[DaveHolmes]

If you can find an A50 1:1.7 I think you will find the convenience of the A setting a benefit over the M version on your K-r.

+1 deffo agree with this...

[RioRico]

The Takumar 58/2 is well worth having. A Helios-44x 58/2 is comparable and much cheaper.
The Takumar 55/1.8 is great and reasonable. The Takumar 55/2 (same optics) is still cheap.
The best 50's, either Takumar/K/M/A/F/FA, are (in order) f/1.2, f/1.4, f/1.7. Avoid the 50/2's.

For low light portraits, any 50-55/1.2 would be great, any 50-55/1.4 would be just fine.
And just about any 50-55 f/1.7-1.8 or 55-58/2 would do well also. Many are still cheap.
By 'any' I mean Pentax, Vivitar, Sears, Ricoh, Petri, Yashica, Mamiya, Porst, Meyer, etc.

[Docrwm]

I've got to add my vote for either the A50/1.7 or a Super Tak 55/1.8. I own a M50/2 (and yes when it says 50:2 it is f2.0 and when it says 50:1.2 it is f1.2 and there is a WORLD of difference as has been said) it is a mediocre performer compared to the others.

The SuperTak's will require a M42 to Bayonet mount so you can use it in a modern camera. Do NOT buy the ones with a large flange as they prevent you from focusing through to infinity with the lenses.

The M models require you to set everything manually. The A models allow you to set Aperture on Automatic and allows the camera to do some of the work but also still allows you to do everything manually. The A lenses are, generally, going to cost more and be a bit newer than the M lenses.

[ajaya]

i saw most of the people in this thread voted for A 50mm f1.7 (8+) but when i saw lens review i can see a good rating for M 50MM f1.7(9+) !!
Pentax-M 50mm F1.7 Reviews - M Series Primes - Pentax Lens Reviews & Pentax Lens Database
Pentax-A 50mm F1.7 Reviews - A Series Primes - Pentax Lens Reviews & Pentax Lens Database

[Docrwm]

i saw most of the people in this thread voted for A 50mm f1.7 (8+) but when i saw lens review i can see a good rating for M 50MM f1.7(9+) !!
Pentax-M 50mm F1.7 Reviews - M Series Primes - Pentax Lens Reviews & Pentax Lens Database
Pentax-A 50mm F1.7 Reviews - A Series Primes - Pentax Lens Reviews & Pentax Lens Database

One reason most vote for the A Model is that it allows the aperture to be set by the camera automatically with its "A" setting on the lens. The cost difference can be significant between a SuperTak, M, and A model with the same lens formula.

[crewl1]

With A version: focus-shoot, focus-shoot, focus-shoot, focus-shoot...

With M version: focus-green button-shoot, focus-green button-shoot, focus-shoot *aw cr-p, forgot to press the green button!*, focus-green button-shoot...

[paperbag846]

*aw cr-p, forgot to press the green button!*

This happens all too often, and that lag caused by the green button can cost you a photo, sometimes.

However, I still think the K55 1.8 is the best bang for your buck portrait lens made by Pentax... and I would heartily recommend it (try to find the K-mount version).

[1r0nh31d3]

I recommend the A 50mm 1.7 as an all round nice lens to use. If you need to soften it up for portraits then you can do that in post production. I have one and I thought my 43mm ltd would urge me to sell the 1.7 but it never happened.

Having shot with both A and M lenses (and I still do) I will say only get a lens without auto aperture if there is some outstanding quality about the lens that outweighs the convenience of the auto aperture. Yes green button is a good work around but it is still one more step that you need to add into your shooting and it will be annoying at some point (like shooting under dynamic lighting conditions).

As far as the lens reviews go take them with a grain of salt. If a lens is getting anywhere from 8-10 it means it is good quality and user have had success using it. The sample groups and demographic who submit ratings are too limited to make any quantitative comparisons between lens ratings that are within a few points of each other. I would value much more what each user comments about the lens rather than the numbers they have assigned to each lens.

Personally I would get the cheapest decent prime you can find to get you into the game. After using it for a while it will become clear what aspects about the lens you like and what you would like to change. Which should give you enough feedback to get you a lens that will be well suited to your actual needs and not your perceived needs.

[ajaya]

With A version: focus-shoot, focus-shoot, focus-shoot, focus-shoot...

With M version: focus-green button-shoot, focus-green button-shoot, focus-shoot *aw cr-p, forgot to press the green button!*, focus-green button-shoot...

thanks well explained !

[Marc Sabatella]

With A version: focus-shoot, focus-shoot, focus-shoot, focus-shoot...

With M version: focus-green button-shoot, focus-green button-shoot, focus-shoot *aw cr-p, forgot to press the green button!*, focus-green button-shoot...

Not really. Unless the light is changing from shot to shot, there is no need to re-meter. You only hit the green button when you notice the light has changed. And if you're accustomed to using M mode even for autoexposure lenses, then there is no adjustment. The only difference between the A and M version of a lens is that the former doesn't make a sound when hitting the green button. Also, you get full time meter reading so you have some feedback as to when the light has changed without needing to test periodically.