[Tonto]

I got my K01 recently WITHOUT the DA40XS (price was basically body with a free DAL18-55) but I am still keen on a 40mm to fit.
The following options and B&H prices as follows:

DA40XS: Pentax DA 40mm f/2.8 XS Lens 22137 B&H Photo Video $246

In terms of sheer smallness and cost obviously the XS gets the nod, especially if bought from a split K01 box. Also arguably has best AF with a K01.

DA40 limited: Pentax SMCP-DA 40mm f/2.8 Limited Series Autofocus Lens 21550 $496

Love the construction,quick focus, 49mm filter and FF compatibility (I shoot film on occasion), but the much higher price for what is basically the same optic is abit hard to get past.

FA43: Pentax SMCP-FA 43mm f/1.9 Limited Series Autofocus Lens 20180 $746

Obviously the best of the bunch for the film bodies, best build and still very small compared with my current FA31, this will pretty much live on the K01.
The aperture ring could come in very handy given the single dial of the K01 and is fast and #2 of the 3 legends ! - although quick shift is again missing.

Also of course there are the MF versions of the 40 mm in Pentax and Voightlander mounts but for this exercise I'm after a AF model.

Final points are I am in the market for a FA50 and a MF 50 but once I get those I feel the 40 will stay on camera most of the time saving the prime swapping for my K7.

[carrrlangas]

if cost isn´t a parameter, go for the FA43... Faster of them and quite small.

[Na Horuk]

My K-01 came with the XS and considering how "cheap" it was in the package, its an amazing lens. But some people who have both the XS and ltd say the ltd is overall better. It also has some convenient features that the XS is lacking. And much more convenient filter size.
The FA 43 is a legendary lens, but some say its not best suited for digital, that its more of a film lens. Though, I doubt you would be disappointed by it.
I don't think you could go wrong with any of these, its mostly a matter of budget

[Giklab]

I suggest the XS. Lower price, and it's not that hard to flick the AF/MF switch. Plus the MF feel on the XS is very good, you can focus using only one finger as well!

[SKwan]

I have got a DA40 Limited before but lost in a bus. I used it on K-5 and the photos are sharp with good contrast.
I bought a K-01 with DA40XS three weeks ago. I can say its photo quality as good as DA40 Limited.

The photos attached are resized from RAW without any PP. The 1st one is K-5 + DA40 limited. The 2nd one is K-01 + DA40XS.

[Sandy Hancock]

I have had the DA40 limited and FA43 limited for quite some time. While the former is a very fine lens, I recently sold it because I never preferred it to the latter.
The FA43 is *vastly* better; it is faster, sharper, has better colours and sooooo much more pixie dust. You have to experience it.
It is only slightly bigger. In fact, that isn't really a negative, because I found the DA40 a little difficult to handle because of its tiny size.

[normhead]

I have had the DA40 limited and FA43 limited for quite some time. While the former is a very fine lens, I recently sold it because I never preferred it to the latter.
The FA43 is *vastly* better; it is faster, sharper, has better colours and sooooo much more pixie dust. You have to experience it.
It is only slightly bigger. In fact, that isn't really a negative, because I found the DA40 a little difficult to handle because of its tiny size.

You have to want what the XS has to offer. Really it's a point and shoot lens, that turns your K-01 into a point in shoot with DSLR image quality. But, sometimes that is a really good thing, if that is what you want that day. I go on a lot of walks with the DA*60-250 or A 400 on the K-5 and the XS 40 or 21 ltd on the K-01. It's not an all purpose camera and it's not an all purpose lens, but they both have their place in the world. It doesn't get out the door as much as a more versatile lens... but it does get out the door.

[Sandy Hancock]

It doesn't get out the door as much as a more versatile lens... but it does get out the door.

But only if you don't own the FA43.

[gda13]

My 40mm ltd spends most of its time mounted to my k01 since the size is ideal on this body and as was previously mentioned the filter size is a plus, especially if you have or intend to have a suite of limited lenses...as for price there are exceptional deals here on market place if you keep a lookout. I bought mine from a PF member for a few dollars more than the 40xs price you mentioned above and it looked brand new as it was rarely used by the seller. Good luck with your decision!

[bdery]

You could go used for both 40s, and save a bunch.

The 43 seems to be the favourite of users but not of testers. There's probably something special about it which can't be measured in a lab.

The 40 LTD is supposed to have better build than the XS, and has quick-shift. The FF compatibility is a clear advantage. Its AF is supposed to be the best of the three, but between the LTD and the XS it's probably near to a wash.

For the record, I recently decided to go with the 40 LTD and I'm awaiting its delivery, so you know where I stand

[hcc]

I suggest the XS. Lower price, and it's not that hard to flick the AF/MF switch. Plus the MF feel on the XS is very good, you can focus using only one finger as well!

+1
MF is so easy with the 40mm xs. This is often overlooked, and yet so nice by combining focus peaking.

My 5 cents.

[manntax]

All depends what you looking for - but I found myself keen on having both XS 40mm and SMC-M version. Both has little bit different charasteric with slightl difference in color rendition and bokeh.Anyway below quick and dirty comparison of both lenses. Both the same aperture, ISO, manual focusing and same light - and both done with K-01.
Edit: Initially I thought that SMC-M is slightly wider than XS - but after another test on tripod this time it turned that XS is actually wider than SMC-M.

SMC-M f 2.8 - appears to have a slight edge in sharpness - this isn't the case after you stop down - but at 2.8 I think SMC-M is sharper - at least my copy


XS40mm f 2.8 - it has more smooth bokeh - but this might be only me or this particular situation


-manntax

[Tonto]

Wow great feedback- I may be leaning toward the FA43, some of those 40XS shots are impressive though!

[Kozlok]

Manntax, I am probably wrong, but the M doesn't look sharper to me, it looks like it has about a 1/3 to 1/2 stop less exposure, leading to more apparent contrast. Try setting the XS with -1/2 exposure bias and recompare.

[THoog]

Just to inject some randomness, by this point someone usually mentions the Voigtlander 40mm f/2 Ultron (by all acounts, an impressive little lens) or the Chinon 45mm f/2.8 pancake (comparable to the M40). There, I did it.

If nothing else, I like to use my 40XS as a body cap when I travel, to have another prime with little space/weight penalty.