I just did some speed tests to see how much the system actually slows down while viewing dynamic highres. I converted a jpg (CPU intensive task, I assume) with HamLab from Workbench screen without viewing it, then I converted the same jpg while viewing a 594x594 dynamic highres image in Visage and timed with a stopwatch. I set HamLab to beep when finished so I would know when it finished while I was viewing the dynamic image. I did three tests:
(in seconds)
No dynamic: 34.81 Dynamic: 35.02
No dynamic: 34.88 Dynamic: 35.04
No dynamic: 34.71 Dynamic: 34.96
As you can see, there's only a slight difference and this could even have been caused by flipping to the dynamic highres screen.
Then I tried the same thing on my Amiga 1000 (stock except 1Mb RAM), except viewing a 640x400 image in Shazam (Visage doesn't work in WB1.3) and converting a smaller jpg in HamLab. It was a whole different story:
No dynamic: 2:48.01 Dynamic: 6:42.38
(I only did one test because it took too bloody long)
So, the lack of "dynamic highres slowdown" on my A500 must have something to do with my upgrade (maybe Fast RAM?). Still, viewing a 640x400 dynamic highres image on an A1000 took "only" 7 seconds (and looked totally amazing for a 1985 computer!), so I still think dynamic highres should have become the standard for viewing high-colour highres images on the OCS/ECS Amigas.
@SamuraiCrow
Thanks for the detailed info. :-)