I use a vivitar 2x converter with my D60 and 10D. It adds about 2 stops, but
it boes come in handy at times. Using it on a Sigma 70-300 will make that
lens very slow. You will need to up the iso and use a tripod.
imo

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www.Digifilm.info
"PeterH" reply to wrote in message
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Do you recommend a Tamron 2x converter for a Canon 300D with Sigma 70-300
APO macro super zoom lens?

Any other recommendations?

regards

PeterH