Canon 7D & the Crop Factor

I am getting tired of reading about critics bashing the Canon 7D for its crop factor.  Most seem to associate a cropped sensor with digital noise.  This argument did not exist before Canon’s marketing campaign created the relationship to promote the Canon 5D Mark II.  But, let’s look at some numbers.

7dcrop1

From the above diagram, you can clearly see that the 5D Mark II sensor is much bigger that the 7D sensor.  Yet, Canon does cram 18 megapixels into that smaller space.

7dcrop2

In actual use, shooting the same subject from the same location would yield the results depicted in the above image.  If the 5D Mark II’s view represented the full frame’s image, then the 7D would capture a much smaller image area.  That’s where the 1.6 crop factor comes into play.  The crop factor magnifies the lens’ focal length so a 35mm lens on the 7D captures the equivalent area of a 56mm lens on a full-frame sensor (35mm x 1.6 crop = 56mm lens equivalent).

But suppose you only wanted to capture that smaller area?

For the 5D Mark II to capture the same smaller area, you would need to either:

  • Switch lens to a 50mm
  • Move closer (and possibly distort the image due to the wide angle lens and a close subject)
  • Crop the image to match.

Cropping is the easy answer. But, what does that REALLY accomplish?

7dcrop3a

7dcrop3b

That’s right – the 5D Mark II’s cropped image is now only 8 megapixels? Is that really large enough for your needs?  If you enlarge the cropped image, will it still look as sharp or will it look grainy/noisy?  That’s like comparing a 8 megapixel shot from the Canon 20D to a 18 megapixel shot from the Canon 7D. Does that make sense?

Personally, after using a camera with a crop factor for over 5-years, I would find it hard to go back to a full-frame sensor. I love the extra magnification created by the 1.6 crop! Boosting a 400mm lens to an “equivalent” 600mm is awesome!  And, considering it is cheaper to buy extreme wide-angle lenses (ex. 22mm lens) than an extreme telephoto lenses (ex. 600mm lens), it is very easy to adapt to the crop factor.

So, don’t knock my 7D for its crop factor. That argument does not hold megapixels.


NOTE: A few readers have commented about the old argument for Depth of Field on a crop sensor.  You can read the discussions below. But, let me be clear – that argument is just wrong.

Ken Rockwell stated “The lens isn’t actually changing its focal length, so the depth of field remains the same. The image formed by the lens is unchanged regardless of the camera behind it.”  To be even clearer, Bob Atkins stated “If you use the same lens on a Canon APS-C crop sensor camera and a 35mm full frame body and crop the full frame 35mm image to give the same view as the APS-C crop image, the depth of field is IDENTICAL.”

So, I am not the one trying to mislead others.  It is the people trying to sell full-frame cameras.

 

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18 thoughts on “Canon 7D & the Crop Factor

  1. Thanks so much for that…I just ordered my Canon 7D and was getting mildly discouraged by the bluster of comments regarding the crop factor. I have been dreaming of the day I could step up to a higher end digital and I’m elated to awaiting it’s arrival! The specs on this camera are awesome, and I know Canon won’t let me down!

  2. Glad to be of help! The 7D is a great camera! I have plenty of articles about he 7D on this blog. Let me know if you have any questions.

  3. And another thing if the user wanted to the get the full scene they’d only need to move back to get the full frame of the scene, full frame has advantages, and so does 1.6x Crop Factor.

    The arguement is really pointless with the full frame as both have disadvantages and advantages, and also buying an EF lense for a 7D is a bonus due to the extra mm 7D gives it and also if you bought the 5D MKII you basically have a compatible lense, EF-S is not made for 5D MKII.

    My first getting into Professional Photography will be the 7D, next 5D MKII.

  4. Yes, it is true. The center is typically the sharpest part of the lens with sharpness degrading towards the edges. It’s like scooping the center out of a pie and throwing away the crust 😉 Just another reason to love the crop “filling”!

  5. I still cannot believe there are some people thinking that number of pixels are the the most important thing in dslrs. Crop bodies do have disadvantages in superwide and depth of field controls. It does not look good when some people just mention what ever they like and keep silence on other stuffs they don’t like, because that can mislead other people.

  6. Sorry Pete, but I disagree with your entire comment.

    If you are a professional photographer, megapixels are important. If you try turning in an 8-meg file to a magazine or some other commercial venue, you will never get another gig from them. Photos used in advertising campaigns (print ads, tv, posters, billboards, etc.) and even fine art reproduction houses all use all hi-res images with resolutions between 200-300 DPI. A small file will not look sharp when blown-up and will not sell. Some companies (like stock houses) may not accept files which have been significantly boosted through a program like Genuine Fractals/Perfect Resize.

    Crop sensors have their own set of super-wides. Have you seen Sigma’s 8mm-16mm lens? It is the widest superwide available without becoming a fisheye. On a 1.6x crop sensor like the Canon 7D, it has the equivalent view of a 12.8mm lens. The widest ultrawide (non-fisheye) for a full-frame camera like the Canon 5D Mark II is 14mm.

    And, as for the old argument about depth of field on a crop sensor, that’s just wrong. Ken Rockwell stated “The lens isn’t actually changing its focal length, so the depth of field remains the same. The image formed by the lens is unchanged regardless of the camera behind it.” To be even clearer, Bob Atkins stated “If you use the same lens on a Canon APS-C crop sensor camera and a 35mm full frame body and crop the full frame 35mm image to give the same view as the APS-C crop image, the depth of field is IDENTICAL.”

    So, I am not the one trying to mislead others. It is the people trying to sell full-frame cameras.

  7. photoframd,

    Full-Frame and “crop” APS-C cameras both have advantages and disadvantages. Neither one is necessarily “better” than the other, it depends on the application. The main advantage with full frame cameras is increased dynamic range, color depth, and light gathering capability of the larger sensor. The full-frame 5D Mark II is far superior for portraits, landscapes and low-light photos and has less noise at any given ISO. The 7D is better for telephoto and macro because you can pull more detail out of the same lenses. APS-C cameras are also less expensive and their EF-S lenses can be made smaller and lighter. But again the disadvantage is a trade-off in terms of having more noise and less dynamic range and color depth.

    Now about this question: Suppose you wanted to capture that smaller area (with a full frame camera). I completely disagree that “Cropping is the easy answer”. No, a good photographer chooses the right lens for the job; he would never shoot the image with the intention of cropping unless he absolutely had to. If he’s using a zoom lens, then he would simply zoom in to capture that smaller area and utilize all of his 21mp. If he only had prime lenses, in the example you gave, he would use the most common prime lens, the 50mm, instead of a 35mm lens, if he wanted to capture that smaller area. Why on earth would anyone shoot a picture intending to utilize only 8mp of his 21mp sensor? He wouldn’t and it’s an unfair argument for giving an advantage to crop cameras. Cropping is NOT the answer, using the correct lens IS.

    Now about this statement:
    “If you use the same lens on a Canon APS-C crop sensor camera and a 35mm full frame body and crop the full frame 35mm image to give the same view as the APS-C crop image, the depth of field is IDENTICAL.”

    While that statement is true, again, CROPPING is NOT what you would typically do to “give the same view”. What you would do to give the same view is change lenses! Again, why on earth would you take a picture intending to utilize only 8 of your 21 pixels? No good photographer, pro or hobbyist, would hamstring his camera that way. What he would do is either simply zoom in or change lenses, and when you change lenses, it DOES affect the depth of field. What we are talking about here is “lens equivalence”.

    And if you read further in Ken Rockwell’s page on Crop Factor, he himself states:

    “If you use a shorter lens to get the same field of view, you get the deeper depth of field of the shorter lens.”

    That is a VERY important point. Example:
    If you use a 30mm f/1.4 lens on a 1.6x crop camera to achieve the same view as a 50mm f/1.4 lens on a full-frame camera, you get the larger depth of field of the shorter 30mm lens, not the 50mm lens.
    So a 30mm f/1.4 lens on a 1.6x camera is not equivalent to a 50mm f/1.4 lens on a FF camera; it is equivalent to a 50mm f/2.24 lens.

    Now if you take that 50mm f/1.4 lens and put it on a crop camera you get the field of view of an 80mm lens while retaining the depth of field of the 50mm lens, therefore becoming equivalent to an 80mm f/2.24 lens. This is what “lens equivalence” is all about.

    You can’t highlight the advantages of a smaller sensor/high pixel density camera and claim it’s “better” without acknowledging the properties that make the full-frame camera better. If you do that then the obvious extension of that argument is that the tiny sensor point-and-shoot cameras must be the “best” because they have the smallest sensor and highest pixel density. And they are obviously inferior to larger sensor DSLRs.

    There are reasons that high-end photographers are willing to pay thousands more for a full-frame camera, and it’s all about the richness of the dynamic range, the deeper color palette, and the low signal-to-noise ratio.

  8. You are making so many assumptions that undermine the credibility of your argument:

    You are assuming it is a “planned shoot”. In that situation, of course you would select the perfect lens for the situation and would not even be thinking about cropping a shot. However, if you are witnessing something unfold in front of you which is NOT planned, then the best lens is THE ONE ON YOUR CAMERA.

    You are also assuming that “you” are the client. You have obviously never dealt with a finicky art director or an uncertain wishy-washy client who can’t make up their mind. Or worse yet, a client that changes their mind after the fact because a buddy convinced them on a new “trend” which they need to jump on. When reshooting is not an option due to costs like models, locations and crew, the ONLY OPTION IS TO CROP.

    You are also assuming the photographer has a collection of lenses to choose from. Every photographer starts with one or two lenses and builds a collection over time. Again, the best lens for a situation is the one you CAN use.

    You are assuming that there is no post-processing of your image files. This is NEVER the case. The captured image is only the starting point. The final image is the one created in Photoshop, Lightroom or even DPP. EVERY IMAGE (whether assignment, stock or personal) benefits from post-processing enhancement. Camera Raw 6 (in Photoshop CS5) and Lightroom 3 have advanced to the point where digital noise can be removed from almost any image without sacrificing image detail. Topaz DeNoise 5 is also a powerful plugin which can accomplish this same feat.

    Finally, you are just wrong about Depth of Field, Color Palette and Dynamic Range. Depth of field is an aspect of the lens and f-stop NOT the camera it is attached to. Color palette is an aspect of the Color Space which is the same sRGB and Adobe RGB on both cameras. Dynamic range is the the ratio between the maximum and minimum measurable light intensities as controlled by the DIG!C4 chip. The Canon 5D Mark II has only one DIG!C4 chip while the Canon 7D and the Canon 1D Mark IV both have dual-chips. Quoting Canon’s site, “Dual DIGIC 4 Image Processors help to ensure smooth, detailed and refined images that are recorded quickly, accurately and reliably.”

  9. I’ve been using a crop framed camera, and what i”ve observed is.. me and my friend were on a photoshoot, shooting a model. He was using his 5d and I my cropped sensor camera with the 50mm f/1.8 lens on both cameras.

    Using a 5d he could capture the full body of the model from about 6 steps away using 50mm at f/1.8.
    And I had to step back about 10 or more steps away for the same shot with same lens at f/1.8.

    Now this is where I observed the difference, both the shots were very identical.
    Other than the background bokeh!!
    5d had blurred the background much better, than my crop sensor body. Why??
    Because he was standing closer to the subject, and i was far away…
    I missed out the beautiful bokeh the 5d produced, and end up with all the background and foreground in visible focus.
    The closer you are to the subject, better the bokeh is produced. Right?

    I use a canon 550d, and i still love my camera for what it is. I’d keep my 550d, and also get a 5d or 1d later sometime for what it does.

    End of the day, it all depends on what you are shooting and what are your needs. I needed bokeh! 🙂

    – Reddy

  10. OK, there are a few things to point out. First, the minimum focusing distance for a lens will be the same regardless of the camera. This is an aspect of the lens, not the camera and not the sensor. Second, because of the crop sensor, you will need to factor in the 1.6x to the lens to account for the smaller sensor. As a result, that 50mm lens on Canon 7D, 60D or Rebel will capture an image similar to an 80mm lens on a full-frame sensor camera like the 5D Mark II. In order for you both to capture a similar view, you would need a 35mm (35mm x 1.6x = 55mm) on the 7D, 60D or Rebel. Finally, if you use the 35mm lens at f/1.4 on the Rebel and your friend uses the 50mm at f/1.4 on the 5DII, the bokeh will be very similar. Hope that makes sense or “crop-sense” 😉

  11. I have a Canon 7D and shoot with a 24-70 F2.8 L , 70-200 F2.8 L IS and 24-105 F4 L IS.

    I was curious if someone can email me directly jimswood4 (at) yahoo I would be curious if you get better bokeh shooting with a crop …say I had my 24-105 bokeh better at 105 then it would have been on a 5D Mark II( and by better I mean better subject isolation)? Even at 70 on the F2.8 since that is about 110mm? Just curious about the answer…

  12. Bokeh is a function of f-stop and lens mm. The sensor is only the thing that captures the created image. The Boken will be the same regardless of the sensor size. The only difference will be whether the resulting image is cropped or not.

  13. Photoframd, you are awesome! Thank you for the help in understanding this. I often deal with people talking down on the 7D because of the sensor size. It really is irritating! If the 7D was full frame I believe it would kick more butt than most. Although, full frame is not important to me. I do a lot of wild life and action shots. I am far enough away that I dont have to deal with “oh is my subject in the frame?” the 7D is my favorite so far, 1DX is nice but completely unrealistic in price for me. Thank you again for your wise answers! Im happy to find a post that someone actually likes the 7D. Ill be back!

  14. Photoframd, i am an amateur photographer. but one which is very keen in wildlife outdoor photography. i love close up portraits or animal in action kinda shots. i want to purchase a DSLR that would serve my purpose and that i would stick with for a long time. and hopefully start taking part if photography competitions. i was just wondering on what camera to get. i was looking up canon 7D or the 6D. any suggestions please.

  15. I really do love my Canon 7D for wildlife. I like the extra ‘reach’ that I can get with reasonably priced long lenses. I do find some limitations with the 7D for landscape photography in that Canon does not provide a decent selection of quality wide angle lenses for their cropped sensor (APS-C) cameras in my opinion. I find that Canon EF-S 10-22 mm lens to be a little soft for my liking. I like the sharpness of the Canon EF 8-15 mm fisheye zoom but not having the option for filters and having to straighten distortion in Lightroom4 with images from that lens is not an elegant solution for landscape photography with my 7D. I am in the process of purchasing a Canon 6D full-frame camera and coupled with my Canon EF 16-35 mm zoom lens will hopefully solve my wide-angle photographic dilemma. If my thinking is correct, I should see less noise and more sharpness in my landscape images with that camera/lens combination. I still plan on keeping my 7D for wildlife photography.

  16. Well said – depth of field for the same f stop on any lens is actually the same. Blow up the background of any wide angle to the same size as that shot with a 300 mm tele and it will be just as unsharp. The depth of field on a wide angle is an illusion brought about by smaller back ground.

    I love your crop photos. Could I have your permission to use them in a talk I am giving (credited of course)?

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