Adaptall 70-150mm f3.5

[nemesis101]

Some more examples... each is a 50% crop of original... I am increasingly convinced the focus on my K10D is off... these seemed ok with focus confirm and split image but... only 20 are sharp, and those are with goodly depth of field... Hmm


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[Orio]

First one is a superbe photo!

[Attila]

Great samples! +1 for first one!

[Schnauzer]

Yes, very nice samples. # 1 for me also.

[scsambrook]

I've learned to ignore the focus indicator on both my Pentaxes - if you watch how long it stays on as you continue to rotate the focusing mount you'll see the problem. If you focus BACK from infinity it kicks in at one distance, and if you focus TOWARDS infinity it kicks in at a different setting. And also I find I need to alter the diopter setting sometimes - if I've been reading or using the computer for some time particularly.

I'm not convinced that split-image screens are actually better than the plain ones -especially with apertures lower than f3.5. Not only do you tend to lose illumination of one half, if you shift your eye off the viewfinder axis you can get a false alignment. And you need a well defined vertical as a target. Always assuming the screen's perfectly seated.

Back in the days when armies and navies used split image rangefinders, a lot of trial and error demonstrated that for reliable results the focusiing gearing needed to be high - i.e. a small turn produced a large movement - and the operator needed to use it quckly - no letting the images creep together, but a rapid movement and a sudden stop. It's worth remembering with MF lenses on DSLRs - and it costs nothing to practice. Remember, the eye actually has some power to accomodate - it will 'hunt' for a plane of focus, so don't let it wander. The old artillerymen spent a lot of time experimenting, as did the makers of rangefinders. The practice was to norm a number of readings ... something that's easy with static photo subjects.

And don't forget that with a split image wedge, one of the images can actually be out of focus at close ranges, so you might be trying to line up a sharp edge with a fuzzy one.

[Jieffe]

[nemesis101]

Thanks for all your comments and advice!

I grew up with split image, and had no troubles with it on 35mm, indeed I still don't - seemingly it's only this Pentax that gives me woes... I was wondering whether the efforts to remove a recalcitrant Ricoh lens with the infamous 'extra' ball-bearing wedged in the auto-focus pit might have fractionally misaligned the lens. That could explain why both auto-focus and split image fail?

The same lens on my *istD is bitingly sharp and easy to focus - so perhaps???

by the by, I took along the beast (EOS 1n-RS as well... pictures awaiting development... and apart from the horrendous weight, lugging it around in high 30's Celsius heat.. it was a joy - so stable in the hand, no feeling it was rolling out of my grasp like some DSLR cameras, and the brightness and clarity of the viewfinder... ahhhhh

I want a full frame 1Ds MK lll... with battery grip.. dammit Father Christmas, are you listening????

Doug.