[stevebrot]

As far as I understood you need a portrait lens. 85mm is a portrait focal length with minimal distortion so you can make face portraits with it. 50mm doesn't intend for face portraits, may be waist-high portraits only, because of aberrations.
Portrait photography - Wikipedia, the free encyclopedia

Don't believe everything you read in the Wikipedia. What defines a portrait lens is working distance for a given in-frame subject size. To put it more succinctly...working distance = perspective. A 50mm lens on APS-C allows for equivalent working distance as a 75mm lens on 35mm film and is a quite affective portrait lens for APS-C. There is nothing magical about the focal lengths between 75mm and 135mm.


Steve

[androsokin]

Don't believe everything you read in the Wikipedia. What defines a portrait lens is working distance for a given in-frame subject size. To put it more succinctly...working distance = perspective. A 50mm lens on APS-C allows for equivalent working distance as a 75mm lens on 35mm film and is a quite affective portrait lens for APS-C. There is nothing magical about the focal lengths between 75mm and 135mm.
Steve

Hi, Steve!
I can 50 multiply by 1.5 for sure.
Besides Wiki, I have my own experience of using lenses of different focal ranges for portraits of my family members. And 50mm on my K-5 is not so good in comparison with 77mm (for example) for face portraits. Of course, to avoid perspective distortion you may choose longer shooting distance and then crop the picture, I have some portraits made with 31mm lens. But some people don't want to use ACR or LR to adjust their pictures, they use camera's JPEG. Thus with 85mm you can get more predictable result in portrait photography. It is only my opinion.
50mm is more universal focal length and of course you can make great portraits with such lens. AF is a serious reason in favor of 50mm lens too. Topic starter have already made his choice so there's no need to argue anymore
Andy

[ChooseAName]

thank you for all your answers, "lowell" you brought up a very good point. The distance to subject is some thing i really had to think about and i do have a vivatar 50mm f1.7 and the lens does a good job and i like the way it frames, and the results it gives. I just dont like the manual focus part so I think im going for the 50mm fa or da. Now what one should i get? The da or fa the new review on here says that the da gives better results but what if pentax comes out with FF in the next 3 years then im stuck with a lens that won't work on that and i will have to reinvest in new lenses when all but 2 lenses i have will work on ff so im leaning toward the FA 50 what do you all think???

Do you mean between the FA 50/1.4 and the DA 50/1.8? Cost would be a consideration for me, and the DA 50 is about $100 cheaper (new) than the FA. But if you have the money and seriously think you'll get into the hypothetical FF, get the FA. I had the FA for several years and took lots of great photos with it. Very usable wide open.

[Lowell Goudge]

if we consider that the OP, based upon his experience with a MF 50mm lens likes the images, etc, and has decided to go for a 50mm lens AF lens he has the trade off between 2 good lenses. and ChooseAName has put it fairly well. If you have a need for full frame, (either perceived FF coming, or shoot film with AF) get the FA 50/1.4, if not get the DA.

[msatlas]

i do have a vivatar 50mm f1.7 and the lens does a good job and i like the way it frames, and the results it gives. I just dont like the manual focus part so I think im going for the 50mm fa or da. Now what one should i get?

The FA has a bit nicer build quality, a little smoother bokeh, and an aperture ring. It absolutely needs a lens hood for best results at wider apertures.

The DA is a tad sharper at wider apertures, has less CA/PF (the FA's not bad, the DA is just better), and is lighter.

I went for the FA. But each one has its merits. Hopefully this helps you choose...

[lguckert79]

hey guys thanks for all the info im going to get the fa 50 and down the road look in to the 85. hey may be pentax will come out with a decent 85 when they decide to put out a FF when ever that will be so thanks for every thing guys later