[Autonerd]

I agree with most of the common wisdom -- 28 and 50 (Pentax 50/1.7 is a nice balance of speed and cost). If you aren't sure how much telephotography you'll be doing, maybe consider a 70ish-210ish zoom? The Pentax 85-210 isn't terribly expensive, and though not perfect at the extremes will work as a portrait lens -- and if you find you're using telephoto a lot, then you could add a couple of long primes to your collection.

I think starting with just one lens is too little, but on the other hand there's no sense in spending a lot of money to solve problems you don't know if you have. FWIW, since I got back into film, I've found I mostly use my 50 and sometimes my 28... I'm itching for a good portrait lens but I've been doing pretty well with the 50.

[LesDMess]

I've never quite been able to figure out the cult of the 40mm, when the M50/f17 is faster, sharper, much cheaper, has much better ergonomics, and is only fractionally larger... An MX + M50/f1.7 is still a pocketable SLR.

The M50/f1.7 and Takumar 55/f1.8 have almost identical optical designs, and both are very good. I have the 50/f1.4 and 50/f1.2, and neither is noticeably better than the M50/f1.7 at shared apertures.)

I would be very interested in seeing the methodology and results of your testing when you get a chance.

Here are the results of my casual testing of the some Pentax primes I have. Casual because I only used my 14.7MP Pentax K20D shooting a 4X4 arrangement of 12233 test targets under ideal conditions (tripod, timer, controlled light, magnification) with the lenses across their apertures.


Full res version -> Lens tests

At this resolution, you can see that all these Pentax primes are about equal in resolution achieved because they are limited by the 14.7MP sensor. Interesting that the f1.2 seems to maintain detail to f22 when all the others drop dramatically at f16 including the macro lenses.
The Soligor CD 500mm f8 mirror lens has a poor showing even with the K20D.

Clearly these Pentax primes are limited by the 14.7MP sensor in the K20D so I had to use a higher resolving sensor and at that time the K1 was not yet available and I only had a 36MP Nikon D800 which does not take Pentax lenses. Fortunately I had some Kodak Techpan and Technidol so I upped the resolution ante and doubled the 12233 test target and conducted the test using the 50mm f4 macro.


Full res version -> Kodak Techpan 04-27 scan compare

I scanned one of the frames and to the left you can see the progression of detail that can be achieved with the K20D, Coolscan 4000dpi as well as the Nikon D800. And to the right I used my K20D+Macro+bellows to achieve about 4.5:1 magnification and you can clearly see much more detail is available that even a 36MP DSLR cannot achieve. With this test, I am not sure what limits the amount of detail these lenses can achieve - is it the lens or the film?

What I learned from these tests is that unless you use Kodak Techpan processed in Kodak Technidol - or equivalent, and you scan with a Coolscan at 4000dpi - or equivalent, then these lenses are not going to be the limiting factor in achieving detail.

I don't have all the lenses nor have I tested them all but there is clearly a trend going on here. So I say pick which ever focal lenght you need at the price you want to pay as they are all excellent performers!

[monochrome]

You should get a three lens kit (28, 55, 105 or 135) and add from there. The bolded 3 lenses are roughly $100 each in either mount. I regularly carry the first five lenses and leave the 135.

Assuming a K film body (K1000) without aperture control:

K28/3.5
• (K35/3.5) - alternate, but an outstanding lens
K55/1.8 or K50/1.4
•(K85/1.8 - very hard)
•(K105/2.8 - hard) - alternate M100/2.8 - fairly easy
K135/3.5

The same optical formula lenses with earlier coating technology can be had in m42 mount (Super Takumar, S-M-C Takumar) if you have an S body (Spotmatic) camera.

[ChristianRock]

With so many options, you'll be up to 10 lenses before you know it

Cheap yet great quality set:
SMC-M 28mm f/3.5 - you want your wider angle shots contrasty and full of beautiful color, so get this instead of the f2.8 version. They cost about the same anyway - around $70.
SMC 55mm f2 (K series) - the M 50 1.7 everyone suggested is an excellent choice and I'm sure you'd be happy with it, but the M 55 f2 has better bokeh, better rendering stopped down, and is beautifully sharp wide open. It really brings the best out of the scene. Do get a hood with it though, not as flare resistant as the M series lenses. About 40 dollars.
Takumar Bayonet 135mm f/2.8 (or f2.5 if you can't find the f2.8). I've had a bunch of 135 2.8 and 2.5 lenses and this is as good as the SMC-A 135 2.8 except the coatings aren't quite as good - but better than people usually assume they are, plus the difference won't be noticed much on film anyway. Fantastic lens for the price. About 40 dollars (I paid 32 for my f/2.8...)
Total: 150 dollars.

Fantastic quality set:
SMC 28mm f/3.5 (K series) - even better than the M 28 3.5, but if's diminishing returns - you'll be paying 3x for an extra little bit of quality. About 150 dollars.
SMC 50mm f/1.2 (K series) - the 50mm lens that all other 50mm lens want to be when they grow up. Yes it's a bit heavy but you won't mind carrying it once you see what it can do... about 350 dollars for one in very good condition. Which to me is a STEAL.
SMC M 100mm f/2.8 - there might be better lenses like the rare SMC 105mm f/2.8 (K series) or the SMC 135mm f/2.5 (K series) but I haven't had either one. What I do know is that the M 100 2.8 renders just about as nicely as the K 50 1.2 in the shared apertures. An absolute joy to use. The low price they usually go for is just a bonus. Get one in good shape for about 120 dollars.
Total: about 620 dollars.

OR

you can do your homework with no rush while enjoying the SMC-A 35-105mm f/3.5 zoom, a.k.a. the "stack of primes". Get that one now for less than 100 dollars, and add on others as you find out what is out there and what will work best for you...

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Last edited by ChristianRock; 12-26-2019 at 10:21 AM.

[LesDMess]

Fun lenses to get maybe a fisheye or mirror lens.

The M42 Fisheye Takumar lens with an M42 adapter can be used on K cameras. It is very compact - almost like the 40mm pancake.


Of course it offers a very wide perspective but it is also surprisingly very sharp. This on Kodak Ektar 100.


This on Kodak Portra 160.


This on Kodak BW400CN.



The advantages of a mirror lens are focal lenght, compact size and low price. The Soligor CD 500mm f8 - and others of it's kind, is not really so terrible as long as you know what to expect.

It is compact and lightweight. Here it is on an MX with a lens hood.


For casual shooting it is pretty good. Taken with Lomography 100.


You get the ring on out of focus elements. Taken with Lomography 100.

[Wasp]

A great K mount lens set in my opinion would be,

SMC Pentax-M 28/2.8
SMC Pentax-M 50/1.7
SMC Pentax-M 100/2.8

I have them all and they are just wonderful. The 100mm can be substituted with the M 135/3.5. Also consider adding the M 200/4 to the list.

[Astro-Baby]

I would go with;

Wide ......either a 35mm or 28mm depending on preference. I prefer 35mm but I also have a 24mm whcih gets not much use.

Standard......50mm I always tend to stay with whatever the canera was sold with. 1.7 is fine and keeps the cost down. I have some cameras with 1.4s, 1.2 is usually insanely priced.

Telephoto.....135mm should be good for most. I get little use out of 200 and 300 lenses.

Zoom......I always like to have a short zoom something like 35 to 70 for walkaround when I am not carrying a gadget bag. Not essential but in the world of old glass try to keep the zoom ratio low as old glass was not good at coping with massive zoom ratios.

Brand, I always prefef the 50mm standard to be whatever the cameras was originally supplied with. The others could be anything. As I have a wide range of bodies I use Tamron for the Adaptall capability but thats just because of the different mounts I have. If I were sticking with K mount I’d be flexible and try for OEM but maybe settle for third parties products.