Just had a thought

Thanks Algernon, I'd forgotten about that, which may explain why areas of the print were obviously softer than slide. And there was me blaming my MX & M 28/2.8!

IIRC correctly, if you did sandwich it between two sheets of glass you got Newton's Rings as well.

Hence anti-Newton's-rings-glass!

One solution is half glass, just to restrain the natural curvature of the film.

Just becuase you enver heard of it doesn't mean it's a real issue

Pentax provide AF fine tuning for a reason. It's nothing to do with faulty lenses it's to do with the nature of the Phase method of AF in the camera and the fact that NO LENS can be manufactured perfectly.

I learned to check the AF calibration of every lens through experience. I own a plethora of Pentax and Sigma lenses and many of them have required AF tuning on all the Pentax DSLRs I have owned.

I would advise everyone to check their lenses. If you're the one in a squillion that owns a set of lenses that are all spot on then great. If not then it's still great as you can dial in the required offset and you're good to go. it's all good.




It's not 'supposedly' spot on, it 'is' spot on as it's the sensor view.

Don't forget that live view will have it's own DOF
Focussing an an 85mm f/1.4 at f/1.4 will be easy.

Try a 28mm at say f/8 it will probably look in focus no matter
where the focus scale is.

Well indeed the inability of the regular focus screen at wider apertures than F/2.8 to show teh correct DOF does make manul focus difficult and live view is a way to get aroudn this. I always use live view to focus my 50/1.2


But when do we actually stop down to focus? unless the max aperture of the lens is f8

Could be an old lens or a mirror lens or a lens that
suffers from bad focus shift. A lot of zooms are f/5.6
or f/6.3

Totally agree with you, Smeggy. It seems strange that anyone would want to write in an apparently negative tone about any feature that is intended to be positively helpful. If an AF check shows up an inaccuracy then that is not only useful knowledge gained, but also Pentax facilitates and stores in camera memory (for up to 20 lenses) the correction of the AF system. In my case, I wish it were just as easy to correct the photographer's errors.

Philip