Having issues with focusing...

ashm09 · Jan 19, 2012

I'm having some issues focusing on an entire object while shooting using the autofocus on my T3i. When I use selective focus it doesn't do what I'm looking for. For example, if I want to focus on a person in a field I'll use my auto focus and it takes a few shots for the focal point to focus on what I want. If I try and select the area in which I want to focus on, just the face or the top half of the body will be in focus. I mainly use my 50mm 1.4 (set at 2.2) for portraits. I love the look of the subject in focus and the back ground very blurred but I'm not getting that at all. I'm about to upgrade my camera to a 7D and my lens to an 85mm 1.8. Will this make a difference?

o hey tyler · Jan 19, 2012

NO! If you are having trouble focusing at wide apertures, do not get the 85mm f/1.8. That's only going to provide you with a shallower DoF at large apertures.

Why don't you post some images so that we can better assess your issue. I'll bet dollars to donuts that your issue is user error rather than a fault with your camera body or lens.

ashm09 · Jan 19, 2012

It very well could be...I'm a newbie. Here are a couple images I'm talking about...

The first one only one of his eyes are in focus when I wanted both of them to be. Using the Auto Focus this is what I got.

Big Mike · Jan 19, 2012

Welcome to the forum.

Firstly,

When I use selective focus it doesn't do what I'm looking for.

What do you mean by that? 'Selective focus' isn't a camera option or setting. You can choose which focus point to use, is that what you mean?
You basically have two options when it comes to the focus points. The first is 'auto point selection', which basically allows all the points to be active, the camera will choose which. The other option is to manually choose one of the points.

Either way, you can only focus the lens to one specific distance. If you are in auto point selection, and more than one point lights up, that means that those points are the same distance away....it does not mean that the camera will focus on more than one thing (distance).

The issue here is Depth of Field. That is the area, in front of and behind the point of focus, that will appear reasonably sharp in the photo. The farther something is out of the DOF, the blurrier it will be.

So if you want the whole person to be in focus, you have to have a deep enough DOF to encompass them. If you want the background to be very blurry, then you have to have a shallower DOF, and have the background be far enough outside that DOF.

If you could show us some examples, that would help.

MTVision · Jan 19, 2012

ashm09 said:
It very well could be...I'm a newbie. Here are a couple images I'm talking about...

The first one only one of his eyes are in focus when I wanted both of them to be. Using the Auto Focus this is what I got.

Shallow DOF (blurry background) can cause one eye to be in focus while the other one is not - especially if the person is at a slight angle to camera. Do you have problems focusing when you are shooting at other apertures like f/5.6?

Are you actually choosing the focal point and where you want to focus? Or are you letting the camera do it all?

ashm09 · Jan 19, 2012

This one is before editing...the whole picture looks blurry. I have to sharpen it a ton to make it look decent but the parents are blurry.

o hey tyler · Jan 19, 2012

OP: http://www.thephotoforum.com/forum/...forum-functions-pictoral-guide-using-tpf.html

Big Mike · Jan 19, 2012

Firstly...http://www.thephotoforum.com/forum/...forum-functions-pictoral-guide-using-tpf.html

About equipment...no, getting a new camera/lens won't fix your problem.

Using the Auto Focus this is what I got.

It's not a matter of 'auto focus'. Whether you use auto or manual, auto point selection or manual point selection, one shot focus mode or AI Servo focus mode....you can still only focus to one specific distance. It's your DOF that is the issue (provided you have focused to the right distance in the first place).

As you can see by the chart above, you can alter the DOF with the lens aperture, the focal length and the distance to the subject (focus distance). But because you would have to back up if you wanted to use a longer focal length (to keep the same framing) the best way to control your DOF is with your choice of lens aperture.

ashm09 · Jan 19, 2012

I'm not sure why my photos aren't posting. Thank you Big Mike, apparently what I thought wasn't not correct. I had been using the manual point selection because I thought that would be the area of focus. Recently I've been using the auto point focus but unless the people are at the same distance they are not all in focus.

Big Mike · Jan 19, 2012

I'd suggest sticking to the manual point selection so that, at least, you know where you are focusing. After that, you can worry about your DOF and if it's deep or shallow enough for the shot that you want.