I was watching a recent episode of D-Town TV with Scott Kelby and Matt Kloskowski and they were explaining why you want to use “full frame” lenses on full frame cameras. It’s the difference between DX and FX lenses for Nikon and EF or EF-S lenses for Canon. But they kind of glossed over something for Canon users: EF-S lenses will not fit on a full frame body. So why does any of this matter?
Take a look at the image above. The “Full Frame” line shows a full-sized sensor. Pictures taken with this sensor will give you the equivalent of a standard 35mm film camera. Canon only makes two full frame cameras: The 5D MKII and the 1Ds MKIII. Nikon has four: the D700, D3, D3s and D3x.
The next line is APS-H. Canon’s 1D MKIV and 1D MKIII have this sensor. Here is where the “crop factor” or “focal length multiplier” comes into play. With these cameras any lens you put on, you have to multipy by 1.3 to get the actual focal length. So your 50mm lens on a 1D MKIV would actually be a 65mm.
The next two lines are APS-C. The majority of Nikon and Canon cameras use this type of sensor. Nikon’s APS-C sensors have a crop factor of 1.5 and Canon’s is 1.6. That means a 50mm on most Nikons is 75mm and on most Canons its 80mm.
The only way to get a true 50mm is to use an EF lens on a full frame Canon or an FX lens on a full frame Nikon. Check out this video to see the difference on a 5D MKII and 7D.
As you can see, the difference is pretty telling. This all comes into play depending on the type of photography you do. If you shoot landscapes or interiors, then you want as much information as possible on your sensor. That’s why I use a full frame camera and a wide-angle lens for my interior and architecture images. If you shoot sports, then you might want the benefit of the crop factor. My 70-200, for example, on most Canons is actually, 112 to 320. I can get an extra 120mm on the long end by using a cropped sensor.
I mentioned DX, FX, EF and EF-S lenses. Canon’s EF lenses will fit any Canon camera. The EF-S lenses are made specifically for APS-C sized sensor cameras. On the body, where the lens attaches to the camera, you’ll notice a white or red dot. The white dot is where an EF-S lens attaches. The red dot is where an EF lens attaches. As mentioned earlier an EF-S lens will not fit on a full frame camera. If you try, the rear lens element will break your mirror. So if you have EF-S lenses and you upgrade to a full frame camera, then you’ll need new lenses too! As I understand it, a DX lens will fit on an FX camera but you can’t really use it on the wide end of the focal length without getting some severe vignetting. Also, your image size is decreased. Click the D-Town link above and watch the video for a more detailed explanation on that point.
Well I hope this helps. I’ve found a lot of DSLR owners never know that the lens they’re using isn’t giving them the focal length they think. Some people also ask what camera or lens they should buy. I always say to think about what you want to shoot and then take the sensor size into consideration.