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10-29-2013, 06:03 AM   #1
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Join Date: Jul 2009
Location: Austin, TX
Posts: 68
Question about teleconverters and macro ratios

Sorry if this is a newbie question, but I was told this by an eBay seller, and I have my doubts.

I saw a 2X teleconverter for sale on eBay, but it was NOT one of the 1:1 macro teleconverters like those from Vivitar. I asked about this, and he said any TC is a "macro" converter, because it allowed you to "get closer" to the subject.

I asked what the macro ratio would be using this TC, and the seller said "2X whatever you had before."

Is that true? In other words if I had, say a 1:4 lens mounted on my camera, would adding any 2X TC give me a 1:2 macro ratio?

Thanks in advance.


10-29-2013, 02:31 PM   #2

Join Date: Oct 2006
Location: Chicago suburb, IL, USA
Posts: 1,535
Hi Greg,

This is essentially true. A TC magnifies the central portion of the image frame by the mag factor of the TC. However, some TCs (I think most, but can't really say for sure) actually allow the lens/TC combination to focus a little closer than the Minimum Focusing Distance of the lens alone, so the multiple to the mag ratio can actually be a bit higher. I've found, for example, that my P F 1.7x Auto Focusing Adapter on a 1:1 dedicated macro, gives me an actual mag ratio of @ 1.9 : 1 at MFD instead of the expected 1.7 : 1.

Don't forget that multiplying the FL with a TC also reduces the amount of light to the VF and sensor by the same factor as the TC is rated, so with a 1.4x, you lose a full stop and with a 2x you lose two full stops, so usability is reduced as max aperture gets slower.


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