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Diff. between Close-up Filters(diopters) and Telephoto Extenders

 
 
bhaskar
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      08-04-2003
Hi,
Since Close-up Filters magnify the subject by factor of 1x,2x,4x etc
and Telephoto Extenders multiply the focal length by factors of
2x,1.5x etc.
Don't both of these acchive the same effect ?

I realise that I may be confusing magnification as achieved by the
close-up lens
versus varying (increasing) focal length length as achieved by
Telephoto extenders.
But isn't increasing focal length equivalent to magnifying ? Or are
they seperate in optical terms ?If so, then in optical terms what's
the exact difference ? What optical parameters
change when a close-up filter is mounted or when a telephoto extender
is mounted ?

In what situation would one use a close-up lens and in what situation
would
one use a telephoto extender ?

Also is the close-up filter in any way related to macro phtography ?

Prosumer cameras like Powershots have macro functionality built in,
but what
is to be used for macro photography using a D-SLR say 10D ?
Can the Canon 28-135MM IS USM lens be somehow used for macro
photography or do
I need special macro lenses ?

And lastly is a close-up filter kit just a poor man's macro lens ?
and is a tele photo extender a poor man's Super Tele (focal length >
300) Lens ?

Thanks in advance for all those who help out,
Just a confused newbie.
bhaskar
 
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Joseph Meehan
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      08-04-2003
Telephoto extenders allow say a 100mm lens to function like a slower,
less sharp 140 mm lens. Things will appear to be 1.4 times closer. So
something 14 feet away will look like something 10 feet away

A Close up filter will not make the subject look closer. What it means
is that something that you might be able to photograph at 18 inches and
resulting in a small object occupying less than 10% of the photo area, can
be photographed at 10 inches and still be in focus.

Tele extenders make it look like you were closer and close-up filters
let you get closer. Not exactly the same thing.

All else being equal the close-up filter/lens (they are really
supplementary lenses) will give better overall sharpness when photographing
something that is to small to photograph properly at the minimum distance
your lens will focus.

--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math


"bhaskar" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) m...
> Hi,
> Since Close-up Filters magnify the subject by factor of 1x,2x,4x etc
> and Telephoto Extenders multiply the focal length by factors of
> 2x,1.5x etc.
> Don't both of these acchive the same effect ?
>
> I realise that I may be confusing magnification as achieved by the
> close-up lens
> versus varying (increasing) focal length length as achieved by
> Telephoto extenders.
> But isn't increasing focal length equivalent to magnifying ? Or are
> they seperate in optical terms ?If so, then in optical terms what's
> the exact difference ? What optical parameters
> change when a close-up filter is mounted or when a telephoto extender
> is mounted ?
>
> In what situation would one use a close-up lens and in what situation
> would
> one use a telephoto extender ?
>
> Also is the close-up filter in any way related to macro phtography ?
>
> Prosumer cameras like Powershots have macro functionality built in,
> but what
> is to be used for macro photography using a D-SLR say 10D ?
> Can the Canon 28-135MM IS USM lens be somehow used for macro
> photography or do
> I need special macro lenses ?
>
> And lastly is a close-up filter kit just a poor man's macro lens ?
> and is a tele photo extender a poor man's Super Tele (focal length >
> 300) Lens ?
>
> Thanks in advance for all those who help out,
> Just a confused newbie.
> bhaskar



 
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