How can I focus on only part of the scene when there are multiple objects at the same distance?

Question

I just wanted to have the red leaf focus only, and not have the nearby twigs in focus too. How can I achieve that?

I locked the focus on the read leaf then move the camera to reposition the scene. Using Fujifilm s7000

Settings: It was 1/2.8f (max) and ISO 200 [aperture priority mode]

I used AE/AF lock to lock the focus to leaf first [fujifilmusa.com/shared/bin/S7000Manual.pdf PAGE 27] I thought it would lock focus to that particular point only? Where the yellow box was. Does my understanding wrong?

Answer 1

Short answer: as the framing is, you cannot achieve this without post-production. If you do not want to use blur-filters in something like Photoshop, you should try to use another framing.

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The twig on the left is as close to the camera as the leaf is - therefore, when you focus on the leaf, the twig will also be in focus, because the focal plane is just that - a vertical (as in: parallel in relation to the camera's sensor, or 90° to the axis of the optical path) plane. If you want to change that, you will have to separate the twig and the leaf distance-wise. Looking at your picture, I'd guess that making one step to the right and then reframing on the leaf would at least improve the situation.

To show you what I mean with the focal plane, here's a stolen picture from Wikipedia's article on focus:

It wouldn't matter if you focussed on "depth" or "field" - both are in the same focal plane - and it is the same with your leaf and twig. However, there would be a difference between focussing on "feet" and "barrel". You can try that out yourself with a ruler (or virtually anything) on a table: focus changes with distance, not from left to the right. (For this assumption, we exclude tilt-shift photography.)

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The twigs in the background are another topic: you could try to either frame closer, pushing for stronger background-blurs (and a faster transition between in-focus and out-of-focus), or you could use a wider aperture (if available).

Answer 2

"Locking focus" really means locking a specific focus distance.

Focus is always in a plane parallel to the sensor, i.e. everything at a specific distance to the sensor is in focus. In front and behind of that distance, objects will be increasingly blurred.

There are ways to change the focal plane: A tilt-shift lens can tilt the plane relative to the sensor, but it will still be a plane.

In your case, to get only the leaf in focus, you'd have to rotate your position so that the twig is at a different distance than the leaf. Of course, that would have changed the whole composition, too.

Blurring the twig in post processing is of course possible, but may result in an unnatural look, since we clearly see the objects to be at about the same distance.

Answer 3

You can't focus on a single object if you have other objects in the same plane relative to the camera sensor.

You either need to move yourself, so you don't have any other objects in the same plane and use a lens with reasonable max aperture, thus making other parts of the image out of focus,
or you need to blur other parts of the image manually during post-process phase in your computer (photoshop or whatever image editor you prefer to process your photos with).

As you're using a compact camera with a fixed lens, I'm afraid you'll be stuck using the post-process blur method. Your lens has max aperture 2.8, which isn't usually sufficient to blur background very nicely when it comes to small sensors, especially with scenes like this. It can do a fairly decent job, but a DSLR with a f/1.2 lens would deliver completely different results.

I used AE/AF lock to lock the focus to leaf first [fujifilmusa.com/shared/bin/S7000Manual.pdf PAGE 27] I thought it would lock focus to that particular point only? Where the yellow box was. Does my understanding wrong?

Yes, your understanding is wrong. By using AE/AF lock you're not locking your focus to a single point, you're locking your focused plane to a certain distance. As both the twig and the leaf are on the same plane, they are both in focus. You need to reposition the whole scene differently or use a software selective blur method as I've explained.

Answer 4

First, you should definitely be familiar with What exactly determines depth of field?. Also a look at Can more than one focus points be selected?, which is really this question in reverse. And, perhaps most of all: Why would I want to select an autofocus point?

Given that, as others have noted, what you want to do is impossible with a normal lens. It might be accomplished with a tilt-shift lens, but those tend to be very expensive. You can also do something in post-processing, but that's surprisingly difficult to get looking good. (You really need a 3D map of the scene to do it right.)

There is, however, a reasonably-priced alternative if you're really into this kind of thing — the Lensbaby Spark. This is a $90 lens for Canon and Nikon (unfortunately, unlike earlier similar models, not available for other mounts) which can bend, making it possible to get the kind of result you are looking for. For example, this image from Lensbaby's sample gallery:

This, of course, does not help you with your non-interchangeable lens camera, but if this is something you really want to do, it's perhaps an avenue to explore. You don't need a very fancy camera body to get stunning results.

If you're really enjoying the Lensbaby thing, or really want to focus on it, or are set on a camera from someone other than Canon or Nikon, you can go for the $400 Lensbaby Composer Pro II with the Edge 50 optic. This gives more fine control (and is available for a wide range of lens mounts, including Fujifilm, Panasonic/Olympus, Pentax, and Sony along with the big two). That's a lot more money, but still not even close to the cost of a full tilt-shift lens.