D500+samyang 135mm Optics advise

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Okky New Member • Posts: 21
D500+samyang 135mm Optics advise

Dear friends,

I need advise on my new purchase. I bought a new Samyang 135mm f.2 lens for my D500. I bought this lens to make a start with astrophotography as a beginner.

I have questions about the optics of my new lens. The situation is that I have 2 copies cause I had my doubts with the first copy.

I did use the following chart for my test http://www.graphics.cornell.edu/~westin/misc/res-chart.html

Focus in the middle:

Sharpness in center seems the same for copy 1 and 2. If I look to the corners then the corners of both copies are less then in the middle. 2 corners of copy 1 are noticeably sharper then copy 2. Other corners are more even with an slightly edge for copy 1.

I also notice a very light colour (seems purple) in the middle and corners of copy 2.

Focus on right down corner:

This time I focused on the right down corner. The corner of copy 1 is sharper. BUT I am very surprised to see that the center of copy 1 is blurry and copy 2 is sharp?!

The remaining corners is slightly sharper on copy 2 (not logical). Copy 1 seems to have a light green colour on the corners. Copy 2 seems to have light purple colour.

Which copy I should keep or is both not normal? I did read on the internet that is very normal that when focus on center the corners are less sharp.

Thank you

 Okky's gear list:Okky's gear list
Nikon D500 Nikon AF-S DX Nikkor 35mm F1.8G Tokina AT-X Pro 100mm f/2.8 Macro Nikon 200-500mm F5.6E ED VR Samyang 135mm F2.0
Nikon D500
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