The 45mm is a lens that gives an 88 degree field of view and makes it between the 21mm and 24mm lenses in the 35 format. It is a compact and light weight lens when compared with other MF lenses. The optical design is a nine element( thick center elements) German-looking, reverse telephoto type. It is the only version that I am aware of for the 45mm. The design is same philosophy used to make the second version 55mm. The 45 is one of the sharpest lenses in the line. Its sharpest stop, in my opinion is f/11 but is very sharp from f/8 to f/16. Only a slight degradation occurs at f/22 with 20X24 inch prints being easily done. At f/4, the images are too soft for pro work. This lens will not be used by many people wide open however. Distortion is very well corrected with only a slight mustache distortion noticable. The DOF scale on the barrel is close to being accurate. It is best to use one stop more conservative than is shown by the scale(i.e. when the aperture is at 22, set DOF to 16). This lens is almost as sharp as the 75mm and new 55mm. Overall, an outstanding lens.

-- Steve Rasmussen (srasmuss@flash.net), February 13, 1999

Answers

Welcome to the forum Tom. Yes, the 45 cap can touch the glass if you put it on crossways in your attempt to attach it. Be careful, SMC is low index soft material and will scratch with plastic caps or fingernails. SR

-- Steve Rasmussen (srasmuss@flash.net), May 14, 1999.

Bruce, my friend has a Linhof 4x5 and I suggested to him the possibility of using a Pentax/Takumar 90mm or 165mm Leaf Shutter lens on his camera. He has never tried it but I'm sure it could work. The 75 shift, with its excellent off axis correction, would be a candidate also. SR

-- Steve Rasmussen (srasmuss@flash.net), June 19, 2000.

I have had good results with my 45 f4 but had a little concern about the lens cap. When I got it, the parts on the cap you squeeze were so smooth it slipped a couple times banging into the front element. A file roughened those areas so it does not slip now. In examining the cap and lens structure it looks like the inside of the cap can touch the lens. Any one else noticed this? I emailed Pentax and they said the cap was correctly made but I might want to look for a "third party" cap!

-- Tom Goodrick (tgoodrick@earthlink.net), May 14, 1999.

I tested my newly acquired 45mm f/4 on a Edmund Scientific lens resolution chart and by taking photographs of a brick building at infinity focus. For both targets, I found f/16 to be slightly sharper than f/11 from center to periphery of the image when viewing the negative with an 8X loupe. I also compared my 45mm against the 55mm under similar conditions. As expected, the 55mm gave me sharper images from center to periphery than the 45mm even opened up to f8. However, the 45mm is still very sharp, and there are times when the 88 degree angle of view is a distinct advantage over the 78 degree angle of view of the 55mm.

-- William Castleman (WCastleman@compuserve.com), July 14, 1999.

There is another amazing thing about the 45/4 lens: its huge image circle. Yesterday I was dinking around with my Sinar 4x5 and bag bellows, comparing the angle of view between a Nikkor 75-SW on 4x5 to the P67 with the 45/4 lens. (Nikkor is wider).

During the play time, I held the P67 45/4 lens over an open lensboard, and was amazed to find the image circle apparently at 100mm or more. This immediately brings to mind the thoughts of using my 45/4 as a cheap ultra-wide for my 4x5 mounted on a behind-the-lens Packard shutter assembly.

-- Bruce Gavin (doc@compudox.com), June 18, 2000.