That is an interesting observation. I too thought 300 was 300 per my
observations. I had a ~270mm telephoto on an old 35mm. I compared what I
saw with my Rebel using 270mm factoring in the 1.6X conversion number for
35mm and the picture information was darn near identical. That old lens was
more than twice the size so I was really curious if they would be the same.
I also compared my Kodak P&S digital to my Rebel and found similar results.

Maybe some of the experts in this group can explain what you are seeing.

Jeff


"advid" wrote in message
om...
... I've got a Canon D30 and a Canon 300D that my wife and I enjoy
using for mainly birds/wildlife....

We've been using a Canon 75-300 usm (sometimes with a 1.4 extender)
for close ups of birds etc...

I've just got a Tamron 28-300 XR and at full 300mm it gets nowhere
near as close as the Canon at 300mm.... Even with the 1.4 on it's only
just about the same as the Canon wothout the 1.4 on - why should there
be such a difference ????

Surely 300mm is 300mm no matter what make of lens..... ?