£50 is ample to get a nice MZ5, probably the best choice from the range in that price bracket. It was an award winning camera is 1988, has a metal mount and is compatible with all Pentax lenses.

Actually that's faulty logic. All it means is that 322 people were here all at once. An hour later it could have been 238 different people....

I've not listed all the lenses, just a selection.

Pentacon Prakticar 50mm f1.8

Decentering: 10%

MTF 10 lpm 88%
MTF 40 lpm 46%

Distortion: -1.5%

That's the only one, hope it helps!

This was just for those who like this sort of thing. It does reveal some interesting choices that different manufacturers make, if you know how to decipher all the figures.

Others may find it a bit OTT!

Decentering affects sharpness and resolution as the lens is not made as well as it should be. The elements are not fitted together perfectly.

This is why I don't like casual dismantling of lenses - without the proper kit it's not possible to guarantee that the recentering is accurate. Also overtightening an element will distort the shape of the soft glass.

MTF is modulation transfer function, an electronic way to express resolution. A target which cosists of black and white patterns starts off as having 100% contrast. A machine can read the image at the film/sensor plane to see how much of that contrast gets through the lens intact. If the figure was 50% then the contrast has halved.

The target that is 10 lines per mm (lpm) gives us a guide to how contrasty a lens is.

The target at some other value (40 lpm here, a very challenging test) tells us how much fine detail can be reproduced.

So a lens with 95% at 10 lpm and 22% at 40 lpm is very contrasty but of low detail resolution.

You can use AF lenses in MF on any manual body.

If you want an AF body then there are plenty around. The MZ series are the most recent and these will seem most like the DSLRs in many ways.

There's a lot if info there for those who can decipher it. It only so far tells part of the story, and to put that into perspective lets take the SMC Pentax 50mm f1.2 which apparently has very poor results...and yet I still want one.

This is where we need to look at the decisions a lens designer makes. Everything is a compromise. Without resorting to aspheric elements (as in the Nikkors) what are the parameters for this Pentax lens?

First it has exemplary control of coma, even at open aperture. Coma is where point light sources are reproduced as smears and oblongs. Will we have point light solurces in images shot with an f1.2 lens? Very probably, and this lens caters for that.

Second what aperture will the lens be used at and for what purpose. In fact, maybe low light hand held shooting for which f1.2 gives us a really bright viewfinder image. Or maybe on a tripod at f8 in reality most of the time. At f8 the lens is as good in terms of resolution as the other 50mm lenses, not shown in these figures, so Pentax were thinking we will expect a cracking good lens when it's stopped down. They may be right.

What will be certain is that flatness of field will be out the window, so not a lens for use on bellows. And yet a slightly soft at f1.2 lens might be very nice for portraiture or flower studies...every lens "fault" has a potential for something.

Apparently it's better than the Leitz Noctilux from the figures quoted (£7000 anyone?) so there is more to lens tests than meets the eye.

Approach them with caution, especially the magazine ones that are really reviews rather than tests.

I'm now going to take that list and add a second % figure - this is the 40 lpm MTF figure and indicates the detailed resolution performance two stops down.

f1.7/f2 lenses:
Canon 93% 60%
Chinon 91% 42%
Hexanon f1.7 89% 51%
Hexanon 40mm f1.8 85% 34%
Summicron-M 94% 59%
Summicron-R 95% 58%
Rokkor f1.7 91% 44%
Nikkor 93% 59%
Nikon Series E 93% 50%
Zuiko 94% 60%
Pentax f1.7 91% 42%
Pentax f2 91% 44%
Pentax 40mm f2.8 93% 59%
Ricoh f1.7 88% 46%
Planar 92% 59%

f1.4 lenses:
Canon 87% 44%
Chinon 87% 34%
Hexanon 86% 37%
Summilux-M 88% 38%
Summilux-R 90% 43%
Rokkor 89% 46%
Nikkor 89% 48%
Zuiko 87% 37%
Pentax 83% 40%
Ricoh 99% 52%
Planar 88% 51%

f1.2 lenses:
Canon 81% 31%
Canon L 80% 33%
Noctilux 73% 22%
Rokkor 83% 35%
Nikkor 74% 28%
Noct-Nikkor 80% 30%
Zuiko 90% 46%
Pentax 75% 25%

With macro lenses you might find that a manual focus one will be fine. It will for static subjects such as plants. Maybe not for butterflies and insects in general, AF can be handy there.

For static subjects a sturdy tripod is essential to avoid camera shake and to ensure accurate focusing.