[RussellW]

I have been asked to take some portraits.
What would be the best option zoom or prime lens,
What size

[RickyFromVegas]

For Portraits, 24-75 would be optimal.
But then again, some people prefer 85mm+ for portraits, so it depends on your personal preferences.

I, personally, love the 55/58mm on Pentax DSLR for portrait.
50mm is great choice too.

[Sandy Hancock]

The Pentax FA Limited 77mm f1.8 is my go-to portrait lens: pin sharp at f2.0, perfect colours and beautiful bokeh. It is also small and unobtrusive which is less likely to intimidate shy subjects.

[RioRico]

Depends on what you mean by 'portrait' and how much money you can part with. If you mean headshots from a comfortable distance, then something in the 70-105mm range works. For half-body or torso shots, 50-55mm is good. For candids or flattened-perspective headshots, got to 135mm. My favorite people-shooting lens is an old M42 Sears-Tokina 55-135/3.5 that cost all of US$8 shipped. The rather more modern DA*50-135/2.8 only costs 100x as much, but could serve all your portraiture needs (except full-body or group shots) for quite a while.

[RussellW]

Cost is not a issue
I have zoom lens which are used for Motorsport
I do have 50 f1.4, just to know what else should be in the bag
I do have two 540 flashes and two K5 bodies

[nixite]

I think portrait lens is more then 50mm, because there is less perspective distortion... I prefer sigma 85/1.4 and pentax DA* 50-135... both very good. Possible DA70, FA77, DA55 also good, but I had never tried...

[WWWench]

I often use a SMC Pentax-A 50mm F2 on APC cameras. Soft enough for portraits.

[JVi]

Cost is not a issue
I have zoom lens which are used for Motorsport
I do have 50 f1.4, just to know what else should be in the bag
I do have two 540 flashes and two K5 bodies

Then get a Biotar 75 1.5 in an M42 mount. It has more radial astigmatism than I have ever seen on any lens and even makes my mug look human.

[elho_cid]

I like FA*24 for portrait in context, people photographed with the enviroment if that has something to add to the picture (like a smith in his workshop etc). FA31 works well for this purpose too.
FA*85/1,4 isolates the person only, leaving everything else absolutely blurred.
For portraiture in atelier with strobes and everything I preferer flexibility of a zoom. Either DA*50-135 or Sigma 28-70/2,8 work well then.

[rockmaster1964]

I like to use my tamron 90mm macro lens. It is very sharp even wide open.

[stevebrot]

For APS-C, I would recommend any "fast 50" and it does not have to be auto focus.

Longer focal lengths (70mm to 135mm) were the traditional portrait focal lengths for 35mm film, but with APS-C, the working distance becomes a little limiting. You need much more room to maneuver. I own the Pentax-FA 77/1.8 Limited and the LZOS MC Jupiter-9 85/2 (both portrait lenses of good reputation), but prefer my K 55/1.8 or M50/1.7 for the job.


Steve

[axl]

The Pentax FA Limited 77mm f1.8 is my go-to portrait lens: pin sharp at f2.0, perfect colours and beautiful bokeh.

I agree 100% on the qualities of the lens although for me it always felt kind of neither here nor there lens (not long enough yet too long)

It is also small and unobtrusive which is less likely to intimidate shy subjects.

But think this is utter bull...
If there is a camera pointing at knowing subject I doubt they mind what size the lens is. They will have picture taken and they know it, with big or small lens, they'll feel about it the same way

[axl]

To OP,
It depends what you are after. For the flexibility good zoom can't be beaten. 24-70, 28-70 or 28-75, whether Pentax, Sigma or Tamron would all be great choices, even Tokina (the later versions). For out door or upper body only DA*50-135 or Sigma 50-150 pop into mind.

With primes it really depends what type of portraits do you have in mind. Otherwise you may end up getting a bagfull of them. My favourite Pentax primes for portraits? FA*24, FA31LtD, FA43Ltd, K50/1.2, K55/1.8, DA*55, M85/2, FA100/2.8 macro

As I said, it really depends on what types of portraits are you planning to take...

[Marc Sabatella]

Frankly, expertise is more important than the specific lens you use. I would suggest reading up on portrait photography; you will find a number of very usefu l suggestions, of which information on lenses is but the smallest part.

[slackercruster]

Buy a Voigtlander 90...while you still can. Great portrait lens. $535 - $600 for a new one.