Sigma SD1 sample photos

Started Jun 26, 2011 | Discussions thread
rf-design Regular Member • Posts: 490
Re: Sigma SD1 vs Canon 5D Mark II (landscape)

Very useful comparison.

The lens for the 5DMKII should be a 24-70/2.8. That match the 17-50/2.8 lens of the SD1.

The aperture should be set to 5.6 at the APS-C and 8.0 at the FF to be geometric equivalent. The effect that the aperture for the highest resolution of the lens shift starting from lower values around 4.0 for high quality 3/4 lenses to about 5.6 for APS-C and about 8.0 for FF up to about 11 for MF and higher for large format lenses has to do with the geometrical precision of the construction. This is not equal to mechanical tolerances because of the lens manufacturing and assembly. An optical construction increases the resolution with increase in aperture value up to the point where diffraction takes place. The diffraction is not tight to any lens geometry. So the crossing point where the maximum resolution appears shift up in aperture value with the absolute dimension of the lens.

So that is the reason to compare a APS-C lens at 5.6 with a FF lens at 8.0

But! Because of additional mechanical tolerances every misalignment of manufacturing tolerance have about 1.5 more impact on a APS-C lens. So in practice a fair comparison would be between 0 and 1 stop more for the FF lens.

Beside this I could clearly see that the pixel level contrast is significant higher for the SD1. That lead to the obvious effect that you could see staircases on the edges of the bridge frames. The 5DMKII does not show sharp staircases at 100% on the screen.

Now if you upscale the SD1 image by 200% ( I done this in Xnview) the image is significant more sharp w/o staircases at 50% in comparison to 100% for the 5DMKII.

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