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Removing vignette in 35mm Depth-of-Field adapters

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clyde villegas
Removing vignette in 35mm Depth-of-Field adapters
on Sep 22, 2010 at 11:49:12 pm

I have one of the lower priced DOF adapters. I asked someone from another forum on how to remove vignetting. I was told to make the camera's lens zoom in closer pass the vignette. However, doing this blurs the entire image because the camera is now very close to the achromat. Is there some kind of a macro filter that I can put between the adapter and the camera so I can zoom in really close? Is this the right approach?

ut in omnibus glorificetur Deus


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Dylan Hargreaves
Re: Removing vignette in 35mm Depth-of-Field adapters
on Sep 23, 2010 at 10:15:46 am

I'm just encountering a similar problem with my new Letus Extreme. Although I can zoom past the vignetting with no loss of focus, it feels like I'm cropping a fairly substantial portion of the image.

Philip Bloom did something on the Letus range which may be of use: but without knowing what make your adaptor is it may not be all that relevant!

If anyone's got any advice on the image cropping or whether I should even be concerned about it, I'd love to hear it.

Cheers!


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Jason Jenkins
Re: Removing vignette in 35mm Depth-of-Field adapters
on Sep 23, 2010 at 3:35:18 pm

[clyde villegas] "I asked someone from another forum on how to remove vignetting. I was told to make the camera's lens zoom in closer pass the vignette. However, doing this blurs the entire image"

Once you lock your focus in on the ground glass you should be able to zoom to any level without affecting the focus. Are you on manual focus with the focus ring locked or taped down? Vignetting can be caused by using lenses that are too slow.

Jason Jenkins
Flowmotion Media
Video production... with style!


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Todd Terry
Re: Removing vignette in 35mm Depth-of-Field adapters
on Sep 23, 2010 at 4:01:04 pm

It might be that you can't do much about it.... vignetting is one of the frequent side effects of the lower-end adapters.

As Jason suggested, it also might be the lens. Do you notice the same clipped corners on all your lenses? Or is the problem only with (or worst) with one in particular?

Also... are you using a matte box? It took me quite a long time to realize that some vignetting I was getting with my 18mm lens was due to the matte box. Now I just don't use the matte box with the 18.

If you find you have to zoom in, obviously you'll want to do it as absolutely as little a degree as possible. Connect your camera to a monitor that will underscan so you see every pixel, and make the minimal adjustment. Zooming more than you have to runs the risk of exposing the grain on the groundglass... and obviously it gives you a different field of view than what is native to the focal length of whatever particular prime you are using.

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com



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clyde villegas
Re: Removing vignette in 35mm Depth-of-Field adapters
on Sep 23, 2010 at 11:37:40 pm

The whole image becomes totally blurred when I zoom in because my camera can't focus at that very close distance (from the camera lens to the achromat). So in order to remove the vignette, I was thinking of enlarging the image instead of zooming in. Do you think that's possible by putting extension rings between the condenser and the achromat?

In another forum, I've read someone using the same adapter (Jag35Pro) putting another achromat between the the condenser and the achromat (making it two achromats screwed together). He said the vignetting was completely gone and the image was sharper, probably as sharp as the more expensive adapters. Has anyone in the Cow tried that? Will the extra glass reduce too much light? Is this better than my first idea? What do you think?

ut in omnibus glorificetur Deus


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david braman
Re: Removing vignette in 35mm Depth-of-Field adapters
on Sep 24, 2010 at 12:58:32 pm

I did some experimenting with focus combinations (still need to do some more). But if I moved the focus on the camera's zoom lens to a mid distance and then used the macro to regain image sharpness, a lot of the vigneting appeared to go away (it also bought me a little more spread from the prime).


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clyde villegas
Re: moving vignette in 35mm Depth-of-Field adapters
on Sep 24, 2010 at 11:10:21 pm

What \"macro\"? A macro lens? Is this the same as an achromat?

ut in omnibus glorificetur Deus


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david braman
Re: moving vignette in 35mm Depth-of-Field adapters
on Sep 27, 2010 at 11:59:19 am

The macro focus on your zoom lens...if you have one.


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clyde villegas
Re: moving vignette in 35mm Depth-of-Field adapters
on Sep 27, 2010 at 12:26:56 pm

I think I don't have that. Will putting another achromat on the lens be the equivalent of switching on "macro focus on zoom lens"?

ut in omnibus glorificetur Deus


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