Originally posted by Wheatfield What makes you decide a lens is worth keeping?
If it does something no other of my lenses do, it's a keeper.
Originally posted by Wheatfield What makes you decide that a lens is junk?
For example, if a lens has good bokeh, but can be forced to show CA/PF, will you keep it for the bokeh or get rid of it for the fringing?
- CA/PF are easily correctable in software (at least with Lightroom it's a breeze) so I don't care too much for that. I've corrected huge CA on DA 12-24 and especially the Tamron 18-250 (which I sold but not for these reason).
- Distortions are a bit more bothering because the current LR doesn't support corrections (but it's going to change with LR 3). Most normal zooms have heavy distortions at the wide end. My DA*16-50mm has certainly too much at 16mm. The
DA 21mm is also an offender. Fortunately it's not concerning on every shot.
- Bokeh cannot be corrected at least not without strong PP (or some specialized plug-ins like Alien Bokeh). I've not enough experience with Bokeh to reject or keep a lens but I can see that my FA77 and FA50 produce nice things in that domain. My DA 55-300mm is awful IMHO unless you put the background completely OOF.
- Flare resistance is very important to me. That's why I consider the DA 15mm even when my DA 12-24mm cover this range particularly well already.
- Vignetting is quite OK. It was only bothering on my old Tamron 18-250mm. It's also easy to correct.
- Sharpness is probably the most important feature of a lens, especially on digital. So if a lens cannot be sharp, it's almost useless. I sold my FA 80-320mm due to its very poor performance at 320mm wide open. It was "junk" at that setting.
BTW, there is a nice article by Thom Hogan about what matters most in a lens:
Qualities to look for in a lens.