Thomas and Blackened,
Focusing screens made for manual focus are ground matte (sp?) in a way that when focus is adjusted perfectly they look clear and sharp. When focus is a bit off they look more blurred than it really is, so to speak. More distinct border between in-focus and out-of-focus. The screen in an Auto Focus camera isn't ground matte at all so it doesn't give any help.
If you guys can tell when the ultimate focus is obtained,
well then I'm probably just old.
and I'll more or less back off here since this is up to the individual photog.
I will however address two things mentioned in posts above:
*Using the focus indicator to focus manually.
This is pretty interesting. Take your AF camera, switch to manual focus and focus on something, say 5 meters away. Don't touch the focus ring after that and slowly move towards or away from the subject you focused on.
How far can you move before the camera indicates out-of-focus? You will not beleive you paid that amount for your camera...
*Checking the sharpness of your slide with a projector.
Unless you have bought some extraordinary lens for your projector this won't work. Anything looks sharp!
I throw away loads of slides that looks sharp thru the proj. When checked with a 10x loupe they turn out unsharp. On the other hand they look sharp under a 6x loupe...
All this leads into another discussion I hope to bring up at some other time...