Thread: Teleconverters
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Old November 11th 06, 11:27 AM posted to rec.photo.digital.slr-systems
Thomas
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Default Teleconverters

Dave wrote:
I have a canon 70-300 IS USM/350d and wondering if there are any
teleconverters out there that will work with this lense just to get a
little more reach? thanks for any info.


I assume you want to use it on a DSLR. One problem here is the format
factor. Since the DSLR sensor is small than regular 35mm film, things
are magnified by the sensor. So DSLRs are already rather demanding when
it comes to lense resolution.

By adding a teleconverter you further enlarge any fuzziness or lense
errors. With a zoom, the result is most likely disappointing. While
teleconverters can be useful, that is usally only the case with really
expensive prime telephoto lenses.

Another problem is light. What is your aperture at 300mm? I guess it
could be f5.6, and with a 1.4x teleconverter that turns into a 420mm
f8, which is not all that useful unless you use a tripod or you have
really brilliant sun shine. AF probably does not work, and even the
focus indicator may give up.

Thomas