My guess is that you're confused by focal length and filter thread. I don't own the lenses mentioned, but it sounds like you have a 55mm focal length macro lens with a 58mm thread. The thread is the thing you can use to attach polarizers and other filters. A flash that "covers" 28mm means that if you use that flash with a 28mm lens, there should be little or no light fall-off on the corners of the frame. Use that same flash with a 24mm (wider) lens, and you'll see light fall-off.
A flash that covers 28mm will work with any lens _longer_ than 28mm (eg 50, 100, 200mm) but you must make sure that the subject is not beyound the flash's "reach".
Does this help?
William Robb wrote:
From: "Charlton Vaughan" Subject: Camera size and lens size.
Hi group,
Since I'm a (what I consider) a novice at photography, I don't do this professionally, I really am not knowledgeable about terms, etc.,
My camera is an SLR, or what I've always thought of as a 35mm camera, one
of
the lens that act as a regular lens with limited macro says it's a 58mm lens, another (Takumar) says it's a 55-58mm lens. I was looking at the Pentax Flash AF360FGZ listed on the Pentax website that someone referred
me
to. The flash is listed as "covering" a 28mm. What does it mean to
"cover"
a 28mm lens? Does this mean that my 58mm 0r 55-58mm lens is incompatible with the flash? Does this also mean that it will not fit a 35mm
camera...as
you can see...I'm soooo confused.
