Auto Sears 50 2.0 PK - sharpness test

[truls]

I hope to improve my lens testing, in all respects. Some newcomer errors have to be ignored. I think the main purpose after all is clear enough. The Sears 50mm 2.0 is a very cheap lens, and easy to get. After using Sears lenses they have become some of my favourite glass. Not only digital, also on a Sears camera shooting film. If one not can afford expensive glass, Sears lenses could do the trick. Today I have tested both center and corner sharpness, and compared to my kit lens, Olympus af zoom 14-42 (28-84 equiv).

I think this Sears lens is a Rikenon rebranded, it says "Made in Japan". Another lens I have, Sears 28mm - made in Korea, could be Samyang. Any comment on this?

Errors could have been made, bear with me

The lens:



The test chart:


Center result:

Left f2, right f2.8


Left f4, right f5.6
Lower left Olympus lens f5.6


Upper left f8, upper right f11
Lower left Olympus lens f8, lower right Olympus lens f11


Left f16, right Olympus lens f16

Corner result:


Left f2, right f2.8


Left f4, right f5.6
Lower left Olympus lens f5.6


Upper left f8, upper right f11
Lower left Olympus lens f8, lower right Olympus lens f11


Left f16, right Olympus lens f16

Any comments welcome, good or bad of course. My small evaluation says the Sears lens is good. There is a warm color cast at f8 and 11, why I do not know..

Edit: I ran out of battery, so here the real world image with Sears lens 50 2.0:

At f2.0
The bokeh is not the best, somewhat distracting.


At f2.0, 100% crop


At f8.0, 100% crop

[philbirch]

A nice lens. Yes there are a lot of makers under the Sears name. To some extent Sears was a priced based brand and so they looked for the best quality at the best price. You get a few dogs, as always. But on a crop sensor camera almost everything performs well.

I have done tests on my lenses and have been surprised at the results when I tested my 28's: Rokkor 28 f3.5, Zuiko 28 f3.5, Optomax 28 f2.8, Soligor 28 f2.8 and Sigma 28-200 the Sigma came second to the Rokkor. It also came in the middle of my 135's test (out of 5) and second in the 200's (out of 4).

Bokeh is subjective, as is lens sharpness. Ultimately I look at how the lens 'draws' the image and its character. Of course if you collect lenses thats not important - but it is nice to have a great lens with great character.

[Stephen]

Very much as expected for the type, pretty well all modern F2 50mm are exactly the same optical formula, sligtly soft full open, with a quick sharpening to F4, with the Olympus catching up at F11 (zooms are nearly always lower at each stop in sharpness).

I have a couple of these, one Vivitar brand, one Ricoh, very much the standard 50mm from the late 70's onwards.

The shift in warmth is due to the effective Iris position moving as the F value alters. Lens have an internal focus point, which in theory should match the iris position, but is altered as the iris alters. It shifts some colour more than others.

Well designed lenses, read expensive Leica, correct for this as much as possible, or in modern zooms aspheric surfaces correct the defect more.

The effect is smaller at infinity focus and smaller apertures, but increases at close focus settings. Notably most Russian lenses are well corrected, and maintain colour balance as aperture alters, but then the Russian F2 standard was a Zeiss designed lens!

Stephen