<<<-- Originally posted by Michael Hamilton : It might be luma undershoot as described at this site:

http://www.dvcentral.org/DV-Beta.html

I've noticed this artifact on some of my stuff. Mostly along vertical edges though. Its really a frustrating thing because you don't see it in the view-finder and you think you've got a pristine image, when you really don't. Every thing else is so great about this camera. I'ts really a shame Canon didn't do something about this problem.

Michael Hamilton -->>>

Hello !

I agree, this is potentially a very costly problem, especially if a client puts a lawsuit against you because you ruined one-of-a-kind footage.

If we could discuss this topic in english, that would be very helpful!

Questions:

Must you rewind and review every take of every scene on an already tight schedule?

What can be done to detect the problem other than that?

What can be done to avoid the problem?

Can Canon do a firmware update??

What else can be done to fix this problem, which is plaguing many of us?


Thanks :-)

Gentlemen,

It itsn't luma undershoot and it isn't luma leakage (though at first I thought it might be - see earlier posts). It's sharpening. Earlier in this thread I posted a line scan of the image in question - the image is still acessible at http://ajdel.wetnewf.org:81/sharpening.jpg. Every vertical edge shows clear evidence that "unsharp mask" has been applied. This isn't a problem: it's a feature by which I mean that the designers put it into the camera in order to render the pictures sharper in appearance. They also gave you control over it (sharpness control in custom settings). If you don't want sharpening you can take it out or at least reduce it. As an alternative you can use a blurring filter in post but be warned that either of these steps will result in a picture that does not appear as sharp. This is one of those situations in life where you can't have it both ways (sharp picture without edge enhancement).

There it is. No Flemish, no geek-speek.

Edge correction in video (also called sharpening, aperture correction...) is indeed frequently used for getting a (subjectively) sharper image. In camera's, but in displays as well. and this double sharpening potential is the problem. Although a calibrated settings in pro equipment (peaking frequency and level) nothing is being standarized, So if the output device strongly sharpens the incoming signal and the source does the same the picture gets oversharpened and gets strong contours. As long a the contour thickness remains within a couple of arc seconds for the viewer it will still be tolerated. If the picture is "too big"or seen from too close it will be seen as an annoying contouring. Too much sharpening also creates higher noise visibility. Advanced sharpening techiques are being used nowadays which sharpen (almost) without contouring

Last week I went outside and tried using a tiffen sfx #2 to see if I could tone down the contouring, but forgot to turn down the sharpen feature. No luck.
Camera: 16x9/24p and 30p
Subject: wide and mcu shots of electrical poles against a semi cloudy sky.
There was no discernable change in the contouring problem.


I just went out again today to test our XL2 again. But this time I turned the shapen all the way down.
Camera: 16x9/24p and 30p
Subject: wide and mcu shots of electrical poles against an overcast sky.
There was no discernable change in the contouring problem.

There is also a pixel with black horizontal line going across the image in all my shots. This is more noticable in 16X9 mode.

A couple of weeks after we got the camera I noticed this and went to our dealer and the canon rep there switched out the cameras.
The new one has the same problem.

I'm playing this out through the camera on different monitors.
So the problem is'nt a bad deck or some other outside source.

Michael

Michael, what you see in the viewfinder is not neccessary what you will get on yr monitor. Except from the small dimensions and reduced resolution (which can hide contouring for the human eye) the viewfinder just shows decompressed DV data. When yout monitor is connected through composite or Y/C, there is one more step involved: NTSC(PAL) encoding. Though the luma part in this process doesn't need further manipulation, those encoder circuits often apply extra sharpening in the Y channel. I would suggest, if you really want to see what's in your footage, to playback on a pro deck and interconnect through components. This excludes the extra encoding process.

Andre,

Thanks for the input.
Yes I think I understand what you are saying.
I just played this back straight from the camera to see if these problems were being enhanced by our equipment.
We normaly stick the tape into a Sony DSR 60 player deck which feeds component to our nle system.
All of the ghosting and the horizontal line still show plainly on output that passes through the computer.

Am I going nuts? Does'nt anyone else see the horizontal black line going across their video in the lower half of the frame?
This is the second XL2 we've had with the problem. Which means one of two things. Either its endemic with XL2, or its something we are doing here to cause the problem. But for the life of me I can't figure it out.



Michael Hamilton

I just tried another brand of dv tape. Its not the tape
Michael

I my post above I ment to say pixel width not pixel with.
Michael

Do you see the line on yr computerscreen and also on a monitor connected directly to yr DSR ?

Michael.. seems simple, but make sure it's not your monitor. We freaked out once, checking some footage that had a thin vertical 'scratch' running through a whole scene. (It was telecined 35mm footage) We called the lab, and they couldn't find a scratch on the neg... then we checked the monitor with a live camera and grey card image. YUP, there was a thin line ON the monitor.

No, no horizontal line and I have never seen a horizontal line in any video or frame grab anyone has posted here. Do you see this if you do a fire wire capture straight into your computer?

Where is the horizontal line located (middle height?). Do you get the line in interlaced mode too?

Thanks for the suggestions.
I looked at the footage on the computer monitor and dragged it around.
The lines are not on the footage, they are on the monitor because they stay in the same place when I drag the screen.
And I tried DVCam tape from another camera. It has nothing to do with a problem in the XL2.
My apologies to Canon and others if I caused any undue concern.

Michael Hamilton