Get rid of that ugly yellow fringe around highlights!

Shooter said:
I have over exposed often. (each time I did it... was a when I screwed up.)

Over and Under exposure is a term that to me, that generally means error. I never say to my AC or Gaffer ..."lets under/over expose the face tones or the green screen or the highlights". What is the point of reference for under / over exposure?

We set exposures to sit within the upper and lower limits of the camera ( wfm) and do it by combination of camera controls and lighting. We set the stop by calling it as an f-stop (t-stop). Adjustments to the stop are called by open /close "eg." 1/2, 1,1/4 stop .....or simply line open, line closed on the specifyed stop ...

I do frequently expose parts of my image into the higher end (high key) of the waveform scale but I call that correct exposure. (ie level control).

Re your issue and my AF102 experience....I burnt out a window - deliberately - on a recent shot and it did not exhibit any fringing.

I also had to deal with some specular highlights on a product shot. (hundreds of tiny spots of moisture on a block of cheese)
I knew they were in the clipper (wfm) but could do nothing about them photographically (or with the art department).
Left it for post to fix and we fixed them in Flame despite the fact they had zero detail...but they also did not have any fringing.

Just working right now on a shot of a fizzing , bubbling coke pour over ice . It has full range of tones from shadow to "highlight" (and speculars) and I can not see any fringing in this either. This camera continues to amaze me.
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I wonder if your AF 102 is different than the 100 or 101. It seems unlikely but I'd be surprised if you've never seen yellow fringed highlights that many of us experience on our units on upper range parts of the image. It seems unlikely that Panasonic would ship them with different image processing, but I could be wrong.
 
I read a story about a new RED Epic camera with HDRx ( http://www.freshdv.com/2011/03/red-updates.html ).
The so called impossible shot can be shot with two Panasoncs link together on a tripod. One with the exposure set for the tunnel and the other set for the exposure out of the tunnel. In the editor you can cut and link the shots together. Who needs the RED?
 
I wonder if your AF 102 is different than the 100 or 101. It seems unlikely but I'd be surprised if you've never seen yellow fringed highlights that many of us experience on our units on upper range parts of the image. It seems unlikely that Panasonic would ship them with different image processing, but I could be wrong.
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It is unlikely that the 102 s any different from any oters apart from the nomenclature.

All I can say that after shooting and finishing 16 national / international tv commercials... all posted thru hi end post suites (on multiple grade one and reference monitors)...we have not seen the issue at all. Be advised there are many very "keen" eyes apart from my own, scrutinising this work at all stages of the process.

I will see if I can induce it next time I have the camera out.

Last time we checked a reported issue that the sensor can reflect and mirror bright subjects in the scene ( eg a window). We could not induce that.
 
I see the fringe all the time in many cameras but since there seams to be a better way to deal with high levels of chroma without having it to skew, like how many DSLR cameras do it, then why couldn't the AF do the same? It's just a matter of limiting/compression and it looks so much better. All digital cameras has a limit. You go past that limit and anything can happen. So why not as a manufacture do it better by making sure it doesn't turn out nasty even when your out of bounce? I'm not talking about overexposing skin but highlights and light sources that trips the camera to go into clipping and skew. I consider this to be so common and even more so when shooting outside of a studio or set where the light can't be controlled 100%.

Anyone having used a Canon DSLR knows it handles highlights better than the AF. Why? Because it compresses when things start to clip. Does it look bad? No, it looks better than video cameras so why on earth not talking this piece of simple technology and apply it to this camera which in some ways share things with a DSLR? Even Panasonics GH1 does it better so it's not a Canon exclusive technique.

We have different gamma curves and the cine curves are the best when it comes to highlights on the AF. We also have knee setting for the other gamma curves. How about a highlight compression setting? Wouldn't that be something we all could benefit from?
 
I agree.

There should be a clipping limiter one could turn on or off to prevent blown highlights in wild situations, of which there are many on even controlled sets but as many documentary film makers could potentially use the AF100 this omission is striking.
 
Is the problem based in the Chroma clipping later than the luma? That is what it seems like to me. The luma level clips out but the chroma has a bit more to go before clipping so you get these kindof fluorescent cyans and yellows. Is this the problem you guys are talking about, or do I have it wrong?
 
Chroma gets taxed out before luma and if you use WFM or zebras you might run into overexposed chroma because WFM is only luma measured. RGB should add up to 100% but if one channel is at 90% and the others are only at 25% it starts to skew since the combined RGB channels reaches higher than 100%
 
Well, sort of...

First, I reject that there is a "problem". What happens is that when something is *overexposed* to the point where the light is oversaturating the chip, then the colors will shift in that scenario.

You can't say that the luma is clipping separate from the chroma, because the luma is made up of a combination of the three color samples. Luma = 60% green + 29% red + 11% blue. If you let any of those color channels clip, it's going to affect how the images are rendered. Using an extreme example of a very greenish yellow (made of green at 90% and red at 10%), what would happen if you opened up the iris a stop? Well, green would go to 100% and clip there, but red would go to 20%. So now you've changed the balance of the color -- whereas in the original (green 90, red 10) you had 9x as much green as red, but in the new image (100% green, 20% red) you have 5x as much green as red. So the color will look redder than it was. Open up another stop and what do you get? Still 100% green, but now 40% red. The red channel can keep rising because it's not clipped, but the green channel can't go any hotter because once you're at 100%, you're done -- overexposing it won't get you any more than 100%. So as you keep overexposing worse and worse, you will see the colors in the overexposed areas shifting to a different color balance.

The obvious solution to this is to not overexpose whenever possible.
 
Understood Barry.

BUT... it would be nice to have the option (that one could turn off of course) that would say:

IF a channel is about to clip (goes over 99.999%)
THEN hold that channel where it is
UNTIL is not clipping anymore.
 
Steve Kahn said:
Understood Barry.

BUT... it would be nice to have the option (that one could turn off of course) that would say:

IF a channel is about to clip (goes over 99.999%)
THEN hold that channel where it is
UNTIL is not clipping anymore.
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How could that possibly be implemented though?

If you want an overall general knee type thing, that could make sense, but even if you did that, it wouldn't make any difference -- the footage would look exactly like what we have now. There's no difference between 100% and 99.999%. The difference is when (for proper color rendition) it should be 120%, but instead is locked at 100%.

Basically what you're asking for is what it already does.
 
Just added a screen grab.

Wondering if this is the type of situation that one should expect ugly yellow fringing on the highlights.

These highlights are in the clipper.

coke-fringe.png
 
I don't know how. I'm not an expert or even a novice at DSP but Editman has more than implied that dSLRs can carry out this sort of thing which leads me to believe it can be done.

Understood that one should not overexpose but with film when you overexpose it turns white. That is a nice, expected result. With video unexpected things are happening when one of the color channels goes into clip.

Is it possible through DSP to limit the clipping of individual color channels of a given pixel?
 
Steve Kahn said:
I don't know how. I'm not an expert or even a novice at DSP but Editman has more than implied that dSLRs can carry out this sort of thing which leads me to believe it can be done.

Understood that one should not overexpose but with film when you overexpose it turns white. That is a nice, expected result. With video unexpected things are happening when one of the color channels goes into clip.

Is it possible through DSP to limit the clipping of individual color channels of a given pixel?
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Film can have yellow highlights too. There's nothing magical there, if you oversaturate the red then the rest will go yellowish (as there's a higher percentage of blue and green which yields yellow).

I'd love to get my hands on a 5D for a couple of days and see what it is that it actually does, and how another camera might compare.

So let me ask this -- what do you guys think of the overexposure characteristics and clipping and yellowishness of this clip? Good, bad, acceptable, not acceptable, what?
 
Barry_Green said:
Film can have yellow highlights too. ..

So let me ask this -- what do you guys think of the overexposure characteristics and clipping and yellowishness of this clip? Good, bad, acceptable, not acceptable, what?
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Looks horrible at many levels to me.
 
Barry you are right about how RGB levels and clipping works. As I remember you did look into GH1/GH2 and how they handled clipping right? And as I recall you found out it compressed to avoid excessive clipping/skew right? So if this is true then it should be a piece of cake to do the same on the AF right?

Anyone having used a Canon DSLR and the AF knows Canon handles highlights way better. Is it due to compression/limiting like on the GH series cameras? Even my GH1 does it better than the AF and they are both based on the same technology when it comes to sensors.

The WFM as Barry stated before the AF was released only measured the luma signal. I don't know if this is the case and I know RGB is combined to form an image so yes RGB is luma in a sence. But looking at outboard WFM monitors you can monitor luma and chroma separate or both together. Then it's easier to get things right and see how RGB values turn out.
 
editman said:
Barry you are right about how RGB levels and clipping works. As I remember you did look into GH1/GH2 and how they handled clipping right? And as I recall you found out it compressed to avoid excessive clipping/skew right? So if this is true then it should be a piece of cake to do the same on the AF right?
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I found that in some modes the GH2 behaves exactly the same as the AF100, and in some modes it behaved differently and did compress the color range as the exposure got hotter. From my perspective each approach is valid, and there are certainly reasons why you would want each method. In "Cinema" mode the GH2 behaved exactly like the AF100 does.

Anyone having used a Canon DSLR and the AF knows Canon handles highlights way better.
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I have used a Canon 7D and an AF100 and didn't notice any such "way better" difference, what I have noticed is that for some reason people seem to just want to overexpose the AF100 more. And, as verified before, having so much more color in the signal obviously causes chroma channels to clip sooner on the AF100; turning down the chroma level to a more typical level greatly extends how far you can push the signal before one of the channels clips.

Now, admittedly I haven't used the Canon and AF100 side by side because I got rid of the 7D long ago, and I really wish I had one here now so I could get to the bottom of this.

If there is such a difference, it's likely I didn't encounter it because I was shooting the 7D like I am used to shooting on regular video cameras.

The WFM as Barry stated before the AF was released only measured the luma signal. I don't know if this is the case and I know RGB is combined to form an image so yes RGB is luma in a sence. But looking at outboard WFM monitors you can monitor luma and chroma separate or both together. Then it's easier to get things right and see how RGB values turn out.
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On an outboard monitor you can split it out for red, green, and blue, that's what I did to verify exactly what was happening in the "chroma clipping" conundrum.

Guys, I really am starting to think that this whole issue is because of the DSLR. Panasonics have behaved exactly the same way for at least the last eight years since the DVX100 came out in late 2002. And if you google "chroma clipping" on our site, I don't think you'll find a single reference to it, ever, in the last eight years. I can't remember anyone bringing it up. This has only been talked about since the DSLRs came out, and then the AF100 came out after it and some DSLR shooters migrated up to the AF100, and I guess what they're used to doing doesn't work anymore on the AF100. I don't know what it is about the way a DSLR teaches you to shoot, that causes people to want to overexpose on the AF100, but there's something there because we have people saying they want to expose their skin tones at 80, 85, and higher -- and that's just grossly overexposed by all traditional measurements.

In any case -- editman, what did you think of the skin rendering and clipping in the youtube I posted?
 
I think skin is very sensitive to overexposure with any camera and once it's to much it's to much and looks bad. Maybe it is DSLR video shooting that makes me argue about how the AF behaves. But since some modes on a GH1 can look better I would really like to see something similar implemented on the AF. Not because it's ever done in any other video camera but because it's possible to do it a little bit better and why not let the AF be the first video camera that does it?

It's really the yellow fringe around highlights that I think could look better. To overexpose skin is just bad to begin with and should be avoided on any camera be it a DSLR or video camera.
 
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