Finally got down to some relatively serious testing today. Shot a $ bill with the PanLeica 100-400 and two achromatic
C-U lenses.
To the big surprise first; The Nikon 5T outperformed the Canon 500D with this particular lens and focal length. F6.3 and
f10 were both softer than f8, so I did my comparison at f8. I downsampled the 500D image to match the 5T and put them on
layers, so I could make careful comparisons. I also did the reverse.
In both cases, the 5T images resolved more, clearer fine detail at 100% than the 500D. That's right, even though the
+1.5 diopter lens enlarged the subject less at its closest focus, when upsampled, it still had more detail than the +2.0.
I don't know that this result is generalizable to other lenses and focal lengths, and imagine it wouldn't be, at least
for different FLs. But it's just what I need to know, which lens and which f-stop to use. The 500D can return to KEH and
I can have a little more working distance.
All shots @ 400 mm and infinity focus, set with AF off.
Canon 500D:
Subject to focal plane = 78.5 cm, 30.9 in.
Subject to front of lens = 50.1 cm, 19.7 in.
Nikon 5T
Subject to focal plane = 95.4 cm, 37.6 in.
Subject to front of lens = 66.9 cm, 26.3 in.
So, as predicted, the 1.5 diopter lens gives 6.6 in. more working distance than the 2.0. It also appears that the rule
that closest focus is the focal length of the C-U lens is the distance to the front of the C-U lens, not the FP. I've
not heard that stated clearly before.
I took a shot at comparison to extension tubes. But with such a long lens, a 21 mm tube, while it brings close focus in,
doesn't enlarge much. When I put three tubes on, the screen went blank. Go back to one, and it's still blank. Wipe off
the contacts, and the view is back. I didn't feel like wiping eight sets of contacts. And tubes lower the effective
aperture.
So perhaps another day, and I'll continue to carry tubes in the bag.
Tested Out Moose
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What if the Hokey Pokey *IS* what it's all about?
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