Vertical & horizontal line distortion at DVinfo.net

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Canon XL and GL Series DV Camcorders
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Old December 2nd, 2005, 09:50 PM   #1
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Vertical & horizontal line distortion

I've had my XL2 for three months, done lots of playing, mostly in outdoor settings, experimented with different camera settings, tripod, hand held etc, but still don't get anything like the fine results I read of in this great site.

Most recently I took a trip to the central west of West Australia to search for locations, and grabbed some footage to check out the colours and light during Spring. I got the same poor quality shots when panning through greens that I read of in this forum, but also have real problems with narrow objects (like windmill supports, narrow posts, fence wires) that are not aligned precisely with the horizontal lines of resolution in the view finder. It's particularly bad with horizontally fixed corrugated iron cladding.

Most of the buildings in the region are clad and roofed with corrugated iron, and the slightest camera movement causes a really annoying 'ripple' affect across the corrugations. But even if the camera is on a tripod, and focused on a wire that's not horizontal, the recorded image has the wire looking like it is made of hundreds of sections, one section for every time the wire crosses a horizontal resolution line.

I shot all my footage in 25p (my camera is PAL), but even when I change to 50i, I see the same affect in the view finder, though it may not be quite so pronounced.

I've tried changing the vertical resolution, and the shutter speed, but can't find a solution.

Unfortunately I live in an area that has no broadband access, so uploading any grabs is impossible, the internet connection is so slow.

Has anyone seen the same problem and found a solution? I'm guessing it has to do with the DV codec problem that causes the 'jaggies' when panning through a scene made up of objects close to pixel size, but hope I'm wrong in that assumption.
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Old December 3rd, 2005, 05:34 PM   #2
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This phenomenon is caused by the fact that Canon has chosen to give you the full resolution of the sensor (as opposed to placing an antialiasing filter in front of it) and let you manage aliasing rather than manage it for you. What you are seeing is quite normal and caused quite a lot of consternation when the camera first came out. You can beat the problem by placing a blur filter in front of the lens or by choosing combinations of focal length and framing which minimize it. With a little experience you'll learn to avoid this problem.
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Old December 3rd, 2005, 07:50 PM   #3
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Surely not...

Quote:
Originally Posted by A. J. deLange
You can beat the problem by placing a blur filter in front of the lens or by choosing combinations of focal length and framing which minimize it. With a little experience you'll learn to avoid this problem.
Thanks for the response A.J. May I just clarify, do you mean that the only solutions to the problem are:
1. Exclude from the frame any straight, sharp edges and lines that are not exactly vertical or horizontal?
2. Use a filter that reduces the crispness of the image?

If so, I see why that problem caused much consternation when the XL2 first hit the market. That problem means that the camera is limited to frames that contain no off-vertical and off-horizontal lines.

With that restriction, and the 'no pans in green foliage' restriction, I seem to have an expensive camera with very limited use. I wonder if there are other setting options I've yet to discover that will stop the problem without having to exclude a hipped roof from my frame. I'll be most disappointed if there aren't.
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Old December 4th, 2005, 08:14 AM   #4
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Phil,

I don't know if those are the only solutions. They are the only ones I can think of. One gets used the situation and can usually work around the sharpness (aliasing) issues. I've certainly seen some beautiful work done with the XL2 but I must admit siding, brick work, cast iron railings, fence lines, roof tiles, etc can be a problem.

The panning in green foliage situation is something else. The "crawling" you see there is an artifact of the DV compression scheme more than an aliasing issue. Any DV camera will exhibit it.

Just noticed where you are posting from. One of the lovliest spots on earth IMO.

A.J.
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