In a recent blog post I mentioned that I was looking forward to testing the Fringer EF-FX Pro II lens mount adapter with my Canon MP-E 65mm Macro lens.
The MP-E 65mm doesn’t have a ring for focusing on the subject — you set the magnification ratio (from 1x to 5x) and move the camera/lens rig back and forth until the subject is in focus. For all photos, I focused on one eye of the model.
Dimetron
The first studio model is a toy Dimetron, photographed at a magnification ratio of 1:1. The toy is ~3.6 cm (~36 mm) long. The size of the APS-C sensor in the Fujifilm X-T3 is 23.5 mm x 15.6 mm. At 1x magnification, the entire length of the toy doesn’t fit on screen.
Dimetron toy | 1:1 magnification | 1/16 flash power ratio
With the camera/lens set for the same f/stop, shutter speed, and ISO (f/5.6, 1/250 s, and 400, respectively), less light reached the sensor when the magnification ratio was increased from 1:1 to 2:1. So I increased the flash power ratio by one stop, from 1/16 power to 1/8 power.
Dimetron toy | 2:1 magnification | 1/8 flash power ratio
Triceratops
The last studio model is a toy Triceratops, photographed at a magnification ratio of 1:1. The toy is ~4.3 cm (~43 mm) long.
Triceratops toy | 1x magnification | 1/16 flash power ratio
As with the first model, when the magnification ratio was increased from 1:1 to 2:1 it was necessary to increase the flash power ratio by one stop.
Triceratops toy | 2x magnification | 1/8 flash power ratio
Gear Talk
The Fringer EF-FX Pro II lens mount adapter enables one to mount Canon lenses on Fujifilm X-Series digital cameras. As you can see, my Canon MP-E 65mm macro lens works well with the Fujifilm X-T3 camera.
The APS-C sensor inside the Fujifilm X-T3 digital camera has a crop factor of 1.5x, so the Canon MP-E 65mm macro lens has a focal length of ~98mm (35mm equivalent) when mounted on an X-T3. The net result is an increase in apparent magnification, …
Post Update Update
Just because something looks like a duck and seems to act like a duck doesn’t mean it’s a duck. And so it is with the Fringer EF-FX Pro II lens mount adapter — although it looks like an extension tube, it isn’t. Why was I deceived by its appearance? Because I didn’t understand something called “flange focal distance.”
For an interchangeable lens camera, the flange focal distance (FFD) … of a lens mount system is the distance from the mounting flange (the interlocking metal rings on the camera and the rear of the lens) to the film or image sensor plane. This value is different for different camera systems. Source Credit: Flange focal distance. Wikipedia.
For example, the FFD for Canon EF-mount is 44 mm and the FFD for Fujifilm X-mount is 17.7 mm. In order to make a Canon EF lens perform properly on a Fujifilm X-series camera body, an adapter must move the Canon lens 26.3 mm farther from the digital sensor. (44 mm – 17.7 mm = 26.3 mm)
Not surprisingly, when I remeasured the thickness of my Fringer EF-FX Pro II lens mount adapter it turns out to be closer to 26 mm than my original course estimate of 30 mm (cited below). The net result is the 17.7 mm FFD of my Fujifilm X-T3 combines with the 26.3 mm thickness of the Fringer adapter, resulting in an FFD of 44 mm — exactly the right FFD for the Canon lens to work properly on a Fujiflm X-series camera body!
It’s worth noting that “apparent magnification” is still a real thing when a camera lens designed for a “full-frame” camera is mounted on a camera with an APS-C size sensor. The image formed by the lens is exactly the same size regardless of the size of the digital sensor used to record the image, but a smaller part of the image is “seen” by an APS-C sensor than a full-frame sensor, resulting in the misperception that the image is magnified.
I hope this sets the record straight. Sincere apologies for any confusion I might have caused — I never heard of “flange focal distance” before I bought the Fringer adapter!
[Post Update: From this point forward everything I wrote is incorrect. Is my face red, or what? I’ll explain further when I have a chance to use a desktop computer to edit this post.] … although the images appear to be magnified more than can be explained by this fact alone.
In the opinion of this author, the Fringer adapter functions like an extension tube. The adapter is ~3.0 cm (30 mm) in thickness. There aren’t any optics inside the adapter but it does move the lens 30 mm farther from the camera sensor. That, my friends, is an extension tube.
I used an online, interactive Macro Extension Tubes Calculator to estimate the effect of a 30mm extension tube on photos taken with the Canon MP-E 65mm macro lens at magnification ratios of 1:1 and 2:1. The calculator shows the magnification ratio increased from 1:1 to ~1.5:1 and 2:1 to ~2.5:1 respectively.
The values for “new minimum focusing distance” are in millimeters, despite the fact that the second “m” only appears when you click an insertion point in the box and scroll to the right. The values for magnification ratio seem reasonable; the values for new minimum focusing distance, not so much.
[End of segment with information that is incorrect.]
Related Resources
Full-size photos of the preceding studio models are featured in the following blog posts. Those photos should help to give the reader a better sense of how much the subjects were magnified by the Fujifilm/Fringer/Canon MP-E 65mm macro lens rig.
Copyright © 2022 Walter Sanford. All rights reserved.
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