[Rondec]

As mentioned above, the FA 35 and 50 are still available, while they are more expensive than they were, they are probably your best options for a fast lens. I have both the FA 50 and the DA40 and use the DA 40 almost exclusively, even though it is two stops slower. As mentioned above, it is a lot easier to push your iso up a little, than to make a faster (and therefore bigger) lens.

I am not certain about your zoom comments. The DA * lenses are as fast as you can expect and probably as small as any other fast zooms out there. The Canon 17-55 f2.8 weighs 22.8 ounces, while the DA *16-50 weighs 19.9 ounces. Fast and small are mutually exclusive in a zoom.

[Class A]

Something fast (F2 or better) that would fulfil the function on my K7 DSLR that a 35mm or 50mm used to serve on a film SLR.

What about the Sigma 28/1.8 or Sigma 30/1.4? It doesn't have to be a Pentax lens, does it?

On the contrary, it is easier to focus as the viewfinder is brighter so that focus is easier for both human eyes and electronics.

A stock focusing screen won't allow you to accurately manual focus below f/2.8. Try using the optical DOF preview between f/1.4 and f/2.8 and you won't see a difference in the viewfinder.

The AF electronics are set to f/5.6. The brighter image is good but the typical spherical aberrations at low f-ratios present a problem of their own. The Pentax FA 50/1.4 doesn't AF better than a f/2.8, on the contrary, it can sometimes be harder for the camera to handle.

[Wheatfield]

Is it rare? Bojidar Dimitrov's site says the M-version is available used several times per month and the A-version a few times a year.

There was also a 35/2 - with Bojidar Dimitrov's site saying the M-version is available used several times per month and the A-version supposedly once in several years (which seems strange as they seem to come up for sale more often than the supposedly more common A28/2).

At any rate, clearly Pentax used to make fast primes in the form of 35/2 and 3 versions of 50s - which would be the equivalent of producing 23mm/2 and 33/1.4/1.7/2.0 today - something they don't do.

I missed a few. I also don't really consider f/2 to be a "fast" lens. To me, faster than f/1.7 is getting into the fast lens range.
If we drop the bar to f/2, then yes there were far more choices.
I've been using Pentax for over 25 years. I've never seen the 35/1.4 or 28/2 in anything other than pictures.
Have you?
I'm sure there are a few kicking around, but they don't, in my experience at least, come up several times a month, or even per year.
As I said earlier, I'm not an optical designer, but it is, from what I understand, very difficult to make a good fast lens that has a focal length significantly shorter than the flange to focal plane distance, and there will be compromises involved.
Look at the size of the wides we are getting now. The 14/2.8 is a horse, and while the 15/4 is much smaller, it is still a fairly large lens when compared to the other Limiteds. The 15 Limited and the 70 Limited are pretty close to the same size. I can only imaging how large a 14/2 or faster lens would be.
I shudder to think how much it would cost.
And, it goes back to the philosophy that Pentax seems to have decided to go with, which is smaller, less cumbersome equipment. The K-7 is being flogged as the travel photographer's alternative because of it's small size, so a compact lens line also makes sense.
To me, they are going back to the philosophy that was so successful for them through the early 80s, just before the AF revolution. Back then, they were making very compact cameras with smallish lenses to match, and people were buying them by the caselot.
As much as I'd like to see a fast 30 Limited, I suspect that what we will get, if we get one at all, will be somewhat slower than f/2.

[Spongefingers]

I certainly appreciate how faster lenses give a brighter viewfinder image. I always prefer a fast prime to a slower zoom, but it's a matter of individual preference.

While it is true that you can simply turn up the sensitivity with a slower lens to achieve the equivalent shutter speed, there is also the issue of Depth-of-Field.
If you want a shot with really good out-of-focus blur, the limitations of a slower lens are only complicated further by the use of a camera with a smaller sensor (APS-C, for instance.) I often find myself opening up a lens as much as I can with portrait shots, even though I know that it won't be as sharp wide open.

Also increasing ISO will always present noise issues, especially for those of us who like to hang on to our [older, but perfectly adequate] gear for as long as possible.

I agree that we need to see more fast prime lenses, and affordable ones too. I would love a 31 Limited, but the price...!

[séamuis]

but how often would someone actually use their lenses wide open to take advantage of the speed anyhow? enough to warrant Pentax putting out that many expensive fast wide-normal lenses? all of my 55 1.8's usually get stopped down to f/2 or 2.8 (id say about 85-90% of the time) it was the same with my 50 1.7. I imagine it would be the same if I had one of the FA limiteds. so we complain, but the extremly shalow DOF, difficult focus and increased softness, decreased flare resistance and increased aberrations at wide aperture push most of us to stop down to just within the threashold of "slow" no matter what the max aperture. for a film camera, yes I would loved to have a 35mm 1,4 if for nothing else than having a brighter easier to focus lens. but since the screens in our digital SLRs cant take advantage of it, and it can make the AF more difficult, whats the point? personally I think Pentax has the right idea. just slow enough that wide pen performance allows a shallow DOF but still retaining sharpness and expected performance, including AF without having to stop down. al the while, allowing them to manufacture much smaller and lighter lenses.

[Wheatfield]

but how often would someone actually use their lenses wide open to take advantage of the speed anyhow? enough to warrant Pentax putting out that many expensive fast wide-normal lenses? all of my 55 1.8's usually get stopped down to f/2 or 2.8 (id say about 85-90% of the time) it was the same with my 50 1.7. I imagine it would be the same if I had one of the FA limiteds. so we complain, but the extremly shalow DOF, difficult focus and increased softness, decreased flare resistance and increased aberrations at wide aperture push most of us to stop down to just within the threashold of "slow" no matter what the max aperture. for a film camera, yes I would loved to have a 35mm 1,4 if for nothing else than having a brighter easier to focus lens. but since the screens in our digital SLRs cant take advantage of it, and it can make the AF more difficult, whats the point? personally I think Pentax has the right idea. just slow enough that wide pen performance allows a shallow DOF but still retaining sharpness and expected performance, including AF without having to stop down. al the while, allowing them to manufacture much smaller and lighter lenses.

As soon as you put a fast lens onto the camera you are taking advantage of the speed. The brighter viewfinder and more light for the AF to work with makes for easier composition and better AF performance even if you stop down to take the shot.
I'm not, and never will, buy into the urban myth that the screens in the camera can't "take advantage" of a faster lens.
If I put a 50/f2 lens on my camera and then change it for a 50/1.4, I can see that the screen is brighter.
I'm not sure where this particular fallacy came from, but I do dispute the truth in it.

[RBellavance]

but how often would someone actually use their lenses wide open to take advantage of the speed anyhow?

I use my FA35 at f/2, and my FA77 at f/1.8-f/2.0 regularly. The large maximum aperture is the main reason I bought these specific lenses.

[séamuis]

I use my FA35 at f/2, and my FA77 at f/1.8-f/2.0 regularly. The large maximum aperture is the main reason I bought these specific lenses.

I use my 55's at f/2 but thats not the 1.8 they and the 77 are capable of. how much more often do you stop them down as opossed to wide open? at f/2 you are already "slow".

[regor]

I missed a few. I also don't really consider f/2 to be a "fast" lens. To me, faster than f/1.7 is getting into the fast lens range.

Hummm, wouldn't a 400mm F/2.8 be pretty darn fast ? Fast is relative to the FL to a large extent. A 100mm F/2 would be considered pretty fast, and so would a 15mm F/1.9.

[Spock]

I've been using Pentax for over 25 years. I've never seen the 35/1.4 or 28/2 in anything other than pictures.
Have you?

I just bought a A28 F2!

[Rich_A]

Spock, I see what you're saying. I know Pentax previously had a 30mm DA on their roadmap that was removed. I wouldn't be surprised if it showed up again (like the SDM rear converter, which I'm painfully awaiting the production of...). Nikon produced a 35mm f/1.8 and a 50mm f/1.4 in the last two years to address these issues for Nikon users. Canon, however has only produced an L lens in the fast 35mm range. Great if you're a millionaire, not great if you're not.

I understand that the limiteds don't cut it for fast work but they truly are a unique offering for digital shooters. Olympus is producing similar products but they are built like plastic toys as are most other consumer lenses these days (the Nikon 35mm f/1.8 falls into this camp too, unfortunately). It will be interesting to see what develops in this area, however. I'll bet Pentax comes through eventually. Hopefully the sale of the K-7 frees up some development dollars for them to go after some new areas where there isn't strong competition. This sounds like it might be one of them.

[Wheatfield]

Hummm, wouldn't a 400mm F/2.8 be pretty darn fast ? Fast is relative to the FL to a large extent. A 100mm F/2 would be considered pretty fast, and so would a 15mm F/1.9.

There's a clown in every crowd who just can't figure out that generalizations and absolutes are not the same thing.
You have my sympathy.

I just bought a A28 F2!

I don't think that makes them common, it just makes you fairly lucky.
I bought an FA200/4 macro a couple of years ago, I suppose that makes them fairly common as well.

[StevenVH]

I just bought a A28 F2!

Congrat's, nice find!

It seems to me we're seeing in the 14/2.8 and 15/4, 12-24/4 and 16-50/2.8 the extent of Pentax's willingness to build wide, fast lenses these days.
I used quite a few faster lenses in the film days and had a similar reaction when I first looked at the current offerings. Since then I've decided 2.8 is fast enough and when it's not that's what a fast 50 is for. So not much has changed really in that sense from the film days.
If 2.8 isn't fast enough or you want better bokeh or both there are the FA Ltds.
If cheaper is better then the DA Ltds. Or you can delve into the world of MF and dig up the gems of the past.
Overall, I'm satisfied with the current offerings. As much as I'd like faster, wide primes I expect they'd be huge and expensive and wouldn't sell well.

cheers

[Marc Sabatella]

I'm not, and never will, buy into the urban myth that the screens in the camera can't "take advantage" of a faster lens.
If I put a 50/f2 lens on my camera and then change it for a 50/1.4, I can see that the screen is brighter.
I'm not sure where this particular fallacy came from, but I do dispute the truth in it.

I would agree there is a difference, but I'd suggest isn't a full stop difference as it "should" be. The extent to which I see the viewfinder dim from f/1.4 to f/2 to f/2.8 is much smaller than to extent to which it dims after that. And I can absolutely verify that DOF is inaccurate - the viewfinder shows far too much in focus, as a simple newspaper test will readily verify.

So I'd say it's wrong to say faster lenses provide *no* advantage in focusing, but it's definitely not as great an advantage as it otherwise might be.

[Marc Sabatella]

Also increasing ISO will always present noise issues, especially for those of us who like to hang on to our [older, but perfectly adequate] gear for as long as possible.

True, but you should also note that noise levels on most APS-C digital cameras are far below what most films could deliver - especially given the ability to easily perform NR on digital images. A common comparison made is between ISO 1600 on digital to ISO 400 on film. So in that sense, an f/2.8 lens on digital really provides the same basic exposure options as an f/1.4 lens on film. I'm sure that would have to be part of Pentax's thinking.

This doesn't help with DOF, of course. Or manual focusing - but then, most AF lenses are relatively lousy for MF anyhow because they tend to favor shorter throws and less resistance in order to make AF faster. So if MF is a major concern, you're normally better off just picking up an MF lens. And with respect to DOF, I guess I wonder how many different lenses one really needs to achieve those effects. I'm sure there *are* situations where one might want a shallower DOF than one can get at f/2.8 but 50mm just won't do as a focal length, but are these situations really common enough to justify production of additional lenses?