More mpix does not automatically mean more resolution.

Started May 20, 2012 | Discussions thread
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chironNYC
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More mpix does not automatically mean more resolution.
May 20, 2012

More mpix does not automatically translate into more resolution under all levels of mpix, all lenses, all ISOs, and under all shooting conditions. There is a law of diminishing returns that operates, and the question is what level of mpix is optimal for your use. This why the pro models of Canon and Nikon do NOT feature the highest levels of mpix. More mpix automatically equals more resolution only on a laboratory test-bench, not in real life.

Using a camera on a tripod, with the mirror locked up, with self-timer release, with live view magnification, with the best possible lens at its best aperture, with a high shutter speed, at low ISO will yield more resolution per mpix. But the same camera used at a wedding or to shoot any kind of live event will not get you more mpix and may well cause you to lose shots because of things like increased motion blur from subject or hand movement, and the need for higher shutter speeds.

Similarly, even the best lens used at it maximum or near-maximum aperture will not produce higher resolution because the lens at a wider aperture cannot resolve the level of detail that the sensor can record.

Similarly if you are using a small aperture with the best lens because diffraction will limit resolution.

Similarly if you are using higher ISOs, because the increased need for noise reduction will smear the higher resolution and smaller and more numerous mpix produce more noise requiring more noise reduction.

In such situations, the 5d3 will usually produce more actual resolution in the final image and much more photographic flexibility in getting the image you want in the first place.

This is why Henri Cartier-Bresson started to use 35mm in the first place--because of the kinds of situations he wanted to shoot in: The constraints and technical practices necessary to get larger-format quality destroyed the ability to get the image in the first place.

This is what DPR's review of the d800 points out when it writes and repeatedly emphasizes that "inordinate lengths" are required to actually get the increased resolution that the d800's mpix are capable of. Many other reviews have made the same points. Luminous Landscape even recommends a focusing loupe, presumably because the live view focusing magnification on the d800 is unusable.

And this is why pro models costing twice as much as the d800 do not feature the d800's levels of mpix--because they make the camera less flexible and usable for making most images.

Nikon did not put the 36 hex on their pro models, but used it to aim at amateurs/prosumers who would be more taken with a big mpix count without really understanding what it means in practice. This is what DPR was repeatedly emphasizing in its d800 review by pointing out the very unusual practices ("inordinate lengths") you need to employ in order to not smear a d800 image.

There is a sweet spot for mpix. More automatically equals better only in advertising aimed at amateurs.
--
Peter

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