Handpicked Software

Dougal Charteris, who read my article “Solve printer problems” in Macworld, wrote in with an excellent tip for solving banding problems. I’ve had a few images in my iPhoto books marred by banding; this tip would have solved the problem.

Dougal writes:

Banding is a common problem when going to print when an image has had a few changes, particularly from adjustment layers. (I use Photoshop, I don’t know about Photoshop Elements).

The resulting image can have severe “banding”. This can be seen in the histogram…

The solution is the addition of a tiny bit of noise, (Filter/Noise) I usually try about 2% to start with a 250dpi image, the amount of noise needed will vary with image resolution. This is invisible on the image but will cure banding (this should be the last thing you do to an image).

Here’s an example:

The above picture is probably not salvageable; it’s out of focus, the colors are washed out and the highlights are blown. You can see this in the histogram below. Notice the spike at the far right, which shows how many pixels are blown to white.

I won’t try to save the image, but let’s see what happens to the histogram when I adjust the levels.

There’s no bringing back the highlights, so I just tried to boost the colors. You can see the difference in the image below.

The colors are richer, but the new histogram after applying the changes shows banding (notice the gaps in the histogram below). The banding would almost certainly be visible in the printed image.

After applying Filter > Noise > Add Noise (Amount: 2%; Distribution: Gaussian; Monochromatic: Checked), you’ll notice there are no gaps in the new histogram:

You might see a bit of noise onscreen (I haven’t included the noisy image here because the noise wouldn’t be visible at this small size), but it won’t be visible in your print.

Thanks Dougal!