Upsizing ~ a recipe using the Gimp and G'Mic

Yesterday I sent a 100mpixel image to a friend to have them inspect it closely and to pixel-peep to their hearts content.  

 

 

The photo started as a 24mpixel Sony A7 image of a motorcycle.  It's a rare beast, the motorcycle, and I used a fine 20mm lens on the tripod mounted A7.  I'm imagining just how glorious a large print might look in going from the native 6000x4000 pixel file size to 12000x8000.

I shared the image with this particular friend because they shoot Fuji GFX 100mpixel cameras.  If there is something amiss, they would spot it.

Their verdict? 

"The detail is just mind blowing really ! ! ! !... no arguments on this end... "

An hour later a pretty little Sony A7R came up on one of my favorite shopping sites for a rather decent price.  Should I get it? was the question of the evening.  Based on my friends reaction I think it's pretty clear the answer would be no if I was thinking in terms of "improved" resolution over what I already own.

Here's the recipe I used -

1. Open the image in RawTherapee, Capture Sharpen and process the 24mpixel image to taste
   
2. Open the image from step #1 in the Gimp and continue with...
3. G'Mic DCCI2x upsize (found under the "Repair" tab)
4. G'Mic Inverse Diffusion sharpen set to between 5 and 10 iterations (found under the "Details" tab)
5. G'Mic High ByPass filter applied to a layer copy of the image from step #4 (also found under the "Details" tab)
6. Set the High ByPass filtered layer blend mode to "Soft Light"
7. Flatten and save the result

A couple comments about the upsizing choices I made - G'Mic DCCI2x does a very good job avoiding pixelation commonly seen on diagonal hard/sharp edges with other upsize operators.  Similarly, I've found that Inverse Diffusion does not over-emphasize pixelation, even when using up to 10 iterations, un-like USM, or Octave or Richardson-Lucy.  Finally, for the continuing avoidance of pixelation reasoning, applying a High ByPass filter layer that is blended in "Soft Light" seems to do the trick.

Occasionally I've found applying a light Noise Reduction in step #1 with RawTherapee and again after step #3 in the Gimp can help keep colors "true" along contrasty, sharp edges.  For the motorcycle image I didn't need to apply any NR.

As always, if something isn't clear, let me know and I'll try to do a better job explaining. I see that the first edit of this entry wasn't clear, so it's been updated to correct my mistakes.