Thanks Daniel. Your post (and Bob Atkins page) helped me understand some stuff.


Quote Originally Posted by Daniel Browning
Jon, you are using a very wrong definition of the word bokeh. I think you are doing it intentionally, since others in this thread have been doing it, but I think something should be said.

Yes, I was using the word in the way I thought Mr. Powers Brent intended, even though it isn't how I would have used the word.


Quote Originally Posted by Daniel Browning


Quote Originally Posted by Jon Ruyle


How does
he define OOF blur?


Diameter of a point source specular highlight at a given distance from the plane of focus.


Okay, that makes perfect sense. Of course, if you really want to quantify blur with a single number (and thus answer which lens has more) you have to specify which given distance you care about . (Correct me if I'm wrong, but I think if that "given distance" is close to infinity, only aperture matters. If the "given distance" is close to zero, only f number matters.)


In addition, I guessed that by "bokeh" the OP wanted to also take into account another feature of long lenses: they magnify background details more. I *thought* this contributed to our perception of a blurred background (quite separate from how big the OOF disk of a background point will be), giving an additional advantage to the long lens. Maybe I'm confused about this as well, though.


Quote Originally Posted by Daniel Browning


So there are three very different things here:
  • Quality of the OOF blur (bokeh)
  • Quantity of the OOF blur
  • DOF



According to Bob Atkins (not that I nececarily would take his word over yours []), bokek is a combination of quality and quantity of OOF blur. This is what I thought the word meant, too, though I never tried to check a definitive source.