There are many elements to creating a shallow depth of field. The most important are to use the correct focal length (the distance between the lens and the film plane) and to make sure the aperture (the size of the opening in the lens that allows light through) is small enough to allow all of the subject to be in focus.
If the lens has a focal length of 40mm (equivalent to 35mm in a standard camera) the maximum depth of field will be equivalent to what is known as the ‘standard depth of field’, which is approximately from 0.7m to infinity. This means that all of the subject will be in sharp focus up to a point, but beyond that, the edges of objects will blur out.
To achieve this effect, the lens will need to be set at the widest aperture (usually f/16) and the depth of field will then depend on how far away you are from the object you are photographing. The further the object is from the lens, the greater the depth of field.
An ideal situation would be to set the camera on a tripod and use a remote control to take the photo, which allows you to choose where to focus. This way, you can choose an object within the scene that you want to remain sharp, or a background that you want to soften.
Alternatively, you could set up a photo shoot with a subject placed in the exact location you want to photograph, and use the camera’s autofocus system to choose exactly what you want to be in focus. In this case, you would need to make sure the object is placed at the exact spot, so you could set the camera’s autofocus system to lock onto it.
Look for a strong central focal point.
The more interesting your subject is, the harder it is to make sure that it is sharply focused. The main thing is to find a strong, central focal point to work with.
Think about what you want to photograph. Is it the flower you are taking a picture of, the edge of the pond or the trees in the background? When you look at your subject, what do you see? Are there any key features that you want to bring into focus?
As soon as you have your answer, you can start planning your approach. For instance, you might decide to focus on the flower, then decide that the leaves should be the main thing in the picture. The background will no longer be a problem as you know where to place your camera, and that the focal point you have chosen will be in focus.
Look for a wide variety of angles.
Even if you have chosen a particular angle for your picture, the chances are that the sun will move across the sky. This means that the whole scene will change and it will be impossible to get all of the elements in focus.
You could make the most of the changing light and create a series of pictures with different angles, and different focal points. This will show your viewer a variety of images, but each of them will be sharp.
Use natural light.
Natural light is usually much better than artificial light. If possible, use a window with a bright, overcast day. If you are photographing indoors, use a room with lots of daylight and, preferably, a skylight. The brighter the light, the easier it will be to focus.
Choose a wide aperture.
The wider the aperture, the larger the opening in the lens, the smaller the depth of field and the more likely it will be that you will have to move the camera to make sure all of the subject is in focus.
The ideal setting is f/8 or f/11. These settings allow you to focus on a part of the picture you want to stay sharp, while the rest will be out of focus.
Set the ISO to 100.
This will ensure that the image is not too dark and will allow you to get the best results. You can adjust the ISO up to 1600, but at higher settings, you will need to use a tripod and the results will not be as good.
Get your focus right.
As soon as you have your camera on your tripod, get your focus set to manual and check the focusing distance. This will allow you to set the exact distance at which you want the camera to focus.
You can also use the viewfinder to make sure that your object is exactly where you want it to be, by aligning the lens with the part of the frame that you want to remain in focus.
Get as close as you can.
If you are using a zoom lens, the closer you get to your subject, the smaller the depth of field will be. If you use a wide-angle lens, the farther away you get, the wider the depth of field.
Take several pictures and compare the results.
It’s important to compare your pictures after they have been developed so you can see which ones worked and which didn’t. There will be times when it looks like everything has been sharp, but there will be other moments when you realise that the whole of the object isn’t in focus.
Use a tripod.
A tripod is essential for getting sharp results. Without it, you will never get the same quality as when you are using a stable camera.
If you are using a zoom lens, try to use a tripod to prevent the movement of the lens as you change the focal length. This will make your photographs consistent.
When you are using a wide-angle lens, you don’t need a tripod to stop movement as the focal length stays the same. Instead, try to use a wide-angle lens mounted on a monopod.
Use a flash.
A flash helps to fill in shadows and makes objects look brighter. This can be useful if you are photographing in low light, but it will not work well if you are using a slow shutter speed, which will cause the flash to fire too soon, before the camera has finished its exposure.