I’ve been running my Aurora adventure tours for 11 years and so far every trip has seen the Northern Lights. This year I had a couple of guests that had already travelled to Iceland and Finland in search of the Aurora, but had not seen it. So it was wonderful to see their faces when the Northern Lights came out to play for us most nights.
For the last couple of years I have been basing the tours out of Alta in Northern Norway, travelling from Alta to some cabins far off the beaten track at very special place just outside of the very small town of Karasjok. We stay at the cabins for several reasons.
1: It’s very different – only accessible by snow scooter.
2: It’s truly beautiful – a chance to get back to a slower way of life for a few days.
3: Clear skies – this location seems to deliver clear skies when many other areas are cloud covered.
4: Adventure – where else can you stand on the top of a hill and not see anything else man made from horizon to horizon.
So why not come and join me for an adventure you’ll remember forever? I’ll help you take your own photos or video of the Aurora if that’s what you want to do. Or just come and enjoy a bit of Sami culture as our host Oskar cooks traditional meals of reindeer, elk and salmon before we enjoy a traditional Sauna. During the day we go ice fishing, head out up on to the arctic plateaux by snow scooter or go dog sledding through the snow covered trees of the forest.
I’ve worked hard this winter to get the very best deals on the hotel and cabins that we stay at. As a result the cost of the tours is now lower than the past couple of years and I am even able to offer a really amazing early bird deal for those that book and pay 6 months before the tour. Full details here.
Normally when I travel up to arctic Norway for my annual Northern Lights expeditions I take a large sensor video camera. Last year it was the Sony FS5, which performed very well and gave me some great results. But this year I decided to down size and instead of taking a bulky camera I chose to take a pre-production sample of Sony’s diminutive new PXW-Z90 camcorder.
On the outside the Z90 looks almost exactly the same as the older PXW-X70 camcorder. I’ve shot several videos with the X70 and it’s a great little camcorder that produces a very good image considering it’s small size. Being a new model I expected the Z90 to offer some small improvements over the X70, but what I didn’t expect was the very big improvements that the Z90 brings.
The Z90 is the first camcorder from Sony to incorporate a new design of sensor. It’s a 1″ type sensor, so like the X70, bigger than you used to find on small handycams, but not as big as the super 35mm sensor found in the FS5, FS7 etc. This is a nice size for this type of camera as it makes it possible to obtain a shallow depth of field by using the cameras built in ND filters (yes- it really does have ND filters built in) and a large aperture. Or if you need a deeper depth of field for easier focussing or run and gun then you can use a smaller aperture by switching out the ND filters. The maximum aperture of the zoom lens is f2.8 but it does stop down to f4 towards the telephoto end.
This new sensor uses a new construction method that allows it to have several layers of electronics immediately below the imager pixels. The “stacked” sensor can as a result incorporate more image processing and a large memory area right under the pixels. This means that the sensor can be read out much more quickly than is normal for this type of camera and as a result rolling shutter is hugely reduced (I didn’t notice any in any of my footage).
As well as a reduction in rolling shutter compared to other similar sensors, the ability to do more on chip image processing appears to bring other advantages as the noise levels from this camera are very low indeed.
The low noise levels mean that this camera performs surprisingly well in low light. Adding in +6dB was not a problem if needed. Even with +15dB of gin the images hold together very well. Clearly the camera is doing a fair bit of electronic noise reduction at higher gain levels and there is a slight increase in image smear as a result. Plus in certain circumstances the noise levels do rise, especially if you have large dark areas amongst in an otherwise brighter scene. In my sample footage during the night time snow scooter ride, which was shot at +15dB gain, you don’t see and noise over the snow, but you can see some grainy noise over the dark jacket of the snow scooter driver (see the frame grab above). The fact that you can push the camera up to +15dB and in most cases get a pretty good image is very nice.
On top of good sensitivity you also have great dynamic range, more than the X70 and enough to make direct HDR shooting and log shooting possible with this tiny hand held camcorder. It doesn’t quite have the dynamic range of an FS5 or FS7, but there is still plenty of range to help deal with challenging lighting situations.
As well as bringing a nice improvement in image quality over the X70 (which is pretty good already) the new sensor brings a vastly improved autofocus system. There are 273 focus detection points which are combined with faster readout, faster on sensor processing and the same AF processing technology as used in the flagship Sony A9 stills camera. This brings a really remarkable autofocus system to this camera. The AF system is a newly developed hybrid system that combines phase detection AF with new algorithms created specifically for video rather than stills photography. At last this is an autofocus system that really works for a video camera. It is intelligent and responsive. There is no hunting for focus, it just seems to get on with the job.
Just about every aspect of the autofocus system can be customised in the camera menu. You can choose between using focus zones, the full image width or selectable focus spot areas. The cameras LCD screen is a touch screen so you tap the screen where you want to focus.
You can also tailor the AF’s response speed, you can adjust the size of the tracking range, using a wide range for occasions when you want the AF to follow an object through the shot, or use a narrow range to restrict the focus depth range.
You can customise how quickly the AF will move from one object to another, from staying locked on to a faster more responsive setting.
In addition it has that wonderful Sony face detection system that allows you to choose one face out of a crowd of people using the thumb stick on the hand grip or the touch screen. Once selected the camera will stay locked to that face.
While I was up in Norway it was between -24c and -30c. In those temperatures you really don’t want to take your mittens off for more than a minute or so. Being able to rely on the cameras autofocus allowed me to keep my fingers warm. Not one shot out of all my rushes from the trip has incorrect focus. That is truly remarkable and made shooting with this camera a real pleasure. I’m not saying that you should always use autofocus. When possible I love to be able to pick and choose how I focus. But in many situations or for less experienced shooters this autofocus system will be a game changer.
For my test shoot in Norway I mostly used Picture Profile number 10 which gives an instant HDR workflow thanks to the use of Hybrid Log Gamma. Using HLG you can shoot as you would do with any other conventional camera. Then take the footage and play it back in HDR on an HDR TV without any grading or other post production work. I also shot at a couple of locations using S-Log2 to test how that worked (I was shooting in UHD and the camera is 8 bit in UHD. For 8 bit I prefer S-Log2 over S-Log3). The Z90 has 10 picture profiles that allow you to tailor how the image looks, including a crunchy DSLR type look. Some filmic looks using Sony’s cinegammas as well as profiles for shooting S-Log2, S-Log3 and Hybrid Log Gamma (HLG).
The Z90 has Sony’s XAVC-L codec. This high quality codec offers 10 bit 4:2:2 broadcast quality recordings in HD and 8 bit 4:2:0 recordings in UHD (3840 x 2160). The camera records to SDXC cards, so media costs are very low. There are two card slots and you can record to each slot singly, record to one card after the other or dual record on to both cards at the same time for redundancy and an instant back. You can even use each of the cameras two record buttons to control the records on each card independently should you wish.
The Z90 is a small camcorder and like all small camcorders this doesn’t leave much room for large buttons and switches. The menu system and many of the cameras functions can be controlled via the touch screen LCD or the small joystick/thumb stick on the hand grip. Iris, shutter speed and gain each have a dedicated access button that selects the function.
Then you use the thumb stick to select the value you want, or you can set each item to Auto. In addition there is a switch to put the camera into full auto on the rear of the camera. Just below the full auto switch is the control switch for the ND filters.
The lens is a Zeiss 12x optical zoom with built in optical image stabilisation. It is controlled by a single ring around the barrel of the lens which can be switched between focus control or zoom control. In addition there is the usual zoom rocker on the handgrip as well as a small zoom switch on the top handle. In addition to the optical stabilisation the camera also has Sony’s electronic “super steadyshot” stabilisation that can be used in addition to the optical stabilisation. Another very handy function is “Clear Image Zoom”. This is a form of electronic zoom function that makes use of a database of textures and object types. When using clear image zoom the camera uses this database to apply just the right amount of image processing during the electronic zoom process. In most cases you can’t see any degradation of the image when using clear image zoom. I left it on for all of the Norway shoot as it turns the 12x zoom into a very handy 18x zoom.
After doing so much shooting on large sensor cameras with restricted zoom ranges getting back to a small camera with a big zoom range was fun. For future Norway trips I am very tempted to switch to a camera like the Z90.
The Z90 body is almost exactly the same as the X70. The cameras top handle has 2x XLR connectors with the audio controls for the two channels on the opposite side of the handle.
If you want to make the camera more compact the handle can be removed, but when you do this you will no longer have any XLR connectors. Instead you will have an MI shoe on the top of the camera body that can be used to connect a Sony UWP-D radio mic or a n XLR adapter. There is also a stereo microphone built into the main body of the camera, so even with the hand grip removed there are plenty of audio options.
The flip out LCD panel acts as the cameras main viewfinder. Opening and closing the LCD screen turns the camera on and off. It starts up and shuts down very quickly. The resolution of the LCD is similar to most other modern camera LCD’s. It’s adequate for this type of camera, but it isn’t the highest resolution screen in the world. To check focus you have a button on the top of the hand grip to activate the image magnification function and the camera has a coloured peaking system to help pick out what is, and what is not in focus. I suspect that with this particular camera, many users will take advantage of the cameras excellent auto focus system and there is a lot of feedback to the user of how this is working including coloured boxes that indicate exactly what the camera is focussing on.
As well as the side LCD panel there is also a small OLED electronic viewfinder on the rear of the camera. This is very useful for use in very bright sunlight, but it is rather small.
The cameras gain, shutter and iris functions each have a dedicated button on the side of the camera. One push of the appropriate button enables that function to be controlled by a small dial wheel just under the front of the lens.
Press the shutter button and the wheel controls the shutter. Press the gain button and the wheel controls the gain. Overall this system works well, but I would still prefer a separate gain switch and a shutter speed up/down switch. On the rear of the hand grip there is a small joystick that sits under your thumb. You can use this thumb-stick to set many of the cameras settings and to navigate through the cameras menu system. In addition you can use the LCD touchscreen to navigate through the menu as well as select your autofocus points etc.
The PXW-Z90 is a small camera that packs a very big punch. It’s never going to give the fine degree of image control that you get with most large sensor cameras and it won’t quite deliver the same image quality either (although it’s really, really close). If you need a small, discrete camera, perhaps you travel a lot, or you just need a “B” camera, then the Z90 offers a possible solution. I haven’t even touched on all the streaming, ftp and wifi capabilities of this camera. The auto focus system is a delight to use and it’s the best AF system I’ve ever come across on a video camera. The new sensor in the Z90 is clearly a fairly large step forwards from the sensor in the previous similar model the X70, it has more dynamic range, a lot less rolling shutter (not that it’s a big problem on the X70) and the final images look better as a result. I might just have to add one to my camera collection.
If you would like to join me on one of my adventures to arctic Norway please see take a look at this page. I’ve been running these trips for 11 years and EVERY tour has seen the Northern Lights. This year was no exception and we got to see some really great Auroras and had a great time dog sledding, ice fishing and exploring the Finnmarksvidda.
An interesting question got raised on Facebook today.
What shutter speed should I use if I am shooting at 50p so that my client can later convert the 50p to 50i? Of course this would also apply to shooting at 60p for 60i conversion.
Lets first of all make sure that we all understand that what’s being asked for here is to shoot at 50(60) progressive frames per second so that the footage can later be converted to 25(30) frames per second interlace – which has 50(60) fields.
If we just consider normal 50p or 60p shooing the the shutter speed that you would chooses on many factors including what you are shooting and how much light you have and personal preference.
1/48 or 1/50th of a second is normally considered the slowest shutter speed at which motion blur in a typical frame no longer significantly softens the image. This is why old point and shoot film cameras almost always had a 1/50th shutter, it was the slowest you could get away with.
Shooting with a shutter speed that is half the duration of the cameras frame rate is also know as using a 180 degree shutter, a very necessary practice with a film movie camera due to the way the mechanical shutter must be closed while the film is physically advanced to the next frame. But it isn’t essential that you have the closed shutter period with an electronic camera as there is no film to move, so you don’t have to use a 180 degree shutter if you don’t want to.
There is no reason why you can’t use a 1/50th or 1/60th shutter when shooting at 50fps or 60fps, especially if you don’t have a lot of light to work with. 1/50(1/60) at 50fps(60fps) will give you the smoothest motion as there are no breaks in the motion between each frame. But many people like to sharpen up the image still further by using 1/100th(1/120th) to reduce motion blur. Or they prefer the slightly steppy cadence this brings as it introduces a small jump in motion between each frame. Of course 1/100th needs twice as much light. So there is no hard and fast rule and some shots will work better at 1/50th while others may work better at 1/100th.
However if you are shooting at 50fps or 60fps so that it can be converted to 50i or 60i, with each frame becoming a field, then the “normal” shutter speed you should use will be 1/50th or 1/60th to mimic a 25fps-50i camera or 30fps-60i camera which would typically have it’s shutter running at 1/50 or 1/60th. 1/100th(120th) at 50i(60i) can look a little over sharp due to an increase in aliasing due to the way a interlace video field only has half the resolution of the full frame. Particularly with 50p converted to 50i as there is no in-camera anti-aliasing and each frame will simply have it’s resolution divided by 2 to produce the equivalent of a single field. When you shoot with a “real” 50i camera line pairs on the sensor are combined and read out together as a single field line and this slightly softens and anti-aliases each of fields. 50i has lower vertical resolution than 25p. But with simple software conversions from 50p to 50i this anti-aliasing does not occur. If you combine that with a faster than typical shutter speed the interlaced image can start to look over sharp and may have jaggies or color moire not present in the original 50/60p footage.
This is a question a lot of people are asking. As I’ve mentioned in other recent posts, sensors have reached a point where it’s very difficult to bring out a camera where the image quality will be significantly different from any other on the market for any given price point. Most differences will be in things like codec choices or trading off a bit of extra resolution for sensitivity etc. Other differences will be in the ergonomics, lens mounts and battery systems.
So it’s interesting to see what Keith Mullin over at Z-Systems thought of the EVA1. Keith knows his stuff and Z-Systems are not tied to any one particular brand.
Overall as expected there isn’t a huge difference in image quality between any of the 3 cameras. The EVA1 seems weaker in low light which is something I would have predicted given the higher pixel count. The dual ISO mode seems not to be anywhere near the same as the really very good dual ISO mode in the Varicam LT.
If using a LUT to judge the exposure of a camera shooting log or raw it’s really important that you fully understand how that LUT works.
When a LUT is created it will expect a specific input range and convert that input range to a very specific output range. If you change the input range then the output will range will be different and it may not be correct. As an example a LUT designed and created for use with S-Log2 should not be used with S-Log3 material as the the higher middle grey level used by S-Log3 would mean that the mid range of the LUT’s output would be much brighter than it should be.
Another consideration comes when you start offsetting your exposure levels, perhaps to achieve a brighter log exposure so that after grading the footage will have less noise.
Lets look at a version of Sony’s 709(800) LUT designed to be used with S-Log3 for a moment. This LUT expects middle grey to come in at 41% and it will output middle grey at 43%. It will expect a white card to be at 61% and it will output that same shade of white at a little over 85%. Anything on the S-Log3 side brighter than 61% (white) is considered a highlight and the LUT will compress the highlight range (almost 4 stops) into the output range between 85% and 109% resulting in flat looking highlights. This is all perfectly fine if you expose at the levels suggested by Sony. But what happens if you do expose brighter and try to use the same LUT either in camera or in post production?
Well if you expose 1.5 stops brighter on the log side middle grey becomes around 54% and white becomes around 74%. Skin tones which sit half way between middle grey and white will be around 64% on the LUT’s input. That’s going to cause a problem! The LUT considers anything brighter than 61% on it’s input to be a highlight and it will compresses anything brighter than 61%. As a result on the output of your LUT your skin tones will not only be bright, but they will be compressed and flat looking. This makes them hard to grade. This is why if you are shooting a bit brighter it is much, much easier to grade your footage if your LUT’s have offsets to allow for this over exposure.
If the camera has an EI mode (like the FS7, F5, F55 etc) the EI mode offsets the LUT’s input so you don’t see this problem in camera but there are other problems you can encounter if you are not careful like unintentional over exposure when using the Sony LC709 series of LUTs.
Sony’s 709(800) LUT closely matches the gamma of most normal monitors and viewfinders, so 709(800) will deliver the correct contrast ie. contrast that matches the scene you are shooting plus it will give conventional TV brightness levels when viewed on standard monitors or viewfinders.
If you use any of the LC709 LUT’s you will have a miss-match between the LUT’s gamma and the monitors gamma so the images will show lower contrast and the levels will be lower than conventional TV levels when exposed correctly. LC709 stands for low contrast gamma with 709 color primaries, it is not 709 gamma!
Sony’s LC709 Type A LUT is very popular as it mimics the way an Arri Alexa might look. That’s fine but you also need to be aware that the correct exposure levels for this non-standard LC gamma are middle grey at around 41% and white at 70%.
An easy trap to fall into is to set the camera to a low EI to gain a brighter log exposure and then to use one of the LC709 LUT’s and try to eyeball the exposure. Because the LC709 LUT’s are darker and flatter it’s harder to eyeball the exposure and often people will expose them as you would regular 709. This then results in a double over exposure. Bright because of the intentional use of the lower EI but even brighter because the LUT has been exposed at or close to conventional 709 brightness. If you were to mistakenly expose the LC709TypeA LUT with skin tones at 70%, white at 90% etc then that will add almost 2 stops to the log exposure on top of any EI offset.
Above middle grey with 709(800) a 1 stop exposure change results in an a 20% change in brightness, with LC709TypeA the same exposure change only gives a just over 10% change, as a result over or under exposure is much less obvious and harder to measure or judge by eye with LC709. The cameras default zebra settings for example have a 10% window. So with LC709 you could easily be a whole stop out, while with 709(800) only half a stop.
Personally when shooting I don’t really care too much about how the image looks in terms of brightness and contrast. I’m more interested in using the built in LUT’s to ensure my exposure is where I want it to be. So for exposure assessment I prefer to use the LUT that is going to show the biggest change when my exposure is not where it should be. For the “look” I will feed a separate monitor and apply any stylised looks there. To understand how my highlights and shadows, above and below the LUT’s range are being captured I use the Hi/Low Key function.
If you are someone that creates your own LUT’s an important consideration is to ensure that if you are shooting test shots, then grading these test shots to produce a LUT it’s really, really important that the test shots are very accurately exposed.
You have 2 choices here. You can either expose at the levels recommended by Sony and then use EI to add any offsets or you can offset the exposure in camera and not use EI but instead rely on the offset that will end up in the LUT. What is never a good idea is to add an EI offset to a LUT that was also offset.
This is another of those frequent questions at workshops and online.
What frame rate is the best one to use?
First – there is no one “best” frame rate. It really depends on how you want your video to look. Do you want the slightly juddery motion of a feature film or do you want silky smooth motion?
You also need to think about and understand how your video will be viewed. Is it going to be watched on a modern TV set or will it be watched on a computer? Will it only be watched in one country or region or will it be viewed globally?
Here are some things to consider:
TV in Europe is normally 50Hz, either 25p or 50i.
TV in the North America is 60Hz, either 30p or 60i (both actually 29.97fps).
The majority of computer screens run at 60Hz.
Interlaced footage looks bad on most LCD screens.
Low frame rates like 24p and 25p often exhibit judder.
Most newer, mid price and above TV’s use motion estimation techniques to eliminate judder in low frame rate footage.
If you upload 23.98fps footage to YouTube and it is then viewed on a computer it will most likely be shown at 24p as you can’t show 0.98 of a frame on a 60Hz computer screen.
Lets look first at 25p, 50i and 50p.
If you live in Europe or another 50Hz/Pal area these are going to be frame rates you will be familiar with. But are they the only frame rates you should use? If you are doing a broadcast TV production then there is a high chance that you will need to use one of these standards (please consult whoever you are shooting for). But if your audience is going to watch your content online on a computer screen, tablet or mobile phone these are not good frame rates to use.
Most computer screens run at 60Hz and very often this rate can’t be changed. 25p shown on most computer screens requires 15 frames to be shown twice and 10 frames to be shown 3 times to create a total of 60 frames every second. This creates an uneven cadence and it’s not something you can control as the actual structure of the cadence depends on the video subsystem of the computer the end user is using.
The odd 25p cadence is most noticeable on smooth pans and tilts where the pan speed will appear to jump slightly as the cadence flips between the 10 frame x3 and 15 frame x 2 segments. This often makes what would otherwise be smooth motion appear to stutter unevenly. 24p material doesn’t exhibit this same uneven stutter (see the 24p section). 50p material will exhibit a similar stutter as again the number of padding frames needed is uneven, although the motion should be a bit more fluid.
So really 25p and 50p are best reserved for material that will only ever be seen on televisions that are running at 50Hz. They are not the best choices for online distribution or viewing on computers etc.
24p, 30p or 60p (23.98p, 29.97p)
If you are doing a broadcast TV show in an NTSC/60Hz area then you will most likely need to use the slightly odd frame rates of 23.98fps or 29.97fps. These are legacy frame rates specifically for broadcast TV. The odd frame rates came about to avoid problems with the color signal interfering with the luma (brightness) signal in the early days of analog color TV.
If you show 23.98fps or 29.97fps footage on a computer it will normally be shown at the equivalent of 24p or 30p to fit with the 60Hz refresh rate of the computer screen. In most cases no one will ever notice any difference.
23.98p and 24p when shown on a 60Hz screen are shown by using 2:3 cadence where the first frame is shown twice, the next 3 times, then 2, then 3 and so on. This is very similar to the way any other movie or feature film is shown on TV and it doesn’t look too bad.
30p or 29.97p footage will look smoother than 24p as all you need to do is show each frame twice to get to 60Hz there is no odd cadence and the slightly higher frame rate will exhibit a little less judder. 60p will be very smooth and is a really good choice for sports or other fast action. But, higher frame rates do require higher data rates to maintain the same image quality. This means larger files and possibly slower downloads and must be considered. 30p is a reasonable middle ground choice for a lot of productions, not as juddery as 24p but not as smooth as 60p.
24p or 23.98p for “The Film Look”.
Generally if you want to mimic the look of a feature film then you might choose to use 23.98p or 24p as films are normally shot at 24fps. If your video is only going to be viewed online then 24p is a good choice. If your footage might get shown on TV the 23.98p may be the better choice as 23.98fps works well on 29.97fps TV’s in 60Hz/NTSC areas.
BUT THERE IS A NEW CATCH!!!
A lot of modern, new TV’s feature motion compensation processes designed to eliminate judder. You might see things in the TV’s literature such as “100 Hz smooth motion” or similar. If this function is enabled in the TV it will take any low frame rate footage such as 24p or 25p and use software to create new frames to increase the frame rate and smooth out any motion judder.
So if you want the motion judder typical of a 24fps movie and you create at 24fps video, you may find that the viewer never sees this juddery, film like motion as the TV will do it’s best to smooth it out! Meanwhile someone watching the same clip on a computer will see the judder. So the motion in the same clip will look quite different depending on how it’s viewed.
Most TV’s that have this feature will disable it it when the footage is 60p as 60p footage should look smooth anyway. So a trick you might want to consider is to shoot at 24p or 30p and then for the export file create a 60p file as this will typically cause the TV to turn off the motion estimation.
In summary, if you are doing a broadcast TV project you should use the frame rate specified by the broadcaster. But for projects that will be distributed via the internet I recommend the use of 23.98p or 24p for film style projects and 30p for most other projects. However if you want very smooth motion you should consider using 60p.
Due to the unexpected redundancy of one of my guests I am now looking to sell on a couple of places on my Northern Lights expedition in January on his behalf.
The trip starts and finishes in Alta, Norway. Food is included for most of the trip. We spend 4 days up on the Finnmarksvidda where we normally get amazing Northern Lights viewing opportunities. I can also help guide anyone that wants to learn how to photograph or video the Aurora.
This is a real adventure and a lot of fun. The only way up to the cabins by snow scooter, crossing frozen lakes along the way. We eat a campfire lunch in a Sami style tent, we go ice fishing, exploring by snow scooter and enjoy traditional sauna nights.
This post follows on from my previous post about sensors and was inspired by one of the questions asked following that post.
While sensor size does have some effect on low light performance, the biggest single factor is really the lens. It isn’t really bigger sensor that has revolutionised low light performance. It’s actually the lenses that we can use that has chnge our ability to shoot in low light. When we used to use 1/2″ or 2/3″ 3 chip cameras for most high end video production the most common lenses were the wide range zoom lenses. These were typically f1.8 lenses, reasonably fast lenses.
But the sensors were really small, so the pixels on those sensors were also relatively small, so having a fast lens was important.
Now we have larger sensors, super 35mm sensors are now common place. These larger sensors often have larger pixels than the old 1/2″ or 2/3″ sensors, even though we are now cramming more pixels onto the sensors. Bigger pixels do help increase sensitivity, but really the biggest change has been the types of lenses we use.
Let me explain:
The laws of physics play a large part in all of this.
We start off with the light in our scene which passes through a lens.
If we take a zoom lens of a certain physical size, with a fixed size front element and as a result fixed light gathering ability, for example a typical 2/3″ ENG zoom. You have a certain amount of light coming in to the lens.
When the size of the image projected by the rear of the lens is small it will be relatively bright and as a result you get an effective large aperture.
Increase the size of the sensor and you have to increase the size of the projected image. So if we were to modify the rear elements of this same lens to create a larger projected image (increase the image circle) so that it covers a super 35mm sensor what light we have. is spread out “thinner” and as a result the projected image is dimmer. So the effective aperture of the same lens becomes smaller and because the image is larger the focus more critical and as a result the DoF narrower.
But if we keep the sensor resolution the same, a bigger sensor will have bigger pixels that can capture more light and this makes up for dimmer image coming from the lens.
So where a small sensor camera (1/2″, 2/3″) will typically have a f1.8 zoom lens when you scale up to a s35mm sensor by altering the projected image from the lens, the same lens becomes the equivalent of around f5.6. But because for like for like resolution the pixels size is much bigger, the large sensor will be 2 to 3 stops more sensitive, so the low light performance is almost exactly the same, the DoF remains the same and the field of view remains the same (the sensor is larger, so DoF decreases, but the aperture becomes smaller so DoF increases again back to where we started). Basically it’s all governed by how much light the lens can capture and pass through to the sensor.
It’s actually the use of prime lenses that are much more efficient at capturing light has revolutionised low light shooting as the simplicity of a prime compared to a zoom makes fast lenses for large sensors affordable. When we moved to sensors that are much closer to the size of sensors used on stills cameras the range and choice of affordable lenses we could use increased dramatically. We were no longer restricted to expensive zooms designed specifically for video cameras.
Going the other way. If you were to take one of todays fast primes like a common and normally quite affordable 50mm f1.4 and build an optical adapter of the “speedbooster” type so you could use it on a 2/3″ sensor you would end up with a lens the equivalent of a f0.5 10mm lens that would turn that 2/3″ camera into a great low light system with performance similar to that of a s35mm camera with a 50mm f1.4.
Every now and again I get asked how to adjust the color matrix in a video camera. Back in 2009 I made a video on how to adjust the color matrix in the Sony’s EX series of cameras. This video is just as relevant today as it was then. The basic principles have not changed.
The exact menu settings and menu layout may be a little different in the latest cameras, but the adjustment of the matrix setting (R-G, G-R etc) have exactly the same effect in the latest camera that provide matrix adjustments (FS7, F5, F55 and most of the shoulder mount and other broadcast cameras). So if you want a better understanding of how these settings and adjustment works, take a look at the video.
I’ll warn you now that adjusting the color matrix is not easy as each setting interacts with the others. So creating a specific look via the matrix is not easy and requires a fair bit of patience and a lot of fiddling and testing to get it just right.
I’m running a digital film making workshop in Dubai, December 15/16th 2017.
This 1.5 day course will take you through composition, lighting, and exposure (including color, gamma and exposure index) as well as post production including different grading techniques including LUT’s, S-Curves and color managed workflows. It will focus on how to create high quality, film-like images using the latest digital techniques. It will also cover one of the hotest topics right now which is HDR.
Day 2 will include practical sessions where different shooting techniques can be tested to compare how they effect the end result.