My only quibble with this test would be that the two snippets are not
equidistant from the lens. What was your focal point?
On Sep 5, 2005, at 5:51 AM, Godfrey DiGiorgi wrote:
Shel,
Here's the whole scene, with the two target snips highlighted in red:
http://homepage.mac.com/godders/test-target-6489.jpg
(This exposure was made with the F50/1.7 - focused by eye.)
The camera was set up 23' from the target (not 10' ... I've measured
the distance accurately now).
The "U-Haul * Med" letting in its snippet is four inches long.
The "Such" lettering in its snippet is one and five-eighths inches
long.
The snippets on the test result page
http://homepage.mac.com/godders/50mm-focus-snips.jpg
are pixel for pixel, with no scaling.
Normally I'd use newsprint at 10x focal length, but Don's test shots
were made from a great deal longer distance and I was curious about
focusing accuracy at greater distance. There was too much wind today
to shoot trees and leaves, I wanted a motionless target. So this test
is at about 140x focal length.
BTW:
I went back and examined the exposure data for each pair of snippets.
From top to bottom:
lens - aperture - shutter - exp mode
F50/1.7 - f1.7 - 1/320 - Av (AF)
F50/1.7 - f1.7 - 1/320 - Av (eye)
F50/1.7 - f1.7 - 1/320 - Av (mag)
A50/1.4 - f1.4 - 1/640 - Av (eye)
A50/1.4 - f1.4 - 1/640 - Av (mag)
K50/1.4 - f1.4 - 1/640 - M (eye)
K50/1.4 - f1.4 - 1/640 - M (mag)
A50/1.7 - f1.7 - 1/500 - Av (eye)
A50/1.7 - f1.7 - 1/500 - Av (mag)
A50/2.0 - f2.0 - 1/400 - Av (eye)
A50/2.0 - f2.0 - 1/400 - Av (mag)
It's curious that the DS exposure meter (on Av mode with EV
Compensation set to +0.3) underexposed with all the A lenses relative
to the F lens setting (for the K lens, exposure was manually set to be
identical to the exposure for the A50/1.4). The light was very
constant over the 8-10 minutes it took to make the test exposures. It
explains to some degree why the F50/1.7 looks a bit more contrasty
than the others.
Godfrey
On Sep 4, 2005, at 7:55 PM, Shel Belinkoff wrote:
How tall is the text on the u-haul boxes?
I've done lens comparison tests with several 50mm lenses, and never
have I
gotten such poor results. However, the subject was different and the
lenses were mounted on manual focus film bodies, so the results may
not
translate fairly.
I'm returning the DS as soon as I can, but I'd like to do a similar
test
before returning the camera.
I set up the tripod and DS body on my porch, used a set of U-Haul
moving boxes (for their printed matter) at about 10' distance as a
focusing target.
