The original in 16-bit mode is linear 12-bit acquire using Canon eos*dcs3 camera into Photoshop 15-bit space and then cropped.

Mosic Tiles filter in gamma space lightens the image in overall and the quality of the effect deteriorates severely.

Linear space processing

1. Open the original linear higher bit-depth image.
2. convert to 8-bit mode.
3. apply Mosaic Tiles filter at tile size=8, Grout width=1 and Lighteng Grout=5.
4. apply inverse gamma 2.2.
5. save as jpeg using quality factor 4.

Gamma-space processing

1. Open the original linear higher bit-depth image.
2. apply inverse gamma 2.2.
3. convert to 8-bit mode.
4. apply Mosaic Tiles filter at tile size=8, Grout width=1 and Lighteng Grout=5.
5. save as jpeg using quality factor 4.