The Mamiya Sekor SX 1.7/85mm is a rare and sought-after portrait lens. It obvioulsly was produced in small numbers and is very difficult to find. My sample was included in a set of Mamiya SX lenses consisting of the 2.8/28mm, the 1.8/55mm, the 1.7/85mm and the 3.5/200mm. Is in very good condition, and at 505 g it feels massive - especially since the lens is not that big. The lens barrel is well made, focusing is slightly stiff, and hte MFD is 0.9 m - overall quite comparable to the contemporary 1.7/85mm and 1.8/85mm lenses of other manufacturers.

The optical construction - officialy stated to be [6/4] in Mamyia DSX 1000 user manuals - is a bit a mystery to me: I can count six strong reflections in front of the aperture, and five reflections on the backside of the aperture (one of them rather faint, indicating a cemented group). This indicates a [6/5] construction, commonly found also on other 1.7/85mm and 1.8/85mm lenses. I've never seen a lens section of the SX 1.7/85mm.

Even though the lens is a portrait lens (and probably optimized for smaller distances) it performs pretty well also at infinity. The following applies to 24 MP FF cameras.

Wide open the SX 1.7/85mm has high resolution, but a relatively low contrast. There are very few lateral CAs, but some purple fringing ist visible (longitudinal CAs). Stopping down to f2.8 increases the contrast of the central part to very good levels, and color fringing is gone. At f5.6 the image is tack sharp even in the extreme corners. Notably, there are no CAs visible at all. This is rather uncommon for a fast portrait lens.

I have compared the SX 1.7/85mm side-by-side with the Minolta MD 2/85mm, the sharpest vintage 85mm lens i know. While the Minolta looks by far "cleaner" at f2 and f2.8, the Mamiya at f5.6 is as sharp and contratsy as the Minolta, and it has less CAs - certainly a respectably performance.

In its overall character, the Mamiya SX 1.7/85mm resembles very much the Konica AR 1.8/85mm, another small portrait lens with a soft character wide open and excellent detailresolution and very little CAs stopped down. 

During the last few years I have seen this lens for sale three times: sold for around 290 EUR at kameratori.fi, not sold for USD 650.-- at ebay.at, and as part of the above mentioned set which I bought myself here in Switzerland.

"I only had my Mamiya Sekor C 1.9/80mm [medium format lens] for one week before I sold it. Bokeh was just too harsh for me. I also sold my copy of the Rokkor 85/1.7 two days after I got my copy of the Mamiya Sekor SX M42 85/1.7."

User "gasrocks" at fredmiranda

Prices:

2019 sold at kameratori, finland, for EUR 285.--

2016 liste at ebay.at for USD 650.-- (listing ended by seller)