FS7: magenta cast in cineIE/slog3

I experienced this blue/purple phenomenon a few years ago when I was demo'ing an F5. I used the 5 for a second angle during some sit-downs with my C300. We lit them 100% tungsten(actual tungsten) and on one subjects blue shirt, it was purple on camera. If you only saw the monitor or recorded image and hadn't been in the room, you would have just thought the shirt was purple. It didn't look like a mistake or technical problem. It just looked like the guy had a purple polo shirt on.

I had actually presumed it was just the F5 and the way it "saw" blue, because I had read that the F55 dealt with blue(especially daylight) better than the F5, since they have different CFA's. Interesting to hear that the F55 can experience the same phenomenon.
 
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Run&Gun said:
I experienced this blue/purple phenomenon a few years ago when I was demo'ing an F5. I used the 5 for a second angle during some sit-downs. We lit them 100% tungsten(actual tungsten) and on one subjects blue shirt, it was purple on camera. If you only saw the monitor or recorded image and hadn't been in the room, you would have just thought the shirt was purple. It didn't look like a mistake or technical problem. It just looked like the guy had a purple polo shirt on.

I had actually presumed it was just the F5 and the way it "saw" blue, because I had read that the F55 dealt with blue(especially daylight) better than the F5, since they have different CFA's. Interesting to hear that the F55 can experience the same phenomenon.
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Exactly my experience. I'm fairly sure "Vinyl" was shot on F55.
 
broughtonfilm said:
Exactly my experience. I'm fairly sure "Vinyl" was shot on F55.
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Everything I've read, Vinyl is an F55 show.

Maybe I'll have to do some testing and see if I can make my F55 "go purple".

BTW: when I experienced it with the F5, I was shooting in Custom mode, preset 3200k and I think standard gamma. It's been a few years, but I know we weren't shooting Cine EI or any type of LOG.
 
Run&Gun said:
Everything I've read, Vinyl is an F55 show.

Maybe I'll have to do some testing and see if I can make my F55 "go purple".

BTW: when I experienced it with the F5, I was shooting in Custom mode, preset 3200k and I think standard gamma. It's been a few years, but I know we weren't shooting Cine EI or any type of LOG.
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I see that you've updated your previous comment and clarified that this was a C300 and F5 that didn't match. What I was describing was a situation where the same camera renders the same fabric blue or very purple depending on a small temperature and possibly exposure shift, as in "Vinyl". The change happens abruptly.

And yes, since Custom mode gives more control over WB, this can be better controlled but still the phenomenon exists.
 
broughtonfilm said:
I see that you've updated your previous comment and clarified that this was a C300 and F5 that didn't match. What I was describing was a situation where the same camera renders the same fabric blue or very purple depending on a small temperature and possibly exposure shift, as in "Vinyl". The change happens abruptly.

And yes, since Custom mode gives more control over WB, this can be better controlled but still the phenomenon exists.
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Yeah, I just wanted to make it a little clearer that one camera, even though different, did read the blue shirt correctly as blue, and the F5 was seeing and rendering the same blue shirt as purple. Sorry if there was any confusion.
 
Well - dialed-in color temperature (the only method available in Cine EI mode) is never precise as far as green vs. magenta; many times I saw the magenta cast in say 3200K preset, and only white/grey card balancing with AWB button was able to get rid with it. I may be wrong, but with AWB unavailable in Cine EI, our only option is grading? At least that's what I've always been doing with S-log footage from my FS7, and using Resolve this always was successful. Am I missing something?

Piotr
 
The lighting was "true" tungsten. Mole 5k's, 2k's, etc. No LED fixtures.

Piotr, I think the point you may be missing is that while yes, it can be removed in post, the client confidence on set that we are capturing the correct colors of their product is shattered when they see that their gray case is purple. When a client hears "fix it in post" they see money flying out the window. So that is why we switched over to custom mode and baked in a look.

I certainly now realize that there were things I could have done on set to try to eliminate or troubleshoot the situation better. But having never seen this particular anomaly before I was a bit dumbstruck.

-Kevin
 
moldcad said:
Well - dialed-in color temperature (the only method available in Cine EI mode) is never precise as far as green vs. magenta; many times I saw the magenta cast in say 3200K preset, and only white/grey card balancing with AWB button was able to get rid with it. I may be wrong, but with AWB unavailable in Cine EI, our only option is grading? At least that's what I've always been doing with S-log footage from my FS7, and using Resolve this always was successful. Am I missing something?

Piotr
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Piotr, have you seen his screen grab and description? Perhaps that's the thing you've missed?
 
It certainly sounds mysterious, but my surprise in that story is why it took 2 days to switch to Custom. Why not do it immediately before having to scare your client and develop distrust for the camera. Blame it on something weird with the lighting and then be a hero by having a solution at hand with your incredibly flexible camera.
 
kevin gallagher said:
After doing some research I found some guy who was selling a "magenta killer" LUT for the FS7 and other Sony cinema cameras but it did nothing to help the overall cast.
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That would be my magenta killer LUT pack. Sorry to hear it didn't help but looking at your image I don't think it would help as it's meant for overall image bias and in your case it looks like you had some type of magenta skew only in specific tone values. Very strange indeed.

kevin gallagher said:
The main weirdness was that we had 5 room sets going and this magenta cast only materialized on one of them. All tungsten lights in the same studio space in the same day. The only difference was that the offending set was devoid of any color. Left me baffled.
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Although it seems like it might have been specific to only the one room, it could also have been coincidence perhaps. The only way to have known for sure would have been to go back to that room after the magenta disappeared and then you'd know for sure if it was just the electronics acting up or if in fact it was something unique to that room.

Is there any chance you switched around use of internal/external ND filters between rooms, etc.. ? I once shot with two F55's and one of them had a magenta cast that baffled me and the client nor I saw until later in post. Lenses were the same. Only thing I can think caused it were the sensors, or perhaps difference in brands of ND filter being used.
 
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Run&Gun said:
I experienced this blue/purple phenomenon a few years ago when I was demo'ing an F5. I used the 5 for a second angle during some sit-downs with my C300. We lit them 100% tungsten(actual tungsten) and on one subjects blue shirt, it was purple on camera. If you only saw the monitor or recorded image and hadn't been in the room, you would have just thought the shirt was purple. It didn't look like a mistake or technical problem. It just looked like the guy had a purple polo shirt on.

I had actually presumed it was just the F5 and the way it "saw" blue, because I had read that the F55 dealt with blue(especially daylight) better than the F5, since they have different CFA's. Interesting to hear that the F55 can experience the same phenomenon.
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The extended CFA of the F55 /F65 cant be seen on any REC709 monitor anyway I believe..? Vinyl was F55 but most likely RAW I would think on that budget.. so no WB
 
I can see the slight tint in the log image.

Do you recall at what IRE you begin noticing the magenta creeping in?

Red wavelengths are much bigger and penetrate photosite troughs much better than the tiny blue wavelengths. As you lose light, you feed the red photosites more than the blue photosites and I could see this potentially being an issue when the software interpolates color from neighboring pixels.

But this is a wild theory and may not be the case.

What you can do is simply add a bit more green to the low end of your image, without adding it to the mids and highs. Specially if you know at what IRE you begin to see the shift, then you can create a custom curve in post that adds green only to the affected area. It wouldn't hurt your skintones because if any area of your skintones dipped into the trouble zone, it would likely be affected by similar issues.

The odd thing is that it seems like your deepest grays are not skewing magenta as much. like at 10 IRE it is fine, at 20 IRE it's magenta, then at 4o IRE it's fine again? Am I seeing this correctly? I'm not sure. In any case, best of luck and do keep us posted on any results!
 
You guys all bring up good points, and I really appreciate it. Just finished up a two day job. CineIe/Slog3. No magenta cast anywhere. Freaky.

To answer a few questions:

Why didn't I switch to custom mode sooner? Well, I just finished convincing the director and DP about how this camera shoots a great image and the virtues of shooting log in cine mode. They were a bit skeptical but trusted me as an operator and fellow DP. To abandon that without a fight meant... what? Hindsight is 20/20 as they say. And from the insights gleaned here I have a better grasp on what I might do better going forward.

I know every camera has it's quirks. Our old Red Scarlet would show magenta in blown highlights. Then after a sensor upgrade, it skewed green overall.

I am now keenly aware of this issue and will keep an eye out for it. If it happens again I'll post about it.

-Kevin
 
I used your camera on the 10th, after you had problems. I reset both cameras to the set-up I needed via an ALL FILE. Your camera responded normally. Mine did not (to the same ALL FILE.) Mine wouldn't output the 709 MLUT on the first load of the ALL FILE. Everything on the MLUT menu was greyed out. I had a moment of panic because my client wouldn't have understood the log image on the monitor. I reloaded the ALL FILE on my camera and after the reboot it responded like yours, all AOK and 2 matching cameras. If the second read of the ALL FILE hadn't worked I guess I'd have shot Custom as you did. Uggg.
 
I used your camera on the 10th, after you had problems. I reset both cameras to the set-up I needed via an ALL FILE. Your camera responded normally. Mine did not (to the same ALL FILE.) Mine wouldn't output the 709 MLUT on the first load of the ALL FILE. Everything on the MLUT menu was greyed out. I had a moment of panic because my client wouldn't have understood the log image on the monitor. I reloaded the ALL FILE on my camera and after the reboot it responded like yours, all AOK and 2 matching cameras. If the second read of the ALL FILE hadn't worked I guess I'd have shot Custom as you did. Anybody experience this on 4.1?
 
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