Rodenstock 75/4 Apo-Rodagon D on GFX 100S at 1:1

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.

I’ve been posting a lot recently about the 120 mm f/4 GF macro lens for the GFX. I found it a good performer at 1:2, at minimum focusing distance (MFD) with no extension tubes, but that it had really soft edges and a lot of focus curvature at MFD with 36 mm of tubes. In this post, I tested it at 1:1 with a 45 mm tube,a and found it credible on-axis but soft on the right edge of the frame.  I reported those results numerically and visually, using the time honored sharpness target of a banknote. The 120/4 GF was soft in the corners and edges at MFD with 18mm, 36mm, and 45mm of extension by tubes.

For copy applications at high magnifications, and for some 3D subjects that require extension tubes, the 120/4 GF just isn’t cutting it. I tried the CV 125/2.5 and it was a big improvement. I’d tried a Schneider 90 mm f/4.5 Apo Componon enlarging lens, and it was a disappointment at 1:1. I’d heard good things about the Pentax 645 120mm f/4 smc FA macro lens. It was almost as good as the CV 125/2.5 — and is substantially easier to find and less expensive. I also tried the Schneider 120/5.6 0058 Makro Symmar, and got very good results. I alos tried a Rodenstock 105mm f/5.6 HR Digaron Macro at 1:1. This lens has a ring on it that you can adjust to optimize it for any reproduction ratio between 1:3 and 3:1. It perfumed about as well as the Schneider 0058.

Now I’m turning my attention to an enlarger lens. I didn’t have good luck with the Schneider Apo Componon 90 mm f/4.5 at 1:1, but I had higher hopes for the Rodenstock 75mm f/4 Apo-Rodagon D, which is characterized by Rodenstock at 1:1.

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, 40 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.

1. The blue and red columns are for the Rodenstock lens on axis, with, respectively, a horizontal and a vertical edge.
2. The yellow and purple columns are for the Rodenstock lens at the right edge with, respectively, a horizontal and a vertical edge.

This is good performance. F/5.6 is the best f-stop.

Here are microcontrast results, with the contrast at a quarter of the pixel pitch being the definition of microcontrast.

Also good performance for 1:1.

Comparing to the Rodenstock 105/5.6 HR Digaron Macro and the Schneider 120/5.6 0058 Makro Symmar:

Pretty much a three way tie. I’m still suspicious of the Digaron center radial edge results. I will retest in the future.

Microcontrast:

Transfocal MTF50 performance in the center:

It looks like using a green filter at f/5.6 might be the plan for digitizing B&W negatives.

The right edge: