lens barrel won't focus to infinity mark

[enochRoot]

i just received a lens that when focussed all the way to the left (ie: infinity), the focussing mark doesn't align w/ the center of the infinity mark on the barrel (as with all other lenses that i have owned). the focussing mark aligns w/ the center of the left hand counter on the infinity symbol. i have no idea if this is just the marks being off, or an indication that the lens doesn't focus to infinity.

is this normal? should i trust that it focusses to infinity, and it is just the barrel that is a bit off somehow? is there any way to test it short of focussing on different distances and performing a test on film?

my main concern is that the focus would be off at closer distances. is that how this works? or would it be fine even if it didn't properly focus to infinity? ie: if the images are aligned in the rangefinder...i will have correct focus even if the reading on the barrel is wrong.

finally, what could possibly cause this?

any help would be appreciated. thanks!

 

[hans voralberg]

If it's off in a faulty way that could be because the lens was taken apart and put back wrongly, I did that countless of time with my lens. Why dont you just go waste a roll of film and see what comes out ?

 

[sepiareverb]

At that kind of distance I don't think you'd ever be able to tell, even wide open. DOF would cover you.

 

[ferider]

It really depends on the lens. If the horizontal camera RF alignment at infinity is OK, it is very likely only a cosmetic problem. For example, I got a 90/2 Summicron v2 from a well-know technician/CLA back, and the focus marks were off significantly. Was very easy to correct, since on that lens, the focus ring is just screwed onto the helix mechanism (similar to, say, a Jupiter {3,8,9}).

I had two CV lenses that I got slightly off wrt focus ring, out of the box. Both of them performed accurately though.

Sometimes, it can be a major issue, when it has been caused by incorrect assembly of the focusing helix. But then the RF is off as well, typically.

Roland.

 

[enochRoot]

thanks for the replies guys. i did shoot a roll today and i'll get it developed tomorrow. if there is a problem, i assume it would manifest in the shots? i shot at all apertures including close up and wide open. hopefully if there is a real problem, it would show. or rather, i hope there is no problem.

the thing that gives me pause is the floating element helical within a helical arrangement in this lens. i just wonder if the outer barrel was off by a thread or two (if that is even possible).

i'm also going to try and focus on the moon and see if it will, or if it truly doesn't focus to infinity.

 

[nanthor]

The lens in question

The lens in question

Here's a picture of the lens in question, focused on infinity. Bob.

 

[David Murphy]

The lens needs to be checked by a professional. This is a common fault, but it can have several causes.