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Canon XL and GL Series DV Camcorders
Canon XL2 / XL1S / XL1 and GL2 / XM2 / GL1 / XM1.


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Old December 31st, 2004, 12:22 AM   #1
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Shooting everything at -3 , 30p , 16:9 , f1.8 --- any light souce that is on camera has white streaks that run the entire verticle of the frame --- what gives -- nothing says video/look like verticle streaks and "breathing" while racking. Any thoughts?
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Old December 31st, 2004, 03:46 PM   #2
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Well, when you're wide open at f/1.8 on any camcorder, just about *any* light source is going to cause these vertical streaks to happen. The technical term for this problem is overloaded shift registers in the CCD block. Solution: don't overload them (this is an operator's error, not the camera's fault). Stop the iris down a bit to something more reasonable, like f/4.8 or f/5.6 -- hope this helps,
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Old December 31st, 2004, 07:32 PM   #3
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Thanks Chris, I don't think that I'm overloading the ccds at f1.8 since I have enough ND on the front of the glass to give me a proper expossure for the scenesm lighting and desired effect (extreme shallow DOF) Even with 2 ND 9 filters on the glass and good expossure and ratio is this still a cause for streaks? I know that faster shutter speeds cause this effect even in film (i.e. the beach fires in Saving Private Ryan) but I am not using fast shutters and I don't recal having this problem with my xl1s. More thoughts please.
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Old December 31st, 2004, 10:33 PM   #4
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You didn't mention the ND filters in your original post, so there goes my theory.
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Old January 1st, 2005, 07:36 AM   #5
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Jonathan,

The technical aspect of your question is beyond my knowledge, but I'm guessing that even if your overall exposure is good, the sort of artifact that Chris mentioned could perhaps still be a player for "hot spots"...light bulbs, highly specular reflections, etc.

I'm pretty sure I've even seen this sort of thing happen on network TV sporting events when the camera catches unexpected hot spots. Chris, does ND filter use necessarily eliminate this Shift Register effect from consideration since it seems to happen even to the Big Boys?

Although I'm assuming that you used the combo of full open aperture and ND to shallow DOF as much as you could, you might have to make a slight compromise by giving up just a little aperture? And I guess to state the obvious, where able, avoid getting those hot spots in-frame.

I tend to shoot with the widest aperture I can get away with and haven't noticed this. Will surely watch for it though!

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Old January 1st, 2005, 08:02 AM   #6
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The problem is most often seen when there are bright lights in an otherwise low light scene - e.g., stadium lights at nght games. The light is so much brighter than the surrounding image that to get normal exposure for the surrounding scene (e.g., f/stop and shutter), the light overloads the CCD. The problem with ND filters is that they reduce all light, so there is no net benefit

The XL1 at least (can't speak to the XL2) is better about this than most moderate priced camcorders, but it still is an issue when the difference between the brightness of light source and the rest of the image is excessive. The solution is to change shot composition, camera angle, use flags, masking, etc to avoid having excessively bright point light sources in the image.
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Old January 1st, 2005, 07:36 PM   #7
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When Iwant to shoot wide open and I choose to see "Hot Spots
" in the Frame ie, bare bulbs (replaced with 15 - 25 watts) I start by opening up all the way then placing ND infront of the glass until the hot spot (Bulds, candles, glare etc) are of good expossure, meaning that I can see just enough detail in the luminance to make it acceptable before it blows out -- then I light "Up" from there. Also exposing areas of the scene to achieve maximum drama and effect. It seems that this was much easier and possible with my xl1 and xl1s --- I am wondering if this has something to do with the new way the realastate is allocated on the chips?
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Old January 1st, 2005, 08:11 PM   #8
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Smaller pixels on the CCD are usually more prone to streaking and smear. The XL1 was better at resisting this because it's pixels were comparatively HUGE... I think there were only 250,000 of them on the CCD, weren't there? Whereas the XL2's pixels are less than half the size. The FX1 exhibits more vertical streaking because it's pixels are even smaller, about half the size of the XL2's. The PDX10 has a small megapixel CCD and also struggles at times with streaking.

So it's not necessarily anything that you're doing wrong, it's a side effect of the higher-resolution/smaller-pixel CCD.

Jonathan, consider getting some dimmers to bring your bare bulbs down into proper exposure range, which should eliminate the streaking. Dimmers can cause a color-temperature shift, but are very handy for controlling the situation you're encountering. Also, smaller-wattage bulbs, if you can take the time to substitute them, can help as well. Or a combination of the two.
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Old January 3rd, 2005, 04:28 AM   #9
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Perhaps (quality of) the ND filters are adding to the "problem" as
well where light is bouncing between filters and such? (just an
extra thought to throw into the mix....)
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Old January 3rd, 2005, 05:27 PM   #10
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Thanks all for you thoughts and assesments -- Barry, I'll try the dimmers - I'll have to get them for all my lights (Arri's) so I can stay as wide open as possible. I've used dimmers for fire effects and lightning but haved done too much with using them to dimm the overall room - I give it a whirl.
BTW - I'm using Tiffen so I hope the filters aren't the issue.
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