I whipped this up for my photography club. Its meant to be simple so no need to explain hyperfocal distance or anything, but seriously what would you add / explain more simply?

Depth of field

Depth of field is the term photographers use to describe how much of a photo is in focus. This is something that most cameras can control which allows for creative choice and can help you choose what settings to use for your camera.

Did you know though that there are three things that can affect depth of field?

1. Aperture: In simple terms this is the size of the hole in the lens. It is represented by a number with the letter f in front of it. Quite simply it is the size of the hole in the lens at its narrowest point and is a ratio between the length of the lens and the diameter of the hole. In its simplest form, a smaller F number means less depth of field. That is less of the photo will be sharp and a larger F number means more of the photo will be sharp. Examples of numbers you might see on your camera are f1.8, f2.8, f4, f5.6, f8, f11, f16, f32. These numbers are called f stops - each of them represents a halving or doubling of the amount of light hitting the sensor. Most cameras can and will show f numbers in between these in either 1/2 or 1/3 increments. Also the F number can change as you zoom the lens because the focal length changes so the ratio changes. Higher quality lenses compensate for this and are said to have a constant aperture as the f number doesn’t change as you zoom.
2. Focal length: The length of a lens alters how much of the photo is in focus. In simple terms the longer a lens is the shallower the depth of field will be compared to the same aperture on a wider lens. This is one reason it can be harder to get sharp focus with long lenses. It is also why many photographers opt for focal lengths of between 70mm - 200mm. These lengths give shallower depths of field than say a 24mm lens at the same aperture.
3. Subject to camera distance: Most photographers don’t realise that the closer something is to the lens the shallower the depth of field will be. This is one reason focusing with macro photography can be so hard.

Sometimes we want more of the photo in focus. To achieve this we can:

1. Use a wider lens or zoom out
2. Close the aperture down to a higher f number
3. Step back from what we are photographing

Sometimes we want less of the photo in focus. To achieve this we can:

1. Use a longer lens or zoom in
2. Open the aperture up - picking a smaller f number
3. Step closer to what we are photographing.

Practicing Depth of Field adjustment

First use a tripod for this if you can. You don’t want to have your photos accidentally blurry because your camera moved.

Now find a place to photograph that has a range of interesting things to photograph at different distances. Ideally youll be outside but in this case we will use several trestle tables end to end and some baubles and string lights as an indoor approximation.

Set your camera up a comfortable distance from the scene. Put your ISO on Auto and your camera on av mode (just so you don’t need to worry about exposure for this exercise close enough is good enough. Focus on an object mid way through the scene. Take some photos at different apertures (f numbers) especially the lowest and highest and middle numbers you can. Pay attention to how much is in focus using the lights to help you see it.

Now zoom in or out (or change lenses if you are using a prime lens) keeping the same object in focus. Try different focal lengths as well as different apertures to see how the two variables work together - it will be a little different for every lens you own.

Finally step closer or further way from the scene or shift your focus point to a closer or further object and. Repeat the process changing aperture and changing lens focal length. Note most lenses have a closest focusing distance. This is how close an object can be to the lens and still have it be focuses.

If you have the time / space. Get  3-5 friends and try having them standing in a line behind each other offset so each person can see the camera over the person in front of them’s shoulder. Try changing your settings to get all of them in focus and try changing your settings until only 1 of them is in focus.

Why wouldn’t I just make the whole photo sharp? Well having a shallow depth of field can remove distractions in the background and it can make the subject stand out more.

Photographers have a word for the aesthetic quality of the out of focus elements in a photo. We call it Bokeh.It comes from the Japanese word for haze or blur and in English is pronounced roughly bo-kay. Bokeh is a property of lens design and manufacture and can both add to an image and detract from it depending on the lens and subject.