jpb@pdx
21-35 Comparison
Comparison of the center versus corner performance of the Leica Vario-Elmar-R 21-35 f/3.5-4 with a Metabones Speed Booster on a Sony NEX-3. Both images at 15mm f/2.9 (the lens was set to 21mm f/3.5). Left image is crop of extreme corner; right image is crop of center. Both images were focused using the 14x live view focus aid. The corner crop was taken at a focus distance of approximately 8 feet, while the center crop was taken at just to the side of the infinity setting. Actual distance between sensor and chimney: approximately 90 feet (calculated using gmap-pedometer.com).
My conclusion:
The Vario-Elmar 21-35, combined with the Speed Booster, has substantial field curvature. (I believe this is due to the zoom lens' nature, not the adapter.) When this is accounted for, however, light editing can reveal meaningful details in even the extreme corners. Pulling back from optimum center focus will result in increased corner focus performance, assuming the same subject distance. Adjusting focus distance can then be considered akin to using small apertures: if one is willing to sacrifice peak performance, meaningful gains can be found elsewhere at the photographer's discretion.
Notes:
Center crop is enlarged 3:1; corner crop is enlarged 2:1. This is to compensate for perspective distortion, giving the subject approximately the same visual size.
Light edits were made in Lightroom. The corner crop has enhanced contrast and clarity. Both crops have edits for chromatic aberrations. I only spent a few minutes trying to equalize the two; as they're both in excess of 100% crops, feel welcome to download the original image and make your own edits.
21-35 Comparison
Comparison of the center versus corner performance of the Leica Vario-Elmar-R 21-35 f/3.5-4 with a Metabones Speed Booster on a Sony NEX-3. Both images at 15mm f/2.9 (the lens was set to 21mm f/3.5). Left image is crop of extreme corner; right image is crop of center. Both images were focused using the 14x live view focus aid. The corner crop was taken at a focus distance of approximately 8 feet, while the center crop was taken at just to the side of the infinity setting. Actual distance between sensor and chimney: approximately 90 feet (calculated using gmap-pedometer.com).
My conclusion:
The Vario-Elmar 21-35, combined with the Speed Booster, has substantial field curvature. (I believe this is due to the zoom lens' nature, not the adapter.) When this is accounted for, however, light editing can reveal meaningful details in even the extreme corners. Pulling back from optimum center focus will result in increased corner focus performance, assuming the same subject distance. Adjusting focus distance can then be considered akin to using small apertures: if one is willing to sacrifice peak performance, meaningful gains can be found elsewhere at the photographer's discretion.
Notes:
Center crop is enlarged 3:1; corner crop is enlarged 2:1. This is to compensate for perspective distortion, giving the subject approximately the same visual size.
Light edits were made in Lightroom. The corner crop has enhanced contrast and clarity. Both crops have edits for chromatic aberrations. I only spent a few minutes trying to equalize the two; as they're both in excess of 100% crops, feel welcome to download the original image and make your own edits.