hat is Depth of Field (DOF)?|
Here is the scientific version:
Depth of Field (DOF) refers to the range of distances from the camera at which acceptable sharp footage is obtained. Easy ...no?
Ok, here is my version:
First of all, be aware that only at one point your subject is completely,
100% in focus (sharp). Everything else around this point is slightly
out of focus (soft(er)). Not noticeable though, just to mention this fact for accuracy sake.
In the real world your camera will give you generally acceptable image quality which is sharp (focused) inside a certain area. It is this focused area we call Depth of Field (DOF). Everything else we call soft focus or being slightly or completely out of focus (blurred).
Can you control the Depth of Field (DOF)?
Yes you can. If you have one of the better consumer cameras it will allow you a manual override, meaning deactivating the automatic settings. You will be able to adjust your settings which allow you to control the DOF accordingly to the light conditions and the footage you want to capture.
The DOF is not constant and it can be changed using, for example, the iris setting. The smaller the iris aperture (opening), the greater is the DOF. A smaller aperture demands good lighting, of course.
Just for clarity: if you have bright sunlight the iris aperture is pretty small. On the flip side, in low light conditions you will be forced to open the iris more or even to its full extend to obtain an acceptable image quality and therefore the DOF will be reduced.
And here we have it: Bright sunlight will minimize the iris aperture and gives you a great DOF. Low light will force you to open up the iris and the DOF will be significantly reduced, meaning the area in front of and behind the subject are noticeably more out of focus (not sharp).
But let's get back to our manual camera settings and controls. So what can you do with your manual override to influence the DOF (Depth of Field)?
Check if you need any filters
In perfect light you may use a Neutral Density (ND) Filter without compromising the DOF too much but avoid any other filter. Basically any filter will reduce light intensity and will have a negative effect on the DOF. Filters are designed either to reduce the amount of light finding its way to your camera's sensor or to change the overall appearance of the final image. As a general rule you have to think of filters in conjunction with DOF as two competitors who are working against each other. I certainly wouldn't use any filters while creating DOF footage.
Set the correct shutter speed.
In perfect light conditions you want a higher shutter speed and a low iris opening. Ideally you want to find the perfect setting for the best DOF, that's small iris aperture and the correct shutter speed. However, be wary with setting the shutter too high as in high shutter speeds the iris has to open wider to get the correct amount of light needed for a good image.
Because different cameras work differently I cannot give you any numbers for the correct settings (shutter speed and iris opening). You have to fiddle with that yourself and go for the trial and error method. I can only point you in the right direction
On a note: the higher the shutter speed, the lower the DOF (Depth of Field) and vice versa. So the correct opening is an important factor for getting the desired DOF effect.
Adjust the Focal Length of your Lens
Basically, zooming in will reduce your DOF and zooming out (using the default focal length of your camera) will increase your Depth of Field. Since you are aiming for the best DOF you better leave the zoom in neutral. There will be, of course situations where you have to make a telephoto shot, meaning you have to zoom in, meaning there will a shallower DOF. The shot can be interesting nonetheless if you can separate your subject from its surroundings, so the subject will be sharp in focus and the surroundings are slightly or even strongly out of focus (blurred).
Position your camera as far away from the subject without sacrificing clear visibility of the subject. The farther away the camera is from the subject, the greater is the DOF and vice versa.
These are the important points where you can creatively manipulate the Depth of Field (DOF) with a manual override, camera position and by discarding the use of filters.
Now why do you want to play with the DOF and manual override in the first place? Why not just leave the camera in automatic mode? The answer is simple, Creativity.
There will be times where you want a shallow DOF or situations where you want a perfect DOF.
Shallow DOF, for example, will create atmosphere. Shots with out-of-focus trees or flowers in the foreground are classic examples. Similarly, subjects can be separated from their background: try a telephoto shot picking out one face from the crowd or, for impact, take a deep-focus shot in the wide angle position that shows for sharp details going from front to back.
Depth of Field can be an interesting playground for videographers. It gives you opportunities to make you footage look more interesting, just a notch or two above the average. Isn't that what we all aim for?
Summarization of Facts
Factors which influence the Depth of Field (DOF)