aperture on camera, no depth of field change, just darkens image? at DVinfo.net

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Old October 31st, 2009, 02:21 PM   #1
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aperture on camera, no depth of field change, just darkens image?

ok so I just got the letus depth of field adaptor, and I have noticed a big difference when I change the aperture on the adaptor vs changing the aperture on my video camera. Changing the aperture on my camera only lightens or darkens the image. when the aperture is closed on the camera, the whole image is black. but when I close the aperture on the depth of field adaptor, the image only darkens a little and the depth of field changes. What I am trying to figure out here, is it just the fact that straight video has no real depth of field and the aperture on the camera will only lighten or darken, but on a real aperture such as the depth of field adaptor, will do what it really should do, change the depth?

I hope that makes sense...
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Old October 31st, 2009, 05:48 PM   #2
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Don't have the Letus but these things work this way.
You should think of the Letus as of a small TV. It should just be in the frame of your camera, in good light and in focus.
All the DOF stuff you should do with the other lenses.. the one you are supposed to put IN FRONT of the Letus

YOUR CAMERA + LENSES --> LETUS --> OTHER LENSES

On the other lenses (for 35mm cameras probably?) you should have the iris wide open (less F-Stop number possible) and (if there is too much light) ND filters in front.

That0s how I see it
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Old October 31st, 2009, 06:13 PM   #3
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ok maybe i didnt ask it the right way. i know how the letus works, i own one. but what i dont understand is why in video when you change the aperture the only thing that happens is the image gets darker and on a real letus adaptor when you change the aperture on the lens, the only real thing that changes is the depth of field?
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Old October 31st, 2009, 06:43 PM   #4
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Well, I'm not sure that's exactly true. When you change the iris on your cam, the DoF does change, just maybe not very much depending on how close you are to the subject, how far you're zoomed in, etc. But it is entirely possible to control DoF in the cam alone, just not as dramatically as with the adapter and better lens.

I'm guessing you have your cam in auto mode, so when you change the aperture in the adapter the cam is compensating.
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Old November 1st, 2009, 12:51 AM   #5
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Depth of field is a function of Iris and focal length..

Ben
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Old November 1st, 2009, 01:24 AM   #6
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Working on the camera lenses aperture is obvious.. there is no DOF.. you are focusing on a plane next to you.. either is all in focus or all off focus. If it is in focus if you rotate the iris you are probably changing the DOF but there are no objects. The only object is the plane of the letus. I mean.. if you put it at 3cm from the lens and it is in focus...changing aperture will put in focus or out of focus the areas at 2.5 cm and 3.5 cm.. but there is nothing to watch in front of the letus screen and you can't watch behind the screen because.. there is the screen.

On the other side.... changing aperture on the second set of lenses should affect not only DOF but also light. Here I can't help. I don't have a Letus.. but maybe there is some settings to compensate light automatically or something.. because.. here you're right... aperture should affect both.

One suggesiton I can give is.. find a good setting with camera lenses that has no vignette, good focus, medium aperture.... and don't touch them anymore. Anything you should do you should do in front
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