[kitestring]

Thanks everyone for your answers, it seems like I'm going to settle with 40mm.

One final thought: Instead of the 21mm, you might consider the DA 15mm Ltd.

It seems like it's not as versatile as 21, I saw a couple of great shots in sample gallery, but I think it would be hard to me to compose a shot for such a wide lens (I never really did a lot of wide-angle before)

[bdery]

FA 50/1.7. The DA is pretty much the same lens optically.

Nope, not by a fair margin.

Poor´s man Quick Shift: Press the mount release button with your right pinky and tada! instant manual focus

Doesn't work as well, on my K20D at least the camera stops communicating well with the lens when you do that.

[thornburg]

My $0.02: I have the DA 40mm Ltd. I absolutely love, LOVE this lens for several reasons.

Multiple times you call out specifically the 40mm Limited. Do you have a particular reason for the Limited over the XS? Do you think it's worth twice as much? If so, why?

[jimr-pdx]

I have 24/40/70 as my prime triplet, and am very happy with the 40. I prefer quick-shift and found an excellent deal on the 40 Limited, and it's a focal length that I like. I owned the 18-135 for a while and found myself shooting near 40mm a lot; that won't be true for everyone of course.

I did own the 35/2.4 (twice) and found image quality to be excellent. And I have an old 50mm f/2 for just in case, you can get the SMC-M for so cheap - but the 40 and 70 are intended to do the work so the 50 sits on an old film body.

[carrrlangas]

Nope, not by a fair margin.

why??

Doesn't work as well, on my K20D at least the camera stops communicating well with the lens when you do that.

Weird... It works perfectly on my K-5 , *istD or MZ-5

[tele_pathic]

Multiple times you call out specifically the 40mm Limited. Do you have a particular reason for the Limited over the XS? Do you think it's worth twice as much? If so, why?

No reason. I happen to have the DA 40mm Ltd., so I refer to that. The XS was on my radar, and I would have bought that lens except that I stumbled upon a great price for a used DA 40 Ltd. And frankly, I don't use quickshift enough to justify the price difference; in fact, I never use the qs feature. But I do like the cosmetics of the 40 LTD vs. the 40 XS. Enough to pay double? Well, for me and my financial situation at the time, yes. Again? I might get the 40 XS. As far as I can tell (and I did a lot of research), they are the same lenses internally, minus the quickshift feature, or optically, but the primary difference is build material and cosmetics.

[kitestring]

Multiple times you call out specifically the 40mm Limited. Do you have a particular reason for the Limited over the XS? Do you think it's worth twice as much? If so, why?

In the place where I live I can get XS for ~$340 and Ltd for ~$440, I've thought that Ltd is better built and has a slightly better image quality.

[carrrlangas]

In the place where I live I can get XS for ~$340 and Ltd for ~$440, I've thought that Ltd is better built and has a slightly better image quality.

Wow, that´s expensive. Where I live I can´t even find these lenses. So I bought the DA40XS used here on the marketplace for U$D140 shipped to a forwarder who brings it to me for 25% of the value...
You can get a DA40 ltd for U$D250 - U$D300 on the marketplace

[boriscleto]

Nope, not by a fair margin.

And what leads you to this conclusion? Both are 6 elements in 5 groups, all of the 50/1.7s were 6 elements in 5 groups. The DA will have a different bokeh because of the 7 rounded aperture blades vs 6 straight aperture blades...

[bdery]

And what leads you to this conclusion? Both are 6 elements in 5 groups, all of the 50/1.7s were 6 elements in 5 groups. The DA will have a different bokeh because of the 7 rounded aperture blades vs 6 straight aperture blades...

The number of optical elements does not mean they are identical. All the user reports, tests, and my humble experience with the DA50 in-store, suggest they are different. The F and FA are sharper wide open (not overly so), the bokeh is busier, the colours "colder" (less true with the FA).

If they were the same, what would have prevented Pentax from making it f1.7?

[carrrlangas]

If they were the same, what would have prevented Pentax from making it f1.7?

The same, optically. Differences in coatings or closing aperture a bit to avoid reflections because the optics are meant for bigger format. Like with the DA35/2.4 and FA35/2

[boriscleto]

If they were the same, what would have prevented Pentax from making it f1.7?

For the same reason Asahi made a 55/1.8 and 55/2 that were identical in every way except the 55/2 was mechanically limited to f/2.

[prime.partisan]

I have 40mm XS and FA 50mm f/1.4. For portrait use, the 40 might be too sharp even at wide open. There's a bit more contrast too. I like FA 50 better for those reasons. And for low light, that F/1.4 is very usable.
Lately there's a bunch of FA 50 copies on marketplace going for very reasonable price.

[Na Horuk]

For portrait use, the 40 might be too sharp even at wide open.

Good point, the 40mm is a sometimes unflatteringly sharp.
I think the most important difference between the 40mm XS and ltd is the filter ring size. It is very hard to get lens caps, lens hoods, and quality filters for the XS lens. A lens hood can be very important, and the 40mm ltd has a great hood. And if you use filters in your photography, it might be a worthwhile consideration.

[twitch]

The DA40 is a solution looking for a problem. It doesn't shrink your DSLR into a m43's or NEX sized camera. I owned a DA40 for a while and traded it for a FA50 which I've been very happy with.

In this range if you go for a prime then it needs to be f/2 or faster; so I'd suggest a FA43, FA50 or FA35. Otherwise you may as well buy a Tamron 17-50.