Photography Cheat Sheet: How Crop Factors Affect Depth of Field

We’ve created a handy photography cheat sheet for you to figure out the crop factor of a lens and the resulting depth of field.

Figuring out the crop factors from one camera system to another can be a bit tedious. Remembering what camera system uses what sensors is also a bit annoying, so we’ve come up with a full Photography Cheat Sheet to help. These are all primarily based on the 35mm frame, otherwise called Full-Frame. From that format, you figure out a whole lot of variations depending on what you’re looking at. That’s why some manufacturers make odd focal lengths that sometimes just don’t make sense.

Deeper Depth of Field, Changing Field of View, Same Light!

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In our Photography Cheat Sheet infographic, we’re using a 35mm f1.4 lens as our base. From there, we’re adapting it to a variety of camera systems. Because the 35mm f1.4 is colloquially developed for the 35mm film system, we go from there, depending on the format. There are two different APS-C formats here that are interesting. While the entire industry uses APS-C sensors at a 1.5x crop factor, Canon remains the outlier: they use a 1.6x crop factor, which is the result of a slightly smaller sensor. These change the field of view. So with a smaller sensor, what you see also becomes narrower. It doesn’t mean that the lens changes, just what you see. You’re primarily using more of the center of the lens than anything.

This all translates into a change in the depth of field too. So at f1.4, a Sony a6600 will render the lens to be the full-frame equivalent of f2.1. This will not change the light-gathering abilities, though, only how much of the scene is in focus at a specific aperture.

You’re probably wondering why this is important? Well, it’s more critical for DSLRs than Mirrorless. The exception is for Sony E mount and Nikon Z mount. Those two camera systems use the same mount of both APS-C and Full-Frame lenses. So if you put a 35mm f1.4 lens meant for full-frame cameras on an APS-C camera body, then you’ll get what’s called the crop factor. That’s all explained in the infographic above.

The Reverse Crop Factor

With systems that are larger than full-frame, like what you get from a Fujifilm GFX camera, you have a reverse crop factor. Since the sensor area is larger than 35mm full-frame, a 35mm focal length lens becomes wider in Full-Frame equivalent. Of course, this applies only to the millimeters. If you put a smaller format lens on a larger format, the camera will only cover what the imaging circle can render.

How It Affects Your Images

All of this affects your images in different ways. The biggest are:

  • What you exactly see when you mount this lens to the camera
  • How much of the scene is in focus at a given aperture

Micro Four Thirds has a ton of advantages here. If you’re shooting street photography and you want to shoot at the equivalent of f8, then just stop the lens down to f4. You’ll get the same depth of field but with the light-gathering abilities of f4. It’s a huge advantage. But if you like bokeh and really shallow depth of field, then your only choice is to go bigger.