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03-17-2012, 04:13 PM   #1
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Compose portrait lens

I have 16-50 lens with K-5. Most of pictures are landscapes... Yes, only landscapes... I have no portrait....

So I'm taking portrait to my friends...

but problem is 16-50 is not enough sharp(If you check closely) why it is problem? corner and center sharpness is not good enough so I can't not use it in F/2.8 mostly. and I don't know how to compose the picture. such as half shot.

I'm thinking about prime lens + learning composing.

this are my special things ^^

1. most of angle of views were 31, 21, 24, and 43 (base on crop)

2. Mostly vertical pictures

3. and hard to come close to my friends (cause... )

Could you help me???

03-17-2012, 04:53 PM   #2
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My recommendation would be to get the FA77mm for portraits.

Pentax Telephoto SMCP-FA 77mm f/1.8 Limited Series 27980 B&H ($784)
SMC Pentax-FA 77mm F1.8 Limited Reviews - FA Prime Lenses - Pentax Lens Reviews & Lens Database

At other focal lengths, just stop your 16-50mm down- no need to get a new lens, IMO.

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03-17-2012, 05:17 PM   #3
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For portraits I like a 50mm standard prime lens, the larger the f-stop the better. I use a 50mm-f1.4 KA mount lens, but stop it down to f4 for taking the portrait. I like this lens because the f1.4 allows me to focus precisely, and f4 gives enough DOF to give a sharp image where important, and blur the non important stuff such as the background, ears, etc. You could do well with a f2.8 too, but the 1.4 lets in more light so I can focus better. I use only manual focus for portraits because I do not want to focus on the nose or ears, but on the eyes. With auto focus you fight the camera to pick where you want to focus.
03-17-2012, 05:21 PM   #4
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Many photographers don't find sharpness to be the most important quality in a portrait lens -- a little softness can be kinder to many subjects.

If you want lots of separation from the background. get yourself a manual focus M or A 50/1.4. Beautiful portrait length and you can go for very narrow depth of field if you wish.

03-17-2012, 05:48 PM   #5
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I worry about other than DA lens like FA or F lens because those lens are compatible to the Film lens...
03-17-2012, 06:36 PM   #6
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(Anyone who's seen the following rant before can skip over it. The rest of y'all, pay attention.)

Portraits can be shot at any focal length, depending on 1) what you mean by portrait and 2) what effect(s) you're looking for. Some folks think that candid street snapshots are portraits. I disagree. A portrait is a portrayal of character and (hopefully) not a surveillance or ID or serendipitous photo.

Some good focal lengths for people-shooting with an APS-C camera are ~30mm for full-body shots, ~40-45mm for 3/4-body shots, ~50-60mm for 1/2-body shots, ~70-90mm for head+shoulder shots, and ~100-135mm for headshots. Desired effects may include context (use a wider lens, like ~10-30mm), thick or thin DOF (see below), romantic softness (use a soft lens, or a vaseline-smeared filter, or some careful PP) or whatever -- but serious portraiture concentrates more on lighting than on lenses.

My favorite people-shooting zoom is an old M42 Sears-Tokina 55-135/3.5 that cost me US$8 shipped. A good modern version would be the DA*50-135/2.8 but it costs about 100x as much.

My favorite lens for serious studio-type H&S shots is an older M39 Jupiter-9 85/2 -- soft wide open, sharp stopped down. Next favorites are a Vivitar-LU 75/3.5 enlarger lens on a focusing helicoid -- very sharp. From my days of shooting multiple formats, I find the best modeling of features comes at about 80/3.5. Or for ultra-thin DOF, I'll screw a cheap Sony VCL-1546A 1.5x tele adapter on the front of my FA50/1.4 (for a 75/1.4 optic) or my Sears-Tomioka 55/1.4 (for an 83/1.4 result). I've tried that on my K50/1.2 also but DOF is WAY too thin at 75/1.2!

If you don't know the rules of DOF, here they are, simplified:
* For thicker DOF use a shorter focal length and/or tighter aperture and/or further lens-subject distance.

* For thinner DOF use a longer focal length and/or wider aperture and/or closer lens-subject distance.
And you can roughly compare the DOF of two lens settings by simply calculating what I call the DOF index or FL/AP (divide focal length by aperture). The higher the number, the thinner the DOF. So a 50/1.2 has FL/AP= ~42 and a 135/2.8 has FL/AP= ~48. That's right, a cheap average 135 has thinner DOF than a costly superfast 50!

Now let's put all this together. Before spending money on a lens, figure out what 'portrait' means to you. If it's ultra-sharp headshots and/or street candids, think of a ~90-105mm macro lens. If you want thin DOF on a budget, get a manual 135/2.8, or try my Fast-Fifty-plus-1.5x-adapter trick. If you want sharp torso shots on a budget, get tubes or a focusing helicoid for a ~75mm enlarger lens. If you want maximum flexibility plus sharpness and budget doesn't matter, get the DA*50-135. I'd have to rob a minimart to afford one, so I'll stick with my Sears-Tomioka, thanks.

People will push their favorite 'portrait' lenses. Yes, the Fast Fifties and Seventies and 85s and 90-105 macros are all splendid portrait lenses. So are cheap enlarger lenses, scavenged medium-format glass, and almost anything else -- if used intelligently. I like old no-iris projector lenses with a Petzval Portrait or similar formula, or a Raynox DCR-250 mounted on M42 bellows, for a 'period' look. But remember that the light is more important than the lens.
03-17-2012, 08:35 PM   #7

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Try the DA*16-50 between 30 and 50mm at no wider than f/3.5 or f/4. Many portraits are taken somewhere between f/4 and f/8, depending on lighting, desired DOF, and other needs.

Most of my portraits are shot with the DA*50-135, FA*85/1.4 (my FA77 was great too), or K50/1.2. Sometimes I'll also use the A100/2.8 (non-macro), which can be excellent.

So I'd try the DA*16-50 a little more, but if you don't have anything longer right now, you probably still need to buy another lens. I'd get one of the above or the DA*55/1.4. The DA*55 is particularly sharp - even wide open - so if that's what you're after, you might consider it.

Also, the DA70/2.4 is an economical choice that may have the type of sharpness you're looking for. But I'd rather put the money toward a faster lens (f/1.8 or faster) or the incredibly versatile DA*50-135 zoom (which is almost as fast as the DA70/2.4, is sharp, and has close-to-prime image quality. Plus you'll find it useful for so many kinds of shooting - including landscapes).
03-17-2012, 09:38 PM   #8

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To more directly answer your question, take a look at this. See what shots you like, and notice what settings and lenses were used:

PENTAX : View the PENTAX Photo Gallery Categories

Also see these shots from the lens Pentax has designed as their current Portrait lens (using the classic portrait angle of view):

Last edited by DSims; 03-17-2012 at 11:15 PM.

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