Hi--

>>The Cosina 100-500mm (f5.6-8 rated, but it appears to be slower...)
>>that I have is excellent (quite sharp 100-400mm, and good out to
>>500mm, center-to-corner, even "wide" open), though it is often too
>>slow to be very practical, and it is quite large...

>Have you ever noticed a bright area in the center of the print when shot at
> 500mm wide open? Mine seems to do this, or do I just need a better sun shade?
> Any comments?
>Thanks
>Ed edmall@aol.com (EdMall)

This zoom will show reflected images at some zoom settings (fireworks
repeated upsidedown-backwards in the image, for instance), so I wouldn't
be surprised, though I have never seen what you describe (but I use
a deep shade on it, which makes the zoom even more awkward...).