A star.

mgoodm3 · Post by **mgoodm3** » Sat Jan 17, 2009 3:00 pm

thought this turned out well: a star on a Morgan dollar dated 1881

5x/0.225 objective on a bellows/ Shot at about 6.5:1.

Stack of 34 images, Helicon focus.

rjlittlefield · Post by **rjlittlefield** » Sat Jan 17, 2009 3:38 pm

Looks good. A little OOF maybe at the extreme upper/lower left corners.

Despite how much stacking I do, I'm always surprised at how many frames it takes to get things both sharp and focused at higher magnifications. After all, coins are "flat" -- aren't they?!

--Rik

mgoodm3 · Post by **mgoodm3** » Sat Jan 17, 2009 3:55 pm

The left side just won't get into focus. I wasn't running at full bellows extension which does help improve the field flatness.

the 5x objective is an infinity corrected objective, but I am running an appropriate mitutoyo tube lens with it. Without the tube lens there is a lot of spherical aberration that mostly corrects with the tube lens, but not all. Maybe a product of a big detector and not enough mag/extension??

I find it interesting that the fuzziness is predominantly on the left. I was thinking that maybe the bellows is slightly out of alignment. I do have a Nikon PB-4 bellows and I tried shifting the lens sideways a little and it helped some.

rjlittlefield · Post by **rjlittlefield** » Sat Jan 17, 2009 8:04 pm

mgoodm3 wrote:maybe the bellows is slightly out of alignment.

Could be. It wouldn't take much twist in the front standard to move the image circle off center on the sensor.

--Rik