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Old July 23rd, 2003, 12:45 PM   #1
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Focusing in high wind

Hey there. I've been shooting some stock footage with my new XL-1S and have run into some interesting challenges with regard to filming in windy conditions.

Recently, I was out shooting on the oceanfront during the Fourth of July. Fireworks are still very much legal where I live, and I figured it would be good practice to get out there and film some of the homegrown fireworks shows that families spend thousands on this time of year. On the beach, there seems to be a constant on-shore breeze at all times, and the fourth was no exception.

The first problem I ran into was moisture condensation warnings between the air conditioning of the car and the 80% humidity and 90 degree plus temperatures that night. I was able to fix this by ejecting the tape and allowing the tape housing to "air out" in the breeze for a few minutes in a parking lot.

The second problem was that I had great difficulty keeping the fireworks displays in focus, even with auto-focus off on the lens. I'm not sure if it was a problem with shooting video in fairly dark conditions already, the fact that a 15 mile an hour wind was giving the lens fits or a combination of both. Once i'd focus in on a subject and stabilize the focus, the lens would drift out of focus constantly in all manual recording and lens modes.

Out of two hours of shooting, I figure I have about 20 minutes of stable, clear useable footage.

I haven't run into this problem shooting during the daytime or at any other time with the camera. The question I have is:

Do you think it was a low light problem? Do you think it was a wind problem? Do you think it was both?
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Old July 23rd, 2003, 01:00 PM   #2
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Its hard to say exactly. One thing you might want to check is if you were shooting from a tripod make sure you have the stabilizer off. The OIS can create all kinds of weird problems while shooting from a tripod.

When you are in manual mode you control everything but the gain, I think. I am not sure if gain can cause the type of problem you have described so someone else will have to answer.
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Old July 23rd, 2003, 01:21 PM   #3
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Yep. I was using the camera in manual mode at 24 fps. The shooting was done shoulder mount so that I could go mobile by walking along the dunes and up onto the pier and whatnot.
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Old July 23rd, 2003, 01:36 PM   #4
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You might check the audio post about 'buzzing.' One of the members there references shooting fireworks creating audio problems due to intense video. It may have implications for you.
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Old July 23rd, 2003, 01:39 PM   #5
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How far away were the fireworks? Do you remember what shutter speed you were using? Did you have IS on or off?
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Old July 23rd, 2003, 03:27 PM   #6
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John,
Regarding your focus issue, I assume that you were using the standard 16x auto lens.(?)

When that lens is in Manual Focus mode (as distinct from the camera being in manual exposure mode) the focus should not be able drift at all, since the focus servo motor is disengaged from the auto-focus system. Generally you'd lock the focus to infinity (focus on a distant object while you still have light) and forget it. If the focus still drifts you might have a problem with the lens or camera.
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Old July 25th, 2003, 09:35 AM   #7
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I don't see how you were recording in 24 fps mode. Gain can be
both set manually or automatic in manual mode and should not
cause these problems. Sounds like the lens was in autofocus
mode (somehow) while you set it otherwise. If you can recreate
it, it might be time to have your camera serviced...
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Old July 25th, 2003, 02:36 PM   #8
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Yes, the lens is the standard AF lens that came with the camera. Perhaps I was wrong in that I did have the camera set to "Film" mode, and not 24 fps. Chalk this up to me being a newbie.

It was far too dark to shoot with AF turned on but I do think that the image stabilizer was engaged during the shooting. Distances varied from approximately three yards to hundreds of yards as I was shooting behind and above the displays. I also took several shots from a pier on the beach to try and capture a significant length of the beach with people shooting off their various fireworks displays.

I'm sure that I probably had the image stabilizer engaged, as i'm used to leaving it on for handheld shooting. The camera was in a manual film mode and I had to do constant focus adjustments by hand. If I had left the camera lens in AF, it would have constantly been trying to focus on the nearest bright light object, which would have been the local hotel lights and such. I didn't encounter any audio buzzing or overexposure problems, and when i could keep the camera in focus, the images turned out crisp and colorful.

All night long though the camera's focus wanted to drift on me. I kept fiddling with it to make sure that AF was disengaged (which it was) but it really didn't seem to make much of a difference. Just when you'd frame a shot and get it focused, it would gently drift out of focus. Perhaps this camera isn't the best choice to use in low light conditions.

I can try doing some test shooting without the image stabilizer on but I will have to mount the camera on a tripod to keep it stable. I never seem to have this problem with the camera during daylight conditions no matter what speed or film mode I happen to be shooting in.
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Old July 25th, 2003, 02:56 PM   #9
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The switch (AF/M) on the side of the lens was set to M, correct? You did not rotate either of the black rubber knurled rings on the lens, correct? The image drifted in and out of focus, while you were stationary, with the camera on your shoulder, correct? If the conditions I described are correct the camera and lens need to be sent to Canon for service. The focus will not drift if it is set to M on the lens.

The other possibility is you are not used to shooting under very limited depth of field (DOF). Once the lens is focused, in manual, the subject will stay in focus, unless the distance from the camera to the subject changes. If you were focusing, then walking around, the lens would need to be refocused because the camera to subject distance changed.

In bright light the aperture stops down (large F number) and DOF increases. With large DOF, focus is not that critical and camera to subject distance can change without subject going out of focus.

In low light the aperture opens up (small F number) to let more light in the lens and provide proper exposure in low light levels. Small F number reduces DOF and changes in camera to subject will result in the lens needing to be refocused.
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Old July 25th, 2003, 03:04 PM   #10
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Yes, the lens was set to manual. However, I was using the rings on the lens to do the focusing for the lens when it would drift out of focus. For the most part, I would stand perfectly still or use the rail of the pier to prop the camera up, frame the shots, and then shoot, rather than walking around during the filming.

I can feel the heat coming with regard to turning the rings on the lens. :c)

Chalk it up to being a newbie, but what did I do wrong? How should I have properly used the rings on the lens?

I'd been using the largest ring like telephoto/wide angle control, to zoom in and out of various displays, from the pier. The other ring i'd been using to fine tune the focus on the subject once the shot was framed.

How bad did I screw up? Please help.
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Old July 25th, 2003, 03:15 PM   #11
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You are operating the zoom correctly, use it to frame the subject for composition. Then focus with the other ring. If nothing else changes i.e., you re zoom or move, the focus should not drift. I would try repeating this on a tripod, at night, and try to duplicate the effect.

If the focus drifts, with the camera on a tripod, then send it in. If the focus is steady, then say its increased sun spot activity, or the deterioration of the Van Allan belt.
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Old July 25th, 2003, 03:21 PM   #12
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I guess i'll have to go out and do some test filming at night to see what the problem is then. Hmmm...

Now i'm second guessing myself.

Well, i'll be heading out this weekend to a few night shots and i'll see how the camera performs then.
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Old July 25th, 2003, 03:25 PM   #13
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You've got to use a tripod, it's really the only way to check these things.
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Old July 26th, 2003, 04:12 AM   #14
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If by accident you have the camera in the "green square" mode, the AF setting on the lens doesn't matter: it's in AF whatever.

Also I have seen a thread on focus drifting that sound a bit similar:
http://www.dvinfo.net/conf/showthread.php?s=&threadid=6021

Maybe this helps.
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Old July 26th, 2003, 12:05 PM   #15
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I agree with Jeff about using a tripod and DOF issues. With the lens opened wide your DOF could be very narrow. The subject moving in and out could make it appear soft.

When you say you are a newbie, do you mean to the cam or videography in general? Ehile the focus and zoom rings are hard to confuse, if during the course of shooting, you inadvertently touch the focus the focus will likely go soft.
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