General Lens ZOOM question....

.... 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..... ?

"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..... ?


I can't answer you what makes the difference bettween lenses. I just sold my
Canon 75-300 IS lens ($400) and replaced it with 300mm f/4 IS prime lens
($1100). I compare the picture quality of the same images I took at 300mm.
The advantage of a good prime lens is not only the sharpness but the color
and contrast are much, much better.

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..... ?

"Jeff Durham" wrote in message
.. .
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..... ?

I misread the question. The focal length are not exactly the same. My new
300mm f/4 IS is slightly longer than the 75-300mm IS at 300mm. Only very
slightly though. If the difference is huge, somebody's cheating...

As you may have guessed, there is some "rounding" (by marketing) of the
actual focal length on virtually all lenses. I believe the industry allows
about 5%...I don't believe that it is a deliberate attempt to mislead, more
likely a convenience (to the customer) for comparison and remembering the
lens. Sounds like your Tamron is rounded "up" on the high end while your
Canon may be rounded "down" a bit. But, I wouldn't expect it to be so
noticeable unless your subject to camera distance is changing as well and
one lens focuses closer as well (from your comments, that would likely be
the Canon).

"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..... ?

In general there is a 10% fudge factor on lenses. (ie anything between
270 and 330 would be a 300, but believe me now one ever called a 325mm lens
300. It could be that for these "super" zooms, a lot of the range has more
to do with advertising than fact. I would say that if you need a 1.4 TC to
get 300mms out of it, it's a good lens to send back.

--
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home of The Camera-ist's Manifesto
The Improved Links Pages are at
http://www.chapelhillnoir.com/links/mlinks00.html
A sample chapter from my novel "Haight-Ashbury" is at
http://www.chapelhillnoir.com/writ/hait/hatitl.html
"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..... ?

"Tony Spadaro" wrote in message .com...

In general there is a 10% fudge factor on lenses. (ie anything between
270 and 330 would be a 300, but believe me now one ever called a 325mm lens
300. It could be that for these "super" zooms, a lot of the range has more
to do with advertising than fact. I would say that if you need a 1.4 TC to
get 300mms out of it, it's a good lens to send back.

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

You will find that the Sigma lenses are the most accurate in terms of
focal length accuracy. I conducted some very thorough testing in this
area last year. My photography students learned quite a bit from the
study. Unfortunately, my sponsors prevented me from publishing the
results due to corporate politics.

In article , Giorgio
Preddio wrote:

You will find that the Sigma lenses are the most accurate in terms of
focal length accuracy. I conducted some very thorough testing in this
area last year. My photography students learned quite a bit from the
study. Unfortunately, my sponsors prevented me from publishing the
results due to corporate politics.

Put down the crack pipe, George.

In message ,
(Giorgio Preddio) wrote:

My photography students learned quite a bit

Did you ask the toddlers if they really wanted the lessons?
--


John P Sheehy

On 26 Jun 2004 07:29:36 -0700, (Giorgio
Preddio) wrote:

"Tony Spadaro" wrote in message .com...

In general there is a 10% fudge factor on lenses. (ie anything between
270 and 330 would be a 300, but believe me now one ever called a 325mm lens
300. It could be that for these "super" zooms, a lot of the range has more
to do with advertising than fact. I would say that if you need a 1.4 TC to
get 300mms out of it, it's a good lens to send back.

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

You will find that the Sigma lenses are the most accurate in terms of
focal length accuracy. I conducted some very thorough testing in this
area last year. My photography students learned quite a bit from the
study. Unfortunately, my sponsors prevented me from publishing the
results due to corporate politics.


Hogwash.


GK