Looking around other sites it doesn't look bad enough to be a disease,
it might be due to the stress of bringing up a lot of young chicks.

Good shots... possibly got a disease

Once you got away from the mass market lenses Olympus made
some pretty good stuff including f/2.0's at every
focal length up to (at least) 250mm

The 180mm reached 69 and 62 lpmm at f/4 way better than
everything else.... see this page at the bottom:

http://www.adaptall-2.org/lenses/63B.html

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Depends on what your using it for, I'm referring to birding
which does need good light with both the Sigma and my Tokina
80-400mm. You need something like the DA*300mm in poor light
but that's not as handy as a zoom.

That's the correct one for actually focusing using the microprism, but it may not work with DOF, although I would expect older screens to work better than modern ones. The original Nikon F screens were ground glass and should work, but probably wont fit Pentax K-5's

In theory what you see through the viewfinder is Lifesize and has nothing to do with 36x24mm. In practise with the K-5 what you see is 92% of Lifesize. The apparent distance in theory would be at infinity, but because that means using the eye muscles to focus most manufactures set it optically at about 1M. The big selling point about the OM-1 used to be that it had a big viewfinder, but they had actually moved the apparent image closer to the eye which made it very hard to see the full viewfinder.

With the old ground glass camera screens... coarse ground ones snapped in and out of focus better than smooth ground, but you couldn't see as much small detail.

Reasonable performance in good light. Should be OK
in the summer at f/8.

I remember going out of the house on the 15th April 1976
and thinking..... it's too HOT for a jacket, so I took it
off and took it back into the house. Never wore a jacket
after that until about October Very hot summer

I certainly saw a lot more DOF than this on the screen




Pentax 50mm f/1.2 on K-5

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The problem is that with an f/1.2 lens you see through the
viewfinder the DOF of an f/2.6 (approx) lens, so because
you can only focus within the DOF of f/2.6 it might be
outside of the DOF of the f/1.2. Some bits that look
in focus through the camera won't be in the actual shot