The Canon 7D and 5D Mark II: Resolution Comparison

I’ve had a chance to make a cursory comparison between some full resolution photos taken by the new Canon 7D and a Canon 5D Mark II, and the results have not been exactly what I expected. Before I go on to describe the results, let me mention that the 7D in question is a pre-production model, and results may improve (where theoretically possible) by the time that they ship. I’d also like to thank Steve Eastwood at Modelmayhem for providing the images.

As I mentioned in my previous discussion of these two cameras, the overall pixel count difference is minimal in terms of final print size, but because the 5D Mark II has a full frame sensor, it has a much lower receptor density (about 156 receptors per millimeter) compared to the 7D (about 233). Even though it may seem that higher resolution on the sensor would lead to sharper photos, we should not expect this to be the case in practice because even our best lenses offer a lower resolution than the 7D sensor, and therefore the sensor’s extra resolution will not be capturing extra detail.

Figure A: Canon 7D - 100% Crop

Figure B : Canon 5D Mark II - 100% Crop, ISO 3200

If this concept is hard to grasp, consider this scenario: suppose that you have a fixed focal length lens (say, a 100mm) on your 5D and you set up an object on a table in your studio so that, with your camera on a tripod 10 feet away, it fills the whole frame.  Now suppose that you put the lens on a 7D and place the camera on the same tripod. Of course, the object won’t fill the frame any more, it will be cropped. In order to fill the frame the same way (or as close as possible), you’ll have to back up a few feet.  After backing up a few feet, you’re now using less of the image that would be produced by the lens on a full frame camera to create the same photo, which also means that you’re magnifying the lens’s flaws.

Figures A and B are from a little less than 1/4 of the distance across the frame horizontally. This means that on the full frame sensor of the 5D, this is getting near the edge of the frame, which we’d expect to be a bit less sharp. On the 7D, this is using a more central part of the lens, so any lack of sharpness is less likely to be related to optical problems with the lens.

As you can see, however, the 5D is still sharper, though not by a tremendous amount. The difference is most noticeable in the “www” text below the logo box. Since the two images were shot at 3200, noise is also a factor.

Digital Noise

Figures A and B display a significant amount of digital noise, but in each case, no more noise than a CCD equipped camera would have produced at ISO 800 a few years ago. The question, however, is whether there is a difference between the cameras. Continue reading »

Which is right for you, the Canon 7D or the 5D MarkII?

The Differences That Matter

The first difference worth mentioning, of course, is the price tag…. about $900 difference, if the current prices listed are any indication (7D at about $1599 at B&H or Amazon and the 5D Mark II at about $2499 at B&H or Amazon). [Note: Canon is currently offering rebates on both] Since we’re looking at a couple of cameras that have the build quality for professional use, with magnesium alloy bodies, full HD video capabilities, top notch processors, and some of the most advanced CMOS sensors around, we can expect professional quality results from either camera. In fact, comparing the columns of features for the two cameras reveals that the vast majority of them are identical.  Something must justify the price difference, though.

Most obviously is the CMOS sensor difference, the 5Dii being a 21M pixel, full frame sensor, and the 7D being an APS-C size holding about 18Megapixels. The 7D has dual Digic4 processors, whereas the 5Dii has only one. Probably as a result of this, the new arrival boasts burst speeds about twice as fast as the 5D. There are many other minor differences (and perhaps a few significant ones), but I think that these are the most important to consider up front. Continue reading »