Using Focal Reducers On Full-Frame Bodies

ProfHankD wrote:

I am considering using a Mamiya 24 mm medium format fisheye lens with a Mamiya-to-Canon adapter and a 0.7 Canon-to-Sony focal reducer. Do you think that would also achieve a true circular image? That could yield a 12 or 18 megapixel image circle depending upon A7 or A7R. - John S.

I would not expect that to work. The Mamiya 24mm is for their 645, which means the native image circle is possibly as big as 40mm diameter. 0.7*40mm=28mm, which means it wouldn't fit on the 24mm height of the A7/A7R sensor. Beyond that, focal reducers made for 135-format SLR lenses don't expect such a large image area as input, so you'd probably see some additional vignetting from the focal reducer itself.

Hi, I hope to make it work! Look at the Mamiya 24mm 360 degree panorama at http://08.ae/panos/Mamiya24FEtest/virtualtour.html. I'm impressed by the fine resolution when zooming way in. I found this url at:

http://www.getdpi.com/forum/medium-format-systems-and-digital-backs/49332-advice-mamiya-24mm-f4-0-fisheye-lens.html

I've been unable to get that resolution with my fisheye panoramas. I currently use a Madoka 180 circular fisheye (Sony e-mount for aps-c) with my a6000 24 megapixel camera. I think my lens quality may be the major problem (??) I usually stitch together 4 circular images using PTGui.

So I'm in process of upgrading my equipment. Mamiya 24 lens due tomorrow. Zhongyi Lens Turbo II due next week. I already have the Mirex Mamiya/Canon shift adapter. All that remains is choosing the best A7 camera - trying to avoid the very expensive A7RII.  I think 36 megapixel sensors would be best for the smaller-sized circular images.

I'll report later on my success or failure -  but it will be a while until I get the camera.  In the meantime I will try the Mamiya 24 with Mirex adapter on my a6000.  I also have a Rhinocam (Fotodiox) with Mamiya adapter which might work well on the a6000 (??)                --  John S