Moving the AF point greatly helps with focus accuracy

Started Sep 17, 2012 | Discussions thread
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wilburpan
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Moving the AF point greatly helps with focus accuracy
Sep 17, 2012

I've been using this technique for a little while, and have alluded to it in a couple of threads here on improving the focus accuracy of the X-Pro 1. So before everyone fixes their focusing issues with tomorrow's firmware update, I thought I'd put this out there.

When I first started using my X-Pro 1, I had issues with focus being a little off here and there the same way many of the posters here and on other forums have mentioned. Over time I found that focus accuracy improved as I got used to the camera. The most recent thing that I did was to get a lot more aggressive about moving the AF point around the screen.

Here's the issue. The AF is point usually in the center of the screen. This may not line up with your subject, as seen in this excellent drawing that I just made. As you can see, this drawing is supposed to represent the OVF with the corrected AF frame on.

In this situation what I used to do was focus and recompose. The problem with this technique is that with a shallow DOF and how sharp the images from the X-Pro 1 can be, you may miss getting perfect focus on the spot that you want because changing the camera position changes the plane of focus. Here's a photo to illustrate. 35mm, f/1.4.

When I shot this picture at a Fourth of July parade this summer, I really just framed and shot, but this illustrates my point above. If you look carefully, the focus point is on the stars on the man's chest. His face is very slightly out of focus. This is not a focus failure. I had the AF point right in the center of the frame, and that's where the camera focused. The face is a little out of focus because of the shallow DOF, and because it's not in the same plane as the stars on the chest. Full disclosure: I think this is an acceptable result. Others have described the focus as missing the face altogether, which is not the description I would use, but I do agree the ultimate focus point is on the stars, not the eyes.

So this is what I've been doing over the past few weeks, with a lot of success. As I'm setting up for my shot, I have in mind what kind of picture I want. Then I move the AF point to the spot where I want the focus. Through the viewfinder, I'll now see this:

I'll then use the adjusted AF frame box accordingly to aim my focus point, and shoot.

What this does is avoid the recompose step that could possibly pull the focus plane away from where I want it. I know that I'm doing well with this technique when the green AF box lights up right where I want it without moving the camera. And I get results like this. Again, 35mm, f/1.4:

In this photo, I put the AF frame on the left eye, which is in focus. The right eye is a little out, but that's because of the shallow DOF and the tilt of the head. It's not because of an AF failure. The camera focused accurately right where the AF box was. One could say that I should have used f/2 or f/2.8 to get both eyes in focus, but I think this picture really illustrates my point well.

Hope that helps.

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