abrupt highlights clipping

[Steven Thomas]

Well, if this is an issue with the standard gamma auto knee, Sony will address it.
Having said that, I use cine gamma curves and they are not showing this issue.

[Piotr Wozniacki]

Originally Posted by Steven Thomas

Well, if this is an issue with the standard gamma auto knee, Sony will address it.

I certainly hope so; nevertheless would appreciate somebody confirming it is not JUST my unit...

Anyway, here is the link to the short clip from which my last two grabs were taken (no PP, STD3 gamma, out-of-the-box settings); it shows how the artefact changes with iris opening/closing (original m2t, even with my Polsih comments in it; the format is SP 1080/50i as I was testing my DR60 drive - BTW, works fine with the EX1's i.LINK):

http://rapidshare.com/files/89637385...SP_108050i.m2t

As most of you don't understand my Polish commentary: at the clip end the iris is at F8, and only then the effect vanishes (but the rest of image is severely underexposed). Also, I deliberately put the trees slightly off focus, as it seems to magnify the artefacting.

Again, please somebody confirm it's not just my unit! TIA.

[Randy Strome]

Piotr,

Please post a similar scene where you:

-Use one of the Cine Gammas
-Center your Histogram
-White balance
-Focus

Then shoot it again in the Std 3 (as you have been) and push it as you see fit to prompt the potential defect that you are seeing from the camera.

I think that should be very helpful in letting others help you determine the likelihood of a camera problem.

Best,
Randy

[Leonard Levy]

Originally Posted by Steven Thomas

Well, if this is an issue with the standard gamma auto knee, Sony will address it.

You want to put money on that guess? I'd like to beleive it but I wouldn't be sure. Not unless we make alot of noise.

[Bill Ravens]

Here's some links to the results of the 8 EX1 gamma preset readings I observed on an HDRack Waveform Monitor. In all cases, I used the factory presets with only the GAMMA preset changed. Everything else was at the factory setting.

Here are the caveats...PLEASE be sure you understand them before you make judgements about the results!!

1-Factory settings except for Gamma preset selection. Auto knee ON in STD mode, disabled in Cine mode.
2-Homemade 11-step gray chart--NO guarantees that the super black and super white are at 0 and 100 IRE
3-Scene illuminated by single 600w halogen lamp, minor skews in WFM due to uneven illumination.
4-White balance set to 2700K
5-Exposure normalized for each plot such that the white point always falls on 100 IRE (except for CINE2, see note 6)
6-CINE2 plot intentionally (over-exposed) clipped. Cine2 gamma clips, by Sony design, at 92IRE. This also accounts for the similarities in the middle gray point amongst the STD gammas.
7-I include a jpeg of the step chart for reference. Don't EVEN begin to think you can make some reasonable judgements from this jpeg. There are so many errors due to color profiles, that you'll send yourself down the proverbial garden path. Suffice it to say that the steps are evenly divided and symmetrical.

I see absolutely no evidence of premature clipping, weird effects, with the exception of Cine2, which is specialized, by design. I am putting some faith in whatever algorithm Sony uses to control the auto knee in the std modes. It's conceivable that this circuit can be fooled under some lighting conditions.

Non-normalized Cine Curves http://www.dvinfo.net/gallery/showimage.php?i=851&c=2
Non-normalized STD Curves http://www.dvinfo.net/gallery/showimage.php?i=853&c=2

[Leonard Levy]

Bill,
I'm confused about by your results because the cross over point is so high. Maybe its the "homemade grey chart"

Just looking at how your chart reproduces on my monitor it looks like there is nothing like a 90% white like you would see on a piece of white paper.
Is that true. Without it its a little hard for em to evaluate because I'm used to looking at a standard chart.
I've added 2 - 90% chips on the old standard chart I own anyway. It really helps understand where the crossover (gamma point) is and what your knees are doing relative to the rest of the scale.
Maybe its just the way I'm seeing your chart on my monitor though, or maybe you intentionally overexposed all the charts to show the knee and clipping?

[Michael H. Stevens]

Originally Posted by Piotr Wozniacki

I certainly hope so; nevertheless would appreciate somebody confirming it is not JUST my unit...

.

We cannot answer that until you post an example that is correctly exposed. How do we know by what amount your exposure is out to be able to exactly duplicate? YOU MUST DO THIS TEST AGAIN USING THE CAMERA PROPERLY AND THEN POST THE PICTURES IMO.

[Piotr Wozniacki]

Originally Posted by Michael H. Stevens

We cannot answer that until you post an example that is correctly exposed. How do we know by what amount your exposure is out to be able to exactly duplicate? YOU MUST DO THIS TEST AGAIN USING THE CAMERA PROPERLY AND THEN POST THE PICTURES IMO.

C'mon Michael - what do you mean "properly"? I've posted here the grabs of my camera malfunctioning, even though handled as usual (the WB and focus not being perfect didn't influence the issue I'm trying to show, the various exposure leveles HAVE been shown).

And yes of course when I use Cine1 gamma and there is no backlight clipping, my camera IS able to produce "proper" images, like one of those here:

http://www.dvinfo.net/conf/showpost....&postcount=103

[Leonard Levy]

Gotta agree with Piotr there was nothing wrong with his exposures. Yes the sky was overexposed but it often is on a daylight shot depending on your main subject matter.

If the sky was under 100% we wouldn't be having this conversation.

[Piotr Wozniacki]

Originally Posted by Randy Strome

Piotr,

Please post a similar scene where you:

-Use one of the Cine Gammas
-Center your Histogram
-White balance
-Focus

Then shoot it again in the Std 3 (as you have been) and push it as you see fit to prompt the potential defect that you are seeing from the camera.

I think that should be very helpful in letting others help you determine the likelihood of a camera problem.

Best,
Randy

Randy, thanks for your input. To address your points:

- if I use a cine gamma, the prroblem is non-existent
- my histogram WAS centered. One thing that has been noticed by many is that - unlike with Vegas, where the whites are shown well over 100 IRE - in the EX1 LCD, it tends to be narrower
- white balance WAS wrong, but that didn't even change the colour of the artefact in question, not to mention its intensity
- focus. Yes, I need to recreate everything more systematically, this time observing not only those factors directly involved with the nature of the artefacting, but the focus, as well.

Cheers. Will keep you posted.

[Bob Grant]

Originally Posted by Piotr Wozniacki

C'mon Michael - what do you mean "properly"? I've posted here the grabs of my camera malfunctioning, even though handled as usual (the WB and focus not being perfect didn't influence the issue I'm trying to show, the various exposure leveles HAVE been shown).

And yes of course when I use Cine1 gamma and there is no backlight clipping, my camera IS able to produce "proper" images, like one of those here:

http://www.dvinfo.net/conf/showpost....&postcount=103

The camera is NOT malfunctioning, the functionality of the user is rather questionable though.
Let's get real here. No one takes a camera like the EX1 and expects to not have problems without testing what they are shooting. Relying on a camera's histogram to guide you without testing and calibrating your metering and yourself is simply bad practice. I'm no great shakes as a cameraman but if there's one thing a few decades of enginering have taught me it's to test and calibrate anything before relying on it. Given that video uses variable non linear transforms, encodes into a system with severe quantization limits and uses metering systems that don't reveal the whole story, exhaustive testing of any planned shot is mandatory, even more so when adjusting things like gamma and saturation.

This would be the equivalent of a DP deciding to shoot on a stock that he's never used before without exhaustively testing it first. The ones that want to keep working still test stocks that they've used many times, they shoot the sames scenes, same lighting, use the same lab and the same print stock well before there's real talent in front of the camera. In other words the whole process, end to end. With cameras like the EX1, that whole process is pretty much under your control in the camera. Change any parameter and you need to test again if you haven't already tested what you're changing. If you get a funky result, maybe go talk to an engineer/technician or as most DPs would do, adjust their exposure and/or lighting or put the knob back where it was. In the digital realm it's for good reason that apart from the DP we now have a Digital Image Technician on the shoot. If you're wondering how relevant this is to using an EX1, change gamma or saturation or any of the other adjustments and it's the same as using a different stock.

I'll own up and admit that I've blown a whole days shoot and wasted the time of a lot of talent by trying to creatively use some of the tweaks in a lowly A1. Sure it looked fine on the histograms, it even looked OK on my CRT monitor. But what the camera had actually recorded was nothing like what the histogram showed or how the image looked on the CRT. The only thing posting screen shots would have proved was how daft I was, not what was wrong with the camera. I learned my lesson, apologised to the client and the talent and put my tail between my legs. Putting my engineering hat on I could understand what had happened and it was my fault it had happened. I'd changed a setup I knew would work without testing the outcome through the entire process. In a different lighting setup, with different things in front of the camera it would have been just fine.

In this situation the answer is very, very simple. You've found a lighting setup and camera setting combination that could produce a bad outcome. Just make a note of it, "need to protect highlights, underexpose 2 stops in high contrast scenes with sky". Now move on, I'll wager good money there's plenty more ways to get the EX1 to produce uglies.

To look at this another way. By your own admission, change the camera setup and your problem goes away. Well, isn't there a very basic lesson there, don't use those camera settings for that lighting condition or if you really must underexpose and accept the outcome. Even the pros shooting film do use different stocks for different conditions.

[Bill Ravens]

Thanks, Bob.
Patient: "But it only hurts when I laugh".

[Piotr Wozniacki]

Well, Bob - I understand the only thing I'm supposed to do after your verdict is "put my tail between my legs", as you put it. I will, as most of what you're saying is true. However, let me just cite what has been said in this thread before, and not by myself, but an experienced videographer (bolds are mine, hope Leonard doesn't mind):

Originally Posted by Leonard Levy

I have only looked at this shot in the stills on the web, but it looks like to me like something is wrong with a camera setting. It should not be neccessary for the operator to have to work around problems where the camera is treating the sky behind the trees differently than in the rest of the picture. I don't know what it is, but telling the operator to underexpose slightly may be a fix in this particular shot, but its important to figure out what is going wrong because a professional camera should not do that in my opinion.

Well, I have nothing to add at this point. Thank you all, and sorry fro bothering you.

[Michael H. Stevens]

Piotr:

Maybe we could see just how you exposed if you posted a frame grab of the vector-scope in your NLE. Then we can see what's illegal and what clipped. Please do this as this thread is getting you nowhere. Many experienced camera men here have contrary opinions mainly due to the lack of information you are giving us. We need more real information from you - we need see your scopes. IMO.

[Piotr Wozniacki]

Originally Posted by Michael H. Stevens

Piotr:

Maybe we could see just how you exposed if you posted a frame grab of the vector-scope in your NLE. Then we can see what's illegal and what clipped. Please do this as this thread is getting you nowhere. Many experienced camera men here have contrary opinions mainly due to the lack of information you are giving us. We need more real information from you - we need see your scopes. IMO.

Here you go Michael; the upper two is an EX1 grab along with its scopes; the bottom - similar scene with the V1E (standard gamma curve, as well). None of the images are perfect (fa from it), but the point is the "shadow" behind the trees only visible with the EX1 and not with the V1E.