how to I recognize a bad copy of a lens ?

[Antonio Correia]

Please admin remove this thread if it is not the right place to post. Thank you.
-
I want to buy a RX100 VII for my wife. A previous RX model was used with great success.
Now that I read in dpreview that one must be aware of copy variations I would like to ask you how do I detect this problem.
Thank you so much !
Have a nice Sunday and... take care.
Cheers !

Subscribe to see EXIF info for this image (if available)

Subscribe to see EXIF info for this image (if available)

 

[Antonio Correia]

OK, OK I got it !
Let me rephrase: how to I recognize a bad copy of a lens ?

 

[bdbits]

Here's a good general post on camera/lens variation on the excellent Lens Rentals blog.

https://www.lensrentals.com/blog/2011/10/notes-on-lens-and-camera-variation/

People most often complain about decentering/tilt of lens elements. Fred Miranda came up with a test I have used from time to time. It is very easy and pretty quick to do.
https://www.fredmiranda.com/forum/topic/1534737/

Apart from that, find a subject you know well and take a lot of pictures at different apertures, then pull them up in your favorite viewer or editor. Just be aware that pretty much all lenses have some variation, and a lot of the times you won't even see any weaknesses unless you are pixel peeping (viewing at 100%).

 

[Antonio Correia]

Excellent Bob ! Thank you !
Great help !
Never had any problems - as much as I can see and I am a pixel peeping guy - with the superbs 24 and 135

 

[Petrochemist]

If it's a really bad copy of a lens it will probably be quite easy to spot. I have a few that fall into this class, as well as several I expected to be poor examples that turned out to be work respectably well - a chunk missing from the front element being completely hidden in the images both the lenses produce.

Slightly poor examples of a lens can be much more difficult & will often be assumed to be a case of a poor lens. I suppose there may be rare examples the other way round where a particularly good example of a generally poor lens is found. I'm sure I've come across both of these in lens reviews!

 

[serhan]

I didn't know that RX100 VII has copy variations... It was a surprise for me. I have VI, bought as lightly used and had no problems... It has very sharp lens. I had more problems with Panasonic P&S's and 1 Canon P&S... I went and shot different shots and found some problems with one side... You can also check the FM link for decentering at Bob's post...

 

[Petrochemist]

I didn't know that RX100 VII has copy variations... It was a surprise for me. I have VI, bought as lightly used and had no problems... It has very sharp lens. I had more problems with Panasonic P&S's and 1 Canon P&S... I went and shot different shots and found some problems with one side... You can also check the FM link for decentering at Bob's post...

Every lens has copy variations. It's simply not possible to manufacture things to be EXACTLY identical.
How much examples vary will in part be down to the quality control at manufacture, but with used lenses will also be combined with how the lens has been abused.