Theories on XH-A1 Blue Fringing? at DVinfo.net

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Canon XH Series HDV Camcorders
Canon XH G1S / G1 (with SDI), Canon XH A1S / A1 (without SDI).


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Old March 12th, 2007, 10:45 AM   #1
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Theories on XH-A1 Blue Fringing?

It's fairly clear in my extensive adapter testing that the XH-A1 will produce blue fringing at the edges of the frame, on dark contrast edges with a light background at 80 to 100 IRE. After reading some discussions on the issue with the XL-H1 (dvinfo archives) and anecdotal comments on the issue not being lens related, I'm starting to wonder about the color splitting to the CCDs. There seems to be general agreement and visual evidence to support both the XL-H1 and XH-A1 seeing the blue fringing. On my old GS400 (also a 3ccd camera) I saw the same fringing..but red.

The issue is definitely not optical chromatic aberration but I'm wondering if it might have something to do with the trichroic prism assembly feeding color to the 3 CCDs? Theories? Experiments to try?
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Old March 12th, 2007, 10:59 AM   #2
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It seems to be less apparent if you use ND to open the iris.
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Old March 13th, 2007, 11:39 AM   #3
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The camera does this without any help from the adapter. Try this:

1. Set your A1 zebras to 80 IRE. Expose a white piece of paper so the zebras just show up.

2. Set up a black upright, or better two, so that they show up like goal posts, on the right and left side of the frame, about 12 inches from the A1. You likely will need to zoom. I'm using a brevis-to-rails support, on rails, 8 inches or so from the lens. The "posts" move with the camera.

3. Try panning across the paper and watch the edges.

Here's a pic. The A1 is at about 50% zoom, lens is at f4.0, and the background is at about 85 IRE. It shows up on all presets, NR1 or 2 have no effect. As you approach 100IRE it gets worse. Note the blue fringing on the inside of the black rim, yellow on the outside. It could just be this particular unit, but any replication of this out there would be great for confirmation. In the world of professional shooting, is 85 IRE for a white background pushing it?

Right now, we have snow on the ground (rapidly disappearing!) so this white background is a real problem for darker objects in the foreground.
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Old March 13th, 2007, 02:06 PM   #4
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Quote:
Originally Posted by Dennis Wood View Post
The XH-A1 will produce blue fringing at the edges of the frame, on dark contrast edges with a light background at 80 to 100 IRE.
Mine gets blue *and* green fringing. Looks like chromatic abberation to me, but I haven't tried stopped down to see if that helps.
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Old March 13th, 2007, 08:39 PM   #5
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Stopping down won't change it...nor will zooming in. It's definitely optical, so that likely points to issues with how colour is being split to the CCDs. I'm pretty much at the point of consulting with Canon to see if there's something they can do. One of the primary reasons for buying this camera was adapter testing...and we have a lot to do. Having predictable fringing that cannot be ameliorated is a real liability when trying to evaluate adapter footage.
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Old September 11th, 2007, 02:14 AM   #6
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Dennis,

Any follow up on this? Were you able to contact Canon; were they helpful?

I just spoke with a cinematographer interested in working on my project. She's fine with me using an HV-20 but she wants a camera with real manual controls. "There's a reason why a $3,000 camera is $3,000." I really can't argue with her.

I'd like to provider her with an XH-A1, but chromatic abberation could be a deal breaker. She's a big HVX fan and it will take some convincing to move her to Canon.

Thanks as always for all your help.
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Old September 11th, 2007, 05:12 AM   #7
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This was a known issue for the DVX100 as well... purple fringing in most cases.
Turn your sharpness down, crank up the coring and if shooting progressive, pray.

For the DVX, it was more the case of pixel shifting that caused this, but for the A1, I wouldn't know.
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Old September 11th, 2007, 10:53 AM   #8
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I'll chime in here with the FX1. I had blue fringing show up with it, using a self built spinning disc adapter. Didn't happen every scene, but in higher contrast situations, I saw it. This seemed more pronounced when viewing on my LCD monitors, and I had dismissed it as some kind of video card issue....
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