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Sigma 24 70 2.8 sony stabilization1/10/2024 ![]() The bokeh is the aesthetic quality of the blur produced in the out-of-focus areas of an image. As you can see the CA pixel width exceeds 4px at 24mm and it's not much better at 70mm. However, as an exception to the rule, we'd like to show you the corner CAs this time. Normally we don't really bother you with the CAs in the image corners because even more charts don't produce more clarity about what's really important. They aren't quite as pronounced in the middle zoom range.Ĭhromatic Aberrations (CAs). This will be visible unless you deal with CAs during post-processing. The average CA pixel width vary around 2px at 24mm and 70mm. Lateral chromatic aberrations (color shadows at the image borders) are fairly high for such a high-priced lens. The border quality is good here whereas the corners continue to struggle on rather low levels. However, once again things aren't quite as good at 70mm. The 35mm and 50mm settings show no obvious weaknesses with just minor drops at f/2.8. Stopping down to f/4 helps, again, and the quality is really nice from f/5.6 to f/11. The extreme corner weakness at 24mm f/2.8 remains albeit the borders are at least acceptable here. This doesn't mean that all is good though. Many users are still using cameras with a more moderate pixel count so let's have a look how the lens performs with the eased requirements at 21 megapixels - also in order to be able to compare the results to older reviews.Īs usual, the results are "better" on pixel level because of the lower pixel density that just can't grasp that much detail. Generally, we are also using a certain degree of sharpening during the image conversion (just like in real life images) and because the 21mp results are "sharper" on pixel level they are relatively more receptive to (mild base-) sharpening. Extreme CAs that may exist at 50mp are therefore less affecting the measurements at 21mp. Lateral CAs are lower in terms of pixel widths at 21mp simply because the pixel density is also lower. MTF (resolution) at 21 megapixels Why are the MTF numbers sometimes "better" on 21 megapixels compared to 50 megapixels ? There are two reasons for this. If you want to know more about the MTF50 figures you may check out the corresponding Imatest Explanations The chart shows line widths per picture height (LW/PH) which can be taken as a measure for sharpness. Please note that the MTF results are not directly comparable across the different systems!īelow is a simplified summary of the formal findings. ![]() The centering quality of the tested sample was good. the borders/corners are showing their misery again and they don't really get much better when stopping down - which is disappointing. The corners are still not great here at large apertures but the results are very sharp from f/5.6 onward till diffraction impacts the quality beyond f/11. The border/corner issue is slightly improved at 35mm and, more so, at 50mm which is the sweet spot in the zoom range. On the positive side, the quality is pretty good between f/5.6 and f/8 here. At 24mm f/2.8, the worst spot of the lens, there isn't much in it at the borders/corners. this trend didn't hold in the outer image region. That's throughout the zoom range and quite an achievement in this lens class. Let start with the positives - the broader center zone is very good at f/2.8 and excellent at medium aperture settings. Note: 50mp are still a killer for most lenses. ![]() At 50mp, it gave us a wild ride from the deepest depth of our quality scale up to the near maximum. Well, you can't state that the Sigma 24-70mm f/2.8 HSM DG OS ART didn't entertain us regarding its resolution characteristic. The vignetting is substantially reduced at f/4 and pretty much gone from f/5.6 here. The light falloff increases again at the far end with a max. Vignetting is a lesser issue in the middle range. Even so, you will still be able to spot traces of vignetting in critical scenes. Stopping down to f/4 helps but it's more acceptable from f/5.6 onward. ![]() The light falloff is worst at 2.5 EV (f-stops) at the 24mm setting - this is clearly visible. The vignetting analysis didn't reveal any special surprises. ![]()
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