image quality - How can I test a new lens to make sure it is operating correctly?

How can I test a new lens to make sure it is operating correctly? I found two similar questions with answers specific to things such as sharpness and focus, but I want to cover any and all possible tests for a new lens. What can I check for or do? What specific things do you do when you are inspecting a brand new lens from the manufacturer?

Related:

How can I/should I check the sharpness of my camera lens?

How can I determine if my Sigma 10-20mm lens copy is appropriately sharp and focusing right?

Answer

More than testing you should learn about your new lens. Although it is good to get some sanity checking first:

• Set up a flat target with sharp details that can cover the field-of-view of your lens.


• Set up your camera on a tripod pointing strait at the target.


• Repeatedly autofocus on your target and see if you can improve accuracy by manual focusing. If it is off, then you'll have to micro adjust your lens (see questions on this site)


• Once you got perfect focus, start shooting.


• Take one shot at each aperture from the widest to the one stop beyond the diffraction limit. Say F/1.4 to F/16 on a modern DSLR.


• Make sure each shot is taken with the self-timer and mirror lockup, preferable remote triggered.


• Repeat above steps for various focal lengths from the widest to the longest.


• Repeat all of the above using a blank completely uniform target.

Loot at all those photos and note:

• How does sharpness change from the center to the corners?


• See how the above changes for each aperture.


• How does brightness change from the center to corners?


• Take note of any apertures you would NOT be happy using.


• Take note if there are focal-lengths you would NOT be happy using.

Then comes the subjective part. You need to judge if this is the quality you expect from such a lens. It is normal for lenses to by softer wide-open, some sharpen after 1/2 stop, some after 2. Personally, I find it easy to avoid certain apertures since I work in A-mode 95% of the time but I do not like having to avoid entire focal-lengths.