5DmkII vs 7d sensor resolution question

[kevin_fuhr]

<p>I have a question about the 5DmkII vs the 7D pertaining to sensor resolution. <br /> <br /> The 5DmkII has a 36x24mm sensor and a resolution of 5616x3744 pixels resulting in a 156x156 pixels/mm.<br /> <br /> The 7D has a 22.3x14.9mm sensor and a resolution of 5184x3456 pixels resulting in approx 232x232 pixels/mm.<br /> <br /> To try to get an apples to apples comparison of the two camera sensors I reduced the 5DmkII by the crop factor of 1.6 resulting in 22.5x15mm which is very close to the 7D sensor (22.3x14.9).<br /> <br /> The question I have is if the two sensors are now similar, but the pixel density is much higher in the 7D, which one would give the better image? Is this a reasonable way to compare the two cameras?</p>

[sattler123]

<p>The 5DMKII has the better Image Quality - no need to get the calculator out!</p>

[alan_green4]

<p>"Is this a reasonable way to compare the two cameras?" -- no. not if you're going to look at the images with your eyes. 5d2 wins.</p>

<p>if you're doing some sort of rez comparison, as in 'pixels per square mm = x rez at a given magnification', i don't know.</p>

[peter_e]

<p>The answer depends on how you define "better". Higher pixel density may provide higher resolution provided the lens and other variables are not the limiting factors. Pixel size is another factor that controls image quality, with a lower pixel density generally giving better results. If you compare a 5DII image shot at 60 mm with the equivalent image shot on a 7D with a 40 mm lens, the 5DII will probably generate the "better" image. If you are a bird or sports photographer trying to get frame-filling images with the longest lens you can afford, the 7D will at least give you more pixels compared to the cropped image taken with the same lens on a 5DII. Depending on how large you intend to print, this may give you an advantage (aka "better" image) or not.</p>

[ben_goren]

<p>Kevin,</p>

 

<p>The proper way of comparing image quality between two cameras is to take two pictures of the

same scene with each camera, adjusting each camera as necessary (focal length / ISO / post-processing techniques / <i>etc.</i>) for each camera. Then, print both pictures and compare the

results.</p>

 

<p>First, at the sizes that desktop printers print at, there’s no effective difference between

the 5DII and the 7D. Both are superlative and surpass the human visual system at those sizes.</p>

 

<p>That said, for LARGE prints, the 5DII will still be superior, for the simple reason that the image

recorded by the camera doesn’t have to be enlarged as much. The naïve approach

would be that, since the sensor in the 5DII is twice the size of that in the 7D, the 5DII should be

able to make prints approximately twice the size of the 7D while maintaining comparable quality.

The higher resolution of the 7D sensor will permit it to be enlarged more as a factor of absolute

magnification, but its largest size will still be smaller than the 5DII’s size.</p>

 

<p>But, again, that only applies if your printer uses paper by the roll and ink by the pint. Otherwise,

you’ll never see the difference between the two.</p>

 

<p>And it’s certainly not to imply that you <em>can’t</em> get excellent

enlargements out of a 7D. With good technique, the 7D should make billboards that will blow your

socks off — and they’ll probably be indistinguishable from 5DII images, too, since

they’ll only be viewed from dozens of yards away at closest.</p>

 

<p>There <em>is</em> however, an area of photography where the 7D will still maintain the edge.

If you need a lens longer than your longest telephoto — as is common with birders —

such that you’ll be cropping your image anyway, then the higher pixel density of the 7D will

be an advantage. But even better quality could be had by getting a longer lens (if one exists and /

or costs less than a car and / or could be lifted by mere mortals) and mounting it to the

5DII.</p>

 

<p>Cheers,</p>

 

<p>b&</p>

[danielleetaylor]

<p>Kevin - technically you are correct that if you must crop to get the field of view you want, the 7D will have the advantage. Practically, between these two bodies, the difference is not enough to matter for most subject / print size combinations.</p>

<p>The flip side is that at low to mid ISO, using the full resolution from each camera, I doubt anyone could reliably tell 5D mkII from 7D prints, even when making very large prints. It's only at high ISO that the 5D mkII starts to pull away from the 7D in image quality. Technically lower pixel density results in less noise and better tonality. Practically, between these two bodies, the difference is just not detectable in print at low ISO.</p>

[jamie_robertson2]

<p>I've nothing to say other than this thread is probably going to explode with opinion very soon ;-)</p>

[stephen_osullivan1]

<p>There are three areas for which the 5D II has a clear advantage: when the DOF is very large, and when the DOF is narrow, and in fast-moving subjects in low light. In the first case, for landscapes for example, your lens will need to be stopped down to f/11, f/16 or smaller. At such apertures, the 5d II will be sharper due to the increased diffraction on the 7D. And that's because of the pixel density and the size of the sites on the sensor. They are bigger on the FF sensor and it'll make a significant difference. Second, for any given focal length and aperture combination, the DOF will be smaller on the FF camera. Open up your 50 1.4 on the 5D II and you'll get really narrow DOF. Lastly because of the ISO advantage on the 5D II, you can afford to crank it up in lowlight and thus stop action better with faster shutter speeds. </p>

[danielleetaylor]

<p><em>In the first case, for landscapes for example, your lens will need to be stopped down to f/11, f/16 or smaller. At such apertures, the 5d II will be sharper due to the increased diffraction on the 7D.</em></p>

<p>This is false. To achieve the same FoV and DoF at the same subject distance (typical landscape scenario) you do not need to stop down as much with an APS sensor as you do FF, therefore diffraction is not any more of an issue.</p>

<p>Consider a 5D2 with a 28mm lens. For the same FoV on a 7D you would choose a 17mm lens. At f/8 and focused to 6.29 ft the 7D has a DoF from 3.15 ft to infinity. To achieve the same with the 5D2 you must stop down the 28mm lens to f/14.3. At that point diffraction is slightly worse for the 5D2.</p>

<p>DoF Calculator: http://www.dofmaster.com/dofjs.html<br>

Diffraction Calculator (near end of page): http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm<br>

Bob Atkins tutorial on DoF: http://www.bobatkins.com/photography/technical/digitaldof.html</p>

<p>As for the opposite, APS-C is not so different from 35mm that it's impossible to throw backgrounds out of focus for portraits and the like. I prefer the DoF characteristics of APS-C because I sometimes find myself wanting more DoF than 35mm can comfortably provide, but I never seem to have trouble blurring a background with APS-C. Never the less, the 5D2 will give you superior narrow DoF control.</p>

<p><em>Lastly because of the ISO advantage on the 5D II, you can afford to crank it up in lowlight and thus stop action better with faster shutter speeds.</em></p>

<p>If you're dealing with action in low light then you're already sacrificing the 5D2 detail advantage at high ISO. The 5D2 will still make cleaner large prints, but are you making 20x30 prints of, say, a night time high school football game? If not then you can comfortably shoot either at ISO 6400. You might squeeze 1 more stop out of the 5D2 in terms of shutter speeds by going to 12800, which is really pushing it on the 7D. The other factor to consider is that with low light action the 7D's AF performance will be better. I don't think the 5D2 is the clear winner here.</p>

[david_littleboy__tokyo__ja]

<p>What Daniel said. The max DoF you can achieve with any camera is limited by your required resolution, and when the resolution is the same or similar, there isn't a significant difference. And the 5D2 resolution isn't enough higher than that of the 7D that you could ever see a difference on a print, even with two prints next to each other and your nose on them looking for differences.</p>

<p>You may be slightly underestimating the 5D2 at high ISO. Pixels are larger and there are more of them, so you can crank the noise reduction a bit more for the same end detail. Of course, you need a longer larger lens to take advantage of that extra ISO.</p>

<p>For narrow DoF, though, the 5DII has a big advantage, and that is that _for the same DoF and angle of view_, you can often put a lot more sharpness on the image plane. The 85/1.8 at f/2.0 is a much sharper lens than the 50/1.4 at f/1.4 and the pixel pitch looking at the 85/1.8 lens' image is wider giving an even sharper image. Similarly for the 50/1.4 at f/2.0 vs. 35/1.4 at f/1.4. For these sorts of images, it's a big difference. But I'm with you on not being particularly fond of the ultranarrow DoF look in portraits.</p>

<p>The wide angle advantage of the 5DII is somewhat overstated unless one throws serious money at the problem. The 17-40/4.0 has really mushy CA riddled corners on the 5D2. Seriously gross. As are all the 20mm primes I've tried (Canon, Sigma, Olympus). So, if one has deep pockets, one needs to look to lenses such as the 17 TSE (which is sharp, CA free, low in distortion, and does TSE things as well), the Cosina Zeiss 21/2.8, and the 24 TSE II (maybe even better than the 17 TSE). At which point, though, it's a slam dunk for the 5D2.</p>

<p>And, of course, there are 14mm primes and the Stigma 12-24, giving you images that simply aren't possible with the 7D.</p>

 

[g dan mitchell]

<p>Ultimately a larger sensor/film always wins in the better resolution contest - if everything else is equal.</p>

<p>That said, unless you are working extraordinarily carefully (tripod, MLU, remote release, very careful focus, etc.) and printing very large (24" x 36"?) with excellent and very careful post-processing techniques there may be more significant differences between the cameras than resolution.</p>

<p>Dan</p>

[matthijs]

<p>For those instances that you want the most magnification from a 100% crop the denser sensor will win. In most other cases the least dense sensor has the edge. Providing that all else is equal: equally young sensor, equally cutting edge technology and comparable lens quality...</p>

[kevin_fuhr]

<p>Thank you all very much for your comments, always very informative.<br>

Kevin</p>