For this week, I will be doing a general overview of depth of field: what is it? How do you change it? What does it do for photos? Once you gain an idea of how depth of field works, it can be one of the funnest things to play around with!
Depth of field can be used to greatly enhance your photos. You can make it so the focus is on something as small as an eyelash or a strand of hair, or make it so that your entire frame is in focus (this also depends on your lenses). Depth of field is one of the funnest but also trickiest parts of photography. Time to open your mind and hopefully how I explain it will make some sense!
Depth of Field
Depth of field is basically the the distance between objects in a photo that are acceptably in focus. It is controlled on your camera by the aperture.
The aperture in a camera is the hole that light enters; okay, easy so far. What you may recognize it as is the f-stop. F-stop refers to how many “stops” or levels it takes to reach a certain depth of field. These are called “stops” because at each f-stop there is a part of the mechanism that is stopping further light from entering (basically, the diameter of the hole).
Okay, so far: depth of field, or the objects in focus in a photo, are controlled by your camera’s aperture, a hole that allows light in. This hole changes size (diameter) to allow different levels of light in; each of these is called an f-stop.
So far so good, right?
These f-stops are recognizable when you go into a store and look at all the camera lenses on sale. You’ll see on the boxes the focal length (200 mm) and usually the f-stop near it: it’s the number f/1.6 or f/4.5, something like that.
these things, circled very professionally by me.
So what exactly do those f-stop numbers mean? When you are playing around with your camera on the manual setting (NOTE: as you all should be doing! There is no way to get to know your camera like manual) or aperture priority, you see these numbers scrolling past and apparently, they are supposed to mean something. Maybe you’ve ignored them for some time. Maybe they are not of much interest. Here is where it gets a bit tricky. It is very important and very interesting, but it takes some reciting over and over and practicing, over and over.
When I refer to f-stop numbers, I mean the maximum aperture of the lens, which here means not the biggest number the maximum ability of your aperture to change its diameter, which can be a small f-stop number because it’s a large diameter (stick with me here…).
- The lower the f-stop number, the wider your aperture diameter.
- The lower the f-stop number, the more light is entering your camera.
- The lower the f-stop number, the shallower your depth of field (meaning you can focus on smaller things, with more being blurred).
- The lower the f-stop number, generally the faster the lens.
- The lower the f-stop number, the more flexibility with aperture sizes the lens has.
For example, f/1.0 is one of the most open apertures. This number means much light is entering your camera. At the same time, it means you have a shallow depth of field, so you can take photos of very specific elements or details of an object, like a leaf, or a ring:
In this instance, I was focusing on the ring. Notice how even the leaves are blurred and my background (which happens to be the window out of my bedroom) is completely blurred. This is at f/2.0 at 1/500 shutter speed, shot with a 50 mm lens with maximum f/1.4
When you are able to focus on only these types of details, conversely you must deal with more light entering (remember, the lower the f-stop the more light coming in). To compensate for this I will usually make my shutter speed faster. If you use aperture priority shooting for these types of shots you may not have to worry about it as much, however I like complete control over my photos so I usually end up adjusting both elements to get the look I want. Another thing to be aware of is your ISO, your camera’s sensitivity to light. All three of these elements play together to get the exposure you want.
You hold your camera up and take a photo. Light from the scene goes through the glass lens and through a hole (the aperture) the size you have made it by choosing an f-stop; right behind it is the shutter curtain, which opens for a fraction of a second to allow the amount of light–determined by the aperture diameter–through. The camera’s overall sensitivity to this light is based off your camera’s ISO levels. And.. tada! Photo!
So there is lots going on despite us just paying attention to the depth of field! I wish I could do a big in depth talk about all of it but that is a bit overwhelming. Basically, just remember this: when working on your depth of field shots, you must compensate for whichever f-stop you are using (shutter speed, for example).
What about if we want a shot with everything in focus, like landscapes? For these shots you would change your f-stop to a larger number, which means less light is getting in, which means…? Right! The deeper your depth of field.
The above barn photo was taken at f/22 at 1/2000 of a second because it was a sunny day. Notice how every detail is in focus, and that is because of my chosen depth of field (f/22). If I had made it smaller, only what my camera had focused on would be in focus.
So what have I talked about so far?
SUMMARY: That the depth of field, or what is in focus in your photo, depends on the aperture diameter you choose, which is controlled by the f-stop. The smaller the f-stop number, the wider the aperture diameter (more light) and the shallower your depth of field (less in focus, small details in focus). The larger the f-stop number, the smaller the aperture diameter (less light) and the deeper your depth of field (all in focus).
So how does one figure this stuff out? This is how I did it. One day I set my camera on manual and refused to take it off. I barely even do now, unless I choose one of the priority shootings (Av, Tv) but rarely. I am comfortable with it now only because I forced myself to use it and only it. I took a lot of photos. I fiddled around with just the aperture number to see the difference it made to my photos. Then I would fiddle around with both it and shutter speed. I took lots of bad photos. LOTS. I still take many bad photos. Do not be discouraged! If the depth of field is not what you want or what you envisioned, ask yourself: why is it not working? What can I do to to change it? The fun part of photography is the playing around and testing new things. Not comfortable with your knowledge of depth of field? Force yourself to learn it by going out and taking photos with depth of field as your priority of the day.
It is easy to take photos with everything in focus. Or just what your camera decides to be in focus based on automatic settings. Try not to do that as much. Make sure you are changing the aperture number! Deal with what the camera does afterward. Understand why suddenly everything went crazy bright and how you can fix that exposure. Turn the focus to manual so you can adjust it to what you want; the smaller the detail, the harder it is for auto focus to figure out what on earth you want to do.
Read about it! Look at diagrams! Depth of field is fun because it adds a unique element. When I bought my 50 mm lens last year with its f/1.4 I fell in love. And I still want more with smaller f-stops. More! It’s especially fun for portraiture:
Wide depth of field is still fun and I love doing landscape photography, but man is it ever fun having a versatile f-stop ability on a lens! I recommend everyone try playing around with both large and small f-stops and see the results.
Hopefully that was somewhat clear and did not overload your brains. Please comment with any questions, ideas, or tidbits! 🙂