From what I can tell, the outer rear thread is 40mm, but there appears to be an inner, smaller thread that could be 32.5mm or 25mm -- and easier to adapt to certain cameras.
In any event, it seems like a great option to, let's say, my Minolta 25mm f2.5 Micro Bellows lens -- or this Canon Macro:
"...the 35mm Tominon is probably one of the strongest and most underrated buys on the market today. While the 35mm Tominon does not have the wide magnification range (or auto-aperture) of the Canon MP-E 65mm f/2.8 1-5x Macro Photo lens, it will get to within 95% of the sharpness at 2x, with much less chromatic aberration for about 5% of the cost of the Canon MP-E lens."
There are currently about a half dozen of these on EBAY right now, and compared to other lenses -- like my Minolta or the Canon MP-E 65mm -- at AMAZING prices!!!
Indeed, a great lens - thanks for highlighting it and sharing the information. We seem to have a lot of shared interests when it comes to lenses!
The Tominon 35 mm f/4.5 really is a wonderful tiny and underappreciated gem. The performance in the closeuphotography comparisons is very impressive and it's true that it's practically impossible to beat it at the price you can usually get one of these.
When I first read that it is a "Reverse Tessar" design made specifically for macro work, I started thinking... What happen's if I reverse-mount it? Does that make it a regular Tessar, which can focus to infinity? The short answer is: YES! However there are some caveats:
- you shouldn't expect any miracles from a lens never made for shooting at infinity, so the best use-case for this experiment is probably for the close-up range - while it has quite a large image circle, it doesn't cover full frame when reversed, even though its not far off, so it should absolutely cover APS-C - you need an option to mount it inside of your helicoid or bellows, otherwise you won't get close enough to the sensor to shoot anything outside of the macro range
It certainly is a 'just for fun' thing, but I found it interesting that it seems to keep its impressive correction for CA even outside of the intended magnification and I always have fun pushing lenses to (and over) their limits.
Here's a shot I took with it (I think reversed, but you could probably do that magnification of around 1:2 even in a normal position, if you've got a short adapter...):