| Minolta AF 4-4.5/28-135mm sample variation |
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If someone looks for a high resolution zoom for the Sony A900, the Minolta AF 4-4.5/28-135 mm may be worth a trial. Stopped down to f5.6 or f8, it has the same detail resolution as the best Minolta primes such as the Minolta AF 2/28mm, the 1.5/50mm, the 2/100mm and the 2.8/135mm. In fact, this 25 year old zoom has an equal (at 28 and 35mm) or better (at 50mm and 70mm) corner resolution than the Zeiss ZA 2.8/24-70mm. However, focusing can be tricky - if the 28-135mm is slightly out-of-focus, the detail resolution remains, but the contrast decreases. In addition, the corner performance is strongly affected by a slight misfocusing. I am quite sure that most reported "bad copies" of the 28-135mm simply were slightly out of focus!
I never had more than four 28-135mm at the same time, but I compared two sets of three lenses each. Here are the results of my second set of 28-135mm lenses. All have an outstanding detail resolution in the image center. There's no need to show 100% crops from the center, since there are no visible differences between the three copies anyway. The extreme corners are most susceptible for decentering and other effects of ageing or damage; therefore 100% crops of the extreme corners are shown here. All four lenses (SN 1008346, SN 11301518, SN 16105409, and SN 19103205) were bought recently here in Switzerland, two of them from a well known shop in Zurich , the two others from private individuals, together with Minolta 7000 cameras. The combination of the Minolta 7000 and the 28-135mm was quite common here among advanced amateurs in the 1980s. Usually the owners cared well for their expensive lens (the 28-135mm was CHF 1090.-- around 1987), and this may explain the good state they are in. The top row are always 100% crops from the center of the image, the bottom row are 100% crops from the corners.On the left side "wide open", then the four samples at their "optimal aperture", then - at the right side - the crops from the corresponding prime lens, usually the best in the Minolta AF system. All images were taken using a Sony A900 DSLR (24 MP). All images were taken with 2s Mirror-Lock-Up (MLU). Professional carbon fiber tripod Giotto 8351B with a three-way-head Manfrotto 410 was used. The RAW data were developped with Photoshop CS4 (sharpening 55, radius 0.5, detail 55). No correction for "Color Aberrations" (CA) was applied! Link to a full size image (taken @ 100mm, f8; no CA correction applied)
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