Originally Posted by
Graham Patterson
Hopefully someone here has tried this particular conversion. My experience comes from coercing my 5x4 enlarger to do 8x10.
Do a back of the envelope calculation: You need a 135mm (up to 150mm) lens at a minimum for 5x4. If you want to start at 5x4 and go up, you need a lens extension of twice the focal length from the film. That's 270 - 300mm, or 11-12 inches. The Magnifax 4 was designed for 6x9 cm, so the current negative stage is a hard constraint of a little over 6cm, say 3"? That width constrains the 'cone' of light visible by the lens at a given extension, so you will not be able to use the full bellows extension for focusing.
My guess, not having access to the equipment, is that you will not be able to mount the negative high enough above the existing negative stage and still have a decent enlarging range without vignetting from the existing negative stage. If you can make that work, you will then need a diffused LED light source, which oddly enough is the easy(-er) part!
Essentially, if you have a 5x4 camera that can be set to do the equivalent range of enlargement, use that as a model and maybe cut paper/card models of the bellows needs and taper and see if you can make it work over a range of enlargements. This does not address the lens axis to column distance which is another constraint on print size.
Personally I wouldn't do irreversible modifications to a decent medium format enlarger.
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