DVX100 lens- iris shift???? at DVinfo.net

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Old October 22nd, 2003, 12:03 PM   #1
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DVX100 lens- iris shift????

Read this in a review online -

"For some reason when set to Manual, the iris automatically closes down when you zoom in or out. I was told that was by design. I do not know why."

I currently have an XL1s w/ 16 manual lens....i had the iris problem with the auto lens on that camera...which drove me nuts when i wanted to shoot wide open....does this same deal happen with the DVX100 and the leica lens?....i am demo-ing one on friday...but thought i'd pose the question to the forum

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Old October 22nd, 2003, 01:00 PM   #2
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You're probably referring to the maximum aperture situation.

At wide-angle the maximum wide-open aperture is f/1.6. At full telephoto it's f/2.8.

If you start at f/2.8 it'll stay at f/2.8 throughout the zoom range. But if you start at a more-open aperture, like f/2.0, it'll gradually become f/2.8 as you zoom in.

Nothing unique to the DVX about that, I think every prosumer camera does it. It's not a "problem", it's just the way lens design works. Designing a constant-aperture lens is expensive and uncommon in this class of camera.
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Old October 22nd, 2003, 03:02 PM   #3
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bad lens design in my opinion
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Old October 22nd, 2003, 03:22 PM   #4
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A constant aperture lens would cost more than the whole camera. Just too limited a market to justify the cost. Most users are willing to give up the constant aperture for a smaller, more compact, lighter design. But I agree, constant aperture lenses would be nice to have as an option.
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Old October 22nd, 2003, 04:33 PM   #5
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The irony is that many projects shot with constant aperture lenses never zoom during the shot and most projects shot without them always zoom in every shot :)
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Old October 22nd, 2003, 04:39 PM   #6
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the manual 16x on the xl1 does not shift...i agree about the cost but seems they should have done it on the dvx100...the main problem i see with it is if you zoom in to focus and you are wide open (or seemingly wide open)...when you zoom back out to set the shot you will lose focus of your subject

i guess you learn to deal with it
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Old October 22nd, 2003, 04:45 PM   #7
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I had an XL1 with the manual lens before my DVX100 that I shot alot of footage with.

I actually find the DVX100 easier to focus due to the LCD screen and the focus numbers in the LCD display. It does hold focus fine when you zoom in and out - no backfocus problems that I've noticed. It's a quality piece of glass.
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Old October 22nd, 2003, 05:00 PM   #8
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Stephen-it wouldn't be a back focus problem....

it becomes a problem when you are shooting wide open.....you zoom in to check focus and the lens closes down....with iris shift comes focus shift.....i don't mean to sound like i am correcting you i just want to make sure we are on the same page with regard to what i am saying is a annoying problem with this type of lens. i'm excited to try this camera out, since i believe it produces a better quality pic than the xl1s...i was just curious about what the deal was with the leica lens and the lack of "fixed" f-stop lens

thanks for the feedback
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Old October 22nd, 2003, 05:59 PM   #9
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Steve:

The DVX100 will hold the focus when you zoom in and out. The iris change affects light and DOF, but not focus setting.
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Old October 22nd, 2003, 08:15 PM   #10
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It would only effect focus if you missed critical focus and DOF at the smaller F stop covered the focus error. When you zoomed out the shallower DOF might show soft focus. I really don't think this would be a large issue with this camera.
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Old October 22nd, 2003, 10:55 PM   #11
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Nice birds Jeff. Beautiful photos.
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