I got to play with a Sony NEX-FS700 camera with the new 3.0 firmware that enables shooting in S-LOG2 gamma and with addition of HXR-IF5 interface unit and AXS-R5 recorder (or Convergent Design Odyssey7Q which was at the moment still very much in beta so they couldn’t lend it to me) 4k raw and continuous 240fps (or 200fps depends on your 50i/60i format) recording at 2k.
I am still waiting for AXSM reader so that I can capture the footage from 512GB card so I can’t talk about shooting 4k and 2k footage, but I did some tests with two cameras simultaneously to compare CINE4 with S-LOG2 and I also did some tests at high ISO values with the new firmware.
As you know this camera lowest ISO setting depends on the gamma curve used. CINE2 uses ISO 320, CINE4 ISO 640 and the new S-LOG2 ISO 2000 as the lowest setting. I wanted to test the noise levels at different settings so I incrementally raised ISO setting at each gamma which and I compensated the exposure with adjusting the shutter speed. I noticed a strange thing for the first time. It is awkward for me not to have noticed this before as I have this camera for almost a year now and I was also one of the beta users before it was presented at NAB 2012. You can change the ISO setting in increments of 1/3 stop (320, 400, 500, 640, 800…) but you can only change shutter in kind of 1/2 stop increments (1/50, 1/60, 1/100, 1/120, 1/150, 1/215, 1/300, 1/425, 1/600, 1/1000,… at 50i format, I didn’t check 60i format). I guess it is hard to notice this if you only use four shutter speeds according to frames per second you are shooting (180° rule) 1/50s for 25fps, 1/100s for 50fps, 1/215 for 100fps and 1/425s for 200fps.
So as I increase the ISO values by 1/3 stop (2000, 2500, 3200, 4000,… ) in shortened the exposure time for 1/2 stop (or so cause there are some times 1/3 stop changes possible). That is why the images are getting darker the higher the ISO value it is. I don’t think that this strange behaviour changes the noise values much.
I was also surprised with the high lowest ISO setting when using gamma S-LOG2. ISO 2000. That is 1 2/3 stops brighter than CINE4 lowest ISO 640 and 2 2/3 stops higher than CINE2 lowest ISO 320.
The exposure values doesn’t look that much different. Highlights are in the same values only the blacks are higher but that an also be due to different gamma setting. It is difficult to judge without more knowledge and more thorough testing. I should just shot a grey card at 50 IRE to know more clearly. The change of base ISO setting also helps with shooting high key (histogram on the right side) as the images come out better when graded if you shoot a bright as you can with highlight protection and then lower the blacks as they come out less noisier.
I ended the S-LOG2 test at ISO 25600 as there was a bug in a firmware where you set the ISO to 32000 in the menu but it changed to 64000 when shooting. CINE4 tests go from ISO 640 to ISO 16000 and CINE2 from ISO 320 to ISO 8000. I shoot mostly CINE4 gamma and I didn’t want to go higher that ISO 1250 before. Looking at this footage I might go to ISO 5000 (S-LOG2), ISO 2500 (CINE4) and ISO 2000 (CINE2) without using any noise reduction software. This tests are completely unscientific and are based on my observations by eye and not using any instruments.
I didn’t do any comparisons with the old firmware just with the new 3.0 one. And I can say that I will be using higher ISOs in the future as the images look cleaner. Maybe this is all because better downresing of the 4k sensor to HD resolution.
Here is the video so that you can decide for your own. The noise is somewhat hidden in the Vimeo compression and you can’t download the original ProRes file that I uploaded, but you can see where the noise kicks in.
Update: You can download the shortened ProRes (LT) file (each ISO setting is 1 second long) to see for yourself. I don’t know how long my server will hold it cause it is a large file and it definitely will be a slow download so be patient. If it starts so behave strangely I will remove the file.