Search the Community
Showing results for tags 'Gamma'.
This question has already been asked once but that thread was 7 years ago, and since then I'm sure much more information has become available to the public and thus better explanations have also become possible. I'd like to take the example of ARRI's image processing pipeline. At a native ISO of 800 there are 7.8 stops above 18% diffuse reflectance available. Therefore, 18% x 2^(7.8) = 4011% diffuse reflectance is the clipping point. As far as my understanding goes, all cinema cameras sensors (but let's stick with Arri) record light linearly and in turn linearly convert the analog signal to 16bit digital values (Linear ADC) with the voltage generated being proportional to the the digital value(I.e Gamma =1) and only then does the conversion from 16bit Linear values to 12bit Arri LogC take place. Let's also assume all of the 16bit data is available for use, so excluding noise and other limiting factors,in order to make life simpler Now let's say I want to expose for an 18% gray card so that it ends up as middle gray on Arri 12bit LogC( I can't remember exactly what IRE they recommended, but let's assume it was 40% IRE). This is where I start getting confused. On a Linear ADC (assuming we expose correctly LINEARLY so that 18% gray card is 0.4486% LINEAR IRE. Because 18/4011 is 0.4486%) : 18%/4011% x 65535= 294 This means that there are only 294 tones from pitch black to 18% gray card on the original data the linear sensor/ADC recorded. Yet, once the 18% gray card gets converted from Linear 0.4486% IRE to Log 40% IRE on 12bit there are 1638 tones from pitch black to 18% gray card. Where are all these extra tones coming from? Is there interpolation happening here? The whole point of Log recording is to allocate more bit values to the darker areas up till 18% gray where we are more sensitive. Yet, the logarithmic values are all just redistributions of the Linear 16bit values if I understand correctly. Thus, there was never more than 294 tones of true information recorded between pitch black and 18% gray. The only other thing I can think of is that when we're exposing for 18% gray card to be 40% IRE on 12bit LogC we're actually OVEREXPOSING on the Linear Readings so that an 18% gray card is read as 1638/65535 x 4011% = 100% diffuse reflectance(or 2.5% LINEAR IRE). Which gives us 1638 tones of true information because 100%/4011% x 65535=1638 on the 16bit linear values I hope I explained my conundrum clearly. If not, feel free to ask I'll try and explain again. Thanks PS: I know this doesn't help in any way with being a great cinematographer. I just got curious haha.
Hello Guys, I am gonna start shooting a documentary next week and our main camera will be the PXW-FS7. I already check many topics, tests and other reviews. I first decided to shoot in 1920 X 1080 in S-LOG 3 / Gamut 3. Two reasons to that, first one being mobility and also wish to keep an good latitude for the grading at the director looking to a specific style. Here an example of the kind of footage we looking to end up with For some of the interview we will have a second camera which will be a Sony A7S. The Director already order a Shogun to go with it. As the A7S is capable of shooting in S-Log 2, I wonder: is the Shogun still relevant? And if I have to keep it, should I still set the camera in the Log mode? My worries are that the Shogun record only the under-expose, milky footage from the S-log but without the possibilities of grading which are suppose to come along with it. Then it is possible some day we will have to shoot with C100 but that will become an other problem. Thanks in advance for your answers All the best
I'm a little confused on how to play with the gamma setting for the lower part of the curve. what's the difference between BLACK LEVEL and BLACK GAMMA and MASTER PED in camera settings? what the relationship with noise? if for instance I want to change the setting of my camera so as to see more into the shadows (without taking into account any color correction in post) I set (just as an example) black level at -2 master ped at +2 so as to lower the contrast black gamma (that alters the whole shape of the gamma curve in its toe) at +2 to brighten the image am I right? my question is: how does noise react to this new setting?
My team is about to take possession of an Amira. We’ve been renting for a while and shooting Log-C as standard. I’m starting to question the merits of shooting Log. Typically we shoot product footage in a studio, with finely tuned and very controlled light. We really craft each shot – bread and butter shots are pretty low DR. Occasionally we go for dramatic contrast. I’ve done a fair but of reading on the theory, pros, and cons of shooting Log, but I have to say I’m still not convinced either way. If I’m careful with clipping and try to get a healthy looking histogram/waveform, is Rec 709 just as good as Log, or in fact would it be better?