Serious doubts on the D7100 at high ISO

Started Mar 25, 2013 | Discussions thread
Bernard Delley
Regular MemberPosts: 240Gear list
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issue is at understanding magnification versus noise
In reply to edo21, Mar 26, 2013

BTW the sunlit bishop figure at iso 1600 looks great, almost unbelievable its high iso.

people keep having difficulty realizing the implications of magnification on noise:

The fair comparison is comparing images at same size, as in prints of same paper size. This type of comparison is done in these measurements by dxo here:

//www.dxomark.com/index.php/Cameras/Compare-Camera-Sensors/Compare-cameras-side-by-side/%28appareil1%29/850|0/%28brand%29/Nikon/%28appareil2%29/680|0/%28brand2%29/Nikon/%28appareil3%29/439|0/%28brand3%29/Nikon

The D5200 is only so slightly better than the D90. A bit more so at very high iso. This is natural. Its based on the fact that these cameras catch closely the same number of photons across their sensor. The detailed scientific explanation is given there:

http://www.dxomark.com/index.php/Publications/DxOMark-Insights/More-pixels-offset-noise!

On the other hand comparison at 100% magnification, is on a per pixel basis. The higher pixel image in its entirety is much larger than the lower megapixel image -- both much larger than your screen. So with 100% you are looking to a much larger image (twice the area D7100 compared to D90) from equally close up. So you can see much finer detail of the whole image. No wonder, you can see the noise much better.

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