Quote Originally Posted by HDNitehawk View Post
That is the part of the theory that doesn't seem to pan out.
If it's true then overall when I am hand holding the high mp body I should be getting worse results than other bodies when comparing equally sized pictures.
In real world shooting I am not seeing that.
If you shoot the exact same scene with both the 5Ds and 5D Mark III bodies, with the same exact movement happening with each shutter click, then the movement recorded will cross more individual pixels with the 5Ds compared to the 5D Mark III. In that way, more motion blur is recorded.

However, if you downsize the 5Ds's native resolution to the size of a 5D III, then some of those motion blurred pixels will get thrown away, thereby making the two bodies similar from a sharpness perspective when the picture dimensions are both set to the smaller size. But on that note, what's the point in having a 50MP body if you're just going to downsample every picture to the size of the 5D III's files? And if you instead crop the image instead of resizing/resampling, the result will be more visible motion blur at the same pixel dimensions (with a tighter framing, of course).

In order to obtain the sharpest possible images when using a 5Ds/5Ds R, you'll need faster shutter speeds than what the traditional 1/focal length gives you.

I know it looks as if I published the post without any input from Bryan, but that is far from the case. Bryan and I discussed the post quite a bit before I fleshed it out, and he proofread it before it went live and gave it the thumbs-up.

As far as he's concerned, this isn't new information. He actually touches on all of the major points in his EOS 5Ds review:

Because there are more pixels in the same amount of sensor space, camera and subject motion causes subject details to cross over pixels at a faster rate, potentially resulting in blur and a loss of pixel-level sharpness. Because of this, you will find that a faster minimum shutter speed is necessary for handholding this camera (and that image stabilization becomes more important). Similarly, fast-moving subjects may require faster shutter speeds to avoid pixel-level motion blur.

This is the 5Ds change with the biggest learning curve. The old 1/(focal length) rule to determine one's shortest shutter speed for handholding (without the aid of image stabilization) no longer works. Many use the 1/(focal length * 1.6) rule to determine APS-C handholdable speeds. This formula uses the 1.6 factor matching the APS-C sensor angle of view difference, but the higher pixel density of the APS-C imaging sensors is the real reason the faster speed has been needed. The same rule or, better yet, 1/(focal length * 2) is a better base estimate for handholding the 5Ds bodies.