Lens sharpness test

[i120D]

I am now considering to get a wide angle, can please enlighten how usualy do you do the testing to check on the sharpness at center and edges?
do we...
- take some shots focusing near/far?
- focusing at flat surface/normal?
- or what other test do you do?


thanks

[jdredd]

if its one of the common wide agnles, theres probably a lot more scientific testing done by the testing websites that u can refer to.

but if u do need to test... its best to do it indoors because u have 100% control over lighting.. if u see DP review, they set up a umber of different items on a table and shoot that..

some people use newspaper taped to the wal.

the importnt things to note -

tripod mount the camera.
use mirror lock up/ cable release if u have it.
take 2 or 3 exposures at each shutter/aperture setting and choose the best one , to eliminate any misfocused shots. this ensures u ahve the best picture at each point of comparison.
the normal comparisons are normally made wide open, mid focal length and maximum focal length (assuming its a zoom).
for F stops, again, compare wide open, one more at F5.6 or F8, and another say at F11 or F16.

[i120D]

what if it's at the camera shop testing a lens before buying, will not have the luxury for the detailed setup.
any fast method to check for a sharp copy?

[jdredd]

well, nothing to prevent you taking ur laptop and tripod there and just shooting off a few test shots..

but of course, i wouldnt recommend u being one of those kiasu types that ask to open 5 new lenses, test everyone and pick the sharpest..

[pokiemon]

if u r testing a lens at a shop, what i normally do is to rest the camera on the table (instead of tripod) and take pictures of a test subject (in this i would use the lens box where there are words) at different apertures, with and without flash. then zoom in to the corners and center of the picture to check for sharpness of the letters. i guess u have to find a method that works for u.

[i120D]

Originally Posted by pokiemon if u r testing a lens at a shop, what i normally do is to rest the camera on the table (instead of tripod) and take pictures of a test subject (in this i would use the lens box where there are words) at different apertures, with and without flash. then zoom in to the corners and center of the picture to check for sharpness of the letters. i guess u have to find a method that works for u.

mmm.... simple and straight to the point answer....
Thanks very much for your sharing. this is really a helpful tips.
btw, can i say that the sharpness will not be much affected by the distance of subject? (depends mainly on location of subject appear on image, right?)

[smallaperture]

Originally Posted by jdredd well, nothing to prevent you taking ur laptop and tripod there and just shooting off a few test shots.. but of course, i wouldnt recommend u being one of those kiasu types that ask to open 5 new lenses, test everyone and pick the sharpest..

Dunno if there is any shop here that stocks up to 5 new lenses of the same mount for you to test and choose. For less common lenses, you'll be lucky to get one for the mount you want. In general, the usual shops would have a copy each in EF and NAF mount.

[EdOkH]

I went once with my friend to buy the sigma 18-50 f 2.8. What he does is to manually set the aperture to 2.8 and take a snap shot at both the wide and tele end.
Repeat the process with a f5.6.

Download it to ur laptop and compare the 4 shots. These should do...

Hope this helps...

[smallaperture]

With a D200, you dun even need a notebook to test. Can view 100% straightaway - this is instant gratification.