Sony A7s Color channel clipping issues

[smon222]

Anyone with a A7s have any strange color clipping issues?  We shot a band the other night that had those led lights that change colors. Everytime they would change to blue the blue channel would clip and give a horrible image that was unusable.  Then today I found someone's post on the sony forum about the same exact thing.

 

He posted some examples in this thread that are exactly what we were experiencing.

 

 

 

 

 

 

[harryllama]

Yes, I read about this on an A7s Event Shooters user group on Facebook.  Exact same trouble!

[hmcindie]

Yup, Sonys have that issue. No reviews actually make mention of it? It looks extremely horrible when your using slog or a flat profile with desatured colors. As then the blue really jumps out and goes "HELLNOO!" One fix is to not shoot s-log and keep white balance at 5000k.

[smon222]

Hi and thanks for the replys. I wasn't shooting S-log2 I was on a Cine2 PP.  Are you recommending not to use a PP or one of the defaults? Because as of right now the camera is useless shooting theatrical/band type situations with colored lighting.

[CarlMiller]

Yup, I got the same exact problem shooting a music video. I was in S-Log and at 32,000 ISO. I haven't been able to determine any settings that avoid this issue.
 
This is really disappointing/frustrating. I'm going to have to mask and fix each frame. 

 

 

[richg101]

i'd suggest firstly not using any lens wide open since the purple fringing tends to promote the blue peaking issue.  also, you might find you want to expose for your blues rather than your overall colour palette.  - changing wb will effectively do this.  it seems to only happen when set at lower kelvin levels since at this point your blues are being pulled up.  In any case, in difficult situations it might be worth exposing to the left to endure your blues dont clip.

[animan]

Not shooting with an open lens or squashing the blue channel with white balance is pretty painful as far as workarounds go in fairness..

[smon222]

I was on another forum and they were talking like its been a problem from sony cameras for a while and they were likely not going to fix it anytime soon. Their recomendation was to adjust your white balance to 4600+ and it would go away.

 

Sounds like a pretty serious problem not being able to shoot anything with theatrical lighting. I can't understand why Sony would not want to fix this problem. I don't mind some small bugs but that is unacceptable.

[Kristoffer_Davidsson]

Have the same problem, I'm pretty pissed about it. It's absolutely destroying the footage!

S-log2, ISO16000.

 

But is this something we're supposed to live with? Sony have to do something about it!

 

[andy lee]

looks bad ,

16000 iso is very very high ,

I've never shot anything over 1250 iso in all my professional career !!

thats  a very hot setting! try lowering the iso and using a faster lens as a work round for this problem

[dafreaking]

looks bad ,

16000 iso is very very high ,

I've never shot anything over 1250 iso in all my professional career !!

thats  a very hot setting! try lowering the iso and using a faster lens as a work round for this problem

 

 

Various posts on the interwebz indicate to it occurring due to over-exposure, so even if you increase your aperture and reduce ISO to get the same exposure it might clip. Try the white balance work around for now.

[Kristoffer_Davidsson]

Yes, ISO16000 is very high, but the camera doesnt clip any other color at that ISO, only the blue. Made a short video straight from the camera. Wrote to Sony yesterday, and they wrote back to me today, so we'll see what they say about this problem.

 

Link to the video:

[Don Kotlos]

looks bad ,

16000 iso is very very high ,

I've never shot anything over 1250 iso in all my professional career !!

thats  a very hot setting! try lowering the iso and using a faster lens as a work round for this problem

 

Yeah it looks bad, but the exposure is correct and the main reason people buy this camera is to use it at these high iso values. Especially in a setting like this one you need quite a bit of DoF. 

[Andrew Reid]

Good video to show the problem with.

 

I've always had similar issues with bright blue lights on Sony cameras. FS700 has it too and that's $8k. It needs to be fixed.

[sunyata]

After looking at Kristoffer's footage, I noticed that in the bright blue areas, the colors that were clipping are actually red and green (at zero) creating a pure blue saturation area, but there was still a little detail left in the blue channel highlights. It makes me wonder if a yellow filter might be enough to prevent this blue threshold from triggering? You would then have to color correct.. not ideal but might work for blue LED lights and lasers! 

 

[smon222]

Why can't Sony fix this obvious defect in several of their cameras? They have to know about it. I mean you can't use the camera in most situations dealing with bands, plays or club scenes and definitely not Disney world at night.

[sunyata]

Very talented people, horrible management. 

[mojo43]

There is a solution posted here: http://www.dvxuser.com/V6/showthread.php?329145-a7s-movie-high-iso-problem

 

"I can reproduce the issue on a color ramp chart and it appears to be a significant discontinuity that only exists in the blue channel a few stops before clipping, right before the point where the highlight primary color shifting issue takes place. It is different from the highlight primary color shifting issue* which I have seen in nearly all Sony cameras. The issue seems to occur in all picture profiles with all gamma curves and all color modes even including Black & White. It also occurs in PP OFF if creative style is set to Standard, Vivid, Neutral, Portrait, Landscape, Sunset, and Night Scene. The issue does NOT seem to occur in CLEAR, DEEP, LIGHT, BLACK & WHITE, SEPIA, and AUTUMN LEAVES. Alternatively, the issue seems most greatly affected by white balance, where in my tests the issue was greatest around 2500K and quickly diminished as WB was adjusted upwards and the issue seemed nearly imperceptible by around 4700K.

Currently I'd say if you are in situation with strong blue lights and are experiencing the issue first try increasing your whitebalance or switch to PP OFF and a creative style of CLEAR, DEEP, LIGHT, BLACK & WHITE, SEPIA, or AUTUMN LEAVES.

*I also see the normal primary color highlight issues that Sony cameras have where blue highlights go cyan and red highlights go yellow etc. Interesting that particular issue seems to be solved by using REC709(800%) gamma, though it seems to fix the issue simply by clipping off all the highlights where such lights would be an issue... Oddly the issue is fixed in my FS700 by using slog2, but while Slog2 and Sgamut seem to minimize the issue on the A7s, it still exists.

Also I would caution against using Color Depth B+7 to fix the issue as it doesn't seem to remove the crazy blues, only to bring the entire blue channel up to the clipped blue saturation level that occurs in the issue. It will likely make your colors look ridiculous like anything blue is a bright flat blue cutout. In my test, Color Depth just shifted where the issue seemed to appear in the luma and WB range."

[Don Kotlos]

It happens more frequently with the blue, but it appears in the other channels too. 

Even the new FS7 suffers from it : 

[smon222]

Thanks Mojo I read that on the other forum too. Its just a workaround but causes quite a bit of headache in post trying to color grade everything to look normal.

 

 Again... its something that I think is unacceptable and bugged. Sony seems to have no intention to fix it since they have known about it for a while. Our Canon & Panasonic cameras are the current goto cameras and don't have weird problems that make them unusable in the many situations we work in.

 

Is it possible that Sony's newer sensor technology is bugged and there is no way to fix it unless they redesign? I can't understand why they havent unless its impossible.