A very common problem plaguing PowerPoint designers today is gradient banding, which is sometimes visible in imported graphics. If you aren’t totally sure what that is, have a look at this example:
Image banding can be very annoying
Nasty, eh? That’s banding at it’s worst (sometimes referred to as “posterization”) and it is basically the result of too few colors being stretched across too large of a space. The human eye is normally pretty good at blending colors for our brains to process, but sometimes there just isn’t enough color information in an image to make things look clean.
Banding can come from many sources, the most common of which is over-processing of the image in editors like Adobe Photoshop or Paint Shop Pro. Too many adjustments (like contrast, levels, saturation, etc) can “stretch” the color information in the image too far, and the result isn’t pretty. But there are several ways to combat this:
The quick fix: Noise
Applying just a slight bit of noise to the image will smooth out the colors a bit, but only to a certain point. Adding noise is essentially adding color information, so the visible “steps” in the banding will start blending together as you add it in. But be very careful with this approach – if you are not careful, you will very easily make your bad image look even worse. Noise is not very attractive in images that will be projected on a large screen, and if you are using a very good projector, it will be noticeable by everyone in the room. Embarrassing! Here’s an example of how using just a little bit of noise can smooth out a heavily banded image:
See how adding just a bit of noise can reduce image banding?
The labor-intensive fix: Masking
For this approach, you’re going to have to roll up your sleeves and get a little dirty. Begin by selecting the banded areas in your image, and then do one of two things:
- Fill the selected area(s) with a solid color
- Fill the selected area(s) with two gradient colors that don’t cause banding. For this you’ll have to experiment a bit to find two colors (a start color and end color) that won’t band when blended together. Don’t worry; it’s not rocket science. Finding two compatible colors shouldn’t take long, and you’ll experience better results if your colors aren’t drastically different.
This masking technique requires a fair bit of image-editing prowess, so if you aren’t very comfortable working in Photoshop, you may not have any luck with it.
Blurring the banded areas of the image will also help, but you’ll very easily end up with a horribly blurry image if you aren’t careful! We don’t recommend this.