10-09-2011, 01:03 PM
Ooh, thanks for the link to "facts" as I didn't notice that one before, only the older "myths".
On a similar note, I've recently observed a degradation I've not determined the source of yet. Too many new variables. I have a modified 450D with the IR block filter replaced with clear filter. In my testing so far, I've found that using it with a fast lens and additional in body filter, the focus varies across the image. If I focus one part, another is out. The shape looks like something is off axis (tilted), not field curvature which I don't think the lens used has anyway. I wonder what impact a non-parallel filter would have placed between lens rear and sensor as that is my prime suspect at the moment. That is, the filter is not parallel to the sensor, but the filter itself I would assume has flat parallel surfaces. Note this isn't noticeable in normal photography, but I'm using it for astrophotography when it is more obvious when pin points of light are not. I think pixel peeping is more valid here...
On a similar note, I've recently observed a degradation I've not determined the source of yet. Too many new variables. I have a modified 450D with the IR block filter replaced with clear filter. In my testing so far, I've found that using it with a fast lens and additional in body filter, the focus varies across the image. If I focus one part, another is out. The shape looks like something is off axis (tilted), not field curvature which I don't think the lens used has anyway. I wonder what impact a non-parallel filter would have placed between lens rear and sensor as that is my prime suspect at the moment. That is, the filter is not parallel to the sensor, but the filter itself I would assume has flat parallel surfaces. Note this isn't noticeable in normal photography, but I'm using it for astrophotography when it is more obvious when pin points of light are not. I think pixel peeping is more valid here...
<a class="bbc_url" href="http://snowporing.deviantart.com/">dA</a> Canon 7D2, 7D, 5D2, 600D, 450D, 300D IR modified, 1D, EF-S 10-18, 15-85, EF 35/2, 85/1.8, 135/2, 70-300L, 100-400L, MP-E65, Zeiss 2/50, Sigma 150 macro, 120-300/2.8, Samyang 8mm fisheye, Olympus E-P1, Panasonic 20/1.7, Sony HX9V, Fuji X100.