FA Limited Lens' focal length question

[Miserere]

Originally Posted by Gooshin

weeellllllll

they COULD have made a mirror and viewfinder the same size as a 35mm SLR, and then simply etch a border in the focusing screen to let you know where your APC's sensor limits are.

its not totaly out of the question...

They could have, but then APS-C lenses don't cast an image circle that covers 35mm film size. There's also the point (if you believe camera makers) that CCD circuitry and stuff take up more space behind the CCD so a larger mirror would make the camera too deep.

[k100d]

Originally Posted by rparmar

I have read this a couple of times, with the 77mm being claimed as 80mm or whatever. Does anyone have the tests where this was determined?

IOW, proof would be nice.

Originally Posted by Alfisti

Is the 77 really 79? If the 70 is really 68 then there is 11mm difference not 7mm. It explains a few things.

somebody asked this before and i answered it but the answer went unnoticed. no concrete evidence but the very well known Godfrey mentioned this before in this post i refer to all the time when people bring up the FA77 vs DA70 question. i might as well put it in my sig.

Should I get 77mm or 70mm? - Photo.net Pentax Forum

[k100d]

that's some really good work Pal Jensen, i heard the "rogue engineer" story, but those details really helped. it'd be nice to hear the FA31 story, cuz out of the limiteds, it is probably the best in technical aspects

[rparmar]

Originally Posted by k100d

no concrete evidence but the very well known Godfrey mentioned this before

Michael Kuhne says "the 70mm comes in at 67.6mm tested" but without evidence. No reason to disbelieve but would be nice to know from where this came. So I've emailed him.

[rparmar]

Michael has kindly replied with a reference to the Pop Photo tests. This review states that the DA70 tests out as a 67.5mm f/2.46 lens. Unfortunately the magazine does not provide similar figures for all their tested lenses, for example skipping the DA40 and DA21.

But thankfully they have test values for the FA77, which are an accurate 76.72mm and f/1.88. The DA31 tests at 31.81mm f/1.82. There is no review at all for the FA43 but they remark elsewhere that it "is marketed at its true focal length".

For completeness, and to save you the searching, the DA 14mm f/2.8 tests at 14.30mm f/2.92.

So the 31 / 43 / 77 is an actual 32 / 43 / 77 if one is really picking nits.

[Arjay Bee]

31 and 43 are cool cos they are both prime numbers- FWIW

[roentarre]

Originally Posted by NaClH2O

There is a story circulating around (somewhere in the wilds of the web) that the ltd's were originally a private project of Pentax's senior design engineer. It seems that he was an avid amatuer photographer, and those were the focal lengths he liked the most. The lenses weren't designed for production, but after seeing how well they performed Pentax was convinced to produce them commercially.
I have searched but I cannot find where I originally read the above, probably somewhere in the bowels of DPR, but it's a cute story none the less.

NaCl(the other response is "occult numerology" )H2O

Great summary. That was what I heard as well and I like your last response "occult numerology". Hehe So cool!