Advice on lens sharpness

On 2006-10-22 13:29:19 -0400, "
said:

Hi,

Came into a bit of money and thought that I would update my EOS350D with an
L lens. Always wanted one of these since I have a 50E many moons ago. Did
a bit of research and purchased a 24-105 F4 L. I just wanted the best
walkabout lens that I could afford that wwas not too heavy, this seemed to
fit the bill.

Got it, did the usual photographed some walls and compared the output with
that of the standard efs 17-55.

See the RAW samples here, I may be expecting too much, I don;t know, but the
difference to my eye does not warrant the expense that I paid for the L
lens. Can someone explain if there is more to it or am I just being
paranoid. To my mind the image is no sharper on the L lens.

Anyway the two raw files in canon format are at www.ukbrown.net/rawtest

Tough to tell at this resolution and magnification,. First, you have
shot a close up with a very shallow depth of field. So the eye gets
fooled. There is a very small plan of sharpness with much out of focus
becauese ot he aperature and distance to subject.


If you want to do a sharpness test, use a copy stand and shoot a flat
subject with fine lines at close range. Light it well to remove all
effects of noise etc. Keep the camera film (or sensor) absolutely
parellel to the subject. Hold the subject as flat as possible. Use a
remote release and mirror lockup if available.. Only then do you
remove enough of the other variables to really see what the lens is
doing.

Don't shoot pictures like that all the time? Then, I believe, your
conclusions are correct. Many great photos were taken with lenses of
much less quality than even some of today's mediocre lenses.


Jim