Cropped Sensor vs. Full Frame Comparison

Awhile back I wrote a post about why sensor size matters when choosing your camera body/lens combination. In it I shared this video which demonstrates the difference in focal length between a Canon 5D MKII and a 7D.

Well just yesterday I had the opportunity to test it out first hand using a 5D and 40D. Here’s the set-up: I was shooting a bedroom with the 5D. I had it on a tripod to make sure I was shooting from the same position when I switched to the 40D.  I was using a 17-40mm f/4 L on the 5D and a 17-55 f/2.8 on the 40D. Below is the shot on the 5D. I thought I had it racked to 17mm but it was actually 19mm; but hey, I’m not gonna cry over 2mm!

f/10, 1/15, ISO 200, 19mm

 Next, I switched to the 40D and dialed in the same exact settings.



f/10, 1/15, ISO 200, 17mm

You can see how dramatic the difference is even without the 2mm discrepancy. I knew that a 17mm on a cropped sensor lens is about 24mm (1.6 x 17 = 27.2) so I put the 5D back on the tripod and set it to about 24mm to compare.

Bedroom shot with a Canon 5D

f/10, 1/15, ISO 200, 25mm

It’s pretty close I think (remember I’m off by 2-3mm). This is just another illustration of the difference between full frame and cropped sensor cameras. It’ not a bad thing or a good thing; just something to be aware of. With the knowledge you can take advantage of either a full frame of an APS-C sensor depending on what type of shooting you do.

I want to take a few moments to share a couple of related stories. First, a photographer friend of mine has a 35mm 1.4 and he wants the 24mm 1.4 to get a wider focal length. For an extra 11mm, I would take a step back when composing and save the $1700.

I was reading a blog about the 17-55mm f/2.8 and it said the lens gives you a wide focal length. I commented that it’s comparable to the 24-70mm f/2.8 but at a lower price point and with the added benefit of image stabilization (IS). The writer wrote back and said because it is an EF-S lens that the true focal length is 17-55. I referred him to some supporting documentation and never heard back. Just goes to show that just because it’s in a review or a blog (even this one) doesn’t mean it’s gospel.

Lastly, I’ve been asked if a full frame camera will deliver sharper images than an APS-C sized sensor. Sharpness is a function of the lens and your camera settings (shutter speed, focus drive etc.). The weakest part of a lens is typically the edges. Now imagine a circle inside a square. The square is your sensor and the circle is the image coming from your lens. Because the square is larger than your circle (full frame) you are going to see every part of the lens. This is why most lenses produce vignetting on full frame cameras but not cropped sensors.

 Now imagine a square inside a circle. Because the square is smaller (cropped sensor) you will not see the edges of the circle. So in general lenses perform better on cropped sensor cameras; but that’s not due to some design flaw in full frame cameras. It’s just the nature of the beast. The better the lens, the fewer the distortions. Again, I am generalizing and simplifying here.  Every lens generally performs better when stopped down from its maximum aperture. You really have to research a camera and lens and test drive it yourself.

Well let me leave you with the final edited image of that bedroom.

Master King Bedroom


Size Matters in Photography: Choosing the Right Camera/Lens Combination

Chart of Sensor Sizes

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.