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07-31-2014, 02:33 PM   #16
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Nice. Can you tell us what aperture did you use? And more important, can you post some 100% crops from the corners?

08-01-2014, 01:12 AM   #17
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Some things to consider when using the 50mm 1:1.2 or any other really fast prime (1.4/1.7 etc.)

Do not use it at 1:1.2, as a general rule of thumb, stop down the fast primes at least one stop.
Why ?

It will reduce the lens aberations significantly.
It will reduce light fallof (although this is generally less of a concern with aps-c sensor and a FF lens)
And in the case of the 1:1.2, it will prevent silly star shapes.

Here are 3 shots of the star Deneb, relatively close to the center of the frame with the K 50mm 1:1.2.
Because I tried to capture the NA nebula (without luck), Deneb is highly overexposed.

IST-D 100% crop


K10D 100% crop


K20D 100% crop


The root cause of these strange square/rectangular shapes are not really clear to me, but are probably caused by the combination of
the anti alias filters and specific pixel/micro lens designs.
The 'V' like distortions are most likely caused by the mirror box, which is too small
See this link
08-04-2014, 01:04 AM   #18
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QuoteOriginally posted by JimmyDranox Quote
Nice. Can you tell us what aperture did you use? And more important, can you post some 100% crops from the corners?
I used f2.0 for these shots.

If you want to see the image at original size, it is on Flickr:
https://www.flickr.com/photos/62460860@N05/14816428463/sizes/o/

But this won't give you fully representative corner shots as the DeepSkyStacker program reduces the picture during re-alignment - causing some of the corners to be lost.
08-04-2014, 04:43 AM   #19
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Thanks. I wanted to see the corners, to see if there is some coma present.

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