If I had the faintest clue what you were talking about maybe I could help you with your problem.

Irfanview should convert the K-5 PEF files. Someone on another forum did so.

K-5. Ah. Now I finally get it. All the talk of other cameras defeated my brain. Nope, no K-5 support yet in any Adobe product. Won't be long though.

To give a real idea of cost, have a look at used pricing. I have bought most of my lenses this way. Right now (or recently, depending on when you read this) the following are/were on offer over at Pentax Forums:

A 50/1.7 for $80
FA 43 Limited for $480

Makes the retail prices look silly.

I think there is a misunderstanding. I am not referring to Adobe Camera RAW but instead Adobe DNG Converter, which is a different programme. It supports the K-7 and even the 645D, though I don't have either camera to test this claim. It certainly supports the K-x which, as we know, is a newer camera than the K-7.

I have just realised that several additional choices exist, unmentioned so far. I was going to edit my previous post but then realised a couple more responses had happened in the meantime. So I'll weave them into this new post instead.

You cannot go wrong with the FA 50/1.4 for the price. From my perspective none of the disadvantages listed actually are downers in use. SDM is a toss-up, since sometimes it results in slower focusing or less accurate focusing, even if it is quieter. Weather-sealing for a prime is entirely optional, unless you really are in the habit of shooting in the pouring rain. It is far more important to have the body weather-sealed. Zooms too -- though I took the DA12-24 under Niagara Falls. Your mileage may vary. Don't try this at home (unless you have Niagara Falls at home). Etc. Etc.

However one disadvantage to the FA50 is the build, which I find both ugly and unappealing to use. Tactility and design matter to me. That is one superior aspect of the old Takumars, though their coatings and imaging have been improved on significantly since.

If the FA50 is "pin sharp" then I wonder what a better lens would be classified as? The FA43 is the sharpest Pentax lens tested at Photozone from f/2.8 through to f/5.6. (Though I imagine the 50mm macro is sharper.) Even at f/2.0 it is as sharp as the FA 50/1.4 in the centre. Some prefer the DA40 to save a few bucks, but the FA43 is sharper wide open at f/1.9 than the DA40 is at f/2.8!

But sharpness is not everything. The FA Limiteds were purposefully designed to image in a different fashion from standard lenses. In the right conditions, this shows.

There are certainly many options. On the cheapest end, if you want the sharpest image, get an older generation f/1.7. An F might run as much as the FA, but an A 50/1.7 will be a lot cheaper if you do not mind forsaking auto-focus. One went here for 90 pounds, which is the bargain of a lifetime.

You could also get an older generation f/1.4. These lose out a tiny bit in sharpness in order to gain the extra bit of light. Choose which is more important to you.

Anything faster than f/2 is difficult to focus, especially in the very low light conditions you will want to use them. Images are unlikely to have the clarity you would otherwise achieve. I think that, all in all, f/2 is fast enough with the small viewfinders we have to deal with. And this from someone with two f/1.2 lenses!

Of course incremental improvements cost substantially more money. Whether they are worth it to you or not is a subjective matter. Some prefer to just buy the best lens once and then forget about the whole issue. That's why the FA Limiteds exist.

Simply convert the PEF to standard DNG and then shoot that way from now on. The Adobe RAW Converter (free download) will do this for you. I do hope it supports the K-7; I used it for K-x images with no problem.

I don't see the point of PEF at all. They are not even appreciably smaller.

True. But you'd be able to see for miles and miles...

All are auto-focus auto-aperture lenses (hence convenient) that will take great images. They are so different that you need to figure out your criteria.

FA 50/1.4
Compact (220g and 37mm long) time-tested performer. Widest FOV of those you specified. N/A from SRS but cheaper than other choices.

DA*55/1.4
Has SDM focus mechanism, Quick-Shift Focus and Weather Resistant (WR) build. Larger (375g) and "non-standard" 58mm filter (all the rest here are 49mm). £549 at SRS.

DA 70/2.4 Limited
Extremely compact (130g and 26mm long) but don't forget to add the hood. Quick-Shift Focus. Significantly slower than above and narrower FOV. Excellent Limited build. £465 at SRS.

D-FA 100/2.8 Macro WR
Still fairly light but huge in comparison to the other lenses here (340g, 81mm plus long hood). Rounded diaphragm blade. WR of course and macro you don't get from the others, but narrowest FOV. I wouldn't say this should be your first prime and comparing it with "fast fifties" is problematic. £495 at SRS.

If you are interested in such a wide range of glass I wonder why you omitted the two best choices? These are the reasons to shoot Pentax. They are also full-frame compatible with proper aperture rings, etc. for film use. If you find them expensive compare to fine glass from Leica, Nikon etc. and realise they are relative bargains. Buy them used.

FA 43/1.9 Limited
Tiny (155g 27mm) piece of magic that is the sharpest lens available and the best fast fifty ever made. £699 at SRS.

FA 77/1.8 Limited
Tiny (270g 48mm) telephoto -- my favourite lens. £779 at SRS.