Shooting Macro on the Mamiya RB System

RB and Fuji Instant Film:

The RB system will accept instant film backs. There are several made including some that require a system adapter, "P" and some that attach directly to the body in place of the rotating adapter. I've used the latter and it works quite well with stocks of Fuji Instant film. This type film tends not to be as sharp IME as slide and negative films, but renders pleasant images. You can also bleach a negative or positive image from the backing which could potentially be sharper than the print.

Tubes and Extenders:

For macro work there are two extension tubes in the system made by Mamiya and several tele-extenders made by Mamiya or others. The #1 tube adds 45mm of length (367gr), the #2 tube adds 87mm (473gr), lengths as marked on the tubes. At 840grams combined, the two tubes weigh almost 2 pounds. This is a huge amount of weight to stick on the front standard of the camera. Then put a lens, say, the 150/4.0 (799gr) and an extender such as the Kenko 2x Teleplus MC6 (657gr), and you have a long lever mounted to the camera that weighs 2,296gr (5.21 pounds!)

Light Falloff and Measuring Exposure:

Now rack the bellows all the way out and you have cut the light showing in the viewfinder by a huge amount, making it almost impossible to focus. And you have to figure a starting exposure: ƒ(exp) == (1/d^2)--T* of the extender; i.e. run a bellows-factor calculation and subtract the filter factor of the extender. This should give a ballpark exposure; I added about 3 1/2 to 5 stops to get close one time. But the lenses and extenders were so heavy that I had to find a way to support them separately from the camera.

So it's really going to depend on how macro you want to shoot as to how possible it will be to assemble, carry and use such a system with system components. The maximum rig above is probably best used in a vertical orientation with a huge amount of light to focus the subject. Longer exposures are fine if well supported, but they can be in the minutes at smaller apertures. By ƒ/32 you may be in the tens of minutes.

Alternatives to Using All RB-System Components:

An alternative to using all system components is to find a lens or chain of lenses that can deliver higher magnification and sufficiently flat field and sharpness at higher magnification while also projecting a sufficient image circle to cover the film. You would probably also want to be able to set the aperture, but at longer exposures, a shutter really isn't necessary. Most lenses extended further away from the film will enlarge the subject, so you could use anything from a 'hand' lens up to a microscope objective or eyepiece. Chances are the smaller the original imaging field design, the more image falloff or even mechanical vignetting when used for this application.