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I got these images using a 5Diii with the venerable Canon 100mm f/2.8 non-L macro lens. The question I have is about focus breathing. To wit.....
Here is the dandelion with lens focused at the front of the dandelion at pretty close to MFD:
CX0A1036 by K Knight, on Flickr
...and without moving the camera, here is the same dandelion with the lens focused at the back of the dandelion, call it MFD + 1.5 inches:
CX0A1064 by K Knight, on Flickr
Note the large difference in field of view, with the closer-focused image having a significantly smaller FOV than one focused just over an inch farther away. Does FOV equate mathematically to focal length? What does this large FOV difference say about the extent of focus breathing for that lens?
And here's the stack, which is fine within the field of view at closer focus.
dand4_stack by K Knight, on Flickr
With the Canon 100mm f/2.8 macro non-L lens, and with a subject the depth of a dandelion at MFD, using a rail, which I also did, creates a significantly smaller change in FOV than refocusing the lens. Given that ~any~ change in FOV is detrimental for focus stacking (where ideally you'd like no change in FOV at all), the rail should produce slightly better results. If the lens didn't focus breathe, the best option would be to refocus the lens rather than use a rail. I suppose a lens that will do 1:1 images at MFD w/out any change of FOV while focusing would be prohibitively expensive. But it would be fun to use!
I welcome any comments and discussion!
keith
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