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Canon XL and GL Series DV Camcorders
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Old November 16th, 2004, 06:52 AM   #1
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Effective Latitude

When I used to shoot chromes back in the bad old days, I could figure an exposure latitude of about three stops from black to white when lighting a scene. How does this compare to what I get with the XL-2 on miniDV tape? Will the shadow - highlight curve change depending on what kind of monitor it is played on? Do some DV CCDs record wider latitude than others? Is there a combination of equipment in the prosumer line that produces the greatest latitude, or is it all the same, ie, video is video? Thanks much
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Old November 16th, 2004, 08:27 AM   #2
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Three stops from black to white? That doesn't seem right. That would basically mean that the contrast ratio is like 8:1.

Anyways, though, I think that top of the line DV camcorders are doing about 8 stops (250:1) of brightness.

Now, I'm getting into territory that I'm not too familiar with, since I'm sorta new to video and have more expirience with still photography. However, I'm pretty sure that most video monitors have like 5 or 6 stops, which is about the same as an XL1.

Here's what I don't understand: Do these cameras with really high contrast ratios like the DVX100A or XL2 record their levels in such a way (really low contrast) that it displays all 8-or-so stops on a video monitor at the same time OR does the extra contrast fall outside of the monitor's contrast range and the image need adjusted to display all levels on a monitor?

Of course I'll be able to answer this once I get my XL2 in a month or so, since I'll have a video monitor, but it would be nice if someone could explain this now. Surely someone knows how XL2 footage displays on a video monitor.
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Old November 18th, 2004, 02:22 PM   #3
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Contrast ratio and latitude are seperate entities. The XL2 has about a 4 1/2 stop latitude based on some quick and dirty tests I've done with a spot meter. The contrast ratio is depedent on the display devise, and also to the image processing. You can set black levels in the XL2 to go down to true black. You can also adjust the contrast of your television or video projector. If you trasfered to film you could get 1000:1 contrast ratio. If you use a crummy video projector you might get 100:1, all with the same original footage.
Contrast ratio is merely the display contrast. Latitude is a factor of highlight and shadow detail actually captured by the camera.
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Old November 18th, 2004, 03:30 PM   #4
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I know that lattitude and contrast ratio are two different things, but they way he used the word made me think he was meaning contrast ratio.

Now, the real meaning of the word lattitude refers to how much your exposure can be off without loosing information. I'm not really sure how to define lattitude on a DV camera. Now, on a digital camera, you can shoot in raw mode and have blown out highlights and recover that information up to a stop or two. I'm not sure you can do that in the DV format.

I'm not sure if the XL2 is capable of a 1000:1 contrast ratio no matter how it's displayed. One would have to do tests. One way to find out without getting into how it's displayed is just to hook it up to a waveform and shoot a very high contrast scene. Use a spot meter to find the darkest and lightest points and see if you can get them between 0 and 100 IRE on the waveform.

I don't have an XL2, but I'll be doing some tests like that when I get it so I know what I can get and what I can't.
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