[ChopperCharles]

So, I'm buying a K-x after Christmas, and I'm looking for an inexpensive, fast, and sharp 50mm. I've read that the M42 screw mount f1.4 50mm is one of the best pieces of glass ever made, and would consider it if it's really that good. Otherwise the M50 1.4, M50 1.7, the A50 1.4, and A50 f1.7 are my other options.

I'd of course prefer the auto aperture lens if they're optically as good as the manual, but they are about twice the price of the M lenses.

Thoughts?

Charles.

[Huck Finn]

IMO the best cost/performance ratio belongs to the A 1.7, unless you have to have AF.
Prices are quite reasonable and you'll still have all the metering options and the program modes.

[jolepp]

M50 1.4 or 1.7 and A50 1.7 are all very good and the prices are reasonable. The A50 1.7 is the dearest (around $100 I would imagine).

[newarts]

Keh.com has a few on hand:
Pentax Manual Focus Fixed Focal Length Lenses - KEH.com

I'd get an A type; f:2 may well be fast enough considering you have a K-x. Much faster may have too shallow a DOF to focus easily.

Dave

[SpecialK]

You can put a "Wanted" post in the marketplace. And get a genuine Pentax adaptor.

[ChopperCharles]

I want the shallow depth of field, that's the point of buying a fast prime

An A lens would be convenient yes, but I'm more concerned with sharpness. Plus I'm really interested in the M42 manuals, as they're *cheap* and I had the pleasure of shooting with one of the 50mm 1.7's a few years back, and the photos were just astounding. The M50 that came with my K1000 was no where near the same class of lens. (f2.8 if memory serves)

How do the old M's and A's compare to the screw mount lenses of the same focal length and f-stop?

Charles.

[Ira]

I've read that the M42 screw mount f1.4 50mm is one of the best pieces of glass ever made, and would consider it if it's really that good.

All I can say is, that's my favorite lens.

[paperbag846]

The screwmount 50mm 1.4 looks to be maybe the best overall deal in Pentax, considering that is built to standards that simply do not exist today and they can be found for a relative steal. Just make sure it's in good condition... as these items are fairly old and may have seen a lot of use by now .

I can vouch for the A 50mm 1.7 as being a good lens, and the A is very handy. It's deadly sharp at f2. Not exactly a bokeh master though. I prefer my K55mm 1.8 for portraits, but I would think that the SMC tak 50 1.4 would obliterate both of them (and the modern FA 50 1.4).

[RioRico]

All those mentioned are good lenses. I personally prefer my ST50/1.4, M50/1.7, and Tak55/1.8. Well, my first lens and still my fave is the FA50/1.4, but that's a bit pricey now. At the other extreme, for DOF almost as thin as a 50/1.2, I got an M42 Sears-Tomioka 55/1.4 for US$2.25 a few weeks ago. TWO BUCKS!! And a C/Y Yashica ML 50/1.4 for US$10.25. TEN BUCKS! But I had to mod its base a little. Other quality M42 lenses in the 50-55/1.4-1.8 and 58/2 range can be had pretty cheap: Mamiya, Petri, Yashica, Chinon, Ricoh, Porst, etc. But remember that an 85/2 has thinner DOF than a costly 50/1.2.

NOTE on how to rate a lens' DOF: Just divide the focal length by the maximum aperture. The bigger the quotient, the thinner the DOF. This index is useful in comparing lenses, that's all. It doesn't indicate the DOF at any subject distance, just that one lens' is thinner or thicker than another's. My thinnest lens is a projector 127/1.8 that cost me ONE BUCK! Even a 135/2.5 beats all Nifty Fifty's except a 50/1.0, which you'll likely never find. Have fun!

[abacus07]

The M42 takumar 50/1.4 and the A 50/1.7 are pretty close to the same price (and there is a benefit/drawback to each). But that's not including the adapter that you have to buy for the M42 ($30+shipping). I bought my A 50/1.7 for $82 shipped and that's about the cheapest you'll find a lens that should definitely be in good condition. You can find cheaper if you are willing to take risks (no guarantees and bad pictures). The M50/1.7 and the tak 55/1.8 seem to go for about the same price also. And probably present the best value while retaining excellent IQ.

Another option is the Helios 58mm f2 lens (M42) for $20-30. I plan on getting one of these just for fun since they're so cheap.

[Douglas_of_Sweden]

Most lens for least money:

SMC Pentax-M 50mm f1.7
SMC Pentax 50mm f1.8 or f2.0
SMC/Super Takumar 55mm f1.8 or f2.0 (same optics as the above)
Super Takumar 50mm f1.4

The other f1.4 costs more, and A contacts double the price.

3rd party
Rikenon XR 50mm f1.7 is also a lot of lens for the money and well made
There is endless of cheap 3rd party 50mm lenses, but mostly you have to try them to know how good they are. Also there, anything f1.4 or faster cost more.

If you buy wise and treat them well, you can sell for the same price and consider shipping the leasing cost

[macTak]

Most lens for least money:

SMC Pentax-M 50mm f1.7
SMC Pentax 50mm f1.8 or f2.0
SMC/Super Takumar 55mm f1.8 or f2.0 (same optics as the above)
Super Takumar 50mm f1.4

You mean SMC Pentax 55mm f1.8 or f2.0. Otherwise, I can't argue with your most lens for the least money listing. Personally, I love the M 50 f1.7 and would go for that (or the A version if the aperture control is worth the extra to you), otherwise, I'd be patient and try to get a good deal on a SMC Takumar 50mm f1.4 (was able to get one for $35 shipped with a Spotmatic on ebay with patience). But if you don't have a M42 adaptor, which adds about another $30, try to get the Pentax K 50mm f1.4, which has the same optics as the SMC Takumar version.

[keyser]

You know, there really are not that many bad fast 50s out there. You can get a helios 44-2 for $5 if you look hard enough and it still matches most of the newer lenses of equivalent spec.

(yes, I know the 44-2 is actually a 58mm f/2 lens, but the point stands).

In terms of sharpness, the Pentax f/1.7 lenses are a bit special; not so much beyond that though. The screwmount f/1.4 will not get you the same level of sharpness, but you will get a really nice vintage look to your shots, especially if you can get one with slightly yellow glass through the radioactivity (yes, some were radioactive!).

So the REAL question is, knowing that there are a number of cheap options out there, what extra qualities are you looking for in the lens?

[paperbag846]

If you are more interested in something that feels special, over sharpness or whatnot, the SMC K 55mm 1.8 will get you there, as long as you are ok stop-down metering.

It's a great lens with great bokeh and a vintage rendering (I suppose due to the older coatings). My 50mm A lens is much more modern feeling... the K has a warm colour cast which is very nice for portriats. More importantly, though, it has a shorter DOF than the 50mm 1.7 wide open, is sharper wide open than the 50mm 1.7, and has really smooth bokeh. The bokeh beings to fall apart as you stop it down (same with the 50mm 1.7), but if you want this lens for shallow depth of field, you will not be disappointed.

[Docrwm]

I've found that the 1.4s sharpen up considerably with the addition of a hood. Many of the reviews in the Review Section talk about this and the design differences between the Pentax 50s but you have to shoot the lens with and without a hood under identical conditions to really see it IMHO. I've now got 4 Fast 50s and each has its own character. The least of them is the M50/2 (which may end up as my reverse Macro lens) and the SuperTak 50/1.4 and 55/1.8 each are nice in their own ways. The M50s are the least expensive in my experience among the Pentax lenses. Ira has me interested in some Russian lenses but I am on lens hiatus.