Yes, Bokeh can be tested.

[MyersPete@aol.com]

Hi to all:

I am sure that I am not going to convince those that dont "believe" in bokeh
that the world is not flat. This post is not for them. It is for those of us
that would like to talk about it - and more to the point - how to test for
it.

I was a consultant to NASA for twelve years. During that time, I had to
devise the math to test a number of perceptual events - like "bokeh".

All the test requires is a black razor edge against a white background at the
distance that you wish to investigate the bokeh. This most likely would be in
the far field - at inf..

Then, a plot of aperature and focal distance of the lens is made against the
test target. A picture is made at each focal lenght and aperature. Each
picture is scanned with a microdensitometer across the "edge" to reveal the
impulse response of the 'edge'. The impulse response will create a distinct
type of curve depending on the performance of the optics.

The "distortion" that has the most objection is  when the impulse "rings" and
creates a double image in the blur- cross eyed. You can see this with the
Fuji GA 645.

Naturally, the trouble with a test like this is the time and expense. And, it
only gives you one answer for each point - not too useful statistically or
practically to "sumarize" the results. It makes the problems we have with MTF
charts look simple!

I am afraid that many people treat photography as a technical event, rather
then an artistic endevour. Art is about having intuative skills along with
practical skill. Intuition and "feel" are an artist's version of statistical
analysis. And, I think it can be said that some lenses have good bokeh and
some do not. If you want to spend a life time measuring, you can find the
data to support it. If you want to make images, then you use your intuition
and go with it.

Pete