Leica APO-Summicron-SL 35 mm f/2 ASPH.
8. Vignetting
Panasonic also has been developing two systems, the L-mount and the Micro 4/3; still they are not compatible with each other so lenses designed for one system cannot be attached to the other system cameras. In case of Leica the situation is different. SL lenses can be attached both to full frame bodies and to a bit older APS-C models such as the Leica T, TL, TL2, or CL. Still, we would like to approach all L-mount devices in the same way so we are going to examine vignetting (and also distortion) only for a full frame detector.
As you could notice in previous chapters the data obtained on the edge of the APS-C/DX sensor are left for resolution and chromatic aberration measurements. In these cases it was important because it provides additional piece of information about the layout of sharpness and chromatic aberration across the whole analysed frame.
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First, let's deal with vignetting observed for uncorrected JPEG files.
| S1R II, FF, JPEG, f/2.0 | S1R II, FF, JPEG, f/2.8 |
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| S1R II, FF, JPEG, f/4.0 | S1R II, FF, JPEG, f/5.6 |
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Huge dimensions of Leica allow it to produce a quite sensible performance in this category. At the maximum relative aperture the brightness loss in the very corner of the frame amounts to 42% (-1.58 EV). The fact that vignetting drops very quickly on stopping down also should be praised. By f/2.8 you deal with a moderate value of 26% (-0.88 EV) and by f/4.0 the level of this aberration becomes low, with results of 18% (-0.59 EV). Further stopping down doesn't provide any measurable effects.
As a kind of bonus, we would like to present vignetting results for uncorrected RAW files as they feature a tad wider field of view than JPEG files.
| S1R II, FF, RAW, f/2.0 | S1R II, FF, RAW, f/2.8 |
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| S1R II, FF, RAW, f/4.0 | S1R II, FF, RAW, f/5.6 |
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In this case at the maximum relative aperture the brightness loss in frame corners reaches 48% (-1.90 EV) and it decreases to 33% (-1.16 EV) on stopping down the aperture to f/2.8. Applying f/4.0 aperture makes this aberration decrease to a value of 25% (-0.83 EV), and further stopping down doesn't provide any meaningful changes.
| Panasonic S1R II, JPEG, 35 mm, f/2.0 |
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