Lens Misalignment?

[Larry Menzin]

I bought a 210mm Sironar-W on fleabay (I know, I know) and tried it today on my Arca Swiss 8x10. The lens focuses (with difficulty) in the middle of the ground glass, but beyond the center everything is blurred. I cannot get anything beyond the center to come into focus at all. Replacing that lens with my regular 210mm APO-Symmar (which barely covers the format) gives me a perfect image on the GG. What would cause the problem I saw with the Sironar-W? Is it misaligned? Damaged? There are no physical signs of damage on the lens.

[ic-racer]

Assuming the rear element is the correct one for the lens, consider that the front-to-rear element spacing may be off.

Try unscrewing the front element and see if it improves. Also, check the specification sheet for the Sironar lens. It should give an "overall length" that would let you know if your spacing is off.

[Paul Fitzgerald]

sounds like an internal element is missing OR installed in reverse.

[Jerry Bodine]

If it were me, I'd check for proper mounting of the lens on the Arca lensboard to insure that the lens axis is perpendicular to board, i.e. one little piece of grit in the interface could in effect cause some tilt and/or swing. Just a thought.

[Dan Fromm]

"The lens focuses (with difficulty) in the middle of the ground glass, but beyond the center everything is blurred. I cannot get anything beyond the center to come into focus at all." No matter how cheap it was, demand a refund.

Good luck,

Dan

[Larry Menzin]

None of the obvious things like spacing, mounting, etc. helped. I did note what appear to be tool marks on one of the front cell rings. My guess is that the seller tried a self-repair and when it failed, put the lens up on Ebay. We'll see how much PayPal buyer protection works.

[CP Goerz]

Since there are marks on the front then there is a good chance the the front element isn't seated properly, it may be a MM or so out of placement. Get a refund.

[Steve Hamley]

Check Paul's comment. I cleaned a friends Sironar once and reversed one of the rear glasses and got the same effect. Basically I turned it into a swirly Petzval or a Holga. I've often thought of buying another with this very intent.

I'll give you $5 for it...

Cheers,

Steve

[Steve Goldstein]

From the cross-section diagram here http://www.prograf.ru/rodenstock/largeformat_en.html it would appear possible to install the innermost element of either cell backwards. Each should be concave when you look at it unscrewed from the shutter.