Pentax 67 wide angle lens question

[brian_legere1]

What is the closest focusing distance available for the 45mm or 55m

pentax 67 lenses to achieve sharpness in the foreground and to

infinity?I am contemplating a move to this setup.

[mel_brown1]

Brian, though the quick answer could come from a formula, let me direct you to some of Harold Merklinger's articles at: http://fox.nstn.ca/~hmmerk/HMArtls.html. Download SHBG01.pdf through SHBG04.pdf. You'll find that there is a lot more to your question than simply looking up the hyperfocal distance in a lens manual.

[steve_rasmussen]

For the 45mm, a lot depends upon how large you are going to enlarge your work. If you use the DOF scale exactly, the Circle of Confusion used by Pentax is such that the image will be soft up front and slightly in the background as well. The closest I shoot the 45mm at f/22 is 3.7 feet but that is pushing it a bit. If you can, shoot this lens one stop conservative from the DOF scale. (Aperture is f/22 with the DOF set at f/16.) I don't own the 55mm. SR

[peter_hughes]

DOF is highly dependent on the degree of enlargement. No scale or chart, however carefully it is figured, takes this factor into account.

 

http://www.ravenvision.com/peterhughes.htm

[gene_crumpler6]

Brian;

 

The new 55/f4 has the following markings on the DOF scale. At f-22, the DOF is 41/2 ft to infinity. At f-16 it is 7 to infinity and at f-11, it is 9 ft to infinity. In practice, when I expect to be making a 16x20 or 20x24 blowup, I will use 2-stops more than the scale, i.e set the lens at f-22 and use the f-11 markings. Therefore for big enlargements I would use f-22 and expect 7-8 ft to be in good focus.

 

The 55 does not seem to exhibit any significant diffraction loses at f-22.

[brian_legere1]

Thanks to all for the information on the pentax wide angle lenses.There is a lot to think about when moving from a 35mm set up to a mf slr.I think that the 55mm or 45mm will suit me fine.

I am a member of various forums.This one is the best.