Sorry for the delay, I just woke up.
Originally posted by xjjohnno
Rico, perhaps your DX 50 f1.7 had some adjustments made to it by a previous owner?
Mine shows no sign of any modification or tampering.
Originally posted by Spodeworld
Wow...now I am getting a little concerned again. The lens just showed up today...I did notice that the barrel extends beyond the auto pin on the back (I'll have to check some other lenses to see if they do too). hmmmm, what to do....
I look at mine and I see the barrel extends about slight over 1mm beyond the pin. I stick a metric ruler against the base and see that the extension is about 9.5mm beyond the base. I measure the mount-to-mirror distance on my Spotmatic as being just about 10mm. I thread the DX50/1.7 tightly into my Spotmatic, set it to Bulb, open the back, press the shutter... and the mirror DOES seem to foul on the rear element. Un-threading the lens about 1/2 turn frees the mirror.
I also used the DX50/1.7 as my lens-of-the-day on my K20D yesterday (with a cheap clone M42-PK adapter) with no problems. I mounted it on my K1000 also, with no problems. I had measured mount-to-mirror on my various K-mount bodies as being 13mm, so their mirrors should clear the lens barrel by 3mm. I'll tag the lens as for K-bodies only, not for M42.