Understanding Focus :: Digital Photo Secrets
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Understanding Focus

by David Peterson 13 comments

What is focus? In photography, it’s practically married to sharpness. An image that is completely sharp is said to be in-focus. An image that’s completely blurry is said to be unfocused. The same metaphor applies to your mind. When you concentrate, your mind is sharp. You are focused. When you’re confused, you lack focus. As you are about to learn, you can use focus to direct your viewer’s attention to the most important parts of a scene. Here’s how.


Before we get to the tips themselves, I want to discuss the mechanics of focus itself. In order for a camera to create a focused image, it takes light and runs it through a lens, concentrating the rays on the image sensor inside. The size of the hole the light travels through (the aperture) determines how focused those rays are once they hit the sensor. Smaller holes do a better job of focusing light than larger holes.


This photo uses close focus to draw emphasis to the soccer ball.
Photo By: Soe Lin

In terms of actual camera settings, larger f-numbers correspond to smaller apertures. At F22, the depth of field (or focus range) is much larger than at F4. You can use depth of field to emphasize certain parts of an image. That’s one reason why F4 is such a good aperture for taking portraits. You can focus on the eyes alone while the background gets completely blurred out. The small depth of field makes your friend’s face stand out from the background.

With that explained, here's how to use focus to improve your images:

Don’t always put everything in focus

There are a lot of situations where you don’t really want the entire image to be in focus. Backgrounds tend to get in the way, and they will distract your viewer from the point you are trying to make. Portraits, as we have just discussed, look a lot better when the background is somewhat out of focus. The effect is akin to bringing your friend into the studio and placing him or her in front of a solid colored background.

I should also mention that it’s simply harder to draw attention to things that don’t stand out on their own. When we focus our eyes, we do something similar. You might not notice it, but everything else in your peripheral vision appears a little more hazy. Most of the time, only one part of your images should be truly sharp. Let the rest get a little fuzzy so the sharp part stands out.

Understand visual depth

What is depth? It’s a measure of the three dimensionality of things. Imagine holding an apple out in front of your face. The apple is fairly three dimensional. It recesses into the background. It isn’t as three dimensional as your entire arm sticking out in front of you, but it is has a sense of depth.

Contrast the apple with a wall or a flat piece of paper being held out in front of you. Neither have that much visual depth at all.

As it turns out, this is pretty important in photography. There are some photographic situations where it really doesn’t matter how large your depth of field is. You don’t need a huge depth of field to focus on a person standing in front of a mural, for example. Any aperture between F8 and F11 will do.


You can get away with using any aperture between F8 and F11
when your subject is standing in front of wall.
Depth doesn’t matter as much.
Photo By: George Parrilla

Just think of it this way. The more visual depth you have, the more important focus becomes. Landscapes have an incredible amount of visual depth, all the way from the foreground to the background. It’s important to capitalize on that depth by making the image as sharp as possible. You’ll want to use a smaller aperture to get the largest possible depth of field.

Test it for yourself

There’s no better way to see how the depth of field can change than to simply try out a bunch of different aperture values. Your camera’s aperture priority mode is ideal for this. You can pick any aperture value you want, and your camera will pick a corresponding shutter speed to give you the right exposure. This is a great way to see how the aperture affects the depth of field, which in turn affects how the focus works on your camera.

Start off with a portrait at F4. After that, go to F8 and then try the same portrait at F22. Be aware that you’ll need keep your camera stable for the last shot. A smaller aperture means your camera gets less light, and if you are in aperture priority mode, your camera will automatically pick a slower shutter speed to compensate. In short, your picture will be subject to camera shake.


Large sprawling landscape like this one require maximum sharpness.
Go with an aperture of F22.
Photo By: Wolfgang Staudt

Focus is nothing more than the degree of sharpness at a certain point. You can focus on different things, or you can change the aperture to get a larger or smaller depth of field. Either present you with a number of creative options that will help you draw attention to the most important parts of your image. Keep the depth of field small for closeups of your friends and large when you’re doing big open landscapes. It’s a simple rule that will give you some great results.

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Comments

  1. Zibbies says:

    I have to take contention to Carl's statement. From what I got out of this article was the intention to explain depth of field as a tool to use to isolate or if wanted, blend in a subject as in nature shots where there isn't necessarily one defined subject and the image as a whole becomes the subjec. Carl, your attack was unfounded and unwarranted. There is no mention of camera shake or motion blur, Or a number of other reasons why a blurry image happens, hence my assumption this article was about d.o.f. And you are also incorrect. A f4 lense does not have a hypo focus sweet spot at f4, it is more likely to be a stop or two down, f5.6 or f7 etc. that's why your primes are so good because they start at f1.8( and suck at that aperture setting 99% of the time). But stopped down to f4 or f7 it's sharp as a razor

  2. ALOR FOSTER says:

    SO WHATS DO WE MEAN BY FOCUS IN AND FOCUS OUT

    • David Peterson says:

      Hi Alor,

      I haven't heard of those terms before. Do you mean "In Focus" and "Out of Focus". The part of your image that is in focus are the parts that are crystal clear and sharp. The rest of your photo that is blurry is regarded as out of focus.

      I hope that helps.

      David.

  3. Ajithaa says:

    Thanks David....your photography tips have helped me a lot and your explanations are so easy to understand.

  4. Carl says:

    you are incorrect about f22 - try a wider aperture and hyperfocal distance and you will get much better sharper images, and you wont need a tripod because you will be shooting at reasonable shutter speeds. Increasing aperture past f8 on a digital camera SOFTENS images with diffraction. Read about hyperfocal, circle of confusion, and diffraction losses on any small format camera. Why do you think point and shoots operate at f4.0??? Please learn the basics before you talk like an expert.

  5. George says:

    Hi David,
    Love your tips and advise,you have helped my photography improve so much. I understand what you are writing,but when you refer to certain images, they don't appear on the page.I don't know if anyone else has the same problem,or is it just me?

  6. Lorraine says:

    Thanks David, your tips are great! I went to Kruger Park, South Africa last year with a view to photographing birds in flight. I was , 'I think' quite successful I bought a Canon 55-250 extra lens and played around a lot with the two lenses. I got some stunning action photo's of birds in flight, esspecially at the water holes. With every new tip from you, I realize just how little I really do know. Thank you for the time you give to folk like myself - 'The beginners' Keep them coming please!!!

  7. Fittipaldi says:

    I have learned so much from you.thank you so muchstephen

  8. Stephen says:

    I have learned so much from you.thank you so much...stephen

  9. MIKE HUTTON says:

    ONCE AGAIN
    THANX FOR EXCELLENT TIPS
    I AM WORKING ON ALL AND GETTING AMAZING RESULTS (EVEN WITH MY MID OF RANGE CAMERA )......
    SLOWLY BUT SURELY

    THEY ARE ALL MAKING ME A BETTER "PHOTOGRAPHER "
    ENJOYING MY CAMERA MORE AND SEEING THINGS "IN A DIFF LIGHT AND FROM LOTSA DIFF ANGLES "
    MIKE

  10. eric graham says:

    i have been following your tips and find them easy to understand better than all the jargon you get from the books i buy which do nothing other than fill your head with a lot of info you cant understand thanks very much for these infomative tips

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Difficulty:
Beginner
Length:
7 minutes
About David Peterson
David Peterson is the creator of Digital Photo Secrets, and the Photography Dash and loves teaching photography to fellow photographers all around the world. You can follow him on Twitter at @dphotosecrets or on Google+.