Double Adaption: for ultimate control in creating a ‘digital XPan’

Those that have been following my recent posts will know that I've been experimenting with sensor bracketing, and, in particular, the 'best' way to simulate a digital XPan, using one of my Canon RF or EF-M cameras (either visible or IR) and various adapters, eg see the Fotodiox site for examples of the many adapters you can get.

In this post I'll be looking at the benifits of double adaption. That is using more that one adapter.

As discussed previously, using Mamiya 645 lenses, with a larger image circle than the Canon RF format, allows one to exploit shift, and one might be tempted to opt for a single adapter, such as the Fotodiox Mamiya 645 (M645) to Canon RF Shift Adapter:

This adapter allows some 30mm of shifting (+/- 15mm); which initially looks great, until you factor in the Mamiya lenses.

As an example, lets look at the 35mm Mamiya - Sekor C f/3.5 N that I have (#107008):

Like all/most Mamiya 645 lenses, the infinity is at a hard, mechanical, stop, and my experience is that infinity can be slightly thrown out when coupled with adapters. In theory one could try and adjust the lens for a more accurate infinity with an adapter, however, this could end up as a wasted effort if you are using different adapters, as each adapter may be a few microns adrift from each other because of manufacturer’s design, quality control and tolerances.

This is where double adaption comes in.

The first adaption is to introduce a shift adapter to go from a Mamiya 645 lens to a Canon EF mount, then add a focus correction adapter to go from EF to RF. The adapters I have used are the Kipon Shift M645 - EOS, and the Fotodiox dlx Stretch EF - EOS R.

 

As can be seen, the additional advantage of using the EF - RF stretch is that it comes with rear, drop in, magnetic ND filters (ND4, 8 and 16). The final double adapter set up looking like this:

Using this arrangement of adapters allows me to capture a 61.75 x 24 mm, stitched, flat, panorama, using my visible band R or my IR (720nm) converted RP. That is creating a digital XPan image, albeit by using a medium format Mamiya film lens, rather than an XPan film lens. 

The in field workflow I've come up with goes like this:

• Set the Mamiya on its widest aperture, eg f/3.5 for my 35mm lens;
• Calibrate the lens for infinity by putting the lens at infinity, zooming in to the farthest point of interest in the image and adjusting for maximum focus at that point, using the stretch adapter;
• Set the required aperture (I tend to use f/16 or f/22 for maximum depth of field, and correct for diffraction softening in post) on the lens and the exposure time, using the histogram and ETTRing;
• Ensure the ETTR exposure covers the shift extremes;
• To ensure maximun pano blending success, I personally take three images, ie at the two extremes (+/- 15mm) and one in the middle with zero shift.

As for post processing I find the following workflow creates what I'm looking for:

• Ingest into Lightroom;
• Use Raw Detail to clean up the images;
• Use pano photo merge;
• Use Topaz AI, including, if required, dust and stratch (although this is now available in Photoshop ACR and hopefully will be in Lightroom soon) and Topaz Superfocus, to tidy up any diffraction softening;
• Tone and finish as required.

The following test shot was taken with the 35mm Mamiya at f/22, and I've zoomed in to show the detail that I obtained. The Image was taken with my IR converted RP and the final image is 10772 x 4217, ie 61.7mm x 24.2mm, and left in RGB space:

The bottom image above is a screen grab from a 1:1 zoom, to illustrate the details.

For completeness here is the B&W version, which I prefer, as colour integrity can be a challenge when post processing IR captures in colour:

I'll wrap up this post at this point as I think I've covered everything I wished to discuss. The bottom line being that double adaption is a viable way to ensure infinity focus on a manual MF lens when sensor bracketing. For me, knowing I can simulate an XPan with my mirrorless digital camera is fun and, I hope, will turn out to be worth while.

As usual I welcome any comments on this post or any of my posts.