focus/recompose

[rachellen]

Can someone explain to me or lead me to where I can find out more about this?
I have the Rebel XT.
I've been using the AF points and changing them to focus in on my subject. I find that sometimes, I can't set that exact point on where I want the focus to be, so I end up cropping the photo in camera, just to get that point on...say the eye. I hope I'm making sense. But then I'm wondering if this focus/recompose is what I really need to figure out.
Please help!!
Rachelle

[Anders Östberg]

Focus/recompose is simply locking the focus (usually using the center AF point on your main subject) by half-pressing the shutter button and then moving the camera to compose the picture before fully depressing the shutter button to take the photo. It's not a good practice really (though we all do it of course) as there's a good chance of getting an out of focus main subject, especially with large apertures. If you have the time it is better to use an off-center AF point.

[vctr]

You must be talking about focus lock. You could find this on page 75 of the XT manual.

[R Hardman]

I think I understand what your saying. You could use center spot only and focus on the eye then move the camera to compose, or, shoot manual focus.

[kwsanders]

Originally Posted by FretNoMore

It's not a good practice really (though we all do it of course) as there's a good chance of getting an out of focus main subject,

If you focus on a point at a given distance, lock the focus, and then recompose the shot, at a given aperture, the same plane relative to your focusing point should still be in focus, right?

[jimlp]

Originally Posted by kwsanders

If you focus on a point at a given distance, lock the focus, and then recompose the shot, at a given aperture, the same plane relative to your focusing point should still be in focus, right?

Once you recompose the focus plane and the focus point are no longer the same.

[Anders Östberg]

Originally Posted by kwsanders

If you focus on a point at a given distance, lock the focus, and then recompose the shot, at a given aperture, the same plane relative to your focusing point should still be in focus, right?

Well, problem is you move the focus plane when you rotate the camera. Normally this isn't a big problem as your DepthOfField will cover the error, but with large apertures (=shallow DoF) you might get a soft photo.

Here's one page discussing the effect: http://www.visual-vacations.com/Phot...pose_sucks.htm

[kwsanders]

Now that I think about it... basic geometry. Thanks guys... you are right. Once I move the camera to recompose, the distance between a point on the same plane as the original focus point and the camera now is slightly further, so with a wide open lens, I can see how the photos may come out soft or possibly OOF.

Thanks for making me think.

[J Rabin]

Rachel:
Break the FLR habit and enjoy better Canon digital photography!
We all learned FLR in manual focus Center-weighted exposure 35mm SLR days.

However,
1. not only will you throw off auto focus at distances under 15 feet as noted above, (longer distances less critical) but;
2. because Canon evaluative exposure metering is focus point weighted, you throw off exposure every photographing day, and:
3. lastly FLR is the sure recipe for poor Canon flash metering results. Even with the new E-TTL II that is supposed to NOT be focus point weighted, it is better to use FEL and/or FEC than to FLR.

Down with FLR with Canon gear unless your are forced into it in low light fast paced situations. Break the habit. Move the focus point. Get better reliable results.
Jack

[rachellen]

Thank you all so much for your help!! I've got to go through each of these posts for more in depth understanding.....it's just the way I learn.
Here's an example:
There are 7 AF points and I want to take a horizontal picture. The focus point I want is actually in the left hand corner, what would I do? Since the left hand corner isn't part of the 7 fp's.
Rachelle

[rachellen]

Here's kind of an example of what I mean. I had to crop this, I was wanting her to be more in the corner of the photo, but there were no FP's in the corner. What could I have done to this for the FP if I wanted to focus on her eyes?
Settings I believe are:
f/4.0 - 1/100 - iso400 or 800
k, I now just have to figure out how to post a pic.....patience please...lol.

[rachellen]

hope this works.

[J Rabin]

Originally Posted by rachellen

What could I have done to this for the FP if I wanted to focus on her eyes?..lol.

No. You can't. You're in a studio. In your example: get lots of modelling light on the subject, fix camera to tripod, manually focus. etc.

At these distances, under 15 feet FLR will give you wrong result. Further, in low light peripheral focus points are not "guaranteed" accurate.

Go to the "Sticky" above. Download "Getting the most from your Series-1 dSLR" by Canon's Chuck Westfall. Even though your are using a Rebel, the need to avoid FLR is covered.

Beautiful creative high key photograph by the way. Just nice, soft, and lovely. The angle on the right tricep makes it look too f-t though.
Jack

[rachellen]

Originally Posted by vctr

You must be talking about focus lock. You could find this on page 75 of the XT manual.

I'm just reading the manual, and maybe this is what I do mean!! So, in the photo above, I would be in one shot mode, put the AF point to the 2nd to the left (of the centre row), press the shutter halfway down, but then to recompose to be on her eyes, I'd just tilt the camera down with the shutter still pressed in halfway?
Rachelle

[rachellen]

Originally Posted by jimlp

Once you recompose the focus plane and the focus point are no longer the same.

Can someone explain the focus plane better to me please?
And what does FLR mean? Sorry for being so 'airy', but I've gotta ask.
Rachelle