Mindy,

As someone who was layering fractals before Photoshop came along, I think I can answer this question. Primarily, it comes down to interactivity. Secondarily, it comes down to printability.

When I started layering I was using FractInt. I created images, saved GIFs, and then brought them into a graphics program to do layering. (It doesn't have to be Photoshop. Lots of programs support layering. For convenience, we will assume I was using Photoshop.) The problem with doing this is that if there was any error in framing, I had to go back to FractInt, re-render the image, save it, and re-import it into my composite in PS. I found the back-and-forth to be more than just annoying, it was interfering with the creative flow and discouraging me from trying certain things.

Being able to do layering directly within one's fractal application is as much a benefit as being able to do it in Photoshop is. Imagine you are making a collage of photos using Photoshop, but it doesn't support it natively--instead, you can edit a single image to your heart's content, but you have to export all your cropped, trimmed, positioned images and use a separate program to composite them. You would think this is ridiculous. Well, that's sort of how I feel about not doing the layering directly in UF. You could, but it sure can cramp your style.

The second reason for layering directly within UF is printability. Now, lots of people who explore fractals don't care one whit about print quality, and that is fine. But for me, being able to reproduce a fractal image that I created at 1600x1200 as a large 8000x6000 print is pretty darned important. If I do my layering inside UF, I can do it on the manageable 1600x1200 image and UF will automatically adjust when it renders the larger size, and it will do the compositing for me on the final render. If I use Photoshop for my compositing, then I get all of Photoshop's wonderful tools, but if I want a print version, I have to be prepared to import many 8000x6000 images into Photoshop and assemble the composite manually. Each of those layers is 137M. I have one image I actually printed that had 52 layers, which would have required over 7G of swap space in Photoshop to handle. Imagine how long that would have taken. I can imagine, and I can promise that if UF didn't handle layering internally, I would never have produced that image, simply because it would have been prohibitive to try printing it. That avenue of creativity would have been closed, by virtue of my tool selection. I can see you're actually running into this with PS already.

This is not to say that Photoshop is not valuable tool. The only people who suggest that PS is useless or has no place are either substantially unaware of what PS can do or are deliberately deluding themselves. But the advantage of being able to layer directly in your primary creative environment should not be ignored. If your primary creative environment is Photoshop, rather than UF, then it's completely reasonable that this might not be obvious.

As to more specific things, what you can do in UF that you can't do in Photoshop: you can control gradients, colors, blending in ways that you can't in PS. You have a couple of merge modes that PS doesn't (particularly HSL Addition, one of my favorites, which produces some very interesting texture effects). The reverse is also true, PS has some that UF doesn't. Moving the entire fractal and re-framing can't be done in PS, you have to go back to the fractal app.

If you're going to build a serious Photoshop rig, you want (1) lots of RAM. See if you can find a system that will take 4G of RAM, and put 4G in it. (That way, your other programs will not be competing with Photoshop for memory.) (2) You want really fast hard drives. When Photoshop runs out of RAM, it uses swap space on disk, and for that you want fast. Find a SATA (Serial ATA) system that supports striped drives (RAID 0). (3) You want the fastest CPU you can afford. Filters eat CPU for lunch. Dual-core may not help you much (it depends on the filter). Dual-core does help with UF, though, as do dual processors and render farm PCs.

Rick,

Celerons should be fine, your bottleneck with UF rendering is rarely memory throughput and almost always CPU/floating-point speed, and Celerons have that.

--Damien