Peleng 17 2.8: Infinity Focus Problem

[Univer]

Hello All,

I would be very grateful to have the benefit of your thoughts on a lens issue.

Not long ago, on a whim, I bought a used 17/2.8 Peleng fisheye. It doesn't seem to be a terribly common lens, and opinion - what there is of it - seems to be divided on the question whether it's better or worse than its 16/2.8 Zenitar cousin in terms of IQ. But it wasn't too expensive, so I thought I'd take a chance on it.

This is an "A" lens, with the screw-on adapter for M42 and Nikon (and maybe others as well). Mine arrived with the Nikon adapter in place, but I knew where I could get a spare Russian M42 adapter, so that wasn't an issue. I bought the new adapter and installed it - no problem there.

I took the lens out for the first time yesterday evening, on my K20D, and I had awful difficulties focusing it. Not the usual difficulties inherent in using an ultrawide - this was different. It took me a few minutes, and a few shots, to realize that the lens wasn't focusing to infinity, or anywhere near it; at the infinity setting, objects about two feet away (maybe even less) were in focus. On the other side of the scale, the lens does seem to be focusing a bit closer than the focus ring would indicate.

My first thought was that the new M42 adapter was too thick, and was acting as an extension tube. But it fits perfectly, and, compared with the Nikon adapter that originally came with the lens, it seems to have the same thickness. Besides, my understanding is that a Russian "A" adapter is a Russian "A" adapter: that they don't come in varying flavors.

I did examine the rear element, and the tube that holds it is threaded for a screw-over filter (in principle, it's just like the rear element of the Peleng 8/3.5 - although the filters from the 8mm don't fit). But there's no filter in place.

Now, I've read, on several occasions, that the clear filter at the rear of lenses like this one is an essential part of the optical arrangement, and that these lenses should not be used without that filter installed. And I've also encountered the opposite view: that the absence of the clear filter makes no difference whatsoever. But my assumption has always been that the difference - if there is one - would be one of IQ, not one of throwing off infinity focus. I will say this: allowing for the focusing problem, I see nothing wrong, so far, with the IQ of this lens.

Hence my question: do you suppose the absence of a rear filter could account for the lack of infinity focus? Or do you think it's more likely that the lens is simply out of adjustment?

(As a final note, I'll point out that the lens shows no signs of ever having been opened, and that the previous owner claimed that she used the lens with great success for several years.)

Thanks for your help!

Cheers,

Jon

[DSG]

[Univer]

Hi,

My experience is like yours; the images from this lens (the few that were in focus) seem very crisp, so I have trouble believing that the missing clear filter significantly degrades IQ. I probably wouldn't even have thought about its absence if not for the focus problem. (And I'm not sure I understand how the missing filter could create that issue either.)

If I were a betting man, I'd be wagering that the lens needs an infinity-focus adjustment.

Cheers,

Jon

[aoleg]

[fatdeeman]

Click here to see on Ebay

Maybe that will help?

[visualopsins]

[aoleg]

Different size. Unfortunately, there are no marking on my filter, only the "H-1" designation, which means "neutral, 1:1 light transmission". It's different of filters used in Zenitar-16 and Mir-20M (interestingly, rear filters for Mir20M aren't flat - but Mir-20 can be used with or without them).

[unclemack]

First I would ask the seller to check the bottom of her camera bags for the filter. I've been lucky nearly as many times as I've been unlucky.
If Aoleg would be prepared to measure the thickness of the glass of his filter you should be able to find something which will at least do the job until you can find the correct filters, even if you have to attach it with Blu-tak.
If the infinity adjustment is easily accessible (no idea - I've never even heard of your lens - sorry!) then adjustment should give satisfactory results but of course then you'll find a set of filters the next day!
Not sure anyone actually NEEDS his own weight in lenses anyway...

[Univer]

Hi,

Thanks, everyone, for the replies. I'm actually glad to know that the missing filter is in fact the culprit - although I don't know how realistic it is to think I'll be able to find a replacement. (I will definitely contact the seller, however.)

Blue-tac occurred to me as well; at a minimum, I could temporarily secure the clear Peleng 8mm filter, just to see if there's any improvement.

I also thought I might contact some of the "usual suspects" who deal in Russian lenses, just to see whether someone might be able to locate a spare filter. The fact that the lens seems to be rather uncommon makes me less than optimistic about this option, but I reckon it's worth a try. Would anyone happen to have a specific suggestion for a dealer who might be a likely candidate? (Please feel free to PM if you prefer.)

Thanks again!

Cheers,

Jon

[lahnet]

I have the lens, and can confirm that it is impossible to use without the rear filter.

I been thinking about selling mine, can I ask how much you payed?

[aoleg]