Full-Frames and APS-C Compared

The Canon 5D Mark II is the update to the camera that created the $3000 full-frame DSLR market - namely the Canon 5D in 2005. Canon had this market all to their self for the first two years, but during the past year Nikon and Sony have both introduced several models to compete in the full-frame DSLR market.

The 5D2 sensor is approximately the size of a frame of 35mm film, which is 24x36mm, and resolution is 21.1MP - a significant increase from the original 5D at 12.8MP.  The new Canon 5D2 compares very well to the reolution of the recently introduced Sony A900, which at 24.6MP is the highest resolution currently available in a full-frame camera. Compare this to most other DSLR cameras today, where the sensor size is closer to APS-C size. The smaller APS-C sensor used in most other cameras results in the lenses appearing to be 150% to 200% longer than the marked focal length.  On the Canon 5D Mark II and other full-frame DSLR cameras lenses behave exactly as they would on 35mm, with no crop factor.


In the computer world, smaller and smaller traces mean higher density, more transistors, and generally better and faster performance. However, the digital sensor is not a digital device; instead, it's an analog device that gathers light and converts it into a digital signal. Thus the reverse is true in sensors in that larger sensor size is almost always better, with everything else equal. As you can see in the chart below, the APS-C sensors aren't even half of the area of a full-frame sensor. With a range of 28.1% to 42.4% of full-frame size, there is clearly a lot more information that can be potentially captured with a full-frame sensor.

DSLR Sensor Comparison
Camera Effective Sensor Resolution Sensor Dimensions and Area % of Full-Frame Sensor Density
(MP/cm2)
Olympus E-520/E-3 10 13.5x18
2.43 cm2
28.10% 4
Canon Xsi 12.2 14.8x22.2
3.28 cm2
38.00% 3.7
Sony A350 14.2 15.8x23.6
3.72 cm2
42.90% 3.8
Pentax K20D 14.6 15.6x23.4
3.65 cm2
42.20% 4
Canon 50D 15.1 14.9x22.3
3.32 cm2
38.40% 4.5
Sony A700, Nikon D300, Nikon D90 12.3 15x23.5
3.66 cm2
42.40% 3.3
Nikon D700/Nikon D3 12.1 24x36
8.64 cm2
100% 1.4
Canon 5D 12.8 24x36
8.64 cm2
100% 1.5
Canon 5D Mark II 21.1 24x36
8.64 cm2
100% 2.4
Canon 1Ds Mark III 21.1 24x36
8.64 cm2
100% 2.4
Sony A900/Nikon D3x 24.6 24x35.9
8.61 cm2
100% 2.9

The last column in the chart is the one that tells the story most accurately, however. Here the resolution of the sensor is divided by the sensor area to yield a sensor density. The lower the density, the larger the individual pixel size, and the more information that pixel can gather - all else being equal. There are a few surprises here, such as the Sony A350 being essentially the same density as the Canon XSi, and the new Canon 50D having the highest density of any current DSLR camera.

The last column does put into perspective the true potential of the full-frame sensor and sheds some light on the true meaning of Canon's 21.1MP sensor and Sony/Nikon's 24.6MP A900/D3x sensor. At 2.4MP per cm2 the 5D2 still exhibits a lower density and theoretically better high ISO performance than any current APS-C DSLR. This is very much at odds with the ridiculous claims many on the web are making about full-frame cameras going too high in resolution. In fact, sensor density on the 5D2 is significantly lower than the 10MP Canon 40D, which has a density of 3.1.

The point is that any issues the 5D2 may have with noise are not the result of pixels being "too small". All else being equal the high ISO noise should be at least as good as an 8 to 10MP Canon sensor. Where the new Canon does suffer is in comparison to sensor density of other full-frame sensors. In that metric the Canon 5D2 has about 65% more pixels per cm2 than the Nikon D3/D700 and Canon 5D, and keeping up in high ISO performance with those cameras would be quite a feat. The Canon 5D Mark II is, however, slightly lower in resolution than the Sony A900 and Nikon D3X that feature 24.6MP sensors, although the difference between 21.1 and 24.5/24.6 has to be considered negligible.

Index Canon 5D Mark II vs. Canon 5D
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  • stefan - Saturday, December 6, 2008 - link

    Thanks for this great comparison!!

    I would love to know how the noise of the 5D II and D700 compare at long exposure times (30 s) at 3200 ASA. That is what I would need for landscape nightshots including a sky full of stars.

    Do you have experiece with this?

    Thanks!
    Stefan
  • Wineohe - Thursday, December 4, 2008 - link

    Maybe someone else has already beefed about this, but I never shoot JPEG's with my 5D. I doubt anyone does. My photos always get post processing, either in DPP or more recently Photoshop. In this category of camera RAW comparisons should somehow be the default method of comparison. Couldn't you just import them to Photoshop and save them to a Jpeg without any post processing. At least they would get the same treatment. This would be a more likely scenario among anyone spending this kind of money on a camera. Throw me a bone here, what am I missing.
  • strikeback03 - Friday, December 5, 2008 - link

    ACR by default does different things to different camera files, so "no post processing" is not the same for each camera's files.

    I too always shoot RAW, but as Wes said the fact that they have samples up already compensates for the fact that they are not perfect.

    And the 5D had a print-share button, so obviously Canon thinks somebody is going to shoot JPEG.
  • golemite - Friday, December 5, 2008 - link

    lets face it, Anandtech camera coverage is strictly from a consumer point of view, until they step up their game, its only useful for a first look or teaser of what to expect. And it's unforgivable that the Sony already exhibits such noticeable noise at such low ISOs. Besides the megapixels, that looks almost like Point and Shoot performance to me...
  • Wesley Fink - Saturday, December 6, 2008 - link

    Actually some evidence is accumulating that the 5D2 may exhibit best performance in JPEG mode. Some users are saying Canon 5D2 in-camera JPEG better controls noise than any current RAW processing software. That is similar to my own experience with the 5D so it does not come as a surprise.

    www.imaging-resource.com has just posted a complete set of RAW files for the 5D2. They can be compared to the D700/D3 and A900 in their comparometer. You may need to download and resize the 5D2 images to properly compare the D2 12.1MP to the Canon 21.1MP.

    I have looked carefully at the data posted ar IR and find they basically support what I have already posted in this review. Multiple confirmations are always good.
  • strikeback03 - Monday, December 8, 2008 - link

    Hopefully the noise suppression software catches up then. The advantages of shooting in RAW are too great.
  • Wesley Fink - Saturday, December 6, 2008 - link

    Obviously we are talking about the D3, not the D2. Edit would be handy here.
  • Wineohe - Thursday, December 4, 2008 - link

    I have the 5D which I always thought was among the best at higher ISO. The Mark II seems to blow it away. No more Talls or Grandes. I'm going to start saving my money and brewing my own so that I can replace my 5D.
  • Roy2001 - Thursday, December 4, 2008 - link

    I used to trust DPR but they are biased against Canon which I don't like. Thanks for post. Cannot wait for a full review.
  • Roy2001 - Thursday, December 4, 2008 - link

    I used to trust DPR but they are biased against Canon which I don't like.

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