Long Post: 28mm Showdown.

[David]

Lens Matchup: 28mm JC Penney Vs. 28mm Vivitar.

Pilots call this weather “sever clear.” These days lack clouds and the sun, in its most relentless, assails the ground with neither compromise nor compassion. These days complicate lighting, casting harsh shadows and preventing forgiving photography. However, on these days landscapes texturize, contrast brilliantly, and become more playful, subtle subjects.
During lunch, seeing the conditions, I skipped the last half of the day and took almost all the camera equipment I own up Mount Diablo, east of San Francisco, California. I brought all my lenses, except one I’m selling and one that needs internal cleaning, and also brought a 35-75mm TOU Five Star I repaired earlier this week.
One of this trips goals: Empirically compare my similar lenses and evaluate their ability to capture the same subjects. The following photo log compares, describes, and analyzes both 28mm lenses.






Bought new in 1967, the Vivtar (top) is about an inch longer than the JCP (bottom.) The Vivtar, an M42 mount, uses a Bower-type adapter to mount on the K-7, which works very well. All metal, very rugged, and hevy, the Vivtar is the clear favorite going in. The Japanese-made, well cared for lens usually has a polarizing lens. However, for fair comparison, I removed the polarizing lens for the sample photos.
The JCP, made in Korea, is also all metal, but of a substantially younger era. Probably made in the 1980s, the JCP represents a early Korean lens of sufficient manufacturing quality to stand up against a Japanese-made lense from the 1960s. I bought the 28mm for $13, used and non-functional. After an almost-complete disassembly, cleaning, and reassembly, the JCP works properly, has snappy aperture blades, and focuses better than as-bought. The only flaw is that the aperture ring moves forward and back about a half millimeter.
To compare the lenses, I took a series of two different landscapes. I photographes landscape one four times: f22 at 1/50, f8 at 1/400, and f 2.8 (JCP) at 1/1600 and 1/2500 (f 2.2 for the Vivtar.) These three represent the smallest and largest openings for both lenses and a middle setting.
I photographs landscape two seven times with each lens: f22 at 1/30 and 1/60, f11 at 1/250, f5.6 at 1/800 and 1/1250, and f2.8 (JCP) and f3.5 (Vivitar) at 1/2500 and 1/3200. Lanscape one was a southward-facing shot while landscape two looks eastward. The following pictures present the results. Also, no phots were subjected to post-processing of any sort.
The photos below present the f22, 1/50 exposure from each photo (Vivtar on top, JCP on bottom)




Notably, despite the polarizing lens having been removed, the Vivtar presents a substantially bluer image. The blue-shifting presents more detail for distant objects, but weakens contrast between shadows and surrounding area. The images below are 100% screen capture of each photo.




At these very small aperture settings, aside from the color shift, the lenses function almost identically. This changes when the lenses are wide open. The following pictures present the f2.5 (2., 1/2500 photos from each lens:




The lenses present the same colro cast differences as seen at f22 setting. However, the Vivtar at this setting exhibits soft edge focus. The JCP at this setting exhibits soft EVERYTHING focus. The 100% photos below present the evidence:




As for the f8 setting, without posting additional photos, the results are approximately halfway between the findings of the far-end aperture settings.
For the second test, I intentionally over- and under-exposed a shot in the series. The series included seven shots: f22 at 1/30 and 1/60, f11 at 1/250, f5.6 at 1/800 and 1/1250, and f 2.5 (2. at 1/2500 and 1/3200. Interestingly, the Vivtar functioned far better than the JCP on the intentionally over-exposed photos (1/30) but not on the under-exposed shots (1/3200). The photos below present the over-exposed photos (Vivtar on left) and underexposed photos (Vivtar on top.)






Photos of this size might not show it, but the lenses again exhibit the same focus issues where the Vivitar retains focus at larger apertures and the JCP steadily loses focus the larger the aperture opens.
The lenses, after facing off, each exhibit some strenths and weaknesses. The JCP’s focusing issues correlating to open aperture settings could be related to it’s loose fit on the mount. However, the lens glass seems to deliver a more “true” color presentation. The Vivitar’s blue-shift would be unnoticeable if not next to a similar lens photographing an identical scene with identical settings.
As for which lens I will use, well, both lenses have foam plucked out of the camera case already, so for the time being both lenses will remain in my camera case. However, at some point, the JCP will have to be phased out in favor of a lens capable of delivering quality results across a spectrum of settings.

To examine all photos, follow this link: https://picasaweb.google.com/102333270936007447976/28mmLenses#
The photos are named thus:
Viv L1 2500.jpg – Vivitar 28mm, Landscape 1, 1/2500 exposure, jpeg file.
JCP L1 50 100.jpg – JCP 28mm, Landscape 1, 1/50 exposure, 100% enlargement, jpeg file.
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[Nesster]

That's very interesting indeed. Perhaps the JC Penney is out of collimation and won't get true infinity? I suppose one way to test this is to focus on something close and see if the focus shifts as you open up.

Otherwise, the JCP does show good promise relative to the Viv - seems to have potential for better definition and as you say better color. Plus it is smaller.

Thanks for the comparison.