Re: [APML] OM2 vignetting

[Matt BenDaniel <matt@exceloncorp.com>]

At 12:00 AM 5/2/2001 -0700, Torsten Clay wrote:
>Some of you noticed some weird vignetting in the corners of my recent
>photos.  Here is a super-stretched full-frame version of the Lagoon:
>
>http://personal.riverusers.com/~tclay/om2.jpg
>
>
>The funny vignetting is in the upper left and right corners. I looked in
>from the back of the camera (Olympus OM2n), and there are two photosensors
>at those locations for metering off the film! I think I'm seeing shadows
>from those sensors. 

Torsten,

As you are probably aware, the standard vignette examination procedure is to mount the camera on the scope, point the scope out the window into the daytime sky and open the shutter. If you hold your eye almost touching the film rails near the corners of the frame, can you see a anything silhouetted against the sky (other than the edge of the primary or baffles)?

I just did this with an OM-1 and I see no sensors. I do see the T-ring itself occluding the view. I can't do this with my OM-4 right now because it's got film in it.

What seems strange to me about that stretched image is that you DON'T have vignetting in the lower corners. I think with my OM-1 images I get vignetting in all four corners (from the T-ring) like you have in the top corners.

What's the diameter of your focuser? 
You use a standard OM T-ring?

Anyway, when push comes to shove, you know there are Photoshop-based techniques to get rid of vignetting.

Matt

>Has anyone else noticed this problem with photos taken
>with an OM2? I have an OM2n, I don't know how different that is from a
>OM2.
>
>It will be easy to confirm, next time I will use my OM4 body which doesn't
>have sensors in those locations. Is this one reason why OM1's are more
>popular for astro work than the newer OM's?
>
>Torsten
>
>
>
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--
Matt BenDaniel
http://starmatt.com


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