My big Dilemma, keep Sigma 35 after buying Nikon 18-35g?

Started 6 months ago | Discussions thread
wisep01
Contributing MemberPosts: 913
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Re: You're forgetting one thing...
In reply to Sloepoke, 6 months ago

Sloepoke wrote:

Modern Nikon zooms, like the DX 17-55 and the FX 24-70 have an extremely curved focal plane.

You can see this also in your shots even though they were taken @ f/8. Look at the text 'poems' in the background (cupboard/closet?), in the picture just above the book you indicated where the Nikon is better. In the background the Sigma is better.

Apparently the Sigma has a flatter focal plane. Or the alignment of the lenses are different, hard to say @ f/8.

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Philip

You're right about the fields being different. I did another test at 4.5 and 5.6. Both lenses showed sharpness in different areas but the nikon was better at the extreme front edges, reading the dvd covers, just like in this f8 image. But both were about as sharp as eachother at 5.6 down, 4.5 the sigma won, but like I said I rarely ever shoot wider than 5.6. I guess some real world testing in various distances and apertures would be the next step.

I'm surprised at how close the images are, but it would be premature to draw any conclusions from the supplied pair of images unless it was  obtained using contrast-detect autofocus.

Phase detect has notorious inter-shot focusing variability, and you probably would need to average at least 10 shots (by using a layer stack in photoshop) and accounting for any meaningless outliers, before drawing any conclusions regarding sharpness.

Focus shift is also a matter of real-world interest. Does the sigma 35 undergo focus shift more than the 18-35mm lens.

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