One of the new photo features started in PSP X is support for 16-bit/channel functionality, which lets the user work with thousands of shades per color channel rather than the 256 shades per channel allowed by the 8-bit RGB color model. Before PSP X, PSP was only been able to handle images with 16 million colors. Starting with version X, PSP can handle images containing as many as 281 trillion colors - quite a box of crayons, huh! What this means to the average user is that when you make color and/or brightness corrections, the extra resolution creates far better results. There's so much more resolution to draw on that when you apply effects to a 16-bit image, the results are always much nicer looking. If you start with an 8-bit image and apply the same effects, the resulting image can become grainy or have noticeable banding and/or other artifacts.
To illustrate this graphically, I created an 8-bit image and a 16-bit image, filled both with a gradient, applied the Gaussian Blur effect twice, Unsharp Mask four times, and the Sharpen effect twelve times:
8 bit vs 16 bit images
Though the series of effects applied to these images is not something a person would normally do, the results are amazing, and illustrate the point that applying effects will/can produce radically different results.
Even though PSP X introduced 16-bit/channel color support, not all of PSP X+'s features support 16-bit images. You can see a complete list of commands, tools, and features that do fully support 16-bit/channel images in the 'What commands and features work with 16-bit per channel color images?' Corel Knowledge Base entry. In addition, none of the third-party plugins and filters will work on 16-bit images in PSP X+. This might change in the future, though many of these same plugins and filters do not work in the competition's 16-bit processing, either.
The average user who does not have a camera producing 16-bit images, or might be interested in printing such images, can ignore the above discussion. Just thought the comparison was interesting. I neither print my images, nor have a 16-bit image-producing camera.
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