Colin Mattson , Aug 23, 2008; 02:50 p.m.
1. Any idea what is causing the difference in output? Clearly I should stay with Printer manages color. But Ian Lyons says, "This option produces by far the best print quality." but doesn't explain why.
If you're happy with the results of "printer manages color," by all means continue to use it. The difference between the two options is that the printer's essentially guessing how it will respond when using Printer Manages, whereas a profile takes into account how the printer will actually respond using Photoshop Manages.
As for the differences in brightness you're seeing... Often if the prints are coming out darker, it's because your monitor backlight is too bright relative to your viewing environment. When the printer's in control, it seems to lean toward assuming your display environment is going to be fairly dark.
You can try turning down the monitor backlight, or putting more light in your workspace, or just keep doing what you're doing if it gets the results you want.
2. In the printer dialog box there is a high speed option. I've tested it both ways and can not perceive a difference. Do you typically leave this checked too or do you see a difference? Could be me or my printer since every printer is slightly different.
Epson has improved the high speed option with every batch of printers, to the point you can often get away with using it seamlessly now.
Under some circumstances, you can still tell the ink was laid down in two different directions, though, and in those cases you can remedy the problem by turning it off. High speed is also more sensitive to proper alignment (but obviously that's easily remedied by running through an alignment). I typically leave it turned on these days.