20D with 1.4 conveter

[seaspray]

I have a 20D. If I use the 17-85 lens at 85 this is the equvilent of @136mm because of the 1.6 muiltipler right? Now if I use the 1.4 converter, do I muiltply the 85 by 3 (1.4 +1.6) or 136 by 1.4? Thanks

[RJSorensen]

Yes as best I know . . . (85x1.6 x1.4 = 190.4mm effective) I don't think the 1.4 TC will work with the 17-85 however. There is a list of lens that will work with it in various form on the B&H website.

[seaspray]

Thanks, but even with the lens it will work with, which way would you calculate it?

[SkipD]

Your original assumption was correct. Calculate the "effective" focal length based on the 1.6 multiplier for the size of the sensor in the 20D and then multiply by the tele-extender's factor. The equivalent effective focal length (with the 20D body) for the 85mm lens is approximately 190mm.

[seaspray]

Thanks RJ and Skip for your replies. I went to the B&H web site and found the compatibility chart. It'll help in the process of which lens to purchase next.

[CyberDyneSystems]

Seaspray,

Check the -=EOS Sticky=- at the top of the page for a link to a much more comprehensive chart on T-cons ;)

Needless to say,. your 17-85mm will not work with a Canon T-con.