In article <1996Feb10.230254@opal.tufts.edu>, dherron@opal.tufts.edu says...

>I'm a new user of an SB-26 unit, and I'm interested in finding a
>bounce-diffuser card I can attach to the unit (that's larger than
>the built-in one, obviously). It seems to me (a naive flash
>photographer) that the built-in card is not much use for other
>than catch lights in subjects' eyes when bouncing off a ceiling.
>Are there commercially-made devices available? Any tricks to
>building your own?

Unless you can TRULY - NO FOOLIN' greatly enlarge the light source
size (most of the flash add-ons claim they do, but if you pop the
flash while looking at it with and without the add-ons, the truth
is soon evident in the relative after-image sizes [with the flash
at a constant distance from you]), there is little point in using
flash add-ons with the SB-26-27 flashes which include the catchlight/fill card. Even if the light source size were increased
two or three times, the advantage would be lost beyond a few feet
(due to basic trigonometry). A Styrofoam cup over the upturned flash
is a (super) cheap and effective add-on for reducing power, broadening
flash coverage, and/or getting the light source above the lens in vertical photos. Notice that I said NOTHING about "diffusion", a
misleading claim of many add-ons. Diffusion is irrelevant to the
exposure unless there are reflecting surfaces VERY near the subject
area of the photo. Shadow depth and edge characteristics are
entirely dependent on light source sizes and number (including
reflections, if any are of sufficient intensity to matter).
Hope this Helps