Focus and recompose?

[Syborg1211]

So one of the more generally accepted methods of nailing focus is to focus your camera on someone's eye using the center AF point (the most accurate AF point in all cameras), and then recomposing after the focus has locked. Doesn't this introduce a certain amount of focus error into every single shot?

This error is definitely smaller the farther away you are from someone, but if you are not physically moving the location of the camera and just changing the angle of your camera during recomposition, you are going to be back-focused a little bit on every shot. This is because the distance from your camera sensor to the eye is going to be longer than the distance from the camera sensor to the chest or general body area of your subject.

Are there better methods out there? How about focusing on the nose then recomposing? I've typically not even gone for the recompose and just focus on the body depending on their body in relation to their face, but this has led to some missed focus as well.

 

[GoSharks]

So one of the more generally accepted methods of nailing focus is to focus your camera on someone's eye using the center AF point (the most accurate AF point in all cameras), and then recomposing after the focus has locked. Doesn't this introduce a certain amount of focus error into every single shot?

I have 10 other points that are just as accurate as the center point on my camera.

And yes, it does.

 

[slashbinslashbash]

Yes, it shifts your point of focus, and it's something to be aware of and take into account, either through sufficient DOF, moving yourself back a bit, or focusing with a different point / on a different location. For casual portraits, I usually don't have a problem focusing on the shirt collar area, as this is usually roughly in line with their eyes, assuming a normal standing posture.

Also, remember, DOF has a rearward bias, i.e., more of the shot will be in focus behind the focus plane, than in front of the focus plane. So in thin-DOF situations it is usually better to focus slightly close.

 

[SecurityTheatre]

So one of the more generally accepted methods of nailing focus is to focus your camera on someone's eye using the center AF point (the most accurate AF point in all cameras), and then recomposing after the focus has locked. Doesn't this introduce a certain amount of focus error into every single shot?

Pre-focusing or focus-compose is a pretty standard thing and has worked well.

Many pulitzer winning photographs were shot this way.

For sure, you have to know what your DoF is and when you should use the technique and when you should not, but the theory is that it should be more accurate than trying to lock focus on a dark-coloured shirt (for example) with no contrast and letting the AF hunt around for several seconds.... or focusing on somewhere you know to be the appropriate distance and then recomposing to where a moving subject is about to come into frame.

There are lots of reasons to use it. If things are completely static and sitting still for you then, by all means, use whatever means is practical and fits your style, but there is nothing inherently wrong with recomposing a shot after focus, to a limit.

 

[elitejp]

Only one reason why i would focus and recompose and thats because my other focus points cant nail the focus. Many award winning photogs also used film but that doesnt mean im not going to use my dslr.

Edit: I think i should add that if i only had film to shoot then thats what i would be shooting.

 

[iGas]

Many successful photographers still use the tried and true focus and recomposed method, and there are some still manually focus and recompose to get their shot.

I have been taking pictures with SLR for over 25 years, and I still use center focus point then recompose for horizontal and vertical shots even those my current camera have 9 focus points. And, sometime I do shift the focus point to another point for vertical shooting.

The only trouble with focus then recompose is that the subject may move, or you may have some slight forward/backward movement that throw off you focus if you use wide aperture, but it is not a main problem for me because I rarely shoot at f2.8 or wider.

My general shooting guide:

f8-f16 -- macro
f5.6-f11 -- landscape
f5.6-f8 -- group portrait
f4-f5.6 -- portrait & head shots (some time I will shoot down to f2.8).
f1.8-2 -- are generally use in desperation (in dimly lit room) even those my fastest lens is f1.4

Perhaps you may want to take a look at a zoom viewfinder, and a split screen and/or a precision matte focus screen to help with fine adjustment when shoot at wide aperture.

 

[Scooby Doo]

Only one reason why i would focus and recompose and thats because my other focus points cant nail the focus. Many award winning photogs also used film but that doesnt mean im not going to use my dslr.

Edit: I think i should add that if i only had film to shoot then thats what i would be shooting.

Ya my t2i has issues with the non-cross focal points (everything outside the center one). If I need to focus and recompose and not in a hurry I'll just use my liveview/contrast-focus and select the focus point from there. Besides contrast focus tends to be more accurate on it.

 

[AViking]

First off never use this technique for a moving subject. In those cases I use continuous focus and generally the AF-ON button. For static subjects (portraits are ok) I only use it if my other 39 points can't get to the right spot. I'd say I focus and recompose quite rarely. If I do, I use a high enough f-stop to ensure that I get what I want in focus. Focus and recompose at something like f2 is a waste of time.

Keep in mind that if you're taking a portrait the odds of you not being able to hit the subject with a focus point is quite rare unless you're framing a weird shot. I don't want my subject to be in the corners of my shot.

 

[slashbinslashbash]

Ya my t2i has issues with the non-cross focal points (everything outside the center one). If I need to focus and recompose and not in a hurry I'll just use my liveview/contrast-focus and select the focus point from there. Besides contrast focus tends to be more accurate on it.

Hint for using the non-cross-type focus points on Canon DSLR's: These points either run vertically or horizontally. I don't have my camera(s) here with me at the moment, so I may be remembering this backwards, but I'll try to go from memory here:

The ones at the top and bottom of the viewfinder run horizontally, the ones at the sides run vertically (when the camera is held in its normal "landscape" orientation). They can detect contrast best when the contrast is held perpendicular to the point's orientation. So if someone is wearing a shirt with horizontal stripes, the top or bottom points will not work very well to focus if you place those points right on the demarcation line between stripes. However, if you put the left or right point on those stripes, it will snap to focus.

A good way to play with this (and the way that I first worked this out) is by finding a subject with contrast in both directions, in different parts of the subject. I used a white, paneled door like this one:

The whole door is painted white, so contrast is only in how the shadows fall. Picking a point on the side edge of a panel (i.e., the part that shows up as a vertical line), I couldn't get the left or right focus points to focus worth jack, but the top and bottom points worked great. And vice-versa for the top edge of a panel: the top and bottom points wouldn't pick it up, but the right and left points worked.

(Once again, I may be remembering this backwards -- the top and bottom points might be vertical, while the side points are horizontal -- but the point would still stand either way. The idea is that you want some kind of contrast that cuts across the direction of the focus point.)

Using this principle, it is usually fairly easy to get good focus using one of the non-cross-type points by focusing on the eye, especially where the iris meets the white of the eye, since there is usually good contrast there. Same with white dress shirts+ties, suit collars, bright lipstick, dark glasses frames, hairlines, etc. Usually you can find some place with good contrast in or around the subject's face.

 

[Scooby Doo]

snip...

Yup, although it's a bit hit or miss, throw servo mode into the mix and it really gets hit or miss.

Edit: let me add, in lower light levels that is, in bright conditions it works better. Contrast detection is general always better, but you pay a price for it. (slooooowwww)

 

[finbarqs]

with my canon, I usually joystick over to the closest AF point, before I "pre-focus" then recompose, so I have minimal movement. But sometimes, people say moving the camera in the direction 'follows' the curvature of the lens, so you'll be fine. YMMV is a definite on this... But really, just make sure you're not shooting super paper thin DOF shots unless you shoot for center and "re-crop" later on.

 

[uOpt]

The major reason why it isn't working quite right (although usually acceptably well) is that the focus plane is flat, not sphere formed like this method assumes. The reason why it comes out OK is that in practice very few lenses actually have a flat focus plane and in many cases the DOF is wide enough to correct for the error.

If you use a tripod and a still subject you could determine a corrective distance in advance.