Field Test Fish Eye 35mm f/4.5 Lens

Lens description: Minimum Aperture: 22 Lens Construction: 7 groups 11 elements Angle of View: 1800 Diaphragm: 8 blades, fully Automatic (inner Bayonet Mount) Minimum Focusing Distance: 0.45m (1.5 ft.) Filter Size: Built-in, UV, Y2, O2, R2- w/gelatin filter clip at rear Lens Hood: N/A Maximum Diameter & Length: 102mm x 73mm (4.0" x 2.9") Weight: 920g (32.5 oz.)

The Pentax 67 35mm lens is like other fisheye leses, it distorts a lot, you have to have the horison in the center of the photo or else the horison will be bent in a u or n shape. All items near the edge of the photo will be bent so it is not suteble for use where there are vertical things such as buldings or trees. As there are almost no trees where I live I can use it a lot for landscape photographs, it is great where you want to take a close foreground photos and focus to infiniti, I often see motives wich I could not take with any other lens and I use it much more than I expected to when I bogth it. I would have liked it to be minimum at least f/32 but it is only f/22. The DOF at f/22 is from 0,65m (2ft) to infinitie compared to 0.29m to infinitie on my 17mm fisheye for a 35mm camera at f/22. The DOF scale on the lens seems to be correct at least at f/22 according to my test.

There is almost no flear in this lens, you can only see a small flear when the sun is close to the center of the photo so there is no problem taking pictures with the sun in the photo.

The biggest problem with this lens is a chromatic problem in the marginal aerias ( in the corners of the photos ), a white dot on a black background has the edge nerer to the corner cyan and the edge nearer to center of the photo red, this can be seen at all f stops but it is less wisible if the marginal area is in focus than out of focus. This problem is much more visible than in the 300mm lens and can often be seen in prints as small as 6x8 if there is high contrast in the photo.

To test the scharpness of the lens I used a focustest from wich I can read a resolution in lines per millimeter on the film, for this test I used a 25 ASA film, shot in dayligth with a Gitso G1549 carbon fiber tripod and Gitso G1570 head, I used a remote release cable and the MLU to minimise all factors that can reduse the resolution. To read the resolution I used a 30X Lupe.

The resolution at the center of the image was : 70 L/mm at f/4.5, It was best 75 L/mm at f/8 and it was 60 L/mm at f/22 For comparason I tested other Pentax 67 lenses at the same time: 45mm was 70L/mm at f/4, it was best 80L/mm at f/11 and it was 60L/mm at f/22 55mm was 50L/mm at f/4, it was best 70L/mm at f/8 and it was 50L/mm at f/22 105mm was 40L/mm at f/2.4, it was best 60L/mm at f/8-16 and it was 50L/mm at f/22

I also tested both 35mm and 45mm at the edge ( in the corner of the photo ), the scale of the focustest was from 40 to 150 L/mm. The resolution for the 35mm was only redable 40L/mm at f/11-16 The resolution for the 45mm was 40L/mm at f/4, its best 60L/mm at f/16 and 50L/mm at f/22. This shows that the lens is among the best Pentax 67 lenses in the center of the image but at the edges it is wery blury.

There is one problem, this lens has a gelatin filter clip at rear identical to that of the 45mm. If you by acident bend this clip away from the lens as my friend did on his 45mm lens then the clip can stop the mirror from going down after taking a picture. This has a dramatic effect wich most would not connect to the lens ( we tried this on 3 bodies). The mirror frose in a locet up posititon and the shutter frose open, after remowing the lens we could wind the film on with the shutter and mirror in that position. It did not help to put a new lens on, the problem got away after we remowed the battery.

The front glass extends front of the metal casing so one has to take great care not to damige the glass when using this lens.

I think that it would be a good idea to open a homepage related with this forum where we could show pictures taken with Pentax 67 lenses to refere to in field tests such as this one to show both the flaws andadvantages of these lenses.

Sigurdur S. shs@mmedia.is

-- Steve Rasmussen (srasmuss@flash.net), May 12, 2000

Answers

Thanks Sigurdur for the excellent test on this rare lens. Sorry about my bad cut and paste ability. The chromatic aberration you describe sounds like Lateral Chromatic because it occurrs at all f-stops. Any forum members are welcome to post tests on lenses(or equipment) that have not been tested(165 2.8/4, 90mmLS and 90 Pentax, 120 soft, 200 Takumar, 500mm, 800mm f/4 and 6.7 etc.). SR

-- Steve Rasmussen (srasmuss@flash.net), May 12, 2000.

Patrick; actually, Sigurdur was the author of the 35mm test. I just transferred it from email. I'm not really a computer guru so buiding a P67 homepage is a bit out of my league. There is however a site on Greenspun's Lusenet under "Show All Forums" called IMAGES OF PHOTOGRAPHY, in which people can post their pictures. You might want to check it out. SR

-- Steve Rasmussen (srasmuss@flash.net), May 13, 2000.

Thanks Steve for another great field test on a lens all of us are interested in. Please help with instruction or guidance on a P67 photo homepage. That's the best idea I've heard in a while. Even though we can't show performance on resolution I'm always curious what people accomplish with their P67's. I would love to contribute but know little about web programming.

-- Patrick Drennon (sierraengineering@worldnet.att.net), May 13, 2000.