Tag Archives: UHD

Should I shoot 8 bit UHD or 10 bit HD?

This comes up so many times, probably because the answer is rarely clear cut.

First lets look at exactly what the difference between an 8 bit and a 10 bit recording is.
Both will have the same dynamic range. Both will have the same contrast. Both will have the same color range. One does not  necessarily have more color or contrast than the other. The only thing you can be sure of is the difference in the number of code values. An 8 bit video recording has a maximum of 235 code values per channel giving 13 million possible tonal values. 10 bit recording has up to 970 code values per channel giving up to 912 million tonal values.
 
There is a lot of talk of 8 bit recordings resulting in banding because there are only 235 luma shades. This is a bit of a half truth. It is true that if you have a monochrome image there would only be 235 steps. But we are normally making colour images so we are typically dealing with 13 million tonal values, not simply 235 luma shades. In addition it is worth remembering that the bulk of our current video distribution and display technologies are 8 bit – 8 bit H264, 8 bit screens etc. There are more and more 10 bit codecs coming along as well as more 10 bit screens, but the vast majority are still 8 bit.
Compression artefacts cause far more banding problems than too few steps in the recording codec. Most codecs use some form of noise reduction to help reduce the amount of data that needs to be encoded and this can result in banding. Many codecs divide the image data into blocks and  the edges of these small blocks can lead to banding and stepping.
 
Of course 10 bit can give you more shades. But then 4K gives you more shades too. So an 8 bit UHD recording can sometimes have more shades than a 10 bit HD recording. How is this possible? If you think about it, in UHD each color object in the scene is sampled with twice as many pixels. Imagine a gradient that spans 4 pixels. In 4K you will have 4 samples and 4 steps. In HD you will only have 2 samples and 2 steps, so the HD image might show a single big step while the 4K may have 4 smaller steps. It all depends on how steep the gradient is and how it falls relative to the pixels. It then also depends on how you will handle the footage in post production.
 
So it is not as clear cut as often made out. For some shots with lots of textures 4K 8 bit might actually give more data for grading than 10 bit HD. In other scenes 10 bit HD might be better.
 
Anyone that is getting “muddy” results in 4K compared to HD is doing something wrong. Going from 8 bit 4K to 10 bit HD should not change the image contrast, brightness or color range. The images shouldn’t really look significantly different. Sure the 10 bit HD recording might show some subtle textures a little better, but then the 8 bit 4K might have more texture resolution.
 
My experience is that both work and both have pro’s and con’s. I started shooting 8 bit S-log when the Sony PMW-F3 was introduced 7 years ago and have always been able to get great results provided you expose well. 10 bit UHD would be preferable, I’m not suggesting otherwise (at least 10 GOOD bits are always preferable), but 8 bit works too. 
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Sony PXW-Z150 Review (with picture settings).

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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.

DSC06728-300x200 Sony PXW-Z150 Review (with picture settings).
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.

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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.

News from NAB – Sony PXW-Z450. 4K, 2/3″ shoulder cam, X400 to get 4K option.

DSC00647-1024x684 News from NAB - Sony PXW-Z450. 4K, 2/3" shoulder cam, X400 to get 4K option.
The new Sony PXW-Z450 UHD ENG shoulder camcorder.

So this is interesting. Sony have launched a new shoulder camera at NAB, the PXW-Z450. On the outside it looks much like any other ENG style shoulder camera, it’s almost a clone of the recently launched PXW-X400.

On the inside though this is a UHD, single chip (I believe), 2/3″ CMOS camera. It records to SxS cards (or XQD via an adapter) using the XAVC codec in UHD and HD at up to 60fps as well as MPEG2 HD422 (XDCAM HD422) up to 30fps.

DSC00653-1024x684 News from NAB - Sony PXW-Z450. 4K, 2/3" shoulder cam, X400 to get 4K option.
The PXW-Z450, looks just like any other ENG shoulder camera.

As the sensor is a 2/3″ sensor (Exmor R, back illuminated)  it takes regular B4 2/3″ ENG lenses, but being a 4K sensor you are going to need a really, really good lens. You don’t want to be using some old SD lens on this camera.

It will have full wireless capability including streaming over WiFi or via a 4G dongle of XAVC proxy  files and even has an “Online” button for live feeds. There’s a slot for a drop in radio mic receiver and 4 control dials for the 4 audio channels.

There’s an SDI input for recording from external sources, so great for news pool applications where you may need to record footage from other cameras or sources.

It will be supplied as a body only and can be used with the HDVF-EL20 or HDVF-EL30 Oled viewfinders.

DSC00656-1024x684 News from NAB - Sony PXW-Z450. 4K, 2/3" shoulder cam, X400 to get 4K option.It won’t be available until the end of the year (which is possibly why there isn’t too much PR for this particular launch) and the camera at the show is a very early pre-production unit, so difficult to asses what the final image quality will be like at this stage. However the camera includes S-Log3 and Hybrid Log Gamma for HDR productions, so clearly the engineers are expecting the dynamic range to be very good.

In addition next year (2017) there will be an upgrade kit to convert the PXW-X400 to UHD. I’m assuming this kit will include a new optical block to swap out the sensor as well as new firmware for the X400 to enable UHD recording.

Flicker, jaggies and moire in down converted 4K.

I kind of feel like we have been here once before. That’s probably because we have and I wrote about it first time around.

A typical video camera has a special filter in it called an optical low pass filter (OLPF). This filter deliberately reduces the contrast of fine details in the image that comes from the cameras lens and hits the sensor to prevent aliasing, jagged edges and moiré rainbow patterns. It’s a very important part of the cameras design. An HD camera will have a filter designed with a significant contrast reduction on parts of the image that approach the limits of HD resolution. So very fine HD details will be low contrast and slightly soft.

When you shoot with a 4K camera, the camera will have an OLPF that operates at 4K. So the camera captures lots of very fine, very high contrast HD information that would be filtered out by an HD OLPF. There are pro’s and con’s to this. It does mean that if you down convert from 4K or UHD to HD you will have an incredibly sharp image with lots of very fine high contrast detail. But that fine detail might cause aliasing or moiré if you are not careful.

The biggest issue will be with consumer or lower cost 4K cameras that add some image sharpening so that when viewed on a 4K screen the 4K footage really “pops”. When these sharpened and very crisp images are scaled down to HD the image can appear to flicker or “buzz”. This will be especially noticeable if the sharpening on the HD TV is set too high.

So what can you do? The most important thing is to include some form of anti-aliasing to the image when you down scale from 4K to HD.  You do need to use a scaling process that will perform good quality pixel blending, image re-sampling or another form of anti-aliasing. A straight re-size will result in aliasing which can appear as either flicker, moire or a combination of both. Another alternative is to apply a 2 or 3 pixel blur to the 4K footage BEFORE re-sizing the image to HD. This seems a drastic measure but is very effective and has little impact on the sharpness of the final HD image. Also make sure that the sharpening on your TV is set reasonably low.

I previously wrote about this very same subject when HD cameras were being introduced and many people were using them for SD productions. The same issues occurred then. Here are the original articles:

Getting good SD from HD Part 1.

Getting good SD from HD Part 2.

Remember to take a look in the TECH NOTES for info like this. There’s a lot of information in the XDCAM-USER archives now.