Originally posted by lytrytyr 1. To avoid getting dust into the camera while you set up the extension tube?
2. Because you've been using the 35/2.3 as a walkaround lens,
and don't have an extension tube with you?
3. To keep the semi-automatic functionality for macro use?
Anyway, it sounds like kind of a cool thing to do.
You may avoid dust on the sensor, but how will you avoid getting dust between the lens elements - how do you protect the single lens element, in the field, without risking scratches etc.? There is a reason, why even in large format lenses, the idea of convertible lenses, which were quite common until the 1960s or so, did not survive. There are still some exceptions and you can get a Cook or Taylor-Hobbs (the brand escapes me now) set lens even today, if you have enough money to invest. I even use an old Schneider Symmar, which you can convert from 300/5.6 to 500/12 (or so), which is not bad, but even these specifically made lenses always presented the problem of storing the removed lens element in the field.
-- Instead of removing the frontal lens element, I would simply add an achromatic close-up lens to the 35/2.4. I bet, the image quality is at least as good as with the crippled 50/4 and you also avoid the possibility of getting dust on the sensor.
Ben