First impressions SMC Pentax-M 50mm f/1.7

[caspert79]

Received this lens last week, and took some quick pictures with it.

What I noticed is that the lens is quite soft and has quite some CA's wide open, so often it's a good idea to stop down until f/2. I like the image at f/2 however. Non distracting bokeh, and the colors are poppy:

PentaxM5017DSC09978 by devoscasper, on Flickr

Another picture at f/2:
PentaxM5017DSC09983 by devoscasper, on Flickr

Center resolution is good at his aperture. Overall image are very pleasing to my eye.

Image @f/5.6:
PentaxM5017DSC09990 by devoscasper, on Flickr

I like the bokeh in general although hexagonal highlights are not my favorite.

Conclusion until now: I quite like this lens, it's also very compact. Resolution seems very good, but I'm not sure if it's at the same level as for instance the Mamiya SX 55/1.8. Hope to test that some other time and come to a final conclusion.

[caspert79]

Some more shots:

@f/2:
PentaxM5017DSC00008 by devoscasper, on Flickr

@f/5.6, focus on flower in corner.
PentaxM5017DSC00002 by devoscasper, on Flickr

@f/5.6:
PentaxM5017DSC00001 by devoscasper, on Flickr

[iangreenhalgh1]

I've had at least two or three copies of this lens, might still have one in my boxes. It's a good lens, but I preferred the 2/50 version, I can't quite remember why though.

[titrisol70]

Haven't used mine in a while, but it was my workhorse in the ME/Super for many years
I use the A 50/1.7 better since the DSLR have full control of the aperture.

I will bring mine out and test to confirm but your copy might have some dust between the elements that gives the glow you mention

[D1N0]

In my experience softness isn't really a problem with this lens. All fast fifties can be a bit glowy wide open depending on light (not talking about today's kg hunks of course). This was shot at 1.7

Mr Wonky ear by The lens profile, on Flickr

[caspert79]

[Dejan]

I've had a few of these lenses (and still have a couple), based on my experience, and of my friends, it's one of the sharpest vintage 50's out there for general purposes. I don't think any vintage lens beats it as a landscape lens considering the sharpness and colours plus small size and weight. Wide open, well... It's definitely sharper than 1.4 version up to F2.8, after that they are practically the same. It's not perfect, but better than most fast-ish 50's I have. Bokeh sometimes works for me, sometimes doesn't (not my first pick for flower pics and such, but I find it okay). It's a bit nervous, but it really depends on all the standard factors. I like the lens and nothing beats it for the price, that's for sure, it's a better lens optically than many competitors I think (especially from the same era). I only wish it had at least 8 aperture blades like F1.4 version, it would really, really help with specular lights, but oh well...

[titrisol70]

The 50/1.7 also has a shallow DoF; in APS-C and at 1.7
Distance Near Limit Far Limit (all in m)
0.5 0.5 0.51
1.0 0.99 1.02
1.5 1.48 1.53
2.0 1.95 2.06
3.0 2.87 3.14
5.0 4.65 5.42

Using the hyperfocal calculation as per Stroebel's View Camera Technique 7ed book

Hyperfocal = ((focal ²) / Aperture * CoC) + focal ) / 1000
And
Near Limit = "(hyperfocal x distance) / (hyperfocal + distance)"
Far Limit = "(hyperfocal x distance) / (hyperfocal - distance)"

I can post a spreadsheet that calculates this if you want to