Full frame vs APS-C: what the sensor size really changes
Crop factor, field of view, background blur, low light and cost: what you gain and give up with a full-frame or APS-C camera, explained without the jargon.
The short version: full-frame sensors are the size of a 35mm film frame. APS-C sensors are smaller, roughly two-thirds the width. Full frame gives you a bit more background blur and cleaner low-light images. APS-C gives you smaller, lighter and cheaper kit, with extra apparent reach from your lenses. Both are capable of excellent pictures.
We use both every week: a Canon EOS R5 Mark II and an R6 for full frame, and a Fujifilm X-M5 for APS-C.
What crop factor means
Because an APS-C sensor is smaller, it records only the middle part of the image a lens projects. The result looks like you’ve zoomed in. How much depends on the brand:
- Canon APS-C: 1.6x
- Fujifilm, Sony and Nikon APS-C: 1.5x
Multiply the focal length by the crop factor to get the full-frame equivalent field of view. A 23mm lens on a Fujifilm body frames like a 35mm lens on full frame. A 50mm lens on a Canon APS-C body frames like an 80mm.
The lens itself doesn’t change. A 50mm lens is always 50mm. Only the framing changes.
Background blur
At the same framing and the same f-number, full frame gives shallower depth of field. As a rule of thumb, multiply the aperture by the crop factor to compare:
- f/2.8 on Fujifilm APS-C looks roughly like f/4 on full frame.
- f/1.4 on Fujifilm APS-C looks roughly like f/2 on full frame.
So APS-C can still give you lovely background blur. You just need a faster lens to match the look.
Low light and noise
A bigger sensor collects more light in total, so at the same ISO, full-frame images are usually cleaner. The difference between full frame and APS-C is roughly one stop. In practice, a modern APS-C camera at ISO 3200 looks about like a full-frame camera at ISO 6400.
For most daylight shooting you won’t notice. At gigs, weddings and night street work, it starts to matter.
Size, weight and cost
This is where APS-C wins. The bodies are smaller, and the lenses can be much smaller because they only need to cover a smaller sensor. Telephoto shooting gets cheaper too, since a 70-300mm lens frames like 105-450mm on Fujifilm APS-C.
Full-frame lenses, especially fast ones like a 50mm f/1.2, are big, heavy and expensive.
Which should you choose?
Choose full frame if you shoot a lot in low light, want the shallowest depth of field for portraits, or want the widest choice of high-end lenses.
Choose APS-C if you want a camera you’ll actually carry every day, you shoot wildlife or sport on a budget and want extra reach, or you’re starting out and want to spend more on lenses than on the body.
Many photographers end up with both: full frame for paid work and planned shoots, APS-C for travel and everyday carry.
Can you mix them?
Often, yes. Full-frame lenses work on APS-C bodies of the same mount, with the crop factor applied. APS-C lenses on a full-frame body usually force the camera into a crop mode, which uses only part of the sensor and lowers the resolution.
Spotted something wrong or out of date? Email hello@shuttersnack.com and we'll fix it.