This is the 29th post in a series of Nikon D850 tests. The series starts here.
In the preceding three posts, I looked at the on-axis sharpness and longitudinal chromatic aberration (LoCA) of the Sigma 135 mm f/1.8 ART, 85 mm f/1.4 ART, and 105 mm f/2.8 macro lenses on the Nikon D850. Now I’ll do the same test with the Sigma 35 mm f/1.4 ART lens.
The target is a backlit razor blade:
The test protocol:
- ISO 64
- Focus shift, silent shutter option
- 40 steps
- Minimum step size (1)
- Target distance, 1 meter
- Aperture exposure mode
- Wescott LED panels set to 5500 K.
- Gitzo legs
- Arca Swiss C1 head
- Vinyl tile flooring over 6 inches of concrete on grade
- Fast Raw Viewer to discard the really out of focus images
- dcraw in document mode to get raw planes
- MTF Mapper to compute MTF50
- Matlab to automate the above
- Excel to graphs the results
Here are the results wide open:
The vertical axis is MTF50, measured in cycles per picture height (cy/ph). The shot taken with the lens focused to the closest position is on the left. There are 11 exposures plotted. There is no way to know the focused distance for these exposures. I used the minimum step size for the Focus Shift Shooting feature, which is too large to reliably catch the actual peaks, but it’s not that bad.
Not bad for f/1.4. There is quite a bit of longitudinal chromatic aberration (LoCA).
The sharpness comes up a lot at f/2.
At f/2.8, it’s starting to get good, but it gets better.
Ignore the title on the above graph. It’s really 35/1.4 at f/4 ,and it’s really 1 meter.
At f/4, this is a seriously sharp lens, and the LoCA is well under control.
Sharpness is falling off at f/5.6, but it’s still excellent.
At f/8, the LoCA is all masked out by the DOF, and it’s still darned sharp.
On-axis, this is an excellent lens.