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Iris problems on XH A 1

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VideoT
Iris problems on XH A 1
on Jan 27, 2008 at 8:35:41 pm

I've had my Cannon XH A 1 for about 6 months now and I'm still trying to figure all of the little things out.
But is it normal for the iris to automatically close as you zoom in???
Im shooting in DV in manual mode and as I zoom my iris closes and won't let me manually open it up. WHen I'm zoomed out it will only open to a certain point.
Is this how it's supposed to be? Is there a setting I need to change? Or is there something wrong with the camera?

Any help wold be extremely appreciated!!!


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James Rhodimer
Re: Iris problems on XH A 1
on Jan 30, 2008 at 7:23:16 am

hi, I just got that camera and maybe this will help. I found that those two dials should operate separately. I just did what you were talking about. As I zoom out, the same motion on the dial at the far back will open it up. I think that your dials are stuck together if moving one is also operating the other. because mine don't do that. they should not effect each other. But that is just based on my little experience.

cheers
jim



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William Busby
Re: Iris problems on XH A 1
on Feb 1, 2008 at 7:57:01 pm

It's normal behavior & I believe it's because it's not a true servo lens. Many if not all cameras in this category do this. I don't like it, but it is what it is.

James, you say yours doesn't do this... but I think you're not understanding. Put your A1 in TV (locked) or manual mode. Start out wide, then zoom in. Your iris WILL close down a bit... such as around f2.6 or whatever it is. Zoom back out to wide & it opens up to the original value.

Bill



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James Rhodimer
Re: Iris problems on XH A 1
on Feb 1, 2008 at 8:14:56 pm

ahh yes, I see. I just did it. it did just that.
luckily that won't hurt my type of use. damn.



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Warren Morningstar
Re: Iris problems on XH A 1
on Feb 7, 2008 at 12:54:11 am

I may be oversimplfying this, but I think what you're experiencing is normal optical behavior. F-stop is technically the ratio between the focal length of the lenses and the aperature opening, so is only indrectly related to the amount of light let through. The longer the focal length, the less efficient the lens is in transmitting light. Which, if I remember correctly, is why cinema lenses use T-stops, which more accurately reflect the amount of light transmitted through the lens. As you zoom in, the lens becomes less efficient or "darker." They compensate for this somehow in the middle exposure ranges, but when you're wide open at wide angle, there's nothing left to adjust when you zoom in. Same thing happens with zoom lenses on still cameras.



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Shiloh Heyman
Re: Iris problems on XH A 1
on Feb 14, 2008 at 7:54:08 am

If you know your going to go in for a zoom don't set your iris any lower than f2.6 or f2.8 to start. I believe you can zoom all the way without going any higher than f2.8. If you need to open wider do a dolly, not a zoom. Yes all HDV cameras exhibit this behavior.


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