Portrait focus points

[corei5]

a quick question about focusing where do focus your focus point when taking a picture of a person?

well so far I point my camera focus at their eyes and some articles says don't focus to their eyes O_o so now I'm a little confused where to point my focus point.

[Anbesol]

Focusing on eyes is the common wisdom. I find an exception in a couple of situations, the more obvious: if you are going for a specific effect where the eyes are out of focus.

I also find that, at certain F-Stops (usually between 2.8 and 5.6), relative to certain distances, I prefer to place focus on or at the tip of the nose. Since focus falls back much better than it does forward, so if in those events I were to focus on the eyes, the nose would be blurry, but not vice versa. This of course will vary greatly depending on focus distance and f-stop used. At a point, with enough distance or narrow enough a stop, you can focus at any part of the face and have a quality focus dof.

I don't know if anybody else does the nose tip focus point, maybe its just me and I'm standing in defiance of conventional practice. Anyway, just my two cents.

[corei5]

anyhow when taking portrait specially outside the background should be blurred (DoF?)

oki ill make it easy for myself about the aperture let say the lowest number (1.8) the wider the "IRIS" is and the background will be blurry, the highest number (22) the "IRIS" will become small and the background/whole scene will be in focus.

so to make the whole scene in focus I need a high number (f/higher than 1.8 or so).

when cropping will you just use the crop tool and just crop the desired size or image that need to be cropped?

[Franglais]

Usually I want to have both eyes, the nose, forehead and part of the hair in focus. Let's assume you're using a 50mm lens on an APS-C camera at a distance of 6 feet. Using the depth of field calculator here:

http://www.dofmaster.com/dofjs.html

The depth of field at f1.8 is 3.5 inches, which is barely enougjh.

Personally I find the 50mm too short for a portait, you're including the upper part of the body. If I do a really tight head shot from 6ft then a 135mm (on APS-C) is better. Longer focal length, less depth of field. To get 3.5 inches of depth of field I would have to set the 135mm lens at f13.5. Just fine for use in the studio with a powerful flash.

BTW yes the camera lens has an iris but usually we talk about the aperture. When you mentioned iris I thought you were talking about the model's eye opening and closing with the intensity of your lighting..

[Anbesol]

dof is very relative to a lot of things, distance from focus point, aperture, as well as linear angle. f/1.8 at or near hyperfocal distance will produce a lot of dof. f/1.8 at 1:1 macro magnification will produce razor thin dof.

when taking portrait specially outside the background should be blurred (DoF?)

Typically, that is what I shoot for and is the conventional practice, but this is certainly not an iron clad rule, it depends on what your goal is to shoot for. Maybe you want a lot of dof, maybe not. You decide how you want the image.

Generally speaking, in typical shooting conditions - f/8 will produce a very wide dof, I rarely go up into the f/22 range.

I'm not sure what you mean by the cropping. I try to frame it in camera the way I want it on print, so most of my cropping is very minor and usually just to fit print aspect ratio. Make sure you crop to the aspect ratio you print for, otherwise there will be clipping.

*edit - 6 feet at 135mm on an APS franglais? Thats an extremely tight crop. Do you actually use 135mm as a portrait lens on an aps body?