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Yashica ML 28-85

FireBirder 1:17am, 29 December 2011
I recently acquired a Yashica ML 28-85/3.5-4.5, and I'm loving it. It's as sharp as a prime, and a really sweet lens. However, I have a question, as I've discovered something odd about it; I'm not sure if this is typical of old zooms or if something is wacky with my copy.

When set to 85mm, the focusing scale is dead on; infinity is infinity, and 6' is 6'. However, as I zoom wider, infinity shifts closer so that by the time I'm at 28mm, I'm focusing to infinity at about the 10' mark on the distance scale. What I find interesting is that 28mm actually seems to line up pretty well with the R line on the distance scale. Very odd.

As far as I am aware, this lens is not a varifocal design, and I'm surprised to see such a great change in focus as I zoom. As I mentioned, the lens is in great shape and is incredibly sharp, so I don't see that it was damaged in any way. But I just find this very...odd. Maybe it is perfectly normal though, so I thought I'd check and see if any of you who have more experience than I can offer some suggestions. Thanks in advance!
headlights2 Posted 6 years ago. Edited by headlights2 (member) 6 years ago
Perhaps check on this guy: www.flickr.com/photos/santapolero/sets/72157623011767682/

At least then you know or it is your copy or it is 'normal' for that lens. (seems weird to me though)

Perhaps also check at the yashica forum: www.yashicaforum.com/

I have a read a post by a Zeiss lover with tons of ML lenses who did state that of the ML lenses the 1.7 and the 28-85 are exellent. Come damm close to his Zeiss onces.
FireBirder 6 years ago
Thanks headlights. I just posted this on the Yashica Forum too. I've never owned a Zeiss to compare with this one, but it sure is a great lens.
FireBirder 6 years ago
Just as an update, I had the opportunity to inspect another copy of the Yashica; it too had the same issue. Interestingly, the difference was much more pronounced in the second lens; infinity focus was at the minimum focus mark. So, this leads me to conclude that this may be a fairly common fault, probably the result of aging, for this lens. I plan to tinker around with my lens a bit, and see if there is a way to adjust the focus on the 28mm end--although I still cannot fathom how it is mechanically possible for 85mm to be correct while 28mm is not.
headlights2 5 years ago
Perhaps i did found the answer to your question:

www.kyphoto.com/classics/kironlens.html
transiently permanent 5 years ago
I suspect it's a varifocal design - a zoom which doesn't hold its focus throughout the range. Most manual focus zooms were designed to be parfocal for convenience, but there were several exceptions.

With the advent of autofocus, it became normal for zooms to be varifocal.
headlights2 5 years ago
@OP I did fount also this. Might be of intereset for you

www.yashicaforum.com/viewtopic.php?f=6&t=6922
FireBirder 5 years ago
Thanks. Although, I happen to be the one who started that thread with this same question. ;-)
headlights2 Posted 5 years ago. Edited by headlights2 (member) 5 years ago
At the bottum they seem to have solved it?
"
Under the rubber grip, take out the little screws and unscrew the helicoid. Then put it back together on the next more clockwise, or anti-clockwise groove in the helicoid and see if it is any better. I do believe that it is the front helicoid, causing the front elements to focus, that compensates for the focus shift when zooming."
FireBirder 5 years ago
No, that only allows you to adjust the focusing helicoid relative to the focusing ring; that is, you can set infinity to be correct for 85mm OR for 28mm, but it doesn't correct for the variation between the two. Basically, I can set the lens up to work correctly at either 28mm or 85mm, but depending on how "off" the lens is, it can change drastically when you zoom to another length. On my copy of the lens the difference is noticeable but not bothersome; on the other I tried, the difference is enough to make the lens hardly useable.

At this point, as far as I can tell the cause of the problem must be some other part of the lens that is out of alinement. It is certainly possible that the lens could be varifocal, but that still doesn't explain why two copies of the lens are so different in the amount of focus variation. I haven't found any documentation on this problem or how to fix it, so the mystery remains unsolved...
FireBirder Posted 5 years ago. Edited by FireBirder (member) 5 years ago
One option I am considering is modifying the lens so that the focusing ring will adjust the helicoid without the usual limits at infinity or minimum focusing distance--I would still need hard stops to keep the front element from entirely unscrewing out of the lens, of course, but the idea would be to modify it to something similar to the Vivitar S1 28-90. This would bypass the focus shift issue entirely, allowing me to set a hard infinity for 85mm, then I can rotate focus as closely as I want to when I zoom to shorter lengths. I now have three copies of this lens, one of which is a fungus-ridden monstrosity that I was given which will make a fine cadaver for experimentation like this.
headlights2 Posted 5 years ago. Edited by headlights2 (member) 5 years ago
Sounds good. Good luck with testing on the fungus copy. Keep us posted. (btw still eager to see that 50/1.2 review ;-)
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