Archive 2014 · Mamiya Auto Bellows N slim camera adapter

jcolwell
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p.1 #1 · p.1 #1 · Mamiya Auto Bellows N slim camera adapter

A recent post by freaklikeme (Brad) asked for info about a thin Canon EF to Sony E adapter, for the rear standard of a Mamiya Auto Bellows N.

Brad's post, "Need thin EF to Sony E adapter- what would you do?",
https://www.fredmiranda.com/forum/topic/1311603

I just happen to have a DIY "slim" M645 to EF adapter for my Auto Bellows N, which is almost exactly the same thing as Brad is looking for. All he has to do is replace the "M42 to EF adapter" (part 1) with a DIY, minimum thickness, M42 to E adapter - think about the bottom mount from an E extension tube glued to whatever type of XX to M42 adapter that it'll fit in.

Of course, given the relatively short regster of the E-mount, Brad will be able to get infinity focus on focal lengths shorter than I can with my EOS cameras. Rats! Foiled again.

Anyway, the first five photos attached below show;

(i) the slim adapter on the rear standard, with accordian bellows,

(ii) a comparison of the slim adapter (top) my 'normal' M645 to EF adapter attached to the camera-rotation gizmo that comes on the rear standard of the Auto Bellows N,

(iii) a look at the inside of the rear standard, with the accordian bellows removed, and

(iv) a crop of photo (iii), to show details of the inside of the DIY adapter, and

(v) a view similar to photo (iv), with the assembled adapter removed from the "camera mount board" of the rear standard

slim adapter on the rear standard, with accordian bellows

comparison of the slim adapter (top) my 'normal' M645 to EF adapter

inside of the rear standard, with the accordian bellows removed

details of the inside of the DIY adapter

assembled adapter removed from the "camera mount board" of the rear standard

Aug 13, 2014 at 04:49 PM

jcolwell
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p.1 #2 · p.1 #2 · Mamiya Auto Bellows N slim camera adapter

The last three images shown below provide details of the DIY slim adapter;

(vi) an annotated, profile view of the assembled adapter, to identify the four parts of the adapter,

(vii) a view of the adapter's two main 'components', and

(viii) an almost-exploded view of the adapter's four components (the middle two are kind of stuck together).

The four parts are (left to right in the photos):

1. M42 to EOS adapter
2. 42mm to 49mm step up ring
3. 58mm to 49mm step down ring
4. 49mm to 58mm step up ring

Basically, it works like this; the assembled left side (parts 1, 2 and 3) goes into the back of the rear standard mount hole, and the right side (part 4) screws into part 3, from the back side of the rear standard board (i.e. camera mount board). Of course, you have to remove the bellows (accordian or bag) before attaching or removing this adapter. This removal of the bellows takes at least three seconds, maybe five if you're being careful.

You'll notice in photos (i) and (ii) that the 'hole' in the rear standard is actually a cylindrical flange (i.e. short tube). The slim adapter is held in place because, (a) the flange on part 1 (M42 to EF adapter) is wider than the tube, and (b) the outer diameter of part 4 (49mm to 58mm step up ring) is greater than the inside diameter of the tube, on the inside of the rear standard.

The combined 8.5mm 'depth' of the "left side", from the part 1 flange to the end of the "stacked" parts 1, 2, and 3, is just slightly shorter than the depth of the rear standard tube. The outer diameter of part 3 (58mm to 49mm step down ring) is just a tad smaller than the inner diameter of the tube. The max. outer diameter of the "right side", a.k.a. part 4, is just slightly larger than the inner diameter of the tube, and smaller than the 62.9mm inner diameter of the hole in the bellows within which it has to fit, when everything is put together.

(I have a lot of adapters and a lot of step-up and step-down rings...)

Here's the vital stats:

part 1 = 63.7mm (min. outer diameter of adapter flange for camera mount adapter to stop against left end of tube)
part 2 = outer diameter equal to or less than part 3
part 3 = 59.95mm (max. outer diameter, at least that's what mine is - it just barely fits inside the tube)
part 4 = 60.5mm (min. outer diameter of 58mm part, just enough to secure part 3, into which it screws, against the inside surface of the rear standard)

Note that the max. outer diameter of part 4 has to fit inside the hole in the rear face of the bellows assembly, which has a 62.9mm diameter.

The butt face of part 1 (M42 to EF adapter) and the inside surfaces of the DIY slim adapter are coated with flat matte black paint, to reduce possible internal reflections. Photo (iv) in the first series suggests that I should apply a second coat of flat black paint to some of the parts.