a7s movie high iso problem

A

Alan Ting Judson

Well-known member
i'm not sure if anybody talk about this topic before, but i would like to confirm is just me or a7s sensor problem.
I found that using high iso on movie mode will make the left side of the frame produce magenta colour noise, right side don't have this problem.
Using aps-c(video mode) and photo mode in full frame also dont have this problem.
Here is the picture(using 80k iso), after compressed it show lesser than what i seen in my video file. This make me wonder how can high iso video been useable. Above 10k iso it start appear abit, and 40k+ it start produce more, it is not useable with this magenta.

a7s problem.jpg
 
just try again only S-gamut will greatly reduce the magenta, slog2 profile help a lot too.
With other profile and color mode, the magenta is too obvious, especially in shadow area.
 
Yes I see this too for ISO's greater than about 50,000ish. SLOG2 has it less since it runs at very different gain levels for the same ISOs, so it doesn't show up until like ISO 200,000 or so. I can't remember if the camera has black balance, but that might help, or it might also be a function of heat or changing temperatures which can cause black balance changes that are not calibrated for without another black balance (if black balance is possible).

You'll also see it a lot less if you aren't underexposing. Frankly if you are at ISO >50,000 and you are still underexposing your image enough to see this issue you may be expecting too much out of the camera. Try turning on a light or getting a faster lens, a flashlight will look like a big HMI at that ISO anyway :P

I think some tests I saw showed that, as is common with still cameras, the last couple ISO stops are basically useless as they don't offer any noise benefit and only clip highlights more. I think ISO50,000 (ISO 100K-200K in SLOG2) is about the limit of what's worth using
 
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I'm not sure why anybody uses the movie mode - it seems like it's crippled compared to the other modes. You can't change the aperture or shutter speed?? Bizarre choice from Sony, unless I'm missing something.
 
wallrc said:
I'm not sure why anybody uses the movie mode - it seems like it's crippled compared to the other modes. You can't change the aperture or shutter speed?? Bizarre choice from Sony, unless I'm missing something.
Click to expand...
LOL, perhaps you should activate manual exposure for movie mode in the menus?
 
nyvz said:
Yes I see this too for ISO's greater than about 50,000ish. SLOG2 has it less since it runs at very different gain levels for the same ISOs, so it doesn't show up until like ISO 200,000 or so. I can't remember if the camera has black balance, but that might help, or it might also be a function of heat or changing temperatures which can cause black balance changes that are not calibrated for without another black balance (if black balance is possible).You'll also see it a lot less if you aren't underexposing. Frankly if you are at ISO >50,000 and you are still underexposing your image enough to see this issue you may be expecting too much out of the camera. Try turning on a light or getting a faster lens, a flashlight will look like a big HMI at that ISO anyway :PI think some tests I saw showed that, as is common with still cameras, the last couple ISO stops are basically useless as they don't offer any noise benefit and only clip highlights more. I think ISO50,000 (ISO 100K-200K in SLOG2) is about the limit of what's worth using
Click to expand...
Thanks, good to know it is not only me having this problem, cause just got my a7s few days go. Yeah changing the black balance will help too. It only appear at shadow at extreme condition, so i guess normally it will look alright while there's enough light
 
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