I think the best thing to do is to take pictures like you will
actually be taking in real life. Test pictures of brick walls,
newsprint, dollar bills… are fine and good for nitpicking
lenses and academic studies but I have found that they rarely tell
enough of the story to make any sort of decision. The lens tests
that I have done that I have actually found useful were along these
lines. Take the lens out for the day, use it exactly how you plan
to be using it most of the time. Take lots of pictures in as many
different situations as you can come up with. When you review the
pictures at the end of the day see how happy you are with them.
The next day take lens #2 out and do the same thing. Testing like
this not only tells you useful information about the image quality
that the lens is producing but it tells you very important
information about how the lens handles.
For instance, a while back I purchased an EF 100-300mm f/5.6L. I
did the usual testing in the house with test targets in controlled
lighting with MLU and the whole nine yards. The image quality
looked great and the lens really looked like a keeper to me. That
weekend I took the lens with me to the renaissance festival. I
found that the lens creep with that lens got very annoying while I
was carrying the lens mounted on my 10D. I also missed lots of
shots of the falconry demonstration and some of the jousting and
sword fighting because the autofocus was so darn slow. When that
lens hunts it takes a long time for it to rack all the way in and
back out. After a few more outings like that one I decided that
the lens was not for me, despite its excellent image quality.
When I got my 70-300 DO and did my controlled testing with it, I
found it to be a bit disappointing in the optical quality
department. I am not saying that the lens was bad but just not
quite up to my expectations, which were admittedly pretty high. If
I had just done that testing I would have shipped the lens back
right away in total disappointment. When I did my real world
testing I discovered a lot more about the lens that I really liked.
The AF speed, IS and general feel of the lens were very good. This
made my decision to keep or return the lens a much more difficult
one. The final clincher for me was that in certain lighting
conditions I got the “dreaminess.” I think you
probably can remember the dragonfly picture (and there were many
others that had similar results). For the type of shooting that I
do I use 300mm and f/5.6 quite a bit and am frequently shooting
under the type of conditions that yield the dreamy effect. For
others this isn’t a problem because they aren’t using
these settings under these conditions as frequently as I do.
I hope this makes some sort of sense and is helpful.
Greg
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