abrupt highlights clipping
 

I've been playing with the standard PP today; keeping the most neutral STD3 gamma curve, I only changed the matrix to Hisat and applied some minor adjustments to the colour pairs (no Knee setting alteration, though).

The outcome is indeed better saturated than the out-of-the-box look; it also seems to span more dynamic range (even and broad histogram distribution). However, one thing worries me: with the automatic iris setting, and the sky being just on the verge of over-exposure (a few 100% zebra patterns here and there), the sky colour gets blown-out to white everywhere except behind the thin tree branches where it stays blue; there is no gradual change (lack of midtones) between the two areas, which causes a nasty looking effect.

Please take a look at those grabs: the first is at the instant of aiming the camera at the sky (it all gets clipped); the next show auto iris closing and the sky behind the trees going blue. The difference between the blue and white is so sharp it looks very bad indeed. Later, I'm closing iris even further to retain the sky true colours, but of course the foregroud is underexposed. BTW, sorry for wrong WB -- didn't care for that at this particular experiment.

Now, my question is this: does anyone see a similar behaviour using the standard setting (STD3 gamma curve), or something is wrong with my camera?

Does this happen when using a cinegamma curve?
And no, I've never noticed this problem with my EX1 (maybe a standardgamma problem? I have always used cinegamma ;))


regards Dennis

Piotr...

Have you read Adam Wilt's review of the EX1? There's a great deal of useful info in there.

One of the comments he makes is the special nature of the cine gamma curves in the EX1. In contrast, the STD curves are linear with fairly abrupt clipping at the hi end(clipping). The CINE curves give a much softer transition to superwhite and black, more like a "S" curve, which should be quite familiar to you.

Also, check the white clip level in the menu. Most user set it to 108%, rather than a hard clip at 100%. I beleive 108% is the factory setting.

What NLE are you using? If you don't have 32-bit processing, the images will be hard clipped at 100%, not revealing the actual performance capability of this amazing camera.

No Dennis, it doesn't happen with cine curves (they have their own highllight compression voodoo, and don't even allow to play with the Knee settings).

However, the STD3 curve - while not the most impressive - is supposed to be most neutral and universal, hence my worries about the camera.

Once somebody recreates it using STD3 and Hisat matrix, I'll accept the fact as another ting one should be aware of when shooting, and will stop worring about my camera. Thanks!

Sure Bill, I know the cine gamma features and have been using them long with great results.

You mean the zebra setting, right? I have it at 100%.

Yes, I'm using Vegas and this abrupt change from unclipped to clipped area is only more pronounced in 32bit video mode...

white clip is not the same as zebras at all. zebra is just a viewfinder alert, the whiteclip is a picture setting and abrubtly cuts off any image above its setting.

I'm not saying it is - I just understood Billl was asking for the zebra. Bill, did you mean zebra? I had said I didn't change the standard Knee setting, if you mean that and I got you wrong...

I could be wrong here but it looks like the EX1s zebras only show you what is at the defined level. So with zebras set at say 100 and only a little bit of the sky showing zebras it could be that the rest of the sky is well over 100.

I think your problem is the mistaken belief that Standard 3 is the most pure image. As everyone tells you it drops of sharply and it WILL blow out easily. For the shot you are doing with STD3 to get what you want you must cut back your iris. Don't rely on the histogram and if using the luminance measure keep highlights below 100% (don't try 108% like you can in Cine4). Your foreground will be dark and that is why when shooting in idiot mode this camera has a backlight button.

Could be that, Bob - this is how zebra 2 behaves (around the set value of say 70%, rather than everything above it). On the V1, the zebra didn't behave like this though, i.e. eeverything above 100 was covered with stripes... Will check tomorrow how it behaves on the EX1, but my impression is it never turns off once above 100 (actually it can be set to 107).

What do you think of these grabs? I never saw a behaviour like this before, and of course I did sometimes use non-cinema curves;) As I said, one should be able to rely on the standard, defualt, factoy chosen gamma curve (STD3) - and advising me to alway use the cine gammas is not answering my doubts.

It does look a bit odd, but without being there a playing with settings... iris, ND, etc... It's hard to say.

Doesn't the auto iris have a compensation parameter in the menu?

P:
Maybe you should go into the menues and reset your camera to factory defaults. Then try this agin watching the LCD and see if you can reproduce this. IF you use auto iris in this type of shot you MUST use the backlight button.

Yes it does - but how would it change in this situation? The sky as either totally blown (overexposed), or can be made all blue by closing the iris - but then the darker areas are severely underexposed... In the middle (i.e. with proper average exposure), I'm getting those blue patches behind the trees - as if they casted shadow on the sky, enough for it to stay un-clipped. What is the problem is the abrupt change between those clipped and unclipped patches - looks awful.

Not necessarily - on other cameras, I could choose to either expose properly the backlit area thus totally blowing out the sky colour (similar to the upper left grab in this thread's initial post), or keep the sky blue at the cost of underexposing the foreground (like in the bottom right grab). But I never got patchy sky like this!

I almost feel like this is someone saying I filmed a person standing with their back to a window when it is bright out and I cannot expose their face properly without blowing out the background. In this situation it looks as if either the sky will be properly exposed or your darker foreground will be properly exposed. If the shot works better with cine (as it would) use that. I don't think this is a problem with the camera. We are given a wide range of image control options with this camera and many of them need to be used to optimize different image situations.