When you have millions of pixels on a video sensor it isn’t surprising to find that every now and then one or two might go out of spec and show up in your footage as a white dot. These “hot” pixels are most commonly seen when using high ISO’s or the upper of the cameras two base ISO’s. Hot pixels are not uncommon and they are not something to worry about.
The Fix:
Thankfully the issue is easily resolved by going to the cameras main menu and – Setup Menu – Setup Option – Pixel Mapping. Then cap the lens or cap the camera body and run the pixel mapping. It only takes around 30 seconds and it should eliminate any white, black or coloured sensor pixel issues. The camera will ask you to do this periodically anyway and you should do it regularly, especially after flying anywhere with the camera.
Sensor pixels can be damaged by energetic particles that come from cosmic events. So a hot pixel can appear at any time and without warning. They are not something to worry about, it is normal to get some bad pixels from time to time over the life of a camera. When you travel by air there is less of the atmosphere to protect your camera from these particles, so there is a higher than normal likelihood of one going out of spec. Polar air routes are the worst as the earths magnetic field tends to funnel these particles towards the north and south poles. So, whenever you fly with your camera it is a good idea to run Pixel Mapping (or APR if you have an FX6, FX9 etc) before you start shooting.
Although I wouldn’t normally recommend removing the screws from Sony cameras there are times when this is something you need to do, for example to remove the microphone mount on an FX6.
Most of the small screws have a thread locking compound applied to the threads to prevent them from shaking or vibrating loose. This can make them hard to unscrew.
JIS NOT Phillips!!
The main issue is that most cross of the commonly found small and miniature head screw drivers are manufactured to the “Philips” standard. But the screws used on the Sony cameras are manufactured to the JIS standard. The differences between these two very similar looking standards means that you will not get a secure and tight fit between a Philips screw driver and a JIS screw head. The edges of a Philips screwdriver are at an angle that is too shallow to properly engage with the full depth of a JIS screw head. So when you try to undo a tight screw the head of the screw will deform or strip, often to the point where it can’t be undone.
Whenever working on Sony cameras you should use JIS standard screwdrivers and ensure the screwdriver is the correct size for the screws you are working with. The smaller screws used for thing like the microphone mount on the FX and Alpha series cameras are JIS size +0 or +00. A JIS size +0 seems to fit most but I would also get a +00.
Don’t try to use a miniature Philips screwdriver on a tight JIS screw. It might look like it fits, but only a very small part of the screwdriver head will be correctly engaged with the JIS screw and once the screw head is damaged you can’t undo the damage and it may become impossible to remove the screw without drilling it out.
If you search for “Vessel JIS” you should be able to find good quality small and miniature JIS screwdrivers on Amazon, ebay or from other suppliers.
Here’s a handy chart of the base ISO levels for Sony’s cinema line cameras including Venice, the FX9, FX6, FX3 and FX30 as well as the A7SIII and A7IV. The new Sony FR7 is the same as the FX6. I’ve include the base ISO’s for both S-Log3 and S-Cinetone. If you use other gammas the base levels may be different to the S-Cinetone base level, so these values should only be used for S-Cinetone and S-Log3. You can click on the image for a bigger version or left click on it to download it.
The base ISO levels for the FX9, FX6, FX3, FX30, and Venice Cameras.
As explained above there is a difference in the way the dual ISO functions work between the FX6/FX3/A7SIII and the other cameras. Venice, the FX9 and FX30 have sensors with two distinctly different sensitivities. These cameras offer near identical performance at either the low or high base ISO. Sony call these cameras “Dual Base ISO” as in most cases the two base ISO’s can be used in exactly the same way depending on which best suits the light level you are working at and a near identical image produced.
The other cameras (FX6, FX3, A7SIII) probably have a dual gain sensor plus additional processing to deliver their 2 distinctly different sensitivity ranges. The result is that there is a more visible increase in noise at the high range (compared to the Dual Base ISO cameras) plus a very slight reduction in dynamic range. However, the noise level in the high base setting is significantly lower than you would have by adding gain to get to the same level and the upper base sensitivities are very usable and allow for shooting at very low light levels.
I’ve just got back from my latest Northern Lights expedition to Norway and thought I would share some real time footage of the Northern Lights shot with the Sony FX3 and a Sony 24mm f1.4 GM lens. The 24mm f1.4 is a lovely lens and brilliant for shooting star fields etc as it is pin sharp right into the corners. It also has near zero comma distortion so stars remain nice and round. It was -27c when this was shot and my tripods fluid head was starting to get very stiff, so that’s my excuse for the bumps on a couple of the camera moves. What you see in this video is pretty much exactly as it appeared to my own eyes. This is not time-lapse and the colours while slightly boosted are as they really are. I shot using a range of ISO’s using S-Log3. Starting at 12,800 ISO but going all the way up to 128000 ISO. I perhaps didn’t need to go that high as the Aurora was pretty bright but when an Aurora like this may only last a few minutes you don’t want to stop and change your settings unless you have to for fear of missing something. The low light performance of the FX3 really is quite phenomenal.
There is a bug in some versions of DaVinci Resolve 17 that can cause frames in some XAVC files to be rendered in the wrong order. This results in renders where the resulting video appears to stutter or the motion may jump backwards for a frame or two. This has now been fixed in version 17.3.2 so all user of XAVC and DaVinci Resolve are urged to upgrade to at least version 17.3.2.
The FX3’s larger brothers, the FX6 and FX9 have a function called “APR” that is used to periodically inspect every pixel on the sensor and normalise or map out any out of spec pixels. With modern 4K cameras having at least 8.8 million pixels the chances of a few going out of spec or being damaged by cosmic rays from time to time is quite high. So on the FX6 and FX9 you will get a reminder to perform the APR process around once a week.
From what I understand, the Alpha series cameras and FX3 also periodically perform a similar process automatically. Because these camera have a mechanical shutter to shut out any external light there is no need for any user intervention to perform this process so you will not be aware that it’s happening. On the FX6 and FX9 the user has to place a cap over the lens or sensor, hence why the camera asks you before it can happen.
But what if you find you have some bright or hot pixels with the FX3? Perhaps you have just travelled on a plane where the high altitude reduces the atmospheres damping effect of the high energy particles from space that can damage pixels. Well you can go into the camera’s menu system and force it to run its pixel mapping process which does the same thing as APR on the other cameras.
You need to go to:
MENU: (Setup) ? [Setup Option] ? select [Pixel Mapping] and then select OK. It doesn’t take long and I would recommend that you do this after flying on a plane or prior to any shoot where you will use large amounts of gain as this is when hot pixels are most likely to show up.
Most of sony’s cameras that support S-Log3 or Hybrid Log Gamma also have a function called Viewfinder Display Gamma Assist.
Viewfinder Display Gamma Assist allows you to monitor with the cameras built in LCD screen or viewfinder with the correct brightness and contrast range when using gamma curves that are not directly compatible with these Rec-709 screens.
Whenever you try to view a gamma curve that is not normal Rec-709 on a Rec-709 screen the brightness and contrast that you will see will be incorrect. The most common scenario is perhaps viewing S-Log3 without any form of LUT. In this case the images will look less bright and have less contrast than they should and this makes judging exposure difficult as well making it less easy to see focus errors.
With a camera like the FX6 or FX9 most people will use the cameras CineEI mode and add a LUT to the viewfinder image to convert the S-Log3 to something that looks more contrasty and on the FX6 and FX9 the default LUT is “s709”. However s709 is not the same thing as Rec-709 (Note that with the FX6, because LUTs are always available in the CineEI mode, viewfinder display gamma assist is not available in the CineEI mode of the FX6, you should instead use a LUT).
I think a lot of people think that the default s709 LUT is the same as Rec-709, it’s not, it is very different. They look very different and result in quite different brightness levels when exposed correctly. s709 when exposed correctly will put skin tones somewhere around 50-60% and white at 78%. If you expose s709 using normal Rec-709 brightness levels (70% skintones, 90% white) this is actually over exposed by just over 1 stop. As a result if you expose the s709 LUT, using Rec-709 levels, and then turn off the LUT and instead use Viewfinder Gamma Assist, the gamma assist will look wrong, it will be too bright and may look washed out and this is simply because the exposure IS wrong.
Almost always, if the viewfinder display gamma assist looks wrong, the exposure is wrong. When it looks right, the likelihood is the exposure is right.
A few things to understand:
The viewfinder is a Rec-709 range display device only capable of showing Rec-709 range and colour.
Feed true Rec-709 to a Rec-709 device and you will have a correct looking image with “normal” brightness, contrast and colour.
Feed S-Log3 to a Rec-709 device and you will have an incorrect dull, flat looking image due to the gamma miss-match between the capture gamma and display gamma.
Feed S-Log3 to a device with S-Log3 gamma and you will once again have the correct brightness and contrast as there is no longer a gamma miss-match (S-Log3 only appears to be flat due to the gamma missmatch between S-Log3 and Rec-709, use the right gamma and you will see that it is not actually flat).
Viewfinder Display Gamma Assist works by changing the gamma curve used in the Viewfinder to a gamma curve similar to S-Log3. When you view S-Log3 with a monitor with S-Log3 gamma you will have the correct contrast and brightness, so correct exposure will look correct.
But because the cameras LCD display screen can only show 6 to 7 stops you don’t get the full S-Log3 viewing range, just the central mid range part that is the direct equivalent of Rec-709. This very closely matches what you see if you use the Sony 709(800) LUT to convert the S-log3 to 709. The 709(800) LUT converts S-Log2 or S-Log3 to vanilla Rec-709 (70% skintones/90% white) with a knee that provides a slightly extended highlight range. It is broadly comparable to how most conventional Rec-709 cameras will look. So as a result viewfinder display gamma assist and Sony’s 709(800) LUT’s will look almost identical, while the s709 LUT will (and should by design) look different.
Viewfinder Display Gamma Assist is extremely useful for scenarios where you do not have a LUT option such as when shooting in CineEI in HD with the FX9. It can help you make good exposure assessments. It can make it easier to see when you are in focus. But it isn’t a LUT, so can’t be applied to the cameras outputs, only the built in viewfinder. Additionally if you use zebras, the waveform or histogram, gamma assist has no effect on these so you must remember that you are still measuring the levels of the actual recording gamma, not Rec-709 levels.
Viewfinder Gamma Assist is useful not only for shooting with S-Log but also when shooting using HLG (Hybrid Log Gamma). HLG is an HDR gamma curve and because the LCD viewfinder isn’t HDR you can’t correctly monitor HLG directly. Viewfinder Gamma Assist allows you to monitor with the correct brightness and contrast when shooting HLG making it easier to confidently get the correct exposure levels, as much like S-log3 the levels required for the correct exposure of HLG are quite different to Rec-709.
One last thing: NEVER use Viewfinder Gamma Assist with a LUT at the same time, this will result in a completely incorrect looking image and could result in very bad exposure as a result.
In the course of my tests with the FX3 and comparing it with the FX6 and FX9 I discovered a strange anomaly with the FX3 and A7SIII ISO ratings when compared to the FX6 and FX9.
The FX3’s default picture profile is PP11 and S-Cinetone. If you have an FX6 or FX9 these cameras also default to S-Cinetone in SDR mode. In the FX6 and FX9 the base ISO for S-Cinetone is 320 ISO. Therefore you would assume that if you also set the A7SIII or the FX3 to 320 ISO and expose all the cameras the same, same aperture, shutter etc that the exposures would match.
BUT THE EXPOSURES DON’T MATCH!!
The FX6 at 320 ISO, 1/50th shutter, S-Cinetone.
The FX3 with the same 320 ISO, 1/50th shutter and S-Cinetone. It’s clearly brighter.
The FX3 and the A7SIIII are just over 1 stop brighter than the FX6 and FX9 when all the exposure settings are matched. I tested all the cameras with the same lens to ensure this wasn’t a lens issue, but it isn’t the lens.
FX3 S-Cinetone is brighter compared to the FX6/FX9 and over exposed according to my light meter by just over 1 stop. The white of the white card should be at approx 83% and my skin tones are well into the highlight roll off and looking flat as a result.
The FX6’s exposure much more closely matches my light meter and is only a fraction of a stop under with the white card just touching the 83% exposure I would normally expect with S-Cinetone.
Here’s the FX3 again, the whites are much, much too bright when exposed against my light meter, even the middle grey is over 60%. The MM+0.7 indication means the camera thinks it is over exposed.
And the FX6 with exactly the same settings and the same lens matches my light meter very closely, white is around 83% and middle grey around 45%, as I would expect. Something odd is going on here, it’s not just my light meter it’s something else as the cameras should at least match, even if they don’t agree with the light meter.
I then went on to test other gamma/picture profile settings and I found a just over 1 stop difference between the FX3 and my FX6/FX9 in any similar combination EXCEPT S-LOG3!
The FX3 shooting S-Log3 now it matches my light meter very closely and the exposure is add I would expect.
This is the FX6 set exactly the same as the FX3 shooting S-Log3. Now they both match and now the both provide the same exposure and closely match my light meter.
When using Picture Profile 2 on the FX3 which is uses Sony’s “Still” gamma and then using the “Still” Profile on the FX6 there is a difference of around 1 stop. If I set the FX3 to PP3 (ITU-709) and the FX6 to ITU-709 then the difference is again around 1 stop, in every case the FX3 is brighter except when you select S-Log3 where the FX3 and the FX6/FX9 match almost perfectly!
I find this very strange. They should not be different. My light meter suggests to me that the FX6/FX9 are correct.
Comparing to my light meter I believe the FX6/FX9 ratings to be correct and the FX3 to be between 1 and 1.3 stops brighter than it should be when using gammas that are not S-Log3. What I really don’t understand is why the FX3/A7SIII match the FX6/FX9 when using S-Log3 but do not match when using the other profiles, normally I would expect to see a consistent offset. This further makes leads me to be sure this is not a problem with my light meter, but something else.
I would love to hear from anyone else that’s able to take a look at the ISO ratings of the A7SIII and compare it with an FX6 or FX9.
The bottom line is – DON’T EXPECT TO PUT THE SAME EXPOSURE SETTINGS INTO BOTH AN FX3 AND AN FX6/FX9 AND GET THE SAME RESULTS, because you won’t, unless you are using S-Log3, then they match.
Also in the clip metadata I found that 0dB for S-Cinetone is 100 ISO, and whether this is a coincidence or not, if I set the FX3 to 100 ISO and the FX6 to 320 ISO and then match shutter speed and aperture then the exposures are very close.
Sony’s new A7S III video centric mirrorless camera.
So Sony have just launched the A7S III. And very impressive it is. Amazing low light performance, great dynamic range and lots of nice 10 bit codecs. You can even get a 16 bit raw output if you want. I can’t wait to get one. But I really don’t see the A7S III as a threat to or replacement of my FX9 or any other 4K professional video camera.
All the same discussions took place when the original A7S was launched. Sony F5 owners looked at the A7S and said – heck how can that little camera shoot full frame 4K while my camera can’t even shoot s35 4K. Why can the A7S have AF when my F3/F5 doesn’t. How can a camera that produces such beautiful images only cost 1/5th of what my F5 costs. But here we are 6 years on and the A7S and A7S II didn’t replace any of the bigger cameras and when the FS5 was launched people snapped up the FS5, often to replace an A7.
Why? Ergonomics.
I don’t ever want to go back to having to carry and use a big box of different ND filters for different light levels. I find the small LCD screen on the back of a DSLR to be of very limited use and while the A7S III does have a very good EVF it’s placement makes it hard to use it on a tripod or in anything other than a simple hand hold with the camera up against your face.
If you want to shoot log then you really want built in LUTs. There are the battery and power questions. How do you power the camera and accessories without needing two or more power systems or a rig to take a big external battery and a bunch of adapters? Then there’s having buttons and switches for all the frequently accessed functions. I could go on but you only have to look at the many franken-rigs that end up built around DSLR type cameras just to make them usable to see the problems. Almost always the first purchase to go with a DSLR is a cage. Why do you need a cage? Because you know your going to have to bolt a ton of stuff to that once small, portable camera to turn it into a professional video making tool.
Sure, I will almost certainly get an A7S III and it will be a great camera to compliment my FX9. And yes, there may even be some projects where I only take the A7S III, just as there have been shoots where I have used just my A7S. But it won’t ever replace my FX9, they are two very different tools, each with its own strengths and weaknesses.
The image quality gap between traditional large professional video cameras and handheld stills type cameras will continue to get smaller and smaller as electronics continue to be further miniaturised, that is inevitable, but the cameras form factor will still be important.
The small cars of today often have all the same bells and whistles as a large luxury car of 10 years ago. Let’s say you’ve gone on vacation (remember those?) and it’s a road trip. You get to the car rental office and you have a choice between a large, spacious, stable, less stressed car or a small car that has to work a bit harder to get you to the same place. Both will get you there, but which do you choose? There might be some instances where the small car is preferrable, perhaps you will be in a lot of narrow city streets a lot. But for most road trips I suspect most people will opt for the big comfy cruiser most of the time.
For me the A7S III will be that nippy little car, a camera that I can pop in a pocket to grab beautiful images where I can’t use a bigger camera. But for my main workhorse I don’t want fiddly, I don’t want a ton of accessories hanging off it just to make it workable. I want the luxury cruiser that will just take it all in it’s stride and get on with the job and right now that’s my FX9.
I have written about this many times before, but I’ll try to be a bit more concise here.
So – You have recorded S-Log2 or S-Log3 on your Sony camera and at the same time recorded on an external ProRes Recorder such as an Atomos, Blackmagic or other ProRes recorder. But the pictures look different and they don’t grade in the same way. It’s a common problem. Often the external recording will look more contrasty and when you add a LUT the blacks and shadow areas come out very differently.
Video signals can be recorded using a several different data ranges. S-Log2 and S-Log3 signals are always Data Range. When you record in the camera the cameras adds information to the recording called metadata that tells your editing or grading software that the material is Data Range. This way the edit and grading software knows how to correctly handle the footage and how to apply any LUT’s.
However when you record to an external recorder the external recorder doesn’t have this extra metadata. So the recorder will record the Data Range signal that comes from the camera but it doesn’t add the metadata. The ProRes codec is normally used for Legal Range video and by default, unless there is metadata that says otherwise, edit and grading software will assume any ProRes recordings to be Legal Range.
So what happens is that your edit software takes the file, assumes it’s Legal Range and handles it as a Legal Range file when in fact the data in the file is Data Range. This results in the recording levels being transposed into incorrect levels for processing. So when you add a LUT it will look wrong, perhaps with very dark shadows or very bright over exposed looking highlights. It can also limit how much you can grade the footage.
What Can We Do About It?
Premiere CC.
You don’t need to do anything in Premiere for the internal .mp4 or MXF recordings. They are handled correctly but Premiere isn’t handling the ProRes files correctly.
My approach for this has always been to use the legacy fast color corrector filter to transform the input range to the required output range. If you apply the fast color corrector filter to a clip you can use the input and output level sliders to set the input and output range. In this case we need to set the output black level to CV16 (as that is legal range black) and we need to set output white to CV235 to match legal range white. If you do this you will then see that the external recording appears to have almost exactly the same values as the internal recording. However there is some non-linearity in the transform, it’s not quite perfect.
Using the legacy “fast color corrector” filter to transform the external recording to the correct range within Premiere.
Now when you apply a LUT the picture and the levels are more or less what you would expect and almost identical to the internal recordings. I say almost because there is a slight hue shift. I don’t know where the hue shift comes from. In Resolve the internal and external recordings look pretty much identical and there is no hue shift. In Premiere they are not quite the same. The hue is slightly different and I don’t know why. My recommendation – use Resolve, it’s so much better for anything that needs any form of grading or color correction.
DaVinci Resolve:
It’s very easy to tell Resolve to treat the clips as Data Range recordings. In the media bin, right click on the clip and under “clip attributes” change the input range from “auto” to “full”. If you don’t do this DaVinci Resolve will assume the ProRes file to be legal range and it will scale the clip incorrectly in the same way as Premiere does. But if you tell Resolve the clip is full range then it is handled correctly.
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