Minolta AF 50mm f/1.7 - LEGACY Test Report
Lens Reviews - Sony Alpha/NEX (APS-C)
THIS IS A LEGACY TEST REPORT BASED ON THE ALPHA 100. AS SUCH IT IS NOT 100% COMPARABLE TO THE CURRENT TESTS BASED ON THE ALPHA 700!

Introduction

The Minolta AF 50mm f/1.7(N) is one of the old standard fix-focal lenses by Minolta. Obviously it is a discontinued item now because Sony took over Minolta's photo department back in early 2006. The lens has no real equivalent in the current Sony line-up. Sony decided to keep the 50mm f/1.4 only but this lens is fairly expensive which is why used AF 50mm f/1.7 are fairly popular over at eBay or 2nd hand dealers. On APS-C DSLRs such as the Sony Alpha 100 (used for testing) its field of view is equivalent 75mm so it behaves more like a basic portrait lens here. Not too bad for about a hundred bucks.

The mechanical quality of the AF 50mm f/1.7 is relatively decent. It is a plastic lens with a metal mount. The focus ring, located at the very front, is rubberized (in this version) and handles Okayish (a bit sticky at times). It rotates during AF operations. Surprisingly the lens features a tiny build-in lens hood. If you bought the item without a manual you may well overlook it because it is a secondary plastic barrel between the inner lens tube and the focus ring. You can lift and lock it in position. The hood is not overly efficient but it is better than nothing. The lens extends slightly towards closer focus distances. The front element does not rotate so using a polarizer is no problem.

Like most (though not all) Sony/Minolta lenses the 50mm f/1.7 relies on the conventional focusing system driven by the camera (via a slotted drive screw). Consequently the AF produces a moderate degree of noise but the speed is fairly fast.

Specifications
Equiv. focal length75 mm (full format equivalent)
Equiv. aperturef/2.6 (full format equivalent, in terms of depth-of-field)
Optical construction6 elements in 5 groups
Number of aperture blades7
min. focus distance0.45 m (max. magnification ratio 1:6.7)
Dimensions38x46 mm
Weight186 g
Filter size49 mm (non-rotating)
Hoodbarrel shaped, build-in
Other features-

Distortion

The AF 50mm f/1.7 shows very slight barrel distortion (0.4%) which isn't really relevant in field conditions.

The chart above has a real-world size of about 120x80cm.

Vignetting

The AF 50mm f/1.7 is a full-frame lens so it can take advantage of a sweet spot effect on the Alpha 100. However, at wide-open aperture the vignetting is still quite pronounced at ~0.9EV but it is negligible from f/2.8 onwards.

MTF (resolution)

50mm lenses are simple beings which were only marginally modified since the late 70s. Usually there's very little room for improvement left here but the Minolta AF 50mm f/1.7 is not among the best normal lenses tested to date. The center performance is already very good at wide-open aperture and stopping down lifts the quality to levels at or possibly even beyond the sensor resolution of the Sony Alpha 100. However, the borders are a different story - at f/1.7 they're downright soft and not much better by f/2.8. It takes f/5.6 to reach very good territories and the peak performance is not reach prior of f/8 here. The Canon or Nikon counterparts show a much better border characteristic.

Below is a simplified summary of the formal findings. The chart shows line widths per picture height (LW/PH) which can be taken as a measure for sharpness. If you want to know more about the MTF50 figures you may check out the corresponding Imatest Explanations

Chromatic Aberrations (CAs)

Lateral chromatic aberrations (color shadows at harsh contrast transitions) are relatively well controlled but not something to rave about for such a lens. With a peak width approaching 1px on the average at the image borders you may see CA traces at times.

Sample Shots

Here're some sample shots taken with the Sony Alpha 100 and RAW-converted via ACR 3.7.

Click on a thumbnail to view the original file (opens in a separate window). Please note that the originals are FULL SIZE (=several megabytes) which requires quite some bandwidth for downloading so please don't waste the limited resources here.

Make SONY
Model DSLR-A100
ISO Speed 100
Focal Length 50.0mm
Exposure Data: f/2.8 @ 1/4000s
Size 2592x3872
Make SONY
Model DSLR-A100
ISO Speed 100
Focal Length 50.0mm
Exposure Data: f/11.0 @ 1/320s
Size 2592x3872
Make SONY
Model DSLR-A100
ISO Speed 200
Focal Length 50.0mm
Exposure Data: f/8.0 @ 1/250s
Size 2592x3872
Make SONY
Model DSLR-A100
ISO Speed 200
Focal Length 50.0mm
Exposure Data: f/3.5 @ 1/1000s
Size 3872x2592
Make SONY
Model DSLR-A100
ISO Speed 100
Focal Length 50.0mm
Exposure Data: f/5.6 @ 1/320s
Size 2592x3872
Make SONY
Model DSLR-A100
ISO Speed 100
Focal Length 50.0mm
Exposure Data: f/11.0 @ 1/320s
Size 3872x2592
Make SONY
Model DSLR-A100
ISO Speed 100
Focal Length 50.0mm
Exposure Data: f/8.0 @ 10.0s
Size 3872x2592

Verdict

The Minolta AF 50mm f/1.7 is a very good lens but it is slightly inferior compared to its cousins over at Canon or Nikon. The center resolution is great but the borders are soft at wide-open aperture and it takes a couple of f-stops till they reach decent levels. Nonetheless it is an excellent lens for portraits where the border performance is not really an issue and it can take superb images around f/8. As you may have noticed in the sample images above the out-of-focus blur (the bokeh) is pretty smooth and buttery - a seldom characteristic actually and it is also very resistant against flare (see the night shot above) so there's also a truth beyond sheer resolution figures. The Minolta AF 50mm f/1.7 is a cheap lens on the used market and for about a hundred €/US$ it is easily worth it - all other 50mm alternatives are a magnitude more expensive.

© by photozone.de