Avoid blurry photos Pt. 3
In this final part of the ‘blurry-photos’ series, we continue to look at focusing issues and why we sometimes don’t get it right.
In part two we looked at image softness caused by shutter speeds that were too slow. Now we tackle burry photos caused by poor focusing techniques and how to ensure that the lens renders a sharp image.
Most people who struggle with locking the focus on their subject do so because they don’t fully understand how the camera’s focusing system works.
To cover every aspect of camera focusing in this article would be a huge task. Not all cameras have the same focus options. Some are quite rudimentary systems, others are highly sophisticated. With this in mind I want to concentrate instead on universal techniques that should reduce some of the most common problems.
The Shutter Button
It all begins with the shutter button on your camera. It has two positions.
1. Full press
Pressed all the way down the shutter opens and picture is taken. In the case of a DSLR, the mirror flips up out of the way first, dropping back into place after the shutter has done its job.
2. Half Press
As you begin to press the button down, a couple of things happen. The exposure is calculated and the lens focuses. Holding the button halfway down is a great technique to lock the exposure and focus before recomposing the shot. But before you learn this technique, let’s talk about how the lens focuses.
When you look in the viewfinder, you should see a display of where the camera is focusing. Many photographers prefer to use a single point, often displayed as a small illuminated square in the centre of the frame. The camera will focus on whatever that focusing square is pointing at.
Some cameras use multiple points, each of which will light up when they hit a subject that’s in focus. This option can be less useful as they tend to focus on whatever is nearest to the camera. Not helpful if a stray object or another person is closer. I personally find a single focus point is more easy to control. Check your camera’s settings to see if you’re able to select single point focusing.
With single point focusing selected, point the camera at the subject you wish to focus on and half squeeze the shutter button. You may hear a bleep or the focus square may change colour to confirm it has locked on the focus. You can now take the picture by pressing the button all the way down. This is fine if the subject is in the centre of the photo, but what do you do if the subject isn’t in the centre?
Lock and recompose
One option, and one that is used by many photographers, is to use a technique called ‘lock & recompose’.
Let’s say you’re trying to photograph someone who is standing off the the right.
Point your camera at them, press and hold the shutter button halfway down to first of all lock the focus. Once it has signalled the ‘lock’, keep your finger pressure on the button and recompose the image so that the subject is now to the right hand side of the frame. NOW press the button all the way down to take the picture.
Your subject should remain sharp, even though it is no longer in the centre of the picture.
Look at these two photos; the first being with the microphone in the centre of the frame and the second one with the microphone to one side. Very often, the shot can look more pleasing with the image off-centre.
Placing the subject bang in the middle, which most people do, doesn’t always look as good as placing them to one side. It depends on the situation, but generally our brains seem to prefer the less symmetrical. In this case, moving the mic to the right, reveals a bit more of the scene, helping to give a bit more context to the shot.
All this was acheived simply by ensuring the focus was locked on the mic when we moved the camera.
There’s another technique that has grown in popularity over recent years and many photographers use it all the time. I must admit I do.
Back-button focusing is not on all cameras, tending to be only available on higher-range models, but it is working it’s way into more and more models as each new generation comes out.
Back-button focusing is exactly what it says it is, a button on the rear of your camera, (labelled AF-L or AF-ON) usually within easy reach of your thumb, that locks the focus when held down. The images below show it on Fuji and Canon cameras (which happen to be the cameras I use).
Nikon have a button on the rear which locks not only the focus, but also the exposure and you can decide whether the button locks both… or either (you have to go through the camera’s menu to set it up).
Canon and Fuji have separate buttons for focus and exposure and other makes of cameras have different options.
I love this button.
It feels sometimes as if my right thumb is permantly attached to it at the molecular level.
When I’m shooting I use the button to focus each shot. As soon as I hit it, the focus engages and locks. Then I can easily recompose the shot, placing my main subject wherever I want in the frame.
Dangers of Lock & Recompose
If you are shooting with a wide open aperture and therefore working with a narrow depth of field, locking and recomposing may not always work. The problem is exacerbated the closer you get to the subject. And it’s all to do with something called the Focal Plane.
This is one of those problems that is difficult to explain without visuals, so I’ve put a few together to hopefully make it easier to understand.
Figure 1: So this is what we are trying to achieve.
We want to lock our focus on the figure in the centre… and recompose to place them at the right hand side of the frame.
The importance of understanding focal plane
Definition of focal Plane:
Focal Plane (or plane of focus) is a plane that is perpendicular to the axis of a lens and passes through the focus.
In figure 2 below we can see the focal plane running perpendicular to the camera lens, focused on the face of the man. Anything along that line (plane) will also be in focus.. So if you were photographing a group of people, any of them that stood along that line would also be sharply focused.
If we now (figure 3) rotate the camera to recompose the shot, putting the man at the right hand side of the frame, the focal plane rotates with us.
We can see that in doing so, the plane is now out of alignment with the man and he is no longer sharp, he’s moved out of the focal plane region.
We have to be careful therefore, that when we rotate to recompose, there is sufficient depth of field to ensure our subject remains sharp.
In most cases this is not a big issue, but when shooting at wide apertures (and when we are close to the subject) we should be aware of the potential dangers… and perhaps look for an alternative way to take the photo.
Moving the Focus Point
Most cameras display their focus points when you look through the viewfinder. They show you where the camera is acually focusing and you can select any of them to determin which part of the image you want to focus on.
In figure 4 below, the far right hand focus point has been selected (indicated in red) and by half-pressing the shutter button or by using the back-focus button, you can easily focus on that area of the photo.
Your instruction manual will tell you how to select the points you want. In some cameras with more sophisticated focus systems you may have hundreds to chose from. The more points there are and the more of the image area they cover, the more accurate you can be in your selection.
In many ways this can be a superior technique, and if you get used to quickly switching between points, you will have much better control over your focusing.
I hope this has been helpful to you and if you have any questions or comments, please post them in the comments section below.
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