Looking to buy a teleconverter

**Conundrum** · 05-29-2007, 02:26 PM

Using a 20D with a 70-200 F4. I've heard the 2x doesn't work the best w/ the F4 and it should only go on the 2.8. True? So, is my other option the 1.6x?

Anyone know of better options than the Canon brand or an inexpensive place to find one?

**pechelman** · 05-29-2007, 02:36 PM

"work the best" is very subjective

if all you want is a 400mm focal length, then it works perfect

if you want a FAST 400mm, then yea, not so great, but hey, its only 2 stops, and you're shooting digi, so just bump up the ISO.

**Dromond** · 05-29-2007, 03:11 PM

Like this?

I apologize for that.

**cj001f** · 05-29-2007, 05:12 PM

I'm not a Canon expert buy I believe you'll have AF issues >f5.6. That means the largest TC you can use is the 1.4x.

If you can't try out a TC locally, order from B&H - they'll allow you to return it if you aren't optically satisfied (put it on a tripod, compare before and after of something like a sign)

**Conundrum** · 05-29-2007, 06:04 PM

Originally Posted by Dromond

Like this?

I apologize for that.

I've already done that

**summit** · 05-29-2007, 06:21 PM

Your AF will fail at anything slower than 5.6 unless you have a fancier camera like an EOS 3 or an EOS 1 which have center AF sensors that can work out to f/8.

You should purchase a Canon EF Extender 1.4X (you don't have to get the II version since your camera doesn't have weather sealing)

**haydukelives** · 05-29-2007, 07:23 PM

the 2x isnt very good anyway even with the 2.8 L so stick with 1.4 or try a sigma 400 5.6 fixed

**Conundrum** · 05-29-2007, 07:25 PM

I pulled the 1.6 number out of my... 1.4 was what I was thinking. Good info Summit, just what I was looking for.

**dipstik** · 05-29-2007, 09:53 PM

http://www.the-digital-picture.com/R...er-Review.aspx

**smalls** · 05-29-2007, 10:25 PM

Originally Posted by digitalpicture.com

Some people are reporting that the pins on the extender can be covered with tape to trick the camera into autofocusing. I doubt Canon condones this - I have not tried it.

what are the potential negative consequences of this taping?

**cj001f** · 05-29-2007, 10:32 PM

The same as if you used a lens without the pins.

**summit** · 05-29-2007, 10:45 PM

consequence: poor AF accuracy...

**smalls** · 05-29-2007, 10:47 PM

m'kay.

so with my 20D, only the center AF point would be usable. however, i often use the AF to get in the ballpark, then flick to MF to dial it in (and for prefocusing). so i could feasibly do the same thing with the TC even at the widest aperture (on a 70-200/2.8)?

**cj001f** · 05-29-2007, 10:50 PM

Originally Posted by smalls

TC even at the widest aperture (on a 70-200/2.8)?

A 2x TC on an f2.8 lens would give you a max aperture of f5.6.... which wouldn't require taping anything.

lower than f5.6 it won't be as accurate (as Summit said) and it will hunt more

**Tippster** · 05-30-2007, 09:58 AM

Originally Posted by Summit

consequence: poor AF accuracy...

...but chuck it into manual focus and it won't mess with it, maybe. Unless you're shooting fast action stuff Autofocus is a crutch... kinda like shooting everything on Program....

**anotherVTskibum** · 05-30-2007, 01:53 PM

I was under the impression that the Kenko 1.4 Pro/Tamron 1.4 SP teleconverters would omit the aperture change info when talking to the body, thereby allowing your AF to try to work at higher aperture than those it's supposed to work at. The catch is more hunting, just like using a slower, crappier zoom lens, because it's that much harder for the AF to find a high-contrast area to focus on.

(FWIW, I intend to buy one of those two--most sources indicate that they're functionally identical--when resources allow, as they seem to be compatible with a greater range of lenses than the Canon 1.4).

**smalls** · 05-30-2007, 02:14 PM

Originally Posted by anotherVTskibum

(FWIW, I intend to buy one of those two--most sources indicate that they're functionally identical--when resources allow, as they seem to be compatible with a greater range of lenses than the Canon 1.4).

that may be, however i have some issues with my images having to go from L glass and then pass through a kenko/tamron TC. it seems somewhat conterintuitive. am i off base?

**cj001f** · 05-30-2007, 02:24 PM

why not try them and see? the tamron pro is pretty good. the tamron pro and kenko pro 300 are identical just different badging/coloring I believe.

**anotherVTskibum** · 05-30-2007, 07:28 PM

Originally Posted by smalls

that may be, however i have some issues with my images having to go from L glass and then pass through a kenko/tamron TC. it seems somewhat conterintuitive. am i off base?

You're going to loose quality either way; the anecdotal evidence I've seen on various forums led me to believe that the quality difference with a 1.4x converter from either source (Canon or Kenko/Tamron) would be barely perceptible except when pixel-peeping. For me, the ability to use the 1.4x on a greater variety of lenses--particularly non-Canon lenses--trumps a small difference in quality. The price difference doesn't hurt the equation in my book, either.

**summit** · 05-31-2007, 09:58 PM

The Canon 1.4x is reputed to be second to none...

Personally, I didn't buy the 1.4x because the small extra reach didn't seem worth the hassle. If I was going for a 1.4x I'd go for the Canon, but I went for a 2x which I felt was more usefull. Then again, I was applying it to a f/2.8 and it only works with 1 lens that I own.

I use a Sigma 2x EX tc. I find it's quality tradeoff well worth it when the extra reach is called for on my 70-200 2.8 L. Then again, I now officially hate Sigma for their customer service attitude. I am just now experiencing some AF issues at certain focal lengths (after having it for 5 or 6 years). I think it is an electronic problem.

Originally Posted by Tippster

...but chuck it into manual focus and it won't mess with it, maybe. Unless you're shooting fast action stuff Autofocus is a crutch... kinda like shooting everything on Program....

I'd tell you that calling AF a crutch on a 1.6x camera without interchangable ground glass is a great exaggeration. Ever try to MF an f/4 lens on a Canon digital rebel? It is a real challenge!

I used MF a lot more on my EOS-3 (and I replaced the ground glass in it) or even my older Elan II (EOS-50) and A2 (EOS-5) than I do on my 20D, even for non-action.

I still MF when it is called for or necessary (even in action). This is why virtually all of my lenses are FTM. It is not rare by any means for me to use MF, but frankly the AF on a 2.8 or 1.4 lens is often more reliable than my Mk 1 Mod 0 eyeball through a 1.6x viewfinder with ground glass that is optimized for brightness, not manual focusing. (MINIMUM 1/3 the DoF range for whatever CoC they are using).

PS I am in full manual exposure mode and and using the "spot" meter for 99%+ of all my exposures (including action). I originally learned SLRs on a Canon FTb, which was manual focus and exposure (needle match). I used to shoot 4x5 and only stopped when I lost darkroom access. I am not "lazy."

AF is NOT a crutch for most APS-C shooters (Canon at least if not all others).

**Tippster** · 05-31-2007, 10:20 PM

What? I couldn't hear you?

Auto Focus
Auto Iris
Auto Exposure
Auto Think

If it's good enough ... it's good enough, I guess. Now hand me a cocktail.

**summit** · 05-31-2007, 11:08 PM

Originally Posted by Tippster

I'm not going to read what your wrote. Instead, I'll thoughtlessly repeat the mantra from some photo teacher who thinks "medium format" first if they see "MF"

OK... then again I usually think "medium format" first

I am amused that you think aperture auto-stopdown on exposure is a crutch. Many would also say that zoom lenses are a crutch (and I used to think so until I got into the mountains).

**Tippster** · 06-01-2007, 05:59 AM

I was under the impression that the 20D is not a Rebel. I guess I'm wrong and you are right... again. Poor Truth, taking such pretty pix with such a shitty camera.

Smalls: My point was it CAN be done, not that it has to be done.

**summit** · 06-01-2007, 09:31 AM

Originally Posted by Tippster

Smalls: My point was it CAN be done, not that it has to be done.

I agree

Originally Posted by Tippster

I was under the impression that the 20D is not a Rebel.

It is not, and while there is a minor improvement in the VF quality, it is still much harder (not impossible) to use, especially for effective MF, especially compared to a FF camera like a 1D, 5D, or a decent film body.

That's all

PS, if you still missed it, I agree with you and support people learning to use full manual exposure for almost everything.

**anotherVTskibum** · 06-02-2007, 07:40 AM

There are split-screen prism screens available for the 20D; just because Canon doesn't claim that the screens are user-serviceable doesn't make it true. I've got a Haoda screen in mine, and it makes life much easier when trying to manual focus (more light through the viewfinder would help, too). I highly recommend it for anyone who's less of a clutz than I am and can manage to install it without scratching it.