Back in the olden days of 35mm film cameras images were all captured on a rectangular-shaped element (“sensor”) that was the same size: 24mm x 36mm. But when digital cameras were invented, engineers initially had to hold back on the size of the sensor (the element on the inside of the camera that “absorbs” the light and “senses” the image projected from the lens) because a larger full frame sensor wasn’t yet possible – technical limitations. And different camera manufacturers engineered different sized sensors.

The result of a smaller, crop sensor (APS-C) means the full potential of a lens isn’t achieved. The lens is trying to project a full image onto the sensor, but the sensor can only capture part of it.

DSLRs come in several formats based on the size of their image sensors. Four Thirds System DSLRs (from Olympus) have sensors measuring 17.3×13.0mm, APS-C DSLRs (Nikon calls this format “DX”) have sensors around 23.6×15.8mm, and “full-frame” DSLRs have sensors measuring 36x24mm, the same as a full 35mm film-image frame.

Nikon: full frame sensors (FX) and crop frame sensors (DX) with a 1.5x magnification effect

Canon: full frame, 1.3x, 1.6x (EF)

Olympus: full frame, 2x

The result of of crop frame sensor, as the name implies, is a cropped image. No big deal. What you see through your camera’s viewfinder is still what you get. The only difference comes in what the lens is capable of producing based on the type of camera you’re using. For example, if you use a 50mm lens on a crop frame Nikon (DX) body you’re going to get an image that is equivalent to 50mm x 1.5 = 75mm. Or, if you use a 200mm lens on a Nikon DX body you’re going to get an image that is 200mm x 1.5 = 300mm. On the other hand, if you use a 50mm on a full frame Nikon (FX) body you’re going to get a true 50mm photo – no zoom effect: 50mm=50mm. The biggest differences are realized when using wide angle lenses. It’s kind of nice to get the maximum width. For example, if you’re using a 14mm wide angle lens you want 14mm, not 14mm x 1.5=21mm.

Within the past few years engineers have made advances. Now we can buy DSLRs with a full frame sensor. But these full frame sensors are still only available on the high-end DSLRs, which are still quite expensive for the normal consumer, or even “prosumer.”

Also, specialized lenses have been made especially for crop frame cameras. For example, Nikon calls these DX lenses.

The Main Differences Between Full Frame & Cropped

1. Full frame sensors are built into the higher end DSLRs. These superb pro-level cameras simply produce slightly better quality images (greater detail, richer color), especially in low light.
2. Cropped frame sensors are what you’ll get with entry level and most enthusiast level (prosumer) DSLRs. Don’t worry, they’re still terrific.
3. Cropped frame cameras give you a “zoom” effect for free! Remember, a 50mm lens on cropped frame D-SLR is really like using greater than a 50mm lens. Again, no big deal because you won’t notice. You’re still going to have to back up, zoom out, move in, zoom in, regardless of what lens you’re using on what camera.
4. If you’re using a full frame sensor DSLR you can’t really use the crop frame lenses (Nikon DX lenses) that have been engineered for crop frame sensors. Well, you can technically use them, but you’re going to get a cropped area around your image. That means if you upgrade to a full frame sensor DSLR body you’re also going to have to upgrade your lenses… which can cost a pretty penny. The reverse, however, isn’t an issue. If you use a full frame lens on a cropped frame sensor body it’s not a problem. You’ll just get that zoom effect and not really get the true size of what that lens produces on a full frame sensor body. See the illustrative graphic I embedded in this post.

NIKKOR Lenses Simulator – FX vs. DX

Nikon has an excellent lenses simulator that allows you to choose a lens and view a simulation of different focal lengths with different bodies (FX vs. DX).

You can pretend like you’re putting a FX format lens on a DX format body, or whatever combination you want to try.

It’s a perfect illustration of the different results you can expect with different lenses on the two types of Nikon sensors (cropped versus full frame): DX versus FX.

Give it a try!