The Crop Factor: One Extra Tip Before You Buy a Lens

by melissa

Here's a photography side note for the day, one I hinted at in my lenses post.

Maybe you've been eying the 50mm lens, because you heard it's the "must have" lens, the closest to being what the natural eye sees, the versatile, do-it-all, can't-go-wrong, nifty fifty. Maybe I'm the one saying all those things :) But before you go jumping on the 50mm train (the very one I suggested in my last post), you might want to know that chances are incredibly high that there's a different lens that you should be getting instead of the 50mm. One that will better do the job for your camera.

Here's why.

(And don't worry, you'll definitely know that lens to get by the end of the post :)

Most digital cameras have cropped sensors instead of full-frame sensors. Having a cropped sensor means that the photo your camera will take with any given lens will be a cropped version of the photo a full-frame sensor camera would take with that same lens. Think of it as being zoomed in. That means any lens you put on your cropped-sensor camera is acting as a cropped version of its actual focal length (mm number), meaning it won't fit as much in the photo as it does at its full capacity on a full-frame sensor. I think this is most important for a fixed/prime lens, since you don't have the option to zoom in and out with the camera to make up for the loss in the crop.

So about that beloved prime 50mm lens...putting a 50mm on a cropped sensor is like putting a mat board over the outer edge of your photo and cutting it off. Which means a 50mm lens on your camera would not be acting like a 50mm lens. It would be acting more like an 85mm—or like a 50mm with a magnifying glass over it.

You can see above how each crop factor (1.3x, 1.5x, or 1.6x) crops in a significant amount from the full-frame photo. This would be the difference between the exact same photo taken at the exact same spot with the exact same lens, but with four different camera sensors.

In other words, you have to have a full-frame sensor to get the true size out of your lens. That said, you don't have to have a full-frame sensor to get awesome photos. The crop doesn’t alter image quality, because you can still take amazing photos with cropped sensors, and they are actually more common than full-frame sensors. But for taking portraits of people, especially when you don't have the space (or time—those kids are lightning fast!) to back away from your subject to get everything you want in your shot, the crop can make quite a difference in what you're fitting in your frame. The key here is to be aware of the crop, and then buy your lenses accordingly.

What crop factor does your DSLR have? (last I checked...)
  • 1.3x: Canon EOS 1D, 1D Mk11
  • 1.5x: Nikon D40, D50, D70s, D80, D90, D200, D3000, D5000, D2XD2Hs Minolta 7D, Fuji S3 Pro Pentax, K100D, K110D, K10D
  • 1.6x: Canon EOS Rebels, 7D, 20D, 30D, 40D, 300D, 400D
  • 2.0x: Olympus E-400, E-500, E-300, E-1

Knowing that you have a cropped sensor can allow you to compensate for the crop when you go to buy a lens, and we've created a lens conversions chart to help you do just that. So if you've read rave reviews about a certain lens that you've now got your eye on, make sure the reviews are particular to your camera's sensor size—and if they're not, check out our chart below to see which lens you should buy to get the right crop that you are expecting from your next lens. My guess is that you're going to walk away wanting a 35mm. What do you think?

Challenge of the week:
Find out if your camera has a cropped sensor. You can do this. Figure out your model. Then google it. Or check your manual. If you have a cropped sensor, now you know, and you're one step ahead the next time you're on the market for a new lens. Then you can start researching a new lens focal length that better suits your sensor (or just use the chart above).

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  1. I did my homework... I have a d60, so a crop factor of 1.5. I want to get a prime lens so I can take pics of my fam inside the house. So it sounds like I should get the Nikon AF-S Nikkor 35mm f/1.8G DX Lens Did I get it right?

    1. You win! Yes, you nailed it. That's the exact lens I would recommend. So glad you could make sense out of it and apply it so quickly! You're a rockstar. But we knew that already :) The lens will be worth it!

    2. I'm loving this blog!!! Seriously the first blog I've read where things make sense. I also have a Nikon D60 and my husband and I are expecting our first child! Based on reading this stuff it sounds like I don't have to break the budget and by a new camera. Maybe I just need to get some good lenses. In general, do you think that's key? That the D60 is probably a perfectly decent DSLR camera? I think I'm going to start with this one that Rachel posted. What would you recommend for taking family shots outside? The same lens? Thank you SO MUCH!

  2. Thanks so much for this post but it's about two months late for me-- I didn't know exactly why my camera had this "weird-automatic-zoom-thing" (as I'm fond of calling it) until learning about cropped sensors! Now saving up for my 35 mm!

    1. It took us a long time to understand this concept, so glad this could help! Good luck! And yes, 35mm. You'll love it.

  3. i have a cannon EOS 1100d which i guess in American market is EOS Rebel T3 so according to you article i should get 35mm if i want the same effect of 50mm lens? Correct me if i'm not right! and thank you so much for all SLR lessons!

  4. This was SO helpful. Thank you!

  5. How do I know which focal length I want? I shoot weddings but am just now upgrading lens, and really just now "learning" photography. I also shoot my two kids though...I have a Nikon D3200...


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