Photoshop showing low quality graphics

Question

I have a strange problem in Photoshop. I had this background image that I had downloaded from a website to try and recreate something like it. After I downloaded it and opened it up it all looked fine. Then the other day when I wanted to start working on my project Photoshop was showing the image in very low quality where it added noise and pixelated the image.

I tried creating a new document and made a standard radial gradient, but noticed that the same thing happened. It added a lot of noise to the edges of the image (Almost like the Dissolve blending mode would) and the newly created image appears at a very low quality.

I'm not sure what to do. I've tried opening up the file at work, and there is nothing to see there. (Same version of Photoshop CS5).

Here is an image of the gradient I tried to create:

Answer 1

Sounds like in the first instance that you saved the file as a gif or some 256 color format. This throws away a lot of colors and dithers the rest. (see: Floyd–Steinberg dithering). Alternatively, you may have inadvertantly changed your desktop color depth to something low (unlikely)

In the second instance, you may just be seing the gradient rendered on a different screen. All monitors render color differently and LCDs vary greatly in their ability to render smooth gradients. Banding is always present.

Answer 2

Just a guess as I'm only on CS4, but at how many bits (8-, 16-, or 32-bits per channel) are you opening the document? The screenshot shows 8. I typically only work in 8-bit and I've always noticed that large, subtle gradients get bands and noise as it tries to interpolate colors to make the effect with the limitations that come with 8-bit.