[geekette]

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I need some recommendations, thanks! I would like f2.8 or faster and around 45-55mm.

[Steinback]

Any AF 50mm or 55mm Pentax prime ever made?

I've used the FA 50mm f/1.4, the D-FA 50mm macro, the M 50mm f/1.7 (which has the same optics as the F and FA 50mm f/1.7), and tested the DA* 55mm f/1.4 briefly. That covers pretty much all of the options made by Pentax and any of them would work as a respectable portrait lens. The various versions of the 50mm f/1.4 are going to produce images very similar to those of your M 50mm f/1.4.

Price wise you're looking at somewhere in the $200-250 range for an F 50mm f/1.7 at the low end unless you get lucky and find a seller who isn't up on current values. A second hand FA 50mm f/1.4 will probably be the next cheapest option starting at $250-300.

[axl]

As above, if you want affordable then you are looking pretty much at F/FA50. Either 1.7 or 1.4 versions.

[Coeurdechene]

The tammy 28-75 f 2,8 is a good all around lens...
It's cheap and versatile.

[newarts]

I need some recommendations, thanks! I would like f2.8 or faster and around 45-55mm.

Keh is currently listing a sigma 50:2.8 macro for $169 that may suit your needs. Pentax Autofocus Non-Mfg Fixed Focal Length Lenses - KEH.com

[paperbag846]

Your requirements for autofocus and affordable bring one lens to mind - the FA 50 1.4, used.

Can be found for a good price if you look around.

[1r0nh31d3]

FA 50mm 1.7

I had both the 50mm 1.4 (M version) and the 50mm 1.7 (A version) I kept the 1.7 because I liked the results better. It was sharper wide open? But not quite as fast. Better contrast? I don't know really what it was but my pics with it looked better with it. That being said everyone seems to like the bokeh more on the 1.4 and for portraits maybe a bit of softness is not a bad thing (but you could always soften in post.)

Shoot I just changed my mind halfway through typing this. You could go FA or F versions of the 50mm in 1.4 or 1.7. Just get which ever one is cheaper as they have pros and cons that probably will break even.

If you are doing portraits you will probably have more control over your shooting surroundings so if you want to go really cheap get a manuel focus of either of these, even just to test the water.

Sorry I just read your sig. Si the only thing you don't like about your 50 and 55 the lack of autofocus?

[newarts]

eBay currently lists a Pentax F-50:1.7 for $239. I have one and like it a lot. It is highly regarded I think and I find 1.7 is fast enough with shallow enough dof for most portrait work.

I paid about $150 a few years back but that was then - prices have gone up as people have discovered quality used lenses.

Pentax Pentax-F F 50mm f/1.7 AF K-7 K-5 K-r K-x | eBay

Earlier I url'd a sigma 50:2.8 macro for $169. I think the Pentax 50:1.7's extra speed & shallower DOF might be worth the extra $70.

On the other hand the sigma's macro capability might be a bonus for you.

To find a good lens at a reasonable price continue to scan Keh.com's BGN grade lenses.

[RioRico]

If you need the speed for thin DOF, here's a cheap workaround: Use the kit lens, or an F35-70, or an old kit-type lens like any Pentax-Sigma-Tamron-Tokina-Promaster-Quantaray-etc AF 28-80mm or whatever. Screw-on a +1 dioptre closeup adapter. Focus range drops to 50-95cm / 20-38in with nice thin DOF. Cost is minimal.

[paperbag846]

If you need the speed for thin DOF, here's a cheap workaround: Use the kit lens, or an F35-70, or an old kit-type lens like any Pentax-Sigma-Tamron-Tokina-Promaster-Quantaray-etc AF 28-80mm or whatever. Screw-on a +1 dioptre closeup adapter. Focus range drops to 50-95cm / 20-38in with nice thin DOF. Cost is minimal.

Aren't there also teleconverters that add autofocus to old lenses?

You could buy an old 50 and turn it into an autofocus 85mm lens on the cheap/ Wrong focal length, though.

[RonHendriks1966]

I vote for DA 40mm/f2.8 since it is cheap and good for portrait (on the short side for this purpose).

[RioRico]

Aren't there also teleconverters that add autofocus to old lenses?

You could buy an old 50 and turn it into an autofocus 85mm lens on the cheap/ Wrong focal length, though.

AF-added TC's are uncommon and fairly costly and their AF is fairly slow IIRC. Let's see, would it be worthwhile to use a 1.4x AF-TC to turn my K50/1.2 into an F70/1.7? That *is* rather tempting... or an ST50/1.4 would become 70/2, almost as good and rather cheaper. I'll have to think about that, next time I have any money.

[littledrawe]

I would go with Tamron if you want NEW and Pentax if you want USED. I don't have anything from Tamron in that range but it seems that a lot of people on the forum are pleased with their zooms that cover the focal length you mentioned. I also read it here on the forum that a portrait lens is really just whatever lens you shoot a portrait with so maybe you already have something that will work?

[Clicker]

You might also want to consider Tamron's SP90 macro K mount.

[pcarfan]

The tammy 28-75 f 2,8 is a good all around lens...
It's cheap and versatile.

+1 and I might add excellent IQ.