20D GOES LONG !
Well sports fans, this week I rented a Canon 2x TeleConverter in order
to test it against my Vivitar Series 1 2x TC as well as a quick
comparison against the Canon 1.4x. I also wanted to test the Super
70-200 f.2.8L w/ the 2x against the Forgotten 400 f/5.6L. Then just
for kicks I stacked all three teleconverters (2x, 2x, 1.4x) on top of
the 400 f/5.6L to make a nice little 2240mm f/32 telescope. With the
20D's 1.6x crop factor, that's an effective focal length of 3,584mm!
For my test lab I went out on my back deck and shot the neighbor's
brick wall across the street. I used my tripod, shutter release cable,
and mirror lockup in an attempt to get the sharpest pics possible. I
even tried manually focusing with my 2x Right Angle "C" viewer and this
helped as well when I lost autofocus capabilities.
Anyway, the test isn't designed to prove anything other than it's a
good way to waste an hour on a hot Sunday afternoon.
Here are some pics from the test:
http://www.pbase.com/bret/2xtest
The first pic shows the test area. This one was taken with a 50mm to
give you an idea of the magnifications involved. The others are
unsharpened actual sized crops. You can reach your own conclusions,
but to me there isn't much quality difference between the expensive
Canon 2x and the cheapo Vivitar. Certainly not $150 worth. I also
didn't notice much falloff in quality between the Canon 2x and the
Canon 1.4x. From what I've read online I got the impression that the
2x was crap. But as my baseball pic I posted the other day
( http://www.pbase.com/bret/image/63505012 ) proves, this is not the
case.
This makes me wonder if some people are getting poorer results with the
2x due to the fact that they lose autofocus with it and must focus
manually.
As you probably know the 20D loses autofocus with anything over f/8 so
since the 400 f/5.6L mated with the 2x gives f/11, that combo must be
focused manually. That is why I did most of my testing with the 70-200
f/2.8L.
Even with my 2x magnification on my eyepiece, I was never able to
manually focus and get as sharp results as the 20D's autofocus. So
anybody who claims they can focus their old manual lenses better than
the modern stuff is full of it.
The most amazing discovery I made from this litle exercise (it must
have been exercise cause I was sweating a lot) was the result I got
when I stacked all three teleconverters on the 400 f/5.6L. It made for
a very nice shot, especially when it was sharpened a tad. Can't wait
to try this combo on some moon shots.
Annika1980
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