Solution when Mirror hits lens at infinity

IB123 · Joined: 30 Dec 2013 Posts: 9 Location: VA

My Super Takumar 50 1.4 hangs up the mirror, I had to defocus after a shot to get the mirror to return, and so I didn't use it. I got an idea from my astrophotography equipment, and tried a plastic T2 adjustment ring between the lens and the M42 adapter. All it took was a thin .5 or .75 mm ring to clear the lens from the mirror, and the ring fit snugly onto the M42 threads. Now, of course this moves my infinity focus farther from the sensor, and since I just learned about focus micro-adjustments last week and cataloged all my lenses, I decided to recheck the Super Tak with the spacer in place.

With just the Big-IS Focus confirm adapter, my right-side max focus was -6, and left side was off the scale at -20. With the spacer included, my right-side max focus became -10. I checked the range since I was off the scale in both cases, by programming my right mark to about +10 then manually off-focusing the lens until the confirmation light came on at +10, then dialed in the settings from there to establish a range +8 to -14, or 22 points. Now going back to the REAL right side max focus point of -10, subtract 1/2 my range of 22 and my midpoint would be -21. So in the end my setting for the lens is very accurate at the lowest end of the scale, -20, and I no longer have mirror hang up.

I also noticed from this that as your micro adjustment moves to the left of zero, you actually want your lens closer. Not possible, so do the adjustment. however, if your micro adjustment is to the right of zero, you can fix by moving the lens farther away with these spacers. If your right side micro adjustment is off the scale, then even more reason for the spacer.

The spacer I use is plastic, comes in a set of 15 with varying thicknesses, they are stackable, and it is Baadar part number 2458102. I got mine from Teleskop Express but they are available from a variety of sources.