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In my book, lenses do not have otherworldly qualities like „3D Pop“, „Zeiss colors“ or a truly unique "rendering". Lens aberrations are a scientific subject since Ernst Abbe turned optics from a craft into a science, and how far this has come! Not even "bokeh" is a secret any longer but the result of engineering decisions (and compromises).

Extraordinary results (impossible to achieve with new glass) cannot be expected from an old projector lens as from any other old lens. If it is a good lens, it is still good, but what looks so special otherwise, is very likely just an optical aberration in the end.

Which doesn't mean that playing with old lenses cannot be fun.

So I remembered that just that very lens, a V/S Heidosmat 2,4/90 was lying in the cupboard, as well as two other projector lenses from an abandoned stereo projector undertaking. There also was a focusing helicoid and a brand new M39 to Sony E-mount adapter (why did I once buy this?)

The Heidosmat turned out to be easily adaptable, especially since I own a small lathe since a while, with which bringing an aluiminium ring to size (as for width and diameter) is a joy. Before the lathe, I would have spent hours filing and filing and filing…

Cutting threads is a different story (I will not show early attempts) and requires more practice and some dedication

Here, the E-mount adapter had to be brought from a M39 thread to M42

On the other (M52) side of the focusing helicoid, an intermediate part had to be fabricated, to accept the 43mm diameter barrel of the lens. I did not find a sufficiently big aluminium piece to make this in one part, so this consists of yet another two elements. These however are such a tight fit that no further clamping is necessary

The Heidosmat indeed does well on the A7, it is sufficiently sharp, even if the contrast falls behind the Sony 2,8/90 Macro. And the bokeh (praised in above article) is plain ugly, if you ask me.

(contrast adjusted to taste)

Good enough for an occasional dog portrait (provided the dog stays put until the lens is focused), and if the contrast is increased a little

There was no real need to cut off the plastic front part of the lens, but shorter is nicer, in this case.

This the end state with Pentax K mount and 49mm filter thread, mounted on an old KX camera

The other lens, unfortunately, did not fare so well, even if this is not the usual garden variety of a 2,8/85 lens but the better 90mm variant, a Will Maginon 2,5/90 from an old Braun Projector, nicely wrapped in black anodized aluminium.

Single coated only, but we did not shoot for top scores anyway, just for a little fun.

Also here the lathe proved to be very helpful and the blank barrel now attracts attention…

The resulting images however do not deserve any attention and can be deleted right away. They are mushy and not sharp (not even in the middle) and can hardly be brought to acceptably quality even with a lot of post processing

So there are really no new frontiers to conquer, for these old lenses…

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