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When is a scratch important

9designs

Well-Known Member
Just picked up a used 135 F2.8, cleaned up well. When I was checking it in the dealers I noticed a black spec on the rear element, which the dealer cleaned off with a lint free cloth, though I can’t be sure I think it caused a couple of semi-circular marks on the rear element, which you can see if you angle it to the light at the right angle.
Now I know the whole point of CZ lens is the optical quality, but is this likely to be serious. Should I take it back, got it for 139 UK pounds, which is cheap for 135MM.

Thanks
Steve T
 

singlo

Active Member
The likelihood is that they are stain marks from the cloth. Try clean it with lens tissue with a little lens cleaning fluid. If they don't go away, then they are scratch marks. You can point the rear of the lens at a table l& at an oblique angle and look through from the front element. A few fine hair line marks have very little effect on optical quality but it does affect its re-sale value. A used 135 Sonnar costs about 200-270 pounds. So your lens seems quite cheap.
 

9designs

Well-Known Member
It gets worse, tried it out at the weekend and found that it does quite achieve infinite focus, looking at a power pylon a mile or two away the split image didn’t align, it seemed to need a another fraction of a turn to perfectly focus/align. I guess at this range the image would come out fine, but not really the point. I’m disappointed now, so this and the scratches, marks made in the coating from what I can see, means I will return it on Saturday. Shame, as the exterior/grip cleaned up really well.

Steve T
 

spejic

New Member
I think what you are describing is quite normal. The lens has the ability to focus "beyond infinity", which is useful in extreme temperatures. To focus at a distant object you need to turn a little from the stop.
 

9designs

Well-Known Member
No mine is working the other way around, it's not reaching infinity, it's not going past it.
 
T

thomar

Look at the pictures - if they are sharp, its probably a problem with your mirrow. Do you use a split image finder? That is an oldfashioned system. Same applies to the scratches - take a photo, have a look. If the picture is okay, everything is ok. As a rule of thum, a scratch on the front lens is not a big problem, a scratch on a rear element can significantly affect the quality of picture.
 

9designs

Well-Known Member
The scratches were visable from viewing the rear of the lens off the camera, I've returned it know and got a mint condition one for £35 more ;-)
 
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