Can anyone tell me why some DP's STILL believe video cameras, even s35 sensor FS7's and such, should be set to -3db. I have this discussion with them often and I am baffled that they believe -3db is cleaner than 0db--"it drops the blacks" is the most common response. I do believe it does a heck of a lot more than that, like change the ISO to 1000 in the case of the FS7, which is fine if you know what you're doing and expect to post it heavily. Not to mention, dropping the gain lessens info getting to the camera via not-so-fast cine zoom lenses, right? Even the new ones from Canon and Fuji ramp up to 3.9 which sounds a whole lot like 4.0 to me. Isn't this -3db thing too old school for s35 sensors? This USED to be a common practice with 2/3" cams to crush the blacks. It isn't really doing the same thing on large sensor cams...or is it? Thanks for your thoughts in advance. Please be kind, it's just a discussion.
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FS7: Do DP's still use -3db out there?
- Thread starter chrisccw
- Start date
Lenilenapi
Carbonite Member
My experience was that -3bd gave you cleaner blacks - less noise - rather than crushing blacks , but it was always at the slight expense of highlight attitude. I agree most large sensors are much cleaner these days so I hardly every use it, other than for a quick way to drop the aperture when desired.
remsyatassi
Well-known member
The spectrum of dynamic range is determined by the base iso setting of any given picture profile. For Cine EI they say this is 2000. If you were to record at 1000 then you would have less dynamic range in the highlights, but also less noise. You don't do this to "crush blacks", you do it for less noise. If your shot is underexposed as a result, then yeah the blacks can be crushed.
Of course people use this. Many people actually rate the camera at 1250. 2000 is a bit noisy for me but it's acceptable in most environments.
Base ISO is different in Custom Mode so be careful when rating the camera.
Of course people use this. Many people actually rate the camera at 1250. 2000 is a bit noisy for me but it's acceptable in most environments.
Base ISO is different in Custom Mode so be careful when rating the camera.
cameramanben
Well-known member
Hi Chris,
first off, -6dB would be a full stop so ISO1000 on an FS7. As lenilenapi suggests, being able to flick between low, medium and high can also be handy in terms of keeping to a stop as light changes.
From my Digibeta days I tended to set low, medium and high to -3, 0 and 3, or 0, 3 and 6 unless I knew that I would be needing a bit more, as it gave me steps between the filter wheel that I would feel completely comfortable in using. I shot a lot of doco stuff and liked to be able to keep my stop consistent (and generally wide) with light levels that were frequently out of my control (UK + sun = busy aperture ring ;-) ).
Believe it or not, ISO 1000 is pretty fast in terms of most of film or video history. I remember in the 90s 5279 Vision 500T was a popular filmstock for night sequences as it was considered very fast but very usable even pushed a stop. Moving forwards, the native ISO on a PDW-F800 is 500, and that camera has shot a lot of available light docs, many not going past 6dB or ISO1000. A great deal of filming doesn't need ISO2000 or six stops of headroom.
In custom mode, -3dB should have no effect on headroom for any of the non-log gamma options. The widest dynamic range - HG7 and HG8 - have around 5 1/3 stops of headroom. The sensor allows for 6, so dropping ISO (or gain) a little will not immediately start to limit your recording white clip. I shoot a lot more on the F5 and F55 than the FS7, and I tend to set my values to ISO rather than dB these days. With that in mind, on those cameras each custom mode gamma defaults to the lowest ISO that will still allow for that gamma's full highlight range. On an F55 (native ISO 1250) that is ISO1000 for HG7 and HG8, and ISO500 for STD5. It also won't allow you to go below those ISOs, as the sensor will then white clip below 100%IRE or 109%IRE depending on the gamma.
At the black end, gamma curves reach a point (in stop terms) where the distinction between a stop and total black is effectively indistinguishable, particularly allowing for the noise floor. -3 dB will tend to make only a small difference in noise reduction, but it certainly doesn't hurt.
So far what I've been on about has tilted towards custom mode. If you are shooting log, the beauty is that it is explicitly designed around being able to bounce around a stop or two (e.g. for aperture purposes) with effectively no change in overall tone or 'feel' of the picture, just the headroom (and shadow room) and if being extravagant the noise in the deep shadows ;-) . When you mentioned 'post it heavily', I suspected you meant CineEI.
A hassle with CineEI is that Sony have not spread the metadata ISO adjustment to other companies' post software. As such, ISO corrections do not automatically get applied outside of Sony software. Furthermore, Sony have kept their CineEI approach simple; whatever the CineEI ISO, the codec records the sensor's entire dynamic range within a 10-bit log curve, and exposure adjustments (as happen in camera in custom mode) are expected to be detected as metadata and then applied in post. This should be simple, elegent and eminently usable across the -2 - +2 stop CineEI range. Unfortunately, not being done automatically makes things a pain in the b*m and has lead to many people saying that log has to be at native ISO and many turning off monitoring LUTs, as though that is helpful.
It is trivially easy to produce a precise 1D ISO adjustment LUT which will replicate Sony's post software. Since this LUT is not trying to bodge things by hand, there should be no consequence to the colour response, just a pure exposure shift. Even if you don't bounce around ISOs, I quite often rate the camera a stop slow for a shoot when I'm unlikely to need five - let alone six - stops' headroom. Everyone gets very worried about shadow noise these days, so if I have more headroom than I need and can take myself a stop further away from it, great. This becomes even more worthwhile shooting green screen - I like making the comper's life easy, so whether custom, CineEI or baked-in CineEI, then with a limited dynamic range lit green screen, reducing the ISO and shadow noise is never a bad thing and should keep you on their Christmas card list!
I can hand over an exposure LUT - which of course can be ignored ;-) - with which the edit will see and be able to grade material exposed exactly as it should be, and matched to any other CinE ISOs that may have been used.
Ben
first off, -6dB would be a full stop so ISO1000 on an FS7. As lenilenapi suggests, being able to flick between low, medium and high can also be handy in terms of keeping to a stop as light changes.
From my Digibeta days I tended to set low, medium and high to -3, 0 and 3, or 0, 3 and 6 unless I knew that I would be needing a bit more, as it gave me steps between the filter wheel that I would feel completely comfortable in using. I shot a lot of doco stuff and liked to be able to keep my stop consistent (and generally wide) with light levels that were frequently out of my control (UK + sun = busy aperture ring ;-) ).
Believe it or not, ISO 1000 is pretty fast in terms of most of film or video history. I remember in the 90s 5279 Vision 500T was a popular filmstock for night sequences as it was considered very fast but very usable even pushed a stop. Moving forwards, the native ISO on a PDW-F800 is 500, and that camera has shot a lot of available light docs, many not going past 6dB or ISO1000. A great deal of filming doesn't need ISO2000 or six stops of headroom.
In custom mode, -3dB should have no effect on headroom for any of the non-log gamma options. The widest dynamic range - HG7 and HG8 - have around 5 1/3 stops of headroom. The sensor allows for 6, so dropping ISO (or gain) a little will not immediately start to limit your recording white clip. I shoot a lot more on the F5 and F55 than the FS7, and I tend to set my values to ISO rather than dB these days. With that in mind, on those cameras each custom mode gamma defaults to the lowest ISO that will still allow for that gamma's full highlight range. On an F55 (native ISO 1250) that is ISO1000 for HG7 and HG8, and ISO500 for STD5. It also won't allow you to go below those ISOs, as the sensor will then white clip below 100%IRE or 109%IRE depending on the gamma.
At the black end, gamma curves reach a point (in stop terms) where the distinction between a stop and total black is effectively indistinguishable, particularly allowing for the noise floor. -3 dB will tend to make only a small difference in noise reduction, but it certainly doesn't hurt.
So far what I've been on about has tilted towards custom mode. If you are shooting log, the beauty is that it is explicitly designed around being able to bounce around a stop or two (e.g. for aperture purposes) with effectively no change in overall tone or 'feel' of the picture, just the headroom (and shadow room) and if being extravagant the noise in the deep shadows ;-) . When you mentioned 'post it heavily', I suspected you meant CineEI.
A hassle with CineEI is that Sony have not spread the metadata ISO adjustment to other companies' post software. As such, ISO corrections do not automatically get applied outside of Sony software. Furthermore, Sony have kept their CineEI approach simple; whatever the CineEI ISO, the codec records the sensor's entire dynamic range within a 10-bit log curve, and exposure adjustments (as happen in camera in custom mode) are expected to be detected as metadata and then applied in post. This should be simple, elegent and eminently usable across the -2 - +2 stop CineEI range. Unfortunately, not being done automatically makes things a pain in the b*m and has lead to many people saying that log has to be at native ISO and many turning off monitoring LUTs, as though that is helpful.
It is trivially easy to produce a precise 1D ISO adjustment LUT which will replicate Sony's post software. Since this LUT is not trying to bodge things by hand, there should be no consequence to the colour response, just a pure exposure shift. Even if you don't bounce around ISOs, I quite often rate the camera a stop slow for a shoot when I'm unlikely to need five - let alone six - stops' headroom. Everyone gets very worried about shadow noise these days, so if I have more headroom than I need and can take myself a stop further away from it, great. This becomes even more worthwhile shooting green screen - I like making the comper's life easy, so whether custom, CineEI or baked-in CineEI, then with a limited dynamic range lit green screen, reducing the ISO and shadow noise is never a bad thing and should keep you on their Christmas card list!
I can hand over an exposure LUT - which of course can be ignored ;-) - with which the edit will see and be able to grade material exposed exactly as it should be, and matched to any other CinE ISOs that may have been used.
Ben
Last edited:
Viddovation
Veteran
Can anyone tell me why some DP's STILL believe video cameras, even s35 sensor FS7's and such, should be set to -3db. I have this discussion with them often and I am baffled that they believe -3db is cleaner than 0db--"it drops the blacks" is the most common response. I do believe it does a heck of a lot more than that, like change the ISO to 1000 in the case of the FS7, which is fine if you know what you're doing and expect to post it heavily. Not to mention, dropping the gain lessens info getting to the camera via not-so-fast cine zoom lenses, right? Even the new ones from Canon and Fuji ramp up to 3.9 which sounds a whole lot like 4.0 to me. Isn't this -3db thing too old school for s35 sensors? This USED to be a common practice with 2/3" cams to crush the blacks. It isn't really doing the same thing on large sensor cams...or is it? Thanks for your thoughts in advance. Please be kind, it's just a discussion.
I'd say the proof is in the pudding. Which is to say - if the DPs shooting -3 db come out with great footage, then their process is vindicated. As others have already said, not all scenes need the full dynamic range newer cameras offer. Not all DPs run so threadbare on electric that they're pushing to expose properly at 0 or -3 either. I wouldn't think to second guess another DP's choice on this if the footage comes out great.
Some technical responses:
* -3 db is cleaner than 0db in that the noise floor drops. Whether this is an appropriate choice really depends on what you're shooting.
* Yes, it changes the ISO. But as others have already said, you can reverse that with a LUT, to the extent the information is still recorded.
* If the image looks good at -3db on set, than it can be appropriate - even better - for productions that will not be heavily posted.
* You say "dropping the gain lessens the info getting to the camera" - gain is only applied after the image sensor captures the light. It doesn't change how much light gets to the sensor. It changes how the light from the sensor is interpreted.
Lenilenapi
Carbonite Member
In custom I would be quite surprised if you noticed the noise difference on an FS7. On a 2/3" sensor yes.
Thank you all
Thank you all
I appreciate all these responses from you guys--understood! And thank you for your thoughts and time on the subject.
Thank you all
I appreciate all these responses from you guys--understood! And thank you for your thoughts and time on the subject.
In custom I would be quite surprised if you noticed the noise difference on an FS7. On a 2/3" sensor yes.