Originally posted by cdw2000 As it happens I just purchased a Pentax Auto Bellows II with Slide holder in excellent condition for around $60 off ebay. The only caveat is that it is M42 mount. Just shows that bargains can still be found. I hope this doesn't offend anybody, but I plan to modify it to hold the camera with macro lens mounted directly to the camera (basically removing the bellows completely and rigging a tripod mount to one of the adjustable blocks) . I intend to use the rig to digitize slides and negatives, but it will also be able to serve as a macro focusing rail in this configuration. I just won't be able to do magnifications beyond what the lens is natively capable of (unless I use extension tubes, of course).
There is no Auto Bellows II. There is a Bellows Unit II however, which is similar to the Auto Bellows but without the dual cable stop-down flapper mechanism. The lens and camera standards are smaller but uses the same or similar X-beam rail. Is this the unit you have?
I'm not clear on what you are trying to achieve. With the Unit II there is a tripod mount on the focus rack on the lower half of the X-beam. Why not close up the two standards at minimum extension?
Originally posted by cdw2000 The main reason is the fact that neither my camera or any of my lenses are M42 mount and that this particular unit was offered cheap and I'm not really that interested in macro photography beyond 1:1 magnification (which some would argue is NOT macro photography, but I'm not going there). I could acquire an M42 lens, but from my research, using an M42 to K-mount adapter to mount the bellows to the camera is problematic since with the bellows bracket, there is no way to get access to the cameras K-mount unlock button to remove it. Though I'm not sure why this is a problem because the bellows mount should still unscrew from the adapter, but I'm not taking any chances, just the same.
Ok, but I'm not sure how you intend on attaching a K-mount lens to either of the bellows standards. If you use the back (to camera) you'd have to rig up a front plate with K-mount and you would still have to use an M42 to K-mount adapter. If you use the front standard then you have to fabricate a K-mount to M42 adapter (K-mount lens side - M42 camera side). Such has been done using rear-caps but I myself wouldn't trust an adhesive bond between dis-similar materials.
Attaching Pentax M42 bellows to a K-mount DSLR is not a problem. Put a short extension tube between the camera and bellows. And I would recommend using a so-called flanged adapter rather then the OEM type. One, it locks securely with not play. Two, it doesn't have openings for light leaks.
And yes, the camera adapter is held in place on the bellows with a thumb screw.
If you are using a APS-C body then you have to face the challenge of getting 1× magnification with the slide copier attachment. The rail isn't long enough to move the sensor far enough away.
Maybe somebody will 3D print a longer X-beam. You could toothed tracks from the original beam and fudge the placement for one or other of the extremes. The internal threading for the slide copier attachment screw would be trick though I image an opening for a proper thread hex nut would work.
Seems more work and money spent to be worth it IMHO.