Printed at 20ppi, pixelation and jpg artifacts appear

The big blocky pixels as well as the grid pattern of jpg artifacts is noticeable even at viewing distance and is absolutely not acceptable. Fortunately, we can clean this image up in 3 quick steps. First, let’s get rid of the blocky grid of jpg artifacts. Its important to do this step first before we resample/ enlarge the image, so it doesn’t look worse.

To remove the jpg artifacts go to the menu bar and choose: Filter>>Noise>>Reduce Noise. This is a very powerful and potentially destructive tool if used with a heavy hand. We are only interested in the bottom check box “Remove JPEG Artifacts.” You can experiment with the “Remove Color Noise” slider, but make sure everything else is set to “0″.

The second step is to resample or enlarge the image so that it has higher ppi/ resolution. Ideal resolution for an inkjet print is 300 pixels per inch, which is a 1500% enlargement from a 20ppi image. That’s overkill. If we enlarged it that much, all we would get is a big blurry mess that will really slow down your computer. We just need to enlarge it enough so that the blockiness of the pixels disappears (Image>>Image Size).

20ppi

100ppi

Sure, if you stick your nose up to the print you’ll notice it starts to fall apart, especially if its a detail critical shot like a portrait. But, its impossible to create more detail. The trick is to fool the eye by giving the appearance of detail or sharpness. So, the final step is to add a subtle layer of film grain or noise.

Create a new layer with overlay neutral color.

If we’re going to add noise we want to do it to a separate layer so that we have the most control over how it blends with the image. In your menu bar, go to: Layer>>New>>Layer. Change “Mode” to “Overlay” and check “Fill with Overlay-neutral color”. This will create a new layer in your layer stack filled with solid gray and set to the Overlay blending mode. Now go to Filter>>Noise>>Add Noise in the menu bar. The amount that you add depends on the ppi you set in the previous step. For my image at 100ppi an amount of 9.6 did the trick. You want the noise to be visible, but not so much that it obscures the image. For most images Gaussian and Monochromatic noise looks best, but feel free to experiment. If the noise looks a little too intense you can lower the layer opacity in your layers palette.

Final image with gaussian monochromatic noise added

I hope this was helpful, though I’m not sure how many people actually want to make prints this large. This process is useful for printing at smaller sizes as well when ever a significant enlargement from the digital file is needed. Also, because this is my first tutorial on here, I’d love to hear any and all feed back. Thanks!