The internet is littered with literally thousands of blog posts and youtube videos about crop vs full frame sensors, and there are millions of comments on the topic across seemingly innumerable forums, message boards, and article comment sections. A great many of them them have to do with noise performance, focal length comparison, or dynamic range. But depth of field is talked about less often, and that’s what this posting is all about.
Crop vs Full Frame: Depth of Field (DoF) in a Nutshell
I could write several hundred words here to try to appease the Google bot gods and maximize my search engine optimization, but really this is a pretty simple distinction. The real difference between crop vs full frame sensors when it comes to DoF comes down to a simple metric: 1 stop. Yep, that’s it. All other things being equal, an APS-C (crop) sensor will have 1 stop more of DoF than a full-frame sensor at any given aperture setting.
So what does that mean? For practical purposes, it means that the DoF (the range in front of and behind your subject that is in focus) will be deeper on a crop sensor than a full-frame sensor. And it will be deeper by about 1 stop. Scroll down for a table that gives a comparison between crop vs full frame across the range of full f-stops (and here’s a link to my Handy-Dandy List of f-stops). But let’s look at a real-world example first.
Crop vs Full Frame: DoF Example
Let’s use the good old 50mm lens as our first example. It’s probably the most common lens in use, and is often the cheapest available prime (new or used). And let’s assume that the crop sensor has a 1.5x crop factor multiplier for equivalent full-frame focal length comparison. Canon APS-C cameras have a 1.6x crop factor, but that’s the only brand that has that size sensor, so we’ll ignore that for our example.
Consider a FujiFilm XT-4 body (crop) with the excellent FujiFilm 50mm f/2 lens. To the old-school 35mm film photog, that sounds like a “normal” perspective setup and fast aperture. But from the mindset of a full-frame camera field of view and DoF, the Fuji setup is going to perform as a 75mm lens with a maximum aperture of f/2.8. So that’s a short telephoto in terms of field of view instead of being in between wide and tele. And the equivalent f/2.8 effective aperture isn’t slow by any measure, but it’s about half the light you would get with a f/2 lens on a full-frame sensor.
A zoom lens gives another way to look at this issue. Say you’ve got a Sony A6100 (crop) body with Sony’s 55-210 kit zoom lens, with its variable aperture of f/4.5 – f/6.3. From the perspective of a full-frame experience, that lens is effectively 82.5mm at f/6.3 on the wide end, and 315mm at f/8.8 on the telephoto end. That extra reach is a real advantage of a crop sensor, but you pay for that in terms of available light.
Full Frame vs Crop: DoF Equivalency Table
Here’s a simple table to show how a given aperture on a crop sensor would perform in terms of DoF versus a full-frame sensor.
|Full Frame f-stop||Crop Equivalent f-stop|
Which is Better: Full Frame or Crop?
This is a bit of a click-bait header, as there isn’t a simple answer. There’s no way to tell which type of sensor took any given picture, and many amazing photographs have been produced with both sensor types.
The advantage to crop setups is that the bodies and lenses are usually (but not always) cheaper, smaller, and lighter than their full-frame counterparts. And the extra focal length reach is great for wildlife and sports photographers. There are also pluses to full frame cameras/lenses, but it’s been beat to death all over the internet already, so I won’t add to the noise here.