If you are struggling to fit everything in the frame is it because you have crop sensor? See here: Everything you Need to Know About Crop Sensor vs Full Frame

If you are anything like me, understanding depth of field (DOF) was one of the biggest hurdles you had to overcome when learning the technical aspects of photography and shooting in manual mode. I would read explanations online, see links to calculators, hear it described as “shallow” or “deep” and couldn’t make sense of it all.

Calculate field of viewmicroscope

When you are shooting more wide open (smaller aperture number) less of the photos will be in focus. Then you will have a narrow depth of field where the background is blurred.

Sensor Size: “I believe this has the least impact on depth of field” and then you state “Changes in DOF depend on whether you use a crop or full frame;”

The only thing that confuses me is the area where you talk about sensor sizes where it seems that you may be contradicting your own argument by stating:

Field of viewcamera

Hey Adam! Thanks for the comment. To clarify sensor size does affect depth of field, but since most people use one camera consistently (and thus one sensor size) I didn’t want to go into too much detail about how changing sensor size affects DOF. That subject could be a whole article on its own but since most readers of this particular blog probably don’t switch between full frame and crop, I felt it was the least important factor to discuss. Hope that makes more sense! Thanks for asking!

FOV to mm calculator

Hi! wonderful article today. Is there any chance you could post the same pics of your “studly” husband with the 50 mm and 85 mm with the same camera settings, to see the difference? Can you tell I’m an an amateur? LOL

Read more: Creating Depth in Your ImagesHow Focus Stacking Will Help You Create Shaper Photos11 Composition Rules to Know to Improve your PhotographyWhy a Wide Angle Lens Will Be Your New Favorite Lens

There is a calculator that will do this at https://www.scantips.com/lights/fieldofview.html (Option 6). The geometry is shown at bottom of that page, however, you must use Trig for angles.

Even though every photograph is two-dimensional, it portrays a three-dimensional world. The distance between the camera and the subject and the distance behind the subject to the “end” of the photo is the “depth” of the photo. The amount of depth that is in focus is the depth of field.

Understanding DOF will allow you to add interest in your photos. If you want your subject to really pop you need to know how to create a shallow DOF. If you want your whole image in focus, like in landscape photography, you will need to create a deeper DOF.

DOF is a range of distances on either side of the focal plane that are “acceptably sharp.” (“Acceptably sharp” is where the confusion begins.) Another way to state this would be, the area behind and in front of your focus point that is in focus as well.

Focal length can affect the depth of field as well since the longer you focal length the more narrow your depth of field is.

The next photo only the wolf is in focus. The other toys are on different focal planes. They have been moved to a different focal plane therefor they are not blurry. You can see this more clearly with the turtle, half of the turtle in in focus while the other half is on a different plane.

To be able to explain depth of field we have to start with defining certain terms. Then I will get into describing some things that affect depth of field.

CCTVfield of viewcalculator

What you need to know for field of view is the camera sensor size (or film size) measured in mm. You must compute with sensor dimensions in mm.

Notice in these next few photos how the subject is in focus but the majority of the rest of the photo is not sharp. This is showing narrow or a shallow depth of field.

Camerafield of viewsimulator

I’m not really sure what James (the above commenter) is talking about as he really doesn’t elaborate what he takes issues with in regards to this article.

As your sensor size is given in pixels (assumed square pixels!), your focal length will also be in pixels. To get it in a more usual unit (m), you need to know the pixel size.

In fact, if you are shooting with your kit lens this is a great trick to give you a more narrow depth of field when you feel restricted by how wide your aperture can go.

Field of viewcalculator astrophotography

You can see in the photos below how when at the same aperture the photo with the wider focal length has less depth of field.

FOV to focal length calculator

Aperture, focal length, and distance from your subject. Using a combination of those 3 things you can create exactly what you need.

The below photos were taken with the same settings and same focal length. The only difference is I moved the stool closer to the plant in the second photo.

The triangles (large and small) are similar, that is angles are the same. So Angle of view will be the same as top angle (at the lens) of the smaller triangle. From that, since you know what sensor size and angle of view is, you can calculate focal length in pixels, as @remco calculated for you.

It's basic geometry: you have a right angle triangle, with half the FOV as one of the angles (a), and half your image size as the opposite side (A). To calculate the focal length F, use tan(a) = A/F, which gives F = A/tan(a).

I hope after reading this you have a better understanding of depth of field. Now go get your camera out and experiment with DOF.

In the photos below you can see how the focal plane affects how much of the photo is in focus. The first photo all the toys are in focus because they are on the same focal plane.

Hikvisionfield of viewcalculator

The distance that is sharp around your focus point. Shallow DOF means not much of your image other than your subject is sharp. Deep DOF means a lot of your image other than your subject is sharp.

It is what Hermann said, focal length is NOT measured in pixels. I strongly doubt the engineering journal said focal length was pixels.

One day it just clicked. I’m not sure where or when, but I have a much better grasp on it now. I love using that knowledge to positively impact my own personal art as well as the art I create for my clients.

In fact, units of the sensor size should be exactly the same as units of the focal length to make sense of F=A/tan(a). What you can get from that is, if you have bigger pixels (in cm), you will need larger focal length (in cm) for same field of view and number of pixels.

As you can see from the example above the 200mm lens really compressed DOF. Even though these images were both shot at the exact same place this lens makes the subject and background seem more pushed together.

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I know a lot of people who initially struggle with getting a grasp on aperture and depth of field especially when starting and and you have laid out it nicely in this article.

In each of the photos below you can see that the focus is on the bunny but how blurry the background is (DOF) changes drastically depending on the aperture.

The article specifies that the horizontal FOV is 47°, so we have to use A = 640/2 = 320, a = 47°/2 = 23.5°, which give F = 736 pixels.