Pentax M 50 f1.7

The Pentax M 50mm f.17 normal lens was, in its day, a “budget” lens. In the late seventies and early eighties, Pentax issued four 50mm lenses: the SMC 50/1.2, the M 50/2, the M 50/1.7 and the M 50/1.4. The Pentax SMC 50 f1.2 was the expensive top-of-the-line lens. And, indeed, it’s one of the best SLR lenses ever made. The M 50 f1.4 might be considered a “prosumer” lens, although it is a superb lens in its own right, overshadowed only by the mighty 50/1.2. The M 50/2 was only sold as part of a kit (usually with the popular K1000). It could not be bought separately. Although the M 50/2 has a fair amount of resolution (what 50mm lens is not sharp?), it lacks the distinctive color rendition and contrast that characterizes most of Pentax’s SMC prime lenses. The last of the bunch, the “budget” lens, is the M 50/1.7. Although it may have been the least expensive 50mm lens sold separately from the kit, don’t let that fool you. This is a low price optic that delivers high priced results. Even though the lens has not been in production for more than 25 years, copies are easy to find at bargain basement prices. Usually, it sells used for under $75, sometimes even under $50. I purchased a copy in 2010 for $45.

Like all of Pentax’s K and M series lenses, the M 50 f1.7 is a manual focus, manual exposure lens. It attaches to any Pentax K-mount SLR, including the current crop of DSLRs. You have to use the green button on the K series of DSLRs to get exposure; and you have to focus the lens yourself (although focus confirmation does work with the lens, as does Shake Reduction). These disadvantages are the trade-off for purchasing first-rate glass for pennies on the dollar.

Here’s what the lens gives you: very good contrast, excellent color rendition, and very good resolution. It is not the sharpest of Pentax’s 50mm lenses. Pentax’s 50mm f2.8 macros and their 50 f1.2 attain greater levels of resolution. But the M 50 f1.7 is already sharp enough so that additional sharpness is hardly needed. Consider the following image, followed by a 100% crop:

Now this is a 100% crop of an image taken at infinity focus, which won’t quite tell us what the lens is capable of. Consider the following example of something taken within 40 feet:

Notice also the rich color and superb contrast of the lens. Some people prefer the M 50 f1.7 to Pentax’s faster 50mm lenses precisely on account of the greater contrast and the darker colors that it produces. To be sure, the colors this fast 50 produces might be a tad on the cool side. Still, they are rich and, in their own way, quite distinctive. I’ve never seen comparable colors produced by either Nikon or Canon’s cheap budget 50mm lenses.

Does the lens have flaws? Yes, a few. The main one is less than stellar bokeh. Consider the following image:

Notice the out-of-focus rendering at the top of the image: it just doesn’t have the smoothness that you’d get from Pentax’s faster 50mm lenses. Here’s another example:

The picture of the snail involves extending the lens with a cheap ebay extender. This works fairly well with the M 50/1.7, as the lens does not suffer from serious field curvature. In any case, the 50/1.7 allegedly works better in macro work than does any of Pentax’s faster 50mm lenses. What you don’t get, however, is excellent bokeh, as the above image demonstrates, particularly in the artifacts around the edge of the snail’s shell.

The lens is small but well made. My copy suffered from a loose filter ring. But as soon as I figured out how to take front plate off, it was an easy fix. It just needed some screws tightened, and now it works like brand new. Especially gratifying is the wonderfully dampened focus, which one only finds with vintage manual focus lenses. Among Pentax lenses, I would place the M 50/1.7 near the very top in terms of best bargains, right below the even more stunning SMC 50mm f1.8. Below are more images from this M series gem: