Images progress from left to right gradually to a deeper Depth Of Field.
Have you ever been frustrated while trying to get that smooth background look you see in so many great photos? Or when you’re trying to get everything in focus but end up just getting a part of the subject in focus? This is because your Depth of Field, or ‘DOF‘, is not shallow or deep enough for your needs. Lets take a look at how we can correct this. Depth of Field is how much of a photo that appears to be in Focus.
First, you’ll need to understand what Aperture is and how it works.
Moving the Iris on a Nikon 50mm F1.8
The aperture is controlled by opening and closing a bladed diaphragm in the lens, called the Iris, which controls how much light is let into the camera via the lens. A larger opening allows more light to enter the camera, and a smaller opening allows less light into the camera. This is one way to control your exposure, along with Shutter Speed and ISO sensitivity. But that’s another topic. Aperture also controls the DOF.
Your aperture is controlled by changing the ‘F-Stop’. Some common F-Stop settings, from largest opening to smallest opening, are as follows:
F1.8 > F2.8 > F4 > F5.6 > F8 > F11 > F16 > F22
You may see larger and smaller apertures from lens to lens.
You may find this a little confusing… as the number gets smaller, the opening becomes larger… and as the numbers get larger, the opening becomes smaller… what!? Yeah, I know, it was annoying to me when I first started too. Essentially, these numbers represent a ratio of how much light is being allowed into the camera.
A lens at an F-Stop of F4 allows 1:4 the amount of light as a ‘wide open lens’. If you take the same lens and stop it down to F8, the iris limits the allowed light down to 1:8. Take the same lens again and open it up to F2 and the iris will allow more light in at 1:2.
Now that we understand aperture, lets move on!
When using aperture to control the DOF you need to know 3 things.
1: The smaller your aperture is (the bigger the number), your DOF will be deeper.
– When you want more area in focus / your subject and background both in focus.
2: The larger your aperture (the smaller the number), your DOF will be shallower.
– When you want less area in focus / your subject isolated from the background.
3: The DOF expands half as far coming back to the lens from the the Point of Focus and twice as far to going away.
– This means that when you want to focus on something, you need your point of focus to be 1/3 of the way into the subject in order for everything you want included to actually be in focus.
Notice the shutter speed needs to get slower to let more light in to compensate for the smaller aperture opening. As soon as you get around 1/60th of a second, it becomes hard take a photo without the help of a tripod or some other stabilization aid.
Click on the image to see a larger version of it.
How do you use DOF best with your subject matter.
If you intend to isolate your subject from a distracting background, a shallow DOF would work best in the situation. Here we have Ruby Rose from Rooster Teeth’s RWBY. I shot her in front of my roommates sewing machine. As can you see in the first image it the background is somewhat in focus, busy and distracting.
ISO 2000, 1/40th of a Second and F5.6
So how do we fix this? We can either remove the items from the background, move the subject someplace else, or move around the subject until the background is not as ‘busy’. What if you can’t do any of that? you can open up the lens to blur out the background into creamy Bokeh. Bokeh refers to the out of focus parts of a photo.
ISO 2000, 1/400th of a Second and at F1.8
Now we have Ruby in focus with the background blurred with no hard lines distracting the eye. Also here we can see that at F1.8 how little is actually in focus. Look at the blade of her Scythe, its not in the area of focus. Just as a reference, in this pose she is just about 3 inches tall.
The distance between Ruby and the sewing machine is roughly 2.5 feet.
But what about a deeper DOF, where you need to include more in your photo? For example you’re shooting a wedding, and all the groom’s and bride’s family are on the steps of the church. But the steps are somewhat narrow and tall, with 30 or so people on them. You now need to photograph all of them and they NEED to all be in focus.
So what do we do? First off you’re going to stop down to something past F8 something like F11 or 16 will work and make sure your shutter speed is fast enough to capture any movement that may be in the shot. Now you have all that setup, you’ll now focus 1/3 of the way into the group. Say there are 5 rows of people, you’ll need to focus somewhere between row 2 and 3.
Now with all that in mind, there are a few things you need to remember.
Your DOF decreases the closer to your subject is to the camera.
Your DOF increases the farther away your subject is from the camera.
Your DOF decreases the Tighter the Focal Length is. (more you zoom in)
Your DOF Increases the Wider the Focal Length is. (more you zoom out)
For example if you have a Telephoto lens and you’re zoomed in with an aperture of F8, the DOF will look similar to if you shot up close with a ‘normal’ lens at F2.8.
Or you’re shooting with a Wide Angle lens with an aperture of 2.8, the DOF will look similar to if you shot farther away with a ‘normal’ lens at F8 or F11.
With that I hope this ‘How To’ post helps you understand Depth of field. If you have any questions leave a comment. I hope you enjoyed this post and found it informative. Stay tuned for more How To and photography related posts! – JPOC
All test photos where Shot my Nikon D7100 with a Nikkor 50mm 1.8D lens.
Your results may vary pending sensor size, lens quality
and maximum aperture on the lens you’re using.
Photos Copyright © 2014 Joseph Comeau aka ‘JPOC’
Special Thank You to my roommate Leanne!
JPOC Photography 