Full Frame Lens on Cropped Sensor

November 15th, 2010 10 Comments

Full-Frame vs Cropped Frame – What’s the Deal?

I often get asked which lens I recommend……as if there exists a lens that can do it all, for everyone, in all shooting conditions. The fact is, you have to decide what kind of shooting you intend to do, and then figure out which lens can help you, and of course, how much it will cost. In the end, I always recommend either the Canon 50mm prime f/1.8 or the Nikon 50mm f/1.8. They are both full-frame lenses, which simply means the image circle they produce will accommodate a 35mm film frame size, which full-frame DSLR sensors are. Only the higher-end cameras have a full-frame sensor, and virtually no one who asks me about a lens has a FF camera. So why do I still recommend them?

Honestly, there is a ton of confusion and bad information about this subject floating around. Right off the bat, You ABSOLUTELY CAN put a FF lens on a cropped-sensor camera!! In fact, there are several reasons why this can be a BETTER choice. It’s tough to make generalizations about lenses, but I don’t see a down-side the using a FF lens on any camera as long as you understand what the REAL angle-of-view (notice I didn’t say “focal-length”) will be in a cropped frame. So throw that FF lens on your Canon or Nikon cropped-frame camera and go shoot. It’s really not worth the time obsessing over stupid stuff like the perfect focal length. Personally, I like shooting with primes, and if I need to change the damn focal length I just MOVE! There’s way too much emphasis placed on technical specs, and if you know how to compose and get proper exposure, and you understand the technical limitations of your equipment, you’ll take great shots. Equipment doesn’t take photographs, people do! However, if you MUST know the why, the how, and the WTF, read on.

What Is a Cropped Sensor?

Most lower-end (non-pro) DSLRs come with a smaller sensor. I’ll refer to these as 1.6 size sensors, because 1.6, to put it in a confusing and misleading way, is the factor by which your focal length changes on a 1.6 sensor. Confused? Simply put, think of a 1.6 sensor as having less angle-of-view, and don’t worry about it any more.

A cropped sensor means that the sensor is not picking up as much image “real estate” as a FF sensor if you use a FF lens. In the 2 images that follow, I shot the lava lamp with both a full-frame camera and a 1.6 cropped-sensor camera using the same 50mm full-frame lens at the same distance:

Canon 40D 50mm from 3 feet

Canon 5D 50mm from 3 feet

The first image above appears closer than the second image, but it isn’t. The difference is caused by the larger sensor in the second image being able to pick up more of the image circle projected by the lens….which, don’t forget, was used for both shots.

In the following image, we see the image circle projected by a full-frame lens, with both a full-frame sensor size (in red), and a 1.6 sensor size (in yellow) superimposed onto the image:

Comparison of a full-frame sensor to a cropped 1.6 sensor

So the yellow rectangle above is “seeing” less of the image than the full-frame red rectangle. The image itself hasn’t changed, but the angle-of-view in the smaller sensor has, so it appears as though the image in the yellow frame is closer, which make it seem like the focal length is larger…neither of which is true.

Let’s understand what we’re dealing with. The focal length number expresses the distance from the aperture to the sensor. So the 50mm focal length in a cropped-sensor camera and a FF camera is EXACTLY the same. What changes is is the sensor size, and consequently the angle-of-view. In terms of the image circle, the image quality, Depth of Field, EV (exposure values) are exactly the same on both cameras using that lens….you loose nothing but image real estate by putting a FF lens on a cropped-sensor camera. Check out the following image shot with a full-frame lens on my Canon 40D, which has 1.6 size sensor:

50mm macro lens at f/2.5 from 8 inches away

Now look at the same shot taken with my Canon 5D…a full-frame camera:

Canon 50mm macro at f/2.5 from 4 inches away

Both shots were taken with the same lens, and I tried to get the subject to fill the frame equally for both cameras as best I could by moving in closer for the full-frame shot. I was using a tripod, so the orientation was different for the full-frame shot as I couldn’t get the 5D close enough without changing the angle.

Just Step Back

So there you have it. The only thing that I changed was the distance from the camera to the subject. That, in a nutshell, is the ONLY significant factor that you need to consider when putting a FF lens on a cropped camera. With a 1.6 camera, you’ll need to be farther away at any given focal length than you would with a FF camera. Now look at this image, shot with a FF 50mm lens from about 12 feet away:

Canon 40D w/ FF 50mm lens from 12 feet

Compare it to the following image, shot with my Canon 5D and the same lens from 8 feet away:

Canon 5D w/ 50mm lens from 8 feet

With the first shot taken with my 40D, I couldn’t get far enough away to have the model completely fill the frame. This is the only potential issue with a FF lens on a non-FF camera. The angle of view changes, so you are shooting at an equivalent of around 75-80mm instead of 50mm. However, if you know this, just plan your compositions accordingly……step back! Obviously I was out of room in the first full-body shot above, but that’s because I planned poorly by not setting up the seamless background far enough back to give me enough room to shoot!

If You Have a 1.6 Sensor, You’re ALREADY Shooting a Narrower Angle-Of-View!!

At this point, I’d like to clear up another area that creates a lot of confusion. You can buy lenses specifically made for 1.6 cameras. They project a smaller image circle that just fits a 1.6 sensor. They are marked with focal lengths, just like any other lens. What confuses people is that if a 50mm lens designed for a 1.6 camera has a focal length of 50mm, that focal length is exactly the same as it is on a full-frame lens……50mm is 50mm after all, so the distance from the aperture to the sensor is exactly the same for either the full-frame OR the 1.6 sized lens. Look at the following shot taken with my 40D and a Tamron 17-50mm lens designed for 1.6 sensors, shot at 12 feet:

Tamron 17-50mm at 50mm from 12 feet

Compare it to the first full-body shot above taken with the same camera and the FF 50mm lens. Do you see a difference in focal length? No, you don’t. Here’s why……in both cases, since we are talking about a smaller 1.6 sensor, the equivalent focal length is @ 80mm. As a result, it doesn’t matter whether you buy a FF lens at 50mm or a lens designed for the smaller 1.6 sensors at 50mm. If you put either lens on a camera with a 1.6 sized sensor, the focal length in both lenses is exactly the same. The image circle projected onto the sensor from the full-frame lens is larger, but gets cropped by the smaller sensor anyway, so the image projected by the 1.6 lens and the full-frame lens is exactly the same size…..the size of the sensor. Also, in both cases, since the image that gets picked up by the sensor is the only image that counts, in both cases you are actually shooting at the 1.6 crop-factor, which turns out to be @ 80mm, not 50mm. The ONLY way to get an image that is projected at a 50mm focal length to LOOK like a 50mm image is by using a full-frame camera! You can put the Tamron lens on a full-frame camera and see a true 50mm image size, but since the image circle is designed for the smaller sensor, you will also see that image surrounded by a black circle.

So we now know that you can put a FF lens on a 1.6 camera, but not the other way around, unless you want to get a very pronounced vignette in your image. We also know that if you use a certain focal length lens on a 1.6 camera, it doesn’t matter whether or not that lens is made for a full-frame or 1.6 sensor, the crop factor means you are shooting at a longer perceived focal length since your actual angle of view is less.

One more series of shots to beat this to death. Look at the following head-shot, taken with a full-frame 70-300mm telephoto lens on my 1.6 40D from 7 feet away:

Canon 40D at 70mm from 7 feet

Compare that to this one, shot with the same lens at the same focal length on my full-frame 5D from 4.5 feet away:

Canon 5D at 70mm from 4.5 feet

Once again, the images look exactly the same in terms of focal length, because they are. However, the first image (Canon 40D 1.6 sensor) was shot from 7 feet away, and the full-frame shot (Canon 5D) was taken from 4.5 feet.

As you can see, there is no problem putting a full-frame lens on a camera with a 1.6-sized sensor. All you need to remember is that on a smaller sensor, any given focal length will appear to magnify more than it does on a full-frame camera. You can simply adjust your composition accordingly. Rather than getting hung up on all of the numbers, conversions, and distances, just look in your viewfinder and don’t worry about it! The bottom line is, if you are a photographer, what you see in the viewfinder is all you need to know. That’s why all of your exposure info is available to you inside the viewfinder…..that’s where the composition is! I laugh when I see people looking at their camera settings on the rear LCD screen, or the info window on top of the camera body. They aren’t composing a shot, they’re worrying about numbers. Look in the VIEWFINDER folks! All the info you need is right there, and you never need to take your eye off the composition…..but I digress.

This is why I always recommend the 50mm f/1.8 lens for both Canon and Nikon people. Canon and Nikon make a very affordable lens (@ $100), that is very sharp and great in low-light. Both B&H Photo and Adorama carry these lenses, and they are super-great about returning stuff, if you aren’t happy, but you will be so no worries.

There is only ONE caveat, and it only applies to people with a Nikon D40, D60, D3000 or D5000. The auto-focus (AF) function will not work on this lens on your camera. For you guys, I recommend the Nikon 35mm f/1.8. It is NOT a full-frame lens, and it’s almost twice as much at $192, but it’s great in low light and still a good deal.

For everyone else the 50mm f/1.8 is really a great buy. Who cares if it’s a full-frame lens? Not me…I’ve been happily shooting a 50mm prime f/1.4 lens on my 40D for almost a year now, and could care less that the crop factor gives me an 80mm or so image magnification. I just adjust my distance as I compose the shot, and never even THINK about the crop factor. So think about it….all of the time you’ve wasted agonizing over what is essentially a non-issue by reading this article, you could’ve been shooting….which is way more important!

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10 Responses

  1. Bo says:

    Position alone defines the perspective of picture. 50mm lens on a 1.6 crop sensor forces you to move back from your target, hence DOES change the perspective, hence composition of the picture. So stating that the same 50mm on both 40D and 5D can give exactly the same picture by moving back and forth is wrong, they are different in terms of perspective.

    • garyAdmin says:

      Thanks for the comment! In theory you are right…..good point. In real-world shooting, the composition won’t significantly change that much by stepping back a few feet….depending on the subject and focal length of course. I noticed you didn’t venture to state by HOW MUCH the composition would, in fact, change. I’m not as smart as you so I just observe what is in my frame. If I were to swap out my full-frame and take the same shot with my cropped-frame camera, I would probably notice a difference, so your point is well-taken. But I mean, who actually DOES that? The point of the article was simply to let folks know you can use a FF lens on any DSLR, and to help them understand what is going on in terms of focal length. Thanks!!

  2. Mehmet Tezel says:

    Hi I still use a Pentax film SLR camera. Can I use a lens by my 35 mm. film SLR camera that was manufactured for a crop sensor Pentax DSLR?

    • Gary Dates says:

      I don’t understand your question, but I’ll try to answer. I don’t know about Pentax specifically. On Canon cameras, you cannot physically attach a crop-sensor lens on a FF body. In general, you CAN put a FF lens on a crop-sensor camera, but not the other-way-around. If you put a crop-frame lens on a FF camera body, you’ll get significant vignetting in the corners at wider apertures (smaller f-stop numbers). I hope that answers you question.

  3. thgun says:

    Hi there. last october I moved over to a Canon 5D MKll. I knew it was full frame so I bought a body only because I alredy had lenses from previous cameras a 400 & 450D. Full frame is what I wantted and I knew my other cameras were not full frame sensors. what I was unaware of was that all my lenses except one were cope frame lenses. I was never told about this when I bought my lenses. It wasnt untill i fitted one to my 5D. I have over come the the vignetting on my 5d by addin a 2x convertor to my 18-200 zoom. I’ve tried to get a full frame equivalent but they all seem to be crop frame. Any advise for me.

    • Gary Dates says:

      What a drag. Many people don’t realize that Nikon, Canon, as well as many other companies, are making lenses specifically for the smaller sensor cameras. You cannot put such a lens on a full-frame camera, as you just discovered. Canon lenses made for cropped-sensor cameras have the “EF-S” designation. For Nikon lenses its “DX”. My advice, and really your only choice, would be to sell your EF-S lenses on eBay and invest in FF lenses. The Canon 50mm f/1.8 is an incredible bargain at @ $110 (after $15 Canon rebate), for example.

  4. Earl says:

    Thanks for this, was a great article! Found it very helpful because i was interested in buying a full frame lens but wasnt too sure if it would fit on my cropped sensor camera. BIG HELP! :)

  5. Shaun says:

    But aren’t full frame lenses calibrated for use with full frame sensors? If this is the case, you’d be wasting money, glass, and also not getting the sharpest image possible because of the fact that you are cropping the center of the glass.

    • Gary Dates says:

      The short answer is “no”. You can ABSOLUTELY put a full-frame lens on a crop-frame body without any of the issues you raise. The focal length of a lens is determined by it’s distance from the image plan. The distance for both a full-frame and crop-frame camera is exactly the same. Hence, there is no reason to “calibrate” a lens to a crop-frame sensor. As far as cropping to the center, most low-end lenses have issues at the frame edge, distortion, blur, chromatic aberration, etc. However, the center is always sharper and overall produces a batter quality image across the entire f-stop range than at the edges. Therefor, it is simply untrue that you would be “wasting money” due to the fact that crop-frame sensors crop to the center. That is an ADVANTAGE! It sounds like you were talking to someone who doesn’t have a clue….probably a salesman at Best Buy. :)

      The only issue is that there would be a difference in the Depth of Field at a given focal length on a FF camera as opposed to a CF camera. The FF DoF would be narrower. That is not a disadvantage, but it is something to be aware of.

  6. Sam says:

    I thought this was a great article explaining the crop factor as I didn’t understand it what all the fuss was about as I am a beginner. I ended up with the D7000 and an AF-S lens.

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