[Papa_Joe]

Your price range is quite limiting. Fast lenses do not come with a budget price usualy.

That said, within your pirce range you might get a used Pentax FA SMC 2.0/35 mm or a used Sigma 1.4/30 DC HSM.

[niels hansen]

I would like to get a fast lens for my KP for those situations when it is getting dark, but I am still having am urge to continue shooting without a tripod. I am considering the two lenses above. I like the FA 50/1.4 better because it is faster, but I am eager to learn what others think. I am totally open to other suggestions. The requirements are a fast lens in 24-60mm range, autofocus only.

The DA 50 1.8 is the lens I have used the most times with AF tuning. As other members have told mine is not a constant AF performer. Others are of the opposite opinion. My unqualified guess is that the difference is caused by sample variation .With the KP low light performance I very seldom need more than 2.8. Stopped down to 5,6 there is very seldom any isue, it is really good
Most test rate the 18 -55 WR as good enough, mine is good

[ChristianRock]

Of those mentioned, I particularly like the F 50mm f/1.7. Super sharp with great contrast from f2.0. Still sharp but less contrast wide open, but even that is a very nice effect.

But I will admit that the FA 50 1.4 will give you better bokeh and is probably overall a better lens. I don't have one because I have other alternatives I like better (Rikenon P 50 1.4 and SMC-K 50 1.2).

The DA 50 1.8 has its admirers but I particularly don't like the way it renders wide open and at f2.0. It needs f2.8 to look right. Otherwise I would have picked one up by now, they're going for 50-60 dollars sometimes in the used market.

[Wheatfield]

I would like to get a fast lens for my KP for those situations when it is getting dark, but I am still having am urge to continue shooting without a tripod. I am considering the two lenses above. I like the FA 50/1.4 better because it is faster, but I am eager to learn what others think. I am totally open to other suggestions. The requirements are a fast lens in 24-60mm range, autofocus only.

I didn't find the FA50/1.4 to be especially good wide open. It's a bit soft and low contrast. I have no experience with the DA-50/1.8. The difference between the two wide open is in the range of 2/3 stop, so you aren't giving up very much speed.
If you can stretch the budget, the D FA* 50/1.4 is excellent wide open right down to f/16 (minor diffraction at that point), but it is expensive and will probably dwarf your KP.
OTOH, if you decide a full frame Pentax is in your future, you will have just about the best 50mm lens money can buy to put on it.

[Jonathan Mac]

I would like to get a fast lens for my KP for those situations when it is getting dark, but I am still having am urge to continue shooting without a tripod. I am considering the two lenses above. I like the FA 50/1.4 better because it is faster, but I am eager to learn what others think. I am totally open to other suggestions. The requirements are a fast lens in 24-60mm range, autofocus only.

Pentax's f/1.7 and f/1.8 50-ish mm lenses are generally better than their f/1.4 counterparts when used wide open. I like the little 50/1.8 a lot, more than the F 50/1.7, it just feels nicer to use and gives better results as the AF is more accurate.

Ideally buy a used copy of each and give it a try, then you won't lose much, if anything, selling them on if you decide against them.

I know it's going off track as you asked about 50mm but 35mm is closer to a normal focal length on APS-C and the HD FA 35/2 is a very good lens despite being a little slower. For general use it would definitely be more useful than a 50mm.

[AfterPentax Mark II]

The DA 50mm F1.8 is a very nice and capable lens. The big advantage is you can get a new, unexperienced, one for less than an experienced FA 50mm f1.4 would cost. It is a light lens and although the mount is "plastic" (but of a good quality) it is strong enough and a sub advantage is that it does not leave scratches on the camera mount.

[johninns]

I have the DA 50mm 1.8 Works great with my K70 and K3.

[jatrax]

Someone once said there is no such thing as a bad "fast 50". At least all of the Pentax ones I've tried were largely indistinguishable in real world use. So bottom line you will not make a bad choice on image quality alone. I would therefore look at things other than just the optical quality. How the focus ring feels, does it have quick shift, and so on.

I personally have the F 50 f/1.7 and the F 50 f/1.4. I like and use them both. The rendering is a bit different but not enough to bother me one way or the other. The 1.4 is in my go bag and the 1.7 in my other bag. I don't use them a lot but it is really nice to have them along when you need them.

I researched and bought the F 50 f/1.7 first and then found the F 50 f/1.4 at an estate sale marked $75. In the box, with the papers and the plastic wrap, not even a fingerprint on it. So what was I going to do? Just leave it there?

[pschlute]

......... M 50 1.4 (supposed to be same optics as the FA 50 1.4 but take large grains of salt with that)

Pentax 50mm 1.4 from the "K" version all the way through (K;M;A;F;FA) to the FA version has identical optics.

[pres589]

Pentax 50mm 1.4 from the "K" version all the way through (K;M;A;F;FA) to the FA version has identical optics.

I don't know if they really do perform the same though. I always put the "take it with a grain of salt" in there and if folks want to spend their money they should check out sample images and such before going with it. Even if the lenses should all act the same.

There's also the issue of copy variation and how some series of lenses seem to be more rugged than others; M's seem tougher than FA's, for instance.

[pschlute]

There's also the issue of copy variation

As well as sample variation you have the issue of coatings. The FA lenses will have had a better coating than the K or M series when new. Add in the fact that coatings can deteriorate over time, and it becomes difficult to do a scientific evaluation of which ones perform best.

some series of lenses seem to be more rugged than others; M's seem tougher than FA's, for instance

Agree with you here. If you like to manual focus your lenses then stick with the K and M series.

[mikesbike]

Don’t forget the F 50 1.7, it can be found for considerably less.

This is a very good lens, even wide open. I've had mine a long time. Got it new way back around 1990 or so when I bought my first AF camera- the Pentax SF-1n. If you can find one in top shape, this lens is better built than the DA 50mm f/1.8 and is designed for FF use in case you should ever decide to shoot some film or to get a FF Pentax DSLR. There may have been a later FA version, with the same optics.

If you go for a MF lens, it is important to get one having the "A" designation, as this will allow access to many functions that are available to AF lenses.

[Jonathan Mac]

This is a very good lens, even wide open. I've had mine a long time. Got it new way back around 1990 or so when I bought my first AF camera- the Pentax SF-1n. If you can find one in top shape, this lens is better built than the DA 50mm f/1.8 and is designed for FF use in case you should ever decide to shoot some film or to get a FF Pentax DSLR. There may have been a later FA version, with the same optics.

If you go for a MF lens, it is important to get one having the "A" designation, as this will allow access to many functions that are available to AF lenses.

I would say that the DA 50/1.8 is better built than the FA 50/1.7, despite being lighter and having a plastic mount. It just feels better put together.

Be careful with the A setting, especially on the 50mm lenses - the aperture rings are made of brittle plastic and tend to break internally leaving an aperture ring that won't turn. The f/1.7 and f/2 50mm lenses in the A series certainly suffer from this. I would avoid them for this reason, unless you get a working one and plan to use it always on the A setting.

[johnha]

I know it's going off track as you asked about 50mm but 35mm is closer to a normal focal length on APS-C and the HD FA 35/2 is a very good lens despite being a little slower. For general use it would definitely be more useful than a 50mm.

Yup, I agree completely for APS-C. My FF preferred focal length is 40-ish, on APS-C this works out as 28 but fast 28s are harder to find.

[ChristianRock]

Yup, I agree completely for APS-C. My FF preferred focal length is 40-ish, on APS-C this works out as 28 but fast 28s are harder to find.

You can find the Sigma 30mm f/1.4 Art for 499 new but significantly less in the used market. There's one on Ebay for 189 dollars right now (not mine, and I don't know the seller). The thing with these is 1. You want the newer Art version as it's optically better than the older versions that aren't sharp in the corners; and 2. You basically need to use center point focus with these lenses and then they work fine. If you use multi-point I'm told it misses focus often (I wouldn't know, I only ever use center point with all my lenses...)

I find it to be a fantastic lens. It's sharp wide open but it does have purple fringing in some situations. If the back light is strong just stop it down to f/2.8 and the fringing is gone and it's deadly sharp. I mean really, really sharp. Colors are beautiful. To me this lens really makes an APS-C kit make sense.