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Sony A7s Color channel clipping issues


smon222
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Guys,

 

What you're seeing, originally from the 5 and 55 cameras, is people misusing SLog2 and 3.

 

On the 5 and 55, it's possible to (in 'Custom' mode), to enable an SLog gamma curve, but to leave active the camera's regular old-school 709 matrix settings and saturation levels.

 

When you get into a situation with deeply saturated colors, like LED color mixer light sources in a concert, you can wind up with the chroma getting clipped out of this world, but the luma not touching clip at all.

 

So yes, it's a problem, but it's more of a result of Sony not telling people how SLog2 or 3 needs to be used. Short story is, on a F5 or 55, if you use SLog 2 or 3, you need to also be using S-Gamut. This scales the chroma down to what fits easily without clipping channels. I own an F55, I've had it since the beginning (serial #110), and I've shot plenty of situations just like the enclosed grabs where it looked beautiful. The answer is SLog 2 or 3, and S-Gamut.

 

Now on the A7S, I have no idea what the options are to go along with SLog2. I haven't gotten my hands on one yet. But if there is an S-Gamut option to go with S-Log2, you need to use it to avoid these crazy artifacts you're seeing.

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Sorry Nate, but I don't buy that. I have 2 Sony A7s and it does the same thing no matter what profile we use or even turning it off. The only way I have found to minimise the issue is to bump the WB to 5000+ .  We do alot of nightclub environments and Its for that reason alone that we do not use the A7s cameras anymore. Its Fing horrible and unacceptable they havent fixed it yet, even after the web is littered with posts about it.

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Tts Fing horrible and unacceptable they havent fixed it yet, even after the web is littered with posts about it.

 

Some of the posts here talk about this problem as if some engineers or employees of Sony boozed it up at lunch and put together some defective cameras.  Sorry, but this is an operator problem.  As Andy pointed out, shoot at a reasonable ISO and pull up what you can.  The sensor always shoots around ISO 100 or 200, when you shoot video at 12,800 or something like that you're actually pushing the signal processor to the point that it might pick up light from a black hole ;)  Please, learn the technology behind the camera.  There are already some people here who have posted some shooting-tactics and are obviously very knowledgeable.  Telling them it's Sony's problem doesn't honor the time they put into their explanations.

 

If I was Sony I might decide to pull s-log from their consumer cameras.  Is it worth the bad press?  Everyone should keep these things in mind before bashing high-end features in these cameras :) 

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Some of the posts here talk about this problem as if some engineers or employees of Sony boozed it up at lunch and put together some defective cameras.  Sorry, but this is an operator problem.  As Andy pointed out, shoot at a reasonable ISO and pull up what you can.  The sensor always shoots around ISO 100 or 200, when you shoot video at 12,800 or something like that you're actually pushing the signal processor to the point that it might pick up light from a black hole ;)  Please, learn the technology behind the camera.  There are already some people here who have posted some shooting-tactics and are obviously very knowledgeable.  Telling them it's Sony's problem doesn't honor the time they put into their explanations.

 

If I was Sony I might decide to pull s-log from their consumer cameras.  Is it worth the bad press?  Everyone should keep these things in mind before bashing high-end features in these cameras :)

 

Isn't super clean ISO above 12800 suppose to be one of the main advantage of this camera. Isn't Andrew and the rest of the blogging community saying that you can shoot very high even to moonlight level http://www.eoshd.com/2014/11/photography-shooting-moonlight-sony-a7s/ . So it not necessarily user errors but a combination of Sony, the reviewers and the users that did not do the research well as it is present in other Sony cameras and I guess won't be corrected.

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Isn't super clean ISO above 12800 suppose to be one of the main advantage of this camera. Isn't Andrew and the rest of the blogging community saying that you can shoot very high even to moonlight level http://www.eoshd.com/2014/11/photography-shooting-moonlight-sony-a7s/ . So it not necessarily user errors but a combination of Sony, the reviewers and the users that did not do the research well as it is present in other Sony cameras and I guess won't be corrected.

 

First, I apologize if my post above was harsh--I had a toothache.  It's been written elsewhere that this large-pixel sensor has a weakness in low-ISO dynamic range.  Every camera, every technology, has trade-offs.  Credit Andrew with not babying his audience ;)

 

> ...combination of Sony

Sony is providing a camera for low light.  They're focused on getting the moonlight right, not the sun blazing through the window.  I'm not sure what they can do in camera that will fix this problem without taking up chip energy.  My guess is that there are post processing tricks to isolating the color blow-outs and removing them.  Fitting 24bit color into an 8-bit color space--ON THE FLY--is difficult for all cameras.  I'd say 80% of this forum is about working around the problems that arise from that.

 

> .... reviewers doing research

I doubt it would occur to reviewers to test against high energy lights, at high ISO, ESPECIALLY the funky color spectrums of LEDs and theatrical lights!  Even at low ISO, those lights play havoc with your colors.

 

> ... I guess it won't be corrected

Again, that implies this is something broken that can be fixed.  It's like hearing about someone driving their Ferarri into a mud bank and complaining that Ferrari won't fix their cars so they can get out ;)

 

You would think Sony would provide s-log in all their cameras.  At least I wondered why they didn't.  This situation has helped me understand why there are very good reasons these gamma curves are not put in consumer cameras.

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Some of the posts here talk about this problem as if some engineers or employees of Sony boozed it up at lunch and put together some defective cameras.  Sorry, but this is an operator problem.

 

That's not true as other Sony cams have the same problem. The older Nex-5n and the Nex-7 have the same issue and you don't need mega ISOs for it to show up.

 

Why are people claiming that this is a low-light problem? Those blue leds will blow up completely on the A7s, regardless of ISO.

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That's not true as other Sony cams have the same problem. The older Nex-5n and the Nex-7 have the same issue and you don't need mega ISOs for it to show up.

 

Why are people claiming that this is a low-light problem? Those blue leds will blow up completely on the A7s, regardless of ISO.

 

If this is a known problem then why is it not an operator problem as I suggested (though again, didn't mean to be so harsh).  

 

As Sunyata explained above this is probably more of a problem with red and green channel data from the sensor.  It seems some people don't understand how color images are created in the camera, how bayer sensors work, what debayering is, the decisions engineers must make in taking 12-14 bit single color data,  marrying it to neighboring color data, and creating a single 8-bit color value.  

 

ALL cameras I've ever worked with struggle with sensor data that is at the extremes.  The Sigmas have magenta fringing, for example.  Nikons don't allow you to set ISO that high with slog type curves (so we'll never know).  

 

This MAY BE a problem that can be fixed.  I don't know.  But if, as you say, this has been a problem since the NEX cameras, it tells me they've made other trade-offs (maybe using the pixels for focusing is hampering some of their in-camera debayering?)   

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With all due respect max, do you even own a A7s? We own several. You sound like you work for Sony or have friends there. The problem isn't just with Slog2 nor high ISO. The issue doesn't happen on any other cameras we have used and the issue happens regardless of iso or PP and is reproducible. I know every camera has a few quirks but this makes the A7s unusable in the night club environments that we mainly shoot in. That's what ticks me off, we have a good bit invested in them and only use them for a few projects.

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No worries Smon22, I don't deserve no respect ;)  I don't work for Sony or have any friends there.  Believe me, I sympathize with your plight.  But what option do you have?  Sony is never going to say what the problem is, or give any indication if, or when, they will ever fix it.  Though I'm putting it poorly, I'm just saying you want to focus on what can be done.  

 

1. If you're shooting a scene without blue-blow-out lights is the A7S the superior camera?  If so, is it worth it?  

2. If you're shooting a scene with blue-blow-out lights can you A) fix it in post (by matting the blue out) find some setting/filter that mitigates it?

 

There are experts who have posted ideas here, so my original message was, A) do you want to engage their help in fixing it; or b) do you want sympathy?  It may be that consumer Sony cameras are just not going to work for the kind of stuff you want to film.   Again, I sympathize, just trying to save you some time ;)

 

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I guess I was hoping that Sony would simply fix the issue in a firmware update and that would be that. But everywhere I see people saying its an ongoing problem with many other Sony cameras and they are unlikely to fix it or even care. I guess we should have been more diligent before purchasing, but the low ISO was the holy grail for us and we jumped in without seeing how deep the water was.

 

Don't get me wrong, I appreciate and took advice from everyone who has chimed in with a workaround to lessen the issue. The main thing that works for us is raising the WB to 5000+ and helps the most. But unfortunately introduces quite a bit of post work to get things back looking right.  I can live with the funky record button, its just frustrating to have an amazing camera with what seems like a minor firmware update. A small company like Blackmagic updated the black hole issue pretty quick.

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I mean I never saw people complaining about this in other cameras even if they shoot high ISO. That is why people consider it a problem, if every camera did the same it would have been considered normal.

 

The FS700 does the same. I have a bunch of shot footage where the 5d next to the FS700 looks better as the FS700 clipped a lot our led lights.

 

Or is that the 5d is really, really good color wise and the Sony is just standard? Could be. I haven't used Panasonic cameras so I don't know if they have that issue but I have never heard about anyone else except Sony running into these things. Sony has always had problems with clipping highlights, my very old Sony HC1 HDV-cam tended to blow red's funnily, like with stop lights. They always went weirdly magenta before clipping, something that my as old Canon HV20 didn't do. Though that's like 10 years ago.

 

I also thought it was weird how my Nex-5n always took worse photos than my Canon 7d, especially in clubbing situations. The LEDs tended to be blown out in the RAW files so I don't think it's something a white balance can easily fix. Though the 7d really did handle them better. This is also something that almost no photographer ever comments on. Everyone shares dxomark figures like crazy but real world actual flaws always tend to be hidden inside few posts in forums here and there.

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 A) do you want to engage their help in fixing it; or B) do you want sympathy?

 

That's a weird attitude because A) it's not gonna be fixed and b ) the camera is already bought by people. So do you want more people to know about these issues or just sweep them under a rug and say : "It's not an issue for me!"? Yeah, it's not an issue for you. We got it. That's not helping.

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That's a weird attitude because A) it's not gonna be fixed and b ) the camera is already bought by people. So do you want more people to know about these issues or just sweep them under a rug and say : "It's not an issue for me!"? Yeah, it's not an issue for you. We got it. That's not helping.

 

Exactly, why do customers have to defend some brand. The problem exist and can be repeated in many Sony camera and does not seem to affect other cameras. Why don't all the bloggers who have been singing A7s praise do at least some test to verify it and at least warn people who do these type of work with blue led if their test are conclusive. Unfortunately it seems that nowadays singing prays rather than thorough research is the norm. The first time I see this problem mentionned it was not necessarily on blue led but very bright highlight like car lights etc (But I am not 100% sure).

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There is no "other camera" to the A7S for low light photography/video ;)

 

Yes it is true but to what extend do people need to shoot that low ISO. To get clean ISO 3200/6400 was considered extraordinary what two years ago like when the Canon 5dmark 3 came out. So what did happen during those last two years, have all places in the world decided to decrease lighting everywhere in town's houses etc... Is shooting in moonlight the new norm now. In photos, if you normalise resolution cameras like the D750 are much closer to the A7s up until 12800/25600, I can't even imagine shooting at that level.

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That's a weird attitude because A) it's not gonna be fixed and b ) the camera is already bought by people. So do you want more people to know about these issues or just sweep them under a rug and say : "It's not an issue for me!"? Yeah, it's not an issue for you. We got it. That's not helping.

I never said "It's not an issuse for me!"  Why are you misquoting me?  (especially since I said I don't own the camera).  Also, I never said to sweep the issue under the rug.  QUITE THE OPPOSITE!  I say, let's all figure it out.  I doubt it can be fixed in firmware.  The black-orb problem with BM is still an issue, from what I understand.  Everyone hates the jello-effect, but no one says to fix it in firmware because most people now have some idea of why it happens.  This problem is probably very similar, a sensor/electronics issue.  If someone knows exactly why this is happening, and how it can be fixed, by all means, let's boycott Sony! :)  Otherwise, let's assume they may know more than we do and that the camera is the best they can do for the moment.  It won't work well in all situations--LIKE ALL CAMERAS.  That's why there are professionals.  They know how to use equipment in the real world!

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Perhaps experiment with filters over the lens and see if one of them reduces the problem. It only seems to occur with very bright blue specular highlights. Try different white balances also. It's worth experimenting by trial and error on this one...

 

Sony cameras have had this issue for a long time. Very weird.

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