02-11-2012, 01:50 PM
[quote name='photonius' timestamp='1328873448' post='15777']
Good point, the inaccuracy (on APS-C, I have Canon) could be anywhere, also in the mount. The distance the lens moves from 0.3 meters to infinity is about 0.5mm,
see http://michel.thoby.free.fr/SAMYANG/Samyang_shaved.jpg
On my lens, when set to infinity, the actual focus was more like 2 meters instead of "infinity", i.e. >10m. Thus, the extension difference from 2 or 3 meters to infinity is a minuscule extension. Any inaccuracies in the focus scale may therefore be also tolerances within the lens mount or the sensor placement. I'll have a look on an older body, and see how it compares.
[/quote]
The verdict is in. Just tried my Samyang 8mm on the old 400D (on which I took most pictures). After having the Samyang calibrated to the 550D, I put it now back to the 400D. The lower resolution of the 400D gives not such a precise answer, but the result is still clear. When set at infinity (at f3.5), tree branches at about 10m distance are less sharp than when the lens is set to 1 meter!
This lens is very sensitive to minute variations in sensor-lens mount distances.
Good point, the inaccuracy (on APS-C, I have Canon) could be anywhere, also in the mount. The distance the lens moves from 0.3 meters to infinity is about 0.5mm,
see http://michel.thoby.free.fr/SAMYANG/Samyang_shaved.jpg
On my lens, when set to infinity, the actual focus was more like 2 meters instead of "infinity", i.e. >10m. Thus, the extension difference from 2 or 3 meters to infinity is a minuscule extension. Any inaccuracies in the focus scale may therefore be also tolerances within the lens mount or the sensor placement. I'll have a look on an older body, and see how it compares.
[/quote]
The verdict is in. Just tried my Samyang 8mm on the old 400D (on which I took most pictures). After having the Samyang calibrated to the 550D, I put it now back to the 400D. The lower resolution of the 400D gives not such a precise answer, but the result is still clear. When set at infinity (at f3.5), tree branches at about 10m distance are less sharp than when the lens is set to 1 meter!
This lens is very sensitive to minute variations in sensor-lens mount distances.