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+--- Thread: Sigma's lousy lens and it's ugly diamond-shaped bokeh (50mm f1.4 ART, Canon full frame) (/showthread.php?tid=1447)
Sigma's lousy lens and it's ugly diamond-shaped bokeh (50mm f1.4 ART, Canon full frame) - popo - 07-07-2014
The mirrorbox theory was in response to the clipped bokeh I posted previously, not the original issue.
It is interesting that PSF is bought up, as that's something that is more tangible in astro than the other usual measures. I'm now wondering if the original shapes seen that started this thread are a manifestation of that. The PSF could be relatively spread at a relatively low level, that it takes a high intensity point source (or approximation thereof) to show it. The examples I posted wouldn't account for that. Reminds me of the arguments we had over the Sony SLT mirror again...
As an actual stress test, I could try a long exposure with the Sigma on a tracking mount. For example, I'd normally use a f/2 or f/2.8 lens wide open for up to 4 minute exposures when doing astro. The 5 seconds at f/1.4 test shot previously are nothing compared to that. The only problem is I need a clear and dark sky, so as we're not far past the summer solstice it could be quite some time before I do that.