Leaf Shutter Vignetting?

[Matthew Rusbarsky]

Kind of interesting. Leaf shutter SLR (Voigtlander Bessamtic).

The camera was on on loan to a friend when the shot was taken, but I assume it was at a fast shutter speed (250 or 500) with the aperture close to wide open. The shadow of all 5 shutter blades are clearly visible. I've done some googling on this effect and all I've found is exposure correction tables for leaf shutters at small f-stops and high shutter speeds. My best guess is that the Bessamatic is a one of those few 35mm leaf shutter SLRs with the shutter behind the lens, rather than in the optimal location (between the elements), resulting in the vignetting rather than plain old over exposure.

 

[srmcnamara]

that is kind of beautiful.

 

[ntenny]

I really like it. I can see where this would be a problematic effect to have appearing at random, but in this particular shot it works just great.

-NT

 

[archphoto]

Sinar uses the "behind the lens leaf shutter" and I have never heard of this in any discussion.
But then the Sinar shutter goes up to 1/125 only....

Strange and beautifull........

By the way, I just use the leaf shutters inbetween the lens only.

Peter

 

[Steve Smith]

I would imagine that the shutter is a bit slow to open and/or close and it is showing up at fast shutter speeds where the time to open and/or close is a larger percentage of the shutter open time than it would normally be.

If it was an in lens shutter it wouldn't vignette like this in the same way as a small aperture does not vignette. But the closer it is to the film plane, the more pronounced the effect will be.

I like it though!


Steve.

 

[Struan Gray]

You can get this effect even with a shutter that is at the optical centre of the lens. Out of focus background highlights take on the shape of the aperture, and wide open at the fastest speeds leaf shuttered lenses have effective apertures which are the time average of the shutter opening - exactly the pattern you see here.

I don't know the layout of the Bessamatic well enough to say whether you have vignetting, or a change in the effective aperture (sometimes called 'apodisation' in technical journals) - it's possible you have a mixture of the two. Vignetting will show the pattern best with a background white wall, apodisation with a background point highlight.

 

[Steve Smith]

I don't know the layout of the Bessamatic well enough to say whether you have vignetting.

If it's the same as my Kodak Retina Reflex III (which I think it is) the shutter is about 1" (25mm) from the film plane.


Steve.

 

[Struan Gray]

Then it could be either. The fact that it covers the whole frame (assuming no crop) suggests it's more of a vignette.

Here's what it looks like with a 150 f3.5 almost wide open at 1/500 on 6x6:

Those aren't bindweed flowers in the background, but specular highlights bokeh-ed into new forms.

 

[ic-racer]

Looks like a slow shutter speed, stopped down lens and a sticking shutter.