Vignetting with the SWC

Hello

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I am noticing slight vignetting with my SWC/M - for example see this photo -

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<a href="http://www.photo.net/photodb/photo?

topic_id=1481&msg_id=00JOiW&photo_id=5414985&photo_sel_index=0">seascape</a><p>I seem to

remember that I took that pretty wide open as I was using 100 film and the extreme wind made me put

shutter speed as fast as I could.

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I don't seem to remember reading about this problem with the SWC anywhere. I must say I still like the

photo, just would be nice to know if it is my particular camera, or all SWCs.

 

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Thanks

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Robert

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[i am not looking for any PS fixes and would rather no-one posted the image reworked in any manner.]

There is some fall-off, Robert and it is most notable in largely evenly lit areas like the sky. It isn't eliminated by stopping down, either. Biogons don't work that way.

 

However, you seem to have more than the usual. Are you using a filter of any kind? Lens shade?

 

Here's a typical shot pushing an earlier SWC to the max (diminished sharpness due to cheap jpeg.)<div></div>

If you go to Zeiss's web site and search around you'll find their technical

specifications and MTF charts for Hasselblad lenses both past and present.

You'll see that the 38mm Biogon vignettes quite badly, about two and a half

stops out in the corners and closing down the aperture doesn't do much to

alleviate the problem. I mainly use my SWC/M with a digital back and then the

vignetting problem is even worse than with film (I'm told the oblique rays from

the symetrical Biogon design means additional vignetting because of the

depth of the pixel wells).

 

There's the alternative of using one of the retro-focus 40mm designs which

vignette less, but then you either lose resolution with the older models or

suffer serious distortion with the new 40mm IF .

 

It just goes to show yet again that there's rarely such a thing as a

photographic free lunch!

<i>about two and a half stops out in the corners</i><p>

I don't think Zeiss puts that stuff on their site anymore.<p>

It doesn't 'feel' like 2.5 stops to me, possibly because we (or I) make some kind of mental adjustment to the actual image.<p>

 

But 2.5 stops? Is that what this chart shows? <p>

TIA!

I used to own an SW/CM about 20 years ago and had slight vignetting like yours. I sort of liked the effect, though I don't remember it being so pronounced. I also did not use mine with filters or lens hood.

Just curious....did you have any filters on the lens?

Pico,

 

Yes, wido open in the corner, 38mm from the center shows 20%, which is fairly close to 2-1/2 stops.

 

I had two SWCs, would like one of them back, the C T*.

No filters - no lens shades. Nothing but pure arsenic and T* glass in a 1981 camera.

 

Maybe the wind was blowing so hard that it stole some of the light from the corners ? ;-|

 

This is all very interesting to hear though - and I understand why it happens now. Strange

to not have seen this flagged up anywhere before.

 

So, Pico - that is a very fine SWC example - please show off a few more. It still looks pretty

sharp to me - but you have no vignetting - or very very little. When you say "pushed to the

max" are you referring to the depth of field ?

 

RX

Reviewing some of my Hassy SWC photos, I see about 1 stop falloff. With negative films, the

light falloff at the corners/edges of the frame always seems negligible, one stop isn't enough

to distract me. With transparency film, the falloff becomes far more noticeable because of the

decreased exposure latitude offered by the film: to avoid burning the center, the corners/

edges become underexposed.

 

Godfrey

Any 38mm Prime wide angle for med format lens will always have some vignetting due to geometry failure. Inverse square rule and all that. You might be able to get a center filter for the 38mm to cancel it out. Retro focus lenses have a greater lens to film distance, so they show this effect less. All lenses have this problem to some extent. The geometry of extreme wide angle prime lenses just exadurates it.

Peter -

 

I think what surprises me is that i hadn't heard about it anywhere. I read pretty much

everything I could find on the lens that people had written on the web. I remember when I

was researching about the voigtlander ultrawides (12mm and 15mm) this was one of the

things that kept coming up whenever they were talked about. Looking at some of the

pictures posted her and there now I guess I can see it, and though it is way less extreme

than on those lenses, I am a little surprised no-one mentioned it. The fact the Biogon is

not retrofocal is one of the things that is always trumpeted in it's favour - not once is this

mentioned. It's one of those things that I think once you have noticed it you keep on

noticing it. It took me six months !

 

We live and learn, we live and learn.

 

I still love using this camera, mind. I am experimenting with a PS fix which seems to work

pretty well - a layer with a heavily blurred circular mask on it seems to act much like a

center weighted filter, and can be easily controlled with opacity - though I am still not sure

I don't just like the effect as is.

 

RX