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Canon XL and GL Series DV Camcorders
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Old July 27th, 2005, 01:16 AM   #1
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Shimmering Closeup Footage

I was shooting out in a rural area today and when I looked at the footage this evening I noticed something I haven't seen before--a shimmering, almost like a visable heat wave--it almost looks like an effect as if it was shot in the Sahara or something! When I was zoomed into an object, for example I zoomed into some daisys and stopped, then just shot about 10 seconds of the daisys, they looked and look on the television very nice, but there's this shimmering, I don't know what else to call it, not a flickering like interlace flicker, not at all. When I shot at a midpoint between closeup and far away, it wasn't there at all. This happened later on when I was shooting a scene, when I came in close to the object.

Has anyone had this happen? Could shooting on a hot humid day cause this?
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Old July 27th, 2005, 02:57 AM   #2
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Not sure what this might be. What settings were you using...aperture, shutter, frame rate, wide or narrow, any custom presets? Any possibility of posting a short clip showing this?
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Old July 27th, 2005, 05:16 AM   #3
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Was optical image stabalising on whilst on a tripod ? I experienced a similar thing when using the 1.6x extender an 20x zoom, but I would have described the effect as vertical bouncing ....
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Old July 27th, 2005, 06:41 AM   #4
 
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Without seeing it, I'm guessing it's exactly what you said it was--heat rising. I don't where you are, but here in Miami you'll see it everyday when you shoot during the summer months (we have six of those down here), using the telephoto.

Jay
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Old July 27th, 2005, 07:45 AM   #5
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Jay,
I composed that very message twice and abandoned it both times. I thought Lucinda would tell me I was a moron, to which I would have replied, "un-uh, I'm more off than I am on".
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Old July 27th, 2005, 03:10 PM   #6
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Wow!...could it really be?! It's been humid here and that as you know makes everything really hot. It really looks like heat rising. It looks like a very cool effect. I just wasn't sure if the lens problem I've been having could have caused it. By the way, a new XL2 is on the way to me today! and Brian at ZotzDigital has checked it over and it's fine! let's hope. The shimmering also looks like a mirage...on the road, that's the sort of shimmering I'm talking about. What is vertical bouncing? and why would the image stabilizer cause that?

So, do you really think the cam could record the heat rising?!

I'm impressed. Have others experienced this?

As for moron Pat, you're far far from it!!

I feel shy about asking anything for fear seeming like a doo doo.
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Old July 27th, 2005, 03:17 PM   #7
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Lucinda,

Don't tell your camera manufacturer or NLE company that you recorded that...normally they make you pay extra for that.

My guess is that you actually recorded optical distortion from heat. At relatively close ranges, our binocular vision will 'edit out' this effect so that our brain records a relatively stable image. When we are looking farther down-range where we are using monocular vision or if the distortion is pronounced enough, we see the distortion. Of course the camera is always seeing the imagery as monocular vision (Except when using this lens at the bottom of this page, or like it).
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Old July 27th, 2005, 05:27 PM   #8
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A trick I learned of on another forum for getting 'heat waves' on command is to shoot over the hood of your car, keeping it just out of the shot. Of course, the car's engine needs to be hot. I haven't personally tried this out but it came from a news photog site so take it FWIW. Perhaps Stephanie Wilson will see this thread and chime in since that is her background.

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Old July 27th, 2005, 05:32 PM   #9
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Quote:
Originally Posted by Lucinda Luvaas
I was shooting out in a rural area today and when I looked at the footage this evening I noticed something I haven't seen before--a shimmering, almost like a visable heat wave--it almost looks like an effect as if it was shot in the Sahara or something! When I was zoomed into an object, for example I zoomed into some daisys and stopped, then just shot about 10 seconds of the daisys, they looked and look on the television very nice, but there's this shimmering, I don't know what else to call it, not a flickering like interlace flicker, not at all. When I shot at a midpoint between closeup and far away, it wasn't there at all. This happened later on when I was shooting a scene, when I came in close to the object.

Has anyone had this happen? Could shooting on a hot humid day cause this?
Hello,

A wild guess... were you using any ND filtering??
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Old July 27th, 2005, 06:31 PM   #10
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Hi All,

Pat, what do you mean?

Don't tell your camera manufacturer or NLE company that you recorded that...normally they make you pay extra for that.

Of course, you're kidding, right?

And Anthony, I don't remember if I used the ND filter for those clips. I know I used them later on during that same shoot. How would that affect the shimmer?

By the way, I used, just for the heck of it, a lower shutter speed and the ND filter to get a clip of large cumulus clouds and it looked really good. Normally, I'm shooting outside during the day at a 60th of a second, but I just wanted to try and see what would happen. That's not when I got the shimmering effect tho....I got that only when I came in close to the dandelions and the barn...the truck was a ways away. That couldn't have caused the shimmering.

Pat, do you think I can use this footage? I do like it.

Lucinda
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Old July 27th, 2005, 07:28 PM   #11
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Quote:
Originally Posted by Lucinda Luvaas
Hi All,

Pat, what do you mean?

Don't tell your camera manufacturer or NLE company that you recorded that...normally they make you pay extra for that.

Of course, you're kidding, right?

And Anthony, I don't remember if I used the ND filter for those clips. I know I used them later on during that same shoot. How would that affect the shimmer?

By the way, I used, just for the heck of it, a lower shutter speed and the ND filter to get a clip of large cumulus clouds and it looked really good. Normally, I'm shooting outside during the day at a 60th of a second, but I just wanted to try and see what would happen. That's not when I got the shimmering effect tho....I got that only when I came in close to the dandelions and the barn...the truck was a ways away. That couldn't have caused the shimmering.

Pat, do you think I can use this footage? I do like it.

Lucinda

Hello,

If you are using the ND filters in bright sunlight, they can give you optical effects that aren't expected... Ghosting, Blurring, and shimmering....

Heat effect is real, but you can see that with the naked eye as well, so you should have noticed it... but it may have been concentrating on other aspects within your frame.

That's why I mentioned it :-)
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Old July 27th, 2005, 07:54 PM   #12
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Quote:
Originally Posted by Anthony Marotti
If you are using the ND filters in bright sunlight, they can give you optical effects that aren't expected... Ghosting, Blurring, and shimmering....
Anthony, I've never had ND filters affect anything but the overall light level reaching the sensors and thus the white balance. That's why they are called Neutral Density Filters, so they don't inject anything like ghosting, blurring, or shimmering. I'd bet if you had that happen when you installed an ND filter, it was a smudge on the filter.

Lucinda, yes I was making an obviously poor jest. And concerning whether or not the footage is useable...well now we are leaving the realm of science (what caused it) and entering the realm of art. You have to take of your technical hat, put on your artist hat and evaluate if it fits well in the piece you are composing. I'd bet that a lot of 'unusual' footage makes it into some films even though the unusualness wasn't planned.

But if it doesn't fit, it'll be like trying to pound a square peg in a round hole; you can include it but it will jar the senses when its displayed instead of perpetuating the feel of the piece you are creating. I'm having to mentally picture what it looks like, but I think you could probably place it between a dutch roll with the sun in the imagery and a rack focus from something close out to something distant.

Or a hundred other possibilities including some of the other footage you've already captured. "Feel the art...be the art." (Parody on a famous Caddy Shack line of dialogue)
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Old July 27th, 2005, 11:41 PM   #13
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Quote:
Originally Posted by Patrick King
Anthony, I've never had ND filters affect anything but the overall light level reaching the sensors and thus the white balance. That's why they are called Neutral Density Filters, so they don't inject anything like ghosting, blurring, or shimmering. I'd bet if you had that happen when you installed an ND filter, it was a smudge on the filter.
Hello Patrick,

In theory you should be right as far as the filter not causing any negative effects, but the Neutral Density filter cuts down light without adding any color temperature change that doesn't mean that the filter is perfect and won't add other influences to your frame. In fact, these filters are not perfect and do add unwanted visual nuisances to your image. How much and how detectable they are depends largely on the quality of the filter.

However, the Canon XL series will cause this type of effect under certain conditions... in fact I believe it is even mentioned in the manual, or in an insert, or it could of been on their website... but I think it is right in the manual.

Bright sun, and zoomed in will cause a ghosting (and other unintentional effects) due to internal reflections or some such thing.

Now this could very well look like shimmering, especially if the heat aberration were to play a part in the overall effect.

Of course, it cold be a number of different things, and the use of the ND filter under certain conditions is certainly one of them.
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Old July 27th, 2005, 11:59 PM   #14
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Thank you Patrick and Anthony!

I think what I'll do is try shooting in the same conditions with Canon's internal ND filter on and off. You see, I didn't shoot all footage with it on. I tend not to use it too much......but, perhaps that's what did it. I've never seen it before. But, I usually shoot around 5pm at this time of year and we've been shooting in the morning lately to avoid the congestion of traffic, etc.

I may use that scene with the beautiful dandelions and create a fire in front of them or some such effect with Commotion Pro or AE or something else....we'll see.

Art is what I'm about Patrick...funny you should mention it. hummm.
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Old July 28th, 2005, 06:27 AM   #15
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Quote:
Originally Posted by Anthony Marotti
However, the Canon XL series will cause this type of effect under certain conditions... in fact I believe it is even mentioned in the manual, or in an insert, or it could of been on their website... but I think it is right in the manual.
I think the statement at the top of page 43 (directly under the bold title) may be what you are referring to:

While recording under bright conditions, the camcorder sets a small aperture value, and the picture may appear blurred. When you are using a lens with built-in ND filter, turn it on/off according to the screen display.

I read this as saying that the ND filter is available to overcome a small aperture blur, in other words, if its blurry in bright light, add the ND to clean it up.

Anthony, I know that no company is immune from a few lemons, but I find it hard to believe that Canon is going to spend so much R&D money to bring a fluorite lens to market and then put a cheap ND filter in the lens that distorts the image. My bet is still on 'optical distortion from convective heat' and not 'optical distortion from ND filter'.
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