This is one in a series of posts on the Fujifilm GFX 100S. You should be able to find all the posts about that camera in the Category List on the right sidebar, below the Articles widget. There’s a drop-down menu there that you can use to get to all the posts in this series; just look for “GFX 100S”. Since it’s more about the lenses than the camera, I’m also tagging it with the other Fuji GFX tags.
Yesterday, I tested the Rodenstock 75mm f/4 Apo-Rodagon D on a GFX 100S at 1:1, and found it to be an excellent performer. Today, I’m testing it at 1:2, where — spoiler alert — it doesn’t do nearly as well.
Here’s the test procedure:
- GFX 100S
- Foba camera stand
- C1 head
- Lens focused to get to 1:1 magnification
- ISO 100
- Electronic shutter
- Indicated f/4 through f/8 in whole-stop steps
- Exposure time adjusted in M mode
- Cognisys rail, 100 exposures, 80 um step size
- Initial focus short of target
- Convert RAF to DNG using Adobe DNG Converter
- Extract raw mosaics with dcraw
- Extract slanted edge for each raw plane in a Matlab program that Jack Hogan originally wrote, and that I’ve been modifying for years.
- Analyze the slanted edges and produce MTF curves using MTF Mapper (great program; thanks, Frans)
- Fit curves to the MTF Mapper MTF50 values in Matlab
- Analyze and graph in Matlab
Here are the results:
The vertical axis is MTF50 in cycles per picture height. Higher is sharper. The horizontal axis is f-stop.
- The blue and red columns are for the Rodenstock lens on axis, with, respectively, a horizontal and a vertical edge.
- The yellow and purple columns are for the Rodenstock lens at the right edge with, respectively, a horizontal and a vertical edge.
The edge performance is poor.
Here are microcontrast results, with the contrast at a quarter of the pixel pitch being the definition of microcontrast.
Well, you can’t win ’em all.