TimWildAstro Offline Upload & Sell: Off
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NatDeroxL7 wrote:
I had a good overnight recently where I got to try my 12-24 on some stars. I did like it better than my previous Sigma 14-24 DG DN. Slightly less coma and little less fringing on the stars. 12mm also adds a little extra dynamic to the scene with a incrementally larger expanse of sky. However, 12mm also makes it very obvious when objects are near the edge of the frame and show perspective distortion from an un-level camera. Had to be extra careful to avoid this.
Got some cloud cover initially (below, still kind looks cool) but eventually I got a clear window.
I forgot to turn off the in camera vignetting correction on my second camera body and unfortunately that one ended up being used for the 12-24 GM so it has the red color shift rings issue....ugh. Was correctable to an extent, and I fixed the issue so next time both cameras are properly set to mitigate this issue as much as possible. its hard to make a perfect master flat frame @ 12-18mm to fix this, especially at higher apertures because the DOF makes details come out AND its very hard to achieve perfectly even illumination. Still working on finding a solution for that. This would hopefully provide total rectification of this issue for critical images using Adobe 'flat field' correction. I may go full-astro mode and buy a flat frame LED light setup.
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Interestingly the red colour ring issue is worse with the shading correction turned off with the 12-24GM. I've always used all corrections off for astro, with all lenses, but something is seemingly baked into the files with the 12-24GM regardless of corrections on vs off (other Sony lenses reportedly do this too, including the 20mm f1.8). It's fairly pronounced at 12mm, a little better at 13mm, and not too bad by 14mm. You'll only see it when pushing files fairly heavily though. I do wonder if covering the lens contacts would stop this happening...
I've finally managed to do an in-depth comparison of the 12-24GM vs the Sigma 14-24 DG DN for Milky Way images, and star shape is better on the Sigma at the wide end; stars are round corner to corner whereas they lose shape in some areas of the frame with the Sony (if corners are focused for round stars, some mid-field stars are slightly stretched, and vice versa). The GM is still superb for astro, but the Sigma 14-24 really is a monster at the wide end. Slightly better light transmission with the Sony, but the 'ring issue' and the mild star deformation is enough to put it behind the Sigma for astro. I didn't expect to be writing that, having owned the Sigma for a while but recently 'upgrading' to the Sony. I'll be keeping both as I shoot both at once. 12mm is nice for Milky Way timelapses too.
Both are staggeringly good overall.
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