The word "such" was used as the focus target. The angle and distance
are such that the other phrase were are less than a centimeter
different in distance, and presenting both in the snippets allows me
to see whether I focused in front of or behind the primary focusing
target.
Godfrey
On Sep 5, 2005, at 4:24 AM, Paul Stenquist wrote:
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.
