Hi,
I got a Zenitar 50/1.7 which is quiet sharp lens as general. It seem that my copy is extremely soft at apertures until 4. In 4 and above it seems ok. I can see some scratch marks on metals around the front optics so i was wondering that maybe it is opened for cleaning and the optics are wrongly aligned afterwards. Is it possible at all? And is there a way to make correct optics aliment or maybe the lens is for trash.

Thanks!

[Na Horuk]

You can look for signs of decentering, but that is usually not something that is only a problem at some apertures. It doesn't care about aperture.
DCShooter's idea is interesting. Honestly, with old lenses, you never know what kind of history they had, who serviced them, who made mistakes (or even intentional "modifications")
Finally, a lens might just be soft. Yes, it is a little odd that a 50mm lens would be soft up to f4, usually they sharpen up by f2.8 (generally speaking, obviously there are big differences between different lens designs), but it is not impossible. Make sure it is not just DoF and contrast that makes the photo look soft. Problem is that "sharpness" is actually a combination of all sorts of things. If a lens has CA, low contrast, soft colours, then people might perceive it as being softer than another lens, which has the same resolution, but stronger colours and better CA control. I don't know if you have done any methodological tests yet, but do some. Take photos of newspapers or something, near the minimum focus distance.

[Cuthbert]

The zenitar 50mm f1.7 is a sharp lens even wide open, if it's not there's something wrong with that.

These are few shots at f1.7 with my Zenit 19 and Fujipro400:





Are your shots more soft?

@dcshooter I will check that. Good idea!

Here are some examples compared with Samyang 85/1.4:
https://mega.nz/#F!W09WwT5B!3GonCr9gdxyd2k3ssZTNHg
The filenames describes lens and aperture

The focus is between mouse eyes.
PS. download and look pictures in fullscreen to notice real difference

[Na Horuk]

The focus is between mouse eyes.

For the wide open photo it seem that focus is more on the whiskers. This difference is already considered big, when it comes to wide open photos.
But yes, the lens might be a little soft. Are there any filters mounted, is the back element nice and clean? It reminds me of a "bad" 50mm I have (not Zenitar, some other brand), with a UV filter. The effect of that lens and its filter is that it makes everything look like it is glazed over. Using a tight, APSC lens hood already helps.

@Na Horuk Yes it is nice and clean without fungus etc. Of course that it is without filter. But considering other reviews on the internet this lens is very good performer. It is not very expensive one but I like its color rendering and bokeh.

P.S I managed to open the lens. I think that the 3-rd front element was loose and not in correct position. I aligned it and now the IQ is better in my opinion. Yes, i left 1 dust inside, but not a big deal... Check the photos.... All at f1.7
The last photo is a backstage