Hello George

Having previously owned the 800mm f4 it is (MANUAL DIAPHRAM & OUTER BAYONET) fitting. A protrusion attached to the aperture ring is used to push to the desired f-stop. The aperture dial is heavy duty as is the lens weighing in at 17Kg

Read about it's smaller brother, the 600mm f4 here...

http://www.luminous-landscape.com/reviews/lenses/600mm.shtml

Same description pretty much applies for the 800mm f4 specifications as above(MANUAL DIAPHRAM & OUTER BAYONET) fitting.

The 1000mm f8 reflex I understand uses neutral density filters as the diaphram control (MANUAL DIAPHRAM & OUTER BAYONET) fitting.

Other Pentax 67 lenses with MANUAL DIAPHRAM but are INNER BAYONET are the 75mm f/4.5 Shift and 120mm f/3.5 soft.

I think those mentioned above are the ones to avoid with your 645/67 adapter.

ALSO

Should point out only the K/67 and the 645/67 adapters have the outer bayonet flange for outer bayonet fitting lenses, the K/645 obviously doesn't as no 645 lenses use outer bayonet fitting.

Mike

Really fine result there Sam...one to be proud of.

If you have a photo editing program perhaps try a little bit of sharpening ...but not too much!

Mike

Maybe 2-3 hours of clear sky slots tonight before the next low pressure system moves in.
Remember there's a bright waxing Moon which will reach around 26 degrees altitude tonight.
Storm in pogress seems to have subsided slightly. Magnetic field is still bias towards north...need it to tip sharply south for any chance.

Mike

Replaced my K5 once with sensor staining, second one is good though level slightly out but hardly a major function.
Mostly long exposure low light photography here.

Given the choice again I would still buy the Pentax K5 ...just love this camera & the versatility of the Pentax system as a whole.

Mike

I stick with Pentax as I like shooting both film & digital. With 3 Pentax adapters K/645, K/67 & 645/67 I can access every possible Pentax lens/body combination be it film or digital so a big choice of crop factors too! If Pentax ever bring out a full frame 35mm DSLR then I'm ready for that too.

Problem with the Canikon for myself is being stuck with only two format sizes.

Pentax ...be it film or digital, the grass really can green on both sides of the fence!

Mike

John

I wanted a wide angle lens that would offer sharpness to the frame corners for astro related night scenes this Autumn. Even checked out the nearest full frame equivalents for this task but couldn't find another that could exceed it's optical performance at this focal length...I think I've fallen in love with this lens!

Mike

Voted Yes, and just did purchase the...Pentax smc DA 12-24 mm f4.0 ED AL(IF)lens from SRS for my K5 with no regrets, exceptional piece of glass!

Mike

Although film as you know is capable of the highest resolution the emulsion upon which it is based scatters light softening the potential highest resolution the film grain technology is capable of and can cause halation around brighter objects which also softens, masks or blurs both the positive effects of a lens... it's maximum possible resolution and the negative effects ...in this case chromatic aberration.

DSLR sensors are not emulsion based but do have the anti-aliasing filter though its effects on light scatter are minimal but perhaps Pentax also considered this into the equation when doing away the anti-aliasing filter in their 645D.

Mike

Perhaps a bit low in price but it was old glass as they say. Not so bad for film but anyone considering it with a DSLR may find problems with chromatic aberration in some lighting situations, modern sensors sure resolve the shortcomings of an optical system. I think an 'ED' or 'APO' somewhere in the lens designation would be a welcome addition for use with DSLR's.

Mike

Yes ...lovely set, really nicely done!

Mike