D800E vs. 5D3: Diminishing Returns or Reversal of Returns?

Started 9 months ago | Discussions thread
The_Suede
Regular MemberPosts: 493
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Scaling images with BiCubic
In reply to anotherMike, 9 months ago

I just thought to add that the BiCubic algorithm in Photoshop is a 4x4 convolution window. And it's not a very GOOD 4x4 - meaning that it has an optimum "working window" between 75% and 45% scale of original.

The window is the area in the original that the algorithm "looks at" when creating a new pixel for the resampled image. So when you scale to 25% or less, you're actually not even getting all the original pixels included into the resampled image.

Scaling 36MP to ~2.2MP is right on the edge - a ~24% scale, meaning that you will quite probably get aliasing in the finished result. You will at the very least NOT get optimal results regarding detail sharpness.

Doing ANY kind of large change in PS Bicubic is a bad idea if you want to preserve information. This means (regarding the ORIGINAL thread discussion material!) that an 1800x1200px end format might actually give better results with a 22MP camera than with a 36MP camera. IF you do the transform in one step. Do both cameras in two steps, with an intermediate at maybe 3600x2400px, and the result may actually change. This depends on how sharp the original is, and how you apply sharpening in the worklow.

But genreally - for 1800x1200px, general signal theory says that anything more than twice the end resolution should give almost identical results. Add in a bit of slack for the raw-converter interpolation engine, and say another 25%.
That's still not more than 2.2MP x 4 x 1.25^2 = 13.75MP original.

So, given a good raw converter, the original 5D "mk1" should give almost identical images as the D800 at 1800x1200px scale. If all scaling operations are made in a sensible way...

.........................

On the raw's presented here, I get very similar - almost perfectly identical - results when the images are at ~6MP, that is 3000x2000px. Given a double-blind ABX test with images as similar as those results, I probably would fail to identify either camera correctly.

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