are also essential.

A nice contrasty image with great color, low noise and minimal artefacts up scaled from HD to 4K may well look a lot better than a 4K originated image that lacks contrast or has other artefacts such as compression noise or poor color.

So it’s not just about the number of pixels that you have but also about the quality of those pixels. If you really want to future proof your content it has to be the best quality you can get today, not just the largest you can get today.

Revealing Signal to Noise and Exposure experiment for PMW-F5, F55 and FS7.

Here’s a little experiment for you to try if you have a PMW-F5, PMW-F55 or PMW-FS7. It should help you understand a few key things about the way these cameras behave, notably:

1: Why ISO does not actually reflect the sensitivity of the camera.

2: Why it is beneficial to expose S-Log2 or S-Log3 brighter than the Sony recommended levels.

3: How to get the best possible S-Log footage.

4: Why S-log may be a poor choice for low light.

Ideally you will want to use an external waveform monitor connected to the cameras SDI output, but it is possible to use the built in waveform display.

Start with the camera in Custom mode. Choose “STD” gamma and Rec-709. Set the gain/ISO settings so that the camera is showing ISO.

Set the ISO to the base ISO (800 ISO on F5/FS7, 500 ISO on F55).

Expose a 90% white card so that white is 90% on the waveform display. This doesn’t need to be 100% accurate, you can use a piece of paper if you don’t have a proper white card. Don’t change the ISO/Gain, light the white card if you need to. Make a note of the aperture.

Now change the gamma selection to S-Log2, do not change the exposure.

Note how white now drops down to about 70% and also note that the ISO becomes 2000 ISO on an F5 or FS7 and 1250 ISO on an F55.

Think about this for a moment: If the ISO has gone up, how can white and the bulk of my image become darker?

Now switch the camera to show dB gain instead of ISO, the gain should be showing 0dB. Repeat the above switching from Standard 709 gamma to S-Log2 and note that the gain remains at 0dB for both rec-709 and S-Log2.

Think about this: The gain is the same for both 709 and S-log2 but the S-Log2 image is darker. As the gain is NOT changing then the sensitivity is not actually changing, so why does the ISO change?

If you were to use a light meter and start off with the light meter set to 800 (500) ISO the light meter would tell you to set the aperture to whatever it is you currently have to give the correct exposure in rec-709 with white at 90%.  If you had a light meter and you change the ISO setting on the light meter from 800(500)ISO to 2000(1250) ISO the light meter will tell you to close the aperture by 1.3 stops.

So, on your camera, while it is set to S-Log2 close the aperture from it’s original setting by 1.3 stops. Now you will find that white will be at the recording levels given by Sony for S-Log2 which is 59% for white and 32% for middle grey.

So what have we learnt from this? The gain is the same for both standard gamma and S-Log2, even though the ISO changes from 800(500) to 2000(1250) ISO. So the sensitivity and amount of noise coming from the sensor is the same in both cases. But the indicated ISO changes so that if you are using an external light meter, when you switch to S-Log the higher indicated ISO  will make the light meter tell you to close the aperture. This means there is less light falling on the sensor. This means that the recorded image will have a worse signal to noise ratio (noise remains the same, but signal is smaller).

To solution of course to this poorer signal to noise ratio is simply to open the aperture back up again by 1.3 stops. When shooting S-Log2 or S-Log3 using the CineEI mode I always recommend using 800EI on an F5 or FS7 or 640EI on an F55. This means your aperture becomes the same as it would be when shooting in vanilla Rec-709, the end result is the same, improved, signal to noise ratio. If you are not using CineEI or LUT’s, then expose white at 70%.

Understanding the all important “Signal to Noise Ratio”.

The Signal to Noise ratio is one of the key factors in determining the quality of a video or stills image. A noisy, grainy picture rarely looks as good as a low noise “clean” image. In addition it’s noise in your images will limit how far you can grade them before the picture quality becomes unacceptably poor.

Almost always what you want is the biggest possible signal with the least possible noise. In a video or film camera the signal is the desired image information or in simple terms the picture. While the noise is…. well….. the noise.

Once upon a time, when film cameras were normal for both still photography and film the noise in the pictures came primarily from the grain structure of the film stock. One of the great features of film cameras is that you can actually change that film stock to suit the type of scene that you are shooting. For low light you could use a more sensitive film stock that was actually truly more sensitive to light. However, often a very sensitive film stock will show more noise as the grain of more sensitive film is normally larger.

With video and digital stills cameras however things are quite different. You can’t normally change the sensor in a video camera and it’s the sensor that determines the sensitivity of the camera and it is the sensor that is the source of the majority of the noise.

Modern CMOS video sensors consist of two parts. The light gathering part and the readout part. The size of the pixels on a sensor is one of the key factors in determining the sensitivity and dynamic range. Small pixels are not good at capturing, converting and storing large numbers of photons of light or electrons of electricity.  Bigger pixels are much better at this, so big pixels typically mean better sensitivity and a better dynamic range. Each pixel is unique and as a result every pixel on the sensor will perform slightly differently. The signal stored in the pixels is a tiny analog signal that is easily disturbed by stray electric currents and variations in temperature. As a result of the small variations from pixel to pixel, the stray signals and heat, there is a small variation from moment to moment in the signal that comes off the pixel when it is read out and these variations are what we see as noise.

The analog signal from the pixels is passed to a circuit that converts it to a digital signal. The analog to digital conversion process normally includes some form of noise reduction circuitry to help minimise the noise. By carefully mapping the A to D circuity to the signal range the pixels provide, a sensor manufacturer can find the best combination of noise, dynamic and sensitivity. Once the signal has been converted to a digital one, the noise level, sensitivity and dynamic range is more or less locked in and can’t be changed (Some cameras have the ability to use slightly different A to D conversion ranges to help give improved noise levels at different brightness/dynamic ranges).

The bottom line of all this is that with the vast majority of video cameras the noise level is more or less fixed,  as is the sensitivity as we can’t actually swap out the sensor.

But wait! I hear you say…. My camera allows me to change the ISO or gain. Well yes it probably does and in both cases, ISO or gain, with a digital video or stills camera what you are changing is the cameras internal signal amplification. You are NOT making the camera more sensitive, you are simply turning up the volume. As anyone with any type of sound system will know, when you turn up the gain you get more hiss. This is because gain makes not only the desired signal bigger but also the noise. As a result adding gain or increasing the ISO is rarely a great thing to do.

So normally we want to use a digital camera at it’s native sensitivity wherever possible. The native sensitivity is where no gain is being added by the camera or 0dB. In ISO, well you need to find out what the native ISO is and be aware that different gamma curves will have different base ISO’s (which is why I prefer to use dB gain as 0dB = native sensitivity, least noise, best dynamic range, no matter what gamma curve).

To get the best possible image we then want to make our signal (picture information) as big as possible. As we can’t swap out the sensor, the only way to do that is to put as much light as possible onto the sensor. Obviously we don’t want to overload the sensor or exceed the limitations of the recording system, but generally the more light you get on the sensor, the better your pictures will be.

As the sensors noise output remains more or less constant, the best signal to noise ratio will be gained when you put a lot of light on the sensor. This generates a very large signal, so the signal becomes big compared to the noise and the noise becomes only a small percentage of the overall image.

If we are unable to get enough light onto the sensor to expose it fully then it is often tempting to add some gain to make the picture brighter. 6dB of gain is the equivalent to 1 stop of exposure. Just like f-stops, each time we go up a stop we are doubling. So adding 6db of gain doubles everything. It makes the picture the equivalent of one stop brighter, but it also doubles the noise. Adding 12dB gain multiplies the noise 4 times, adding 18dB multiplies the noise 8 times.

What if instead of adding gain to make the picture brighter we let 4x more light fall on the sensor (2 stops)? Well the image gets brighter by the equivalent of 2 stops but as we are not adding gain this means the desirable signal, the picture is now going to be the equivalent of 12dB bigger than the noise than it was before we added the 2 stops of light. That’s going to give you a much cleaner looking image.

How do you get more light onto the sensor? There are many ways such as using a faster lens with a larger aperture that will let more light through. Or you could try using a slower shutter speed (I often find it beneficial in low light to use a 1/24th or 1/25th shutter if there is not too much motion to cause the image to become excessively blurred). Then of course you can also add light to your scene by lighting it. It’s very rare to find noisy and grainy night scenes in feature films and that’s because the night scenes normally have well lit foregrounds but keep dark backgrounds to maintain the sensation of night time or darkness. High contrast is the key to good looking night scenes, well lit foregrounds or actors with deep, dark shadows and backgrounds.

The desire to have a good signal to noise ratio is one of the reasons why when shooting in log or raw you want to expose as brightly as you can (while still maintaining consistent exposure from shot to shot, scene to scene). It’s a little bit harder with standard gammas as we have things like the knee or highlight roll off to deal with. Plus the need to have a shot that looks correct straight out of the camera. But at the end of the day the best results are almost always gained when the gain is kept to a minimum (but don’t use negative gain as this can effect the dynamic range) and the amount of light falling on the sensor as high as possible.

In the next article I’ll give you an interesting experiment to try on a PMW-F5, F55 or PMW-FS7 that is very revealing  about the way ISO, gain, exposure and noise behaves that will show why exposing log or raw at +1 to +2 stops is so important.

What is “Exposure”?

This comes up in many of my workshops. It seems like a very simple question and the correct answer is really very simple, but many cameramen, especially those from a TV and video background actually get this a little wrong.

The word “expose” means to lay open, reveal or un-mask. In film terms it’s obvious what it means, it is opening the shutter and aperture/iris to let the correct amount of light fall on the film stock. In the video world it means exactly the same thing. It is how much light we allow to fall on the sensor.

Exposure is controlled by the speed of the shutter (how long we let the light in) and the aperture of the lens (the volume of light we let in).

So why do video people get a bit confused about exposure? Well it’s the down to the way we measure it with video cameras.

In the film world you would use a light meter to measure the intensity of the light in a scene and then perform a calculation to determine the correct amount of light we need to allow to fall on the film based on the sensitivity (ISO) of the film stock. But in the video world it is common practice to look at a monitor and asses the exposure by looking at, or measuring, how bright the picture is using a waveform meter, zebras or histogram etc.

What are we measuring when we look at a video picture or measure a video signal? We are not measuring how much light is falling on the sensor, we are measuring how bright the picture is on the screen or what the recording levels of the video signal are. Most of the time there is a direct relationship between on screen brightness and exposure, but it is important to make a clear distinction between the two as variations in brightness are not always due to changes in exposure.

It’s important because something like changing a cameras gamma curve will alter the brightness of the on screen image. This isn’t an exposure change, this is a change in the recording levels used by that particular gamma curve that in turn result in a change in the brightness levels you see on the screen. This is why if you take a camera such as the FS7 or F5/F55 and correctly expose the camera using Rec709 as the gamma curve you will find middle grey at 42% and white at 90%. Then switch to a Cinegamma or Hypergamma without adjusting the shutter speed or aperture and you will find middle grey at and white at much lower, perhaps the very same white target as low as 70%.

In both cases the exposure is correct, but the on screen brightness greatly different. The difference in on screen brightness comes from the different recording levels used by 709 and Hypergammas/Cinegammas. In order to be able to record a greater dynamic range than the 6 stops offered by 709, we need to compress the original 6 stop 709 range into a much smaller  range to make room for the extra  stops of dynamic range that the Hypergammas or Cinegammas can record.

So as you can see, exposure should really be the absolute measurement of the amount of light falling on the sensor. Brightness is related to exposure, but just how bright the picture should be depends on many factors of which exposure is just one. Once you realise that brightness and exposure are not always the same thing it becomes easier to understand how Cinegamma, Hypergamma, log and raw recording works. Levels are just levels and it doesn’t really matter whether something is recorded at 90%, 70% or 61%. Provided you have enough data (and this is where 10bit or better recording really helps) you have the same amount of picture information at both levels and you can easily shift from one level to the other without degrading the image in any way in post production.

Of course we do want to have our video levels in the finished production at the right levels to match the levels that the TV, monitor or display device is expecting. But when shooting, especially with non standard gammas such as Hypergamma or log it’s perfectly normal to have levels that are different to what we would see with plain vanilla 709 and these typically lower levels should not be considered too dark or under exposed, because they are not. Dark does not necessarily mean under exposed, nor does it mean a noisy image. How much noise there is depends on the signal to noise ratio which is dependant on the amount of light that we let on to the sensor. I’ll be explaining that in my next article.

PXW-FS7 firmware version 4.0 now available to download.

FS7-Firmware-V4 PXW-FS7 firmware version 4.0 now available to download.Sony have released firmware update version 4.0 for the PXW-FS7. This new firmware brings some welcome updates to the FS7 including the ability to move the focus magnification area away from the center of the screen.  Other new features include true 24p (as well as 23.98fps).

1. Support for Flexible Spot in Focus setting.
2. Support for XAVC-I 4K 24.00P.
3. Display for Video Signal Monitor is improved.
4. Operability of S&Q setting by assignable button is improved.
5. Remove Basic Authentication from items saved in all file.
6. Auto knee stability is improved.
7. Overall stability and operability of the camera is improved.
The firmware can be downloaded from here: https://www.sony.co.uk/pro/support/software/SET_BPE-SS-1238