Testing Lenses

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rabaroo

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Hi - I have a couple of lenses and will be getting a couple more soon - I'd like to do some comparison testing of them to see how they rate, though in reality this is all new to me and i have no idea how to do it

can anyone explain a good way of testing various lenses side by side... my initial thought was to mount camera on my tripod, have an item to take a pic of, and snap throughout the zoom ranges on each lens, and at various apertures at each focal length.....

anyone recommend anything better?

FYI current lenses are (450D Cam):
18-55 IS Kit
55-250 IS

Soon to be added are:
28-105 (3.5-4.5)
50 (1.8)

... i would prefer to do the test of teh lenses i have now and then do the same test when i get the others, but guessing that may make the test invalid due to positioning and light levels etc?

Thoughts or suggestions? - if only of what object to take pics of, there'll be lots - and i'd rather do this indoors given the declining weather :-)
 
These tests are notoriously difficult to do and unless they're set up very accurately, they're pretty well meaningless and can give you a very false impression of the performance of a lens.

If you really want to test though, then a sheet of newsprint will enable you to do the two tests you really need to do.

Test one for focus accuracy can be done just by focusing on a single line of print an angle of about 45 degs with a large aperture, to see if there's any tendency for the lens to front or back focus.

Test Two for overall sharpness can be done by photographing the sheet of newsprint at 90 degs, to see if there's any fall off in sharpness towards the edges.

This latter test really needs to be set up with great accuracy or it's really meaningless. Keeping the paper dead flat and the camera accurately positioned in relation to the paper in both the horizontal and vertical planes is extremely difficult. An old fashioned copy stand would be your best bet, but no-one seems to use them these days.
 
The problem with testing lenses is that most often the test image is a newspaper or some equally flat surface.

Normal (non-macro that is) lenses do not provide their best image quality when photographing a flat field image.

I would shoot "normal" imagery which would duplicate the types of images that you will shoot day-to-day.

See if your lenses do well. Don't worry too much about pixel peeking. BTW: Recent medical tests have discovered that pixel peeping causes baldness and impotence.
 
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