Focus and recompose

[amy_bb]

Working off the premise that "there is no such thing as a stupid question" (insert giant eye roll here)....

What exactly does "focus and recompose" mean? Can someone describe to me in a series of steps and camera actions what exactly this DOES mean?I understand what it means to focus my camera, I understand the various focusing modes (continuous, single shot) and the focus area (on my camera it is "wide, local, center" or something like that. But the recompose part is throwing me....

TIA.

Amy

[SusanH1970]

It's when you focus on what you want to be the sharpest part of a photograph (for example, the eyes in a portrait) - you hold the shutter halfway down to lock your focus. While still holding it halfway, you move the camera slightly to get the composition you want, then you click the shutter to take the shot.

[amy_bb]

Ok....this is probably ridiculously obvious....(I feel like we're going through that exercise "explain how to make a peanut butter and jelly sandwich" in my kid' classes at school).
In your portrait scenario, you focus on the eyes (which you would like in focus), then you recompose to focus on something else in the composite. Is the new object of your focus then in focus? Is that object the same focal length from the lens and therefore is automatically in focus?
In a portrait, why would you focus on the eyes and recompose to something else?
Why is the sky blue? Why is the grass green? Why can't my brain grasp this?
I

[SusanH1970]

Originally Posted by amy_bb

Ok....this is probably ridiculously obvious....(I feel like we're going through that exercise "explain how to make a peanut butter and jelly sandwich" in my kid' classes at school).
In your portrait scenario, you focus on the eyes (which you would like in focus), then you recompose to focus on something else in the composite. Is the new object of your focus then in focus? Is that object the same focal length from the lens and therefore is automatically in focus?
In a portrait, why would you focus on the eyes and recompose to something else?
Why is the sky blue? Why is the grass green? Why can't my brain grasp this?
I

LOL...it's kind of hard to explain without showing you. I'll give this a try.

You lock focus (in a portrait scenario, on the eyes), then you shift the camera to compose the photograph. You're not focusing again on a different part - the focus is already locked from pressing the shutter halfway.

Pardon the crappy quality of the quick snaps I just took to illustrate, lol (uncooperative model, bad light, etc.). In both of them, I used the center AF point in my viewfinder. In the first one, I focused on the inner corner of her right eye (pressed the shutter halfway), then did NOT move the camera at all, and pressed the shutter all the way to take the photograph. Obviously, the dead-center composition sucks. So....in order to get a more pleasing composition (following the ROT; I wanted her eyes on the top third line, more or less), I again locked the focus on the inner corner of her right eye by pressing the shutter halfway, then moved my camera slightly to frame her differently, and pressed the shutter all the way. The focus was still locked on her eye, even though the camera position had slightly changed.

Hope this helps.

ETA: I just noticed that the 2nd one isn't quite as sharp as it should be - high ISO and low shutter speed because my livingroom is a dark cave this time of day and I think there was a little camera shake going on.

[amy_bb]

Thanks so much for the visual aids! So important....(and cute kid, of course!).

So the camera understood that they eye was was to remain focused on even though you moved the camera? I realize that once you hit the shutter halfway down it focused on the center point, as directed, but I didn't realize that if you moved your camera slightly it would know to stay focused on the eye if the eye was no longer where it was when the focus was obtained. Is that correct?

This is like having my own personal instructor. Thanks!

[SusanH1970]

You're welcome. In a nutshell, yeah, the camera "knows" to keep focus there. Why, I have no idea (Inkista, where are you when I need you???).

Although I use this technique a lot, it's not always accurate, particularly when shooting at wide apertures. The DOF is so thin at wide aperatures that a shift in position could throw the focus off. The above examples I shot at f/2.8, but when I'm shooting totally wide open at f/1.8, I usually toggle my focus points.

[amy_bb]

I was wondering about how this would work with the camera wide open. I have enough trouble getting sharp pics when I'm stopped down to 1.8....can't imagine what would happen if I moved the camera (lens blur would happen, I'd imagine).

Yes, please, let's get a technical analysis of how the camera knows how to do this. I tried to follow the "rule of thirds/Fibonacci's ratio article and I ended up chuckling. And my brain hurt. And then I followed the rule of thirds discussion here:
The history of "rule of thirds"

I almost quit taking pictures at this point....

I'm sure the explanation of how the camera focuses and stays focused on the eyes can't be all that bad compared to THAT!

[IABoomer]

When the camera focuses, it adjusts the focus to a certain distance from the lens. If you're shooting the head of a pin at 10' and set your focus, as long as the camera doesn't move closer or farther away from the pin, but stays precisely 10' away, then the head will be in focus, even if you shift the camera to put the head somewhere else in the frame.

Of course, if you go back to your high-school trig, you'll recognize that tilting the camera will induce a small movement in the position of the lens, which depending on how shallow your DoF is, might cause some softness in focus.

It's not that the camera knows the eye is supposed to be in focus. It knows that objects X distance from the lens should be in focus.

[Tamster]

I was wondering a little about this also. But Wanted to ask, is there anything moted on your screen that indicates that you ahve locked focus? Or is it just basically trial and error and looking after the fact to see if you have accomplished what you were trying to do?
Also, do you ahve to be out of Auto to use this?
Thanks!

[SusanH1970]

Originally Posted by IABoomer

When the camera focuses, it adjusts the focus to a certain distance from the lens. If you're shooting the head of a pin at 10' and set your focus, as long as the camera doesn't move closer or farther away from the pin, but stays precisely 10' away, then the head will be in focus, even if you shift the camera to put the head somewhere else in the frame.

Of course, if you go back to your high-school trig, you'll recognize that tilting the camera will induce a small movement in the position of the lens, which depending on how shallow your DoF is, might cause some softness in focus.

It's not that the camera knows the eye is supposed to be in focus. It knows that objects X distance from the lens should be in focus.

Hey, thanks for that explanation! Good point regarding the distance - that was sort of a "duh" moment for me - especially after all the time I've spent studying the DOF calculator.

LOL...I never did study trig or calculus. Algebra and geometry were all I got.

Originally Posted by Tamster

I was wondering a little about this also. But Wanted to ask, is there anything moted on your screen that indicates that you ahve locked focus? Or is it just basically trial and error and looking after the fact to see if you have accomplished what you were trying to do?
Also, do you ahve to be out of Auto to use this?
Thanks!

As far as I know, there's nothing in-camera that shows where your focus is falling. On my camera, I can zoom way in on the LCD and check focus if I feel the need to check; I suspect this is pretty standard in DSLR's. (ETA: just noticed you use a T1i - so yeah, you can do the same.)

And nope, you don't have to be out of auto if you're more comfortable shooting that way. Even photos shot in auto should have correct focus. But it is fun to start learning the manual modes. Not to go on a tangent and change the subject of this thread, but I highly recommend starting in P mode. The camera will choose aperture and shutter speed, but you can play with different ISO's. Then move on to Aperture priority - you choose your aperture, the camera chooses the shutter speed. Etc., etc.....it's a fun and easy way to transition to shooting in manual, if you have the desire to do so.