Lens Performance

I have the RebelXT and am considering upgrading to get better AF performance from my lenses, particularly my 100-400L alone and in combination with the 1.4x TC.

Does anyone know how much of a performance jump I would get moving to the 30D? Would I get AF with the 100-400/TC combo?

How much more could I expect from the 5D?

Are the camera/lens AF speed relationships quantified anywhere on the web?

Thanks,

Carl

I've never used both a RebelXT and 30D so I can't comment on speed increases between them

But you won't get autofocus with the 100-400 TC combo. Type II bodies won't autofocus if the f number is greater than f/5.6. You need a type I body (Like the 1D) for that.

Thanks Jim. I wasn't sure where the cutoff was. I know there are ways of taping the pins to get AF, though I haven't had success trying them.

I'd still be happy with faster AF on the 100-400 by itself though.

Thanks again.

Tape over the 3 left pins (looking at it from the front) and your 100-400 should AF with the XT, but the image quality suffers past 300mm so you actually defeat the purpose of the TC.

no focus with 30D. 1 Series only. You could expect more IQ from the 5D. I do not know about AF, but I would have to say AF would be snappier. 1 series AF is god like.

Canon 100-400 is a f/4-5.6. It means that with a x1,4 TC can work in the lowest focal (100 mm) correctly with normal Canon bodies. Only 1-Series cameras work the AF until f/8. SO, unless you buy a 1-Series camera, you can expect problems with the rest of the bodies.

You can tape the 3 pins, it will be able to work, but the performance (speed) of the AF is going to be decreased drastically and with low or dim light is going to hunt a lot.

Another draw back of the Rebel XT is the ONLY 7 AF points and their sensitivity; so you are not able to track in movement a medium/small target in the distance in AI Servo correctly. The 30D as far as I have read has better perfomance in AF and 9 AF points: So it´s an improvement in that aspect.

Juan Zas wrote in post #2242458
You can tape the 3 pins, it will be able to work, but the performance (speed) of the AF is going to be decreased drastically and with low or dim light is going to hunt a lot.

Not true actually. I have used an XT with 100-400mm and Kenko 300DG Pro with taped pins and the AF is only slightly slower.
It only hunts in very low light.

Thanks for the info, guys. I'll have to try the tape again. The 30D is probably on the horizon for me. If there was a huge difference in AF between it and the 5D then I could possibly convince myself to save up for it.

evandavies wrote in post #2242729
Not true actually. I have used an XT with 100-400mm and Kenko 300DG Pro with taped pins and the AF is only slightly slower.
It only hunts in very low light.

Sorry I forget to mention that this was working in AI servo. With good light there is not problems. For steady shots, the problem is only in very low light conditions, I agree.

Af performance on the 30D will be better than the AF on the XT, but I don't know of any quantifying tests available to show how much the difference is. My guess it won't be a whole lot, but the 20D/30D AF point selection system and layout was a reasonably noticeable performance boost over the 10D.

Beware the Tape trick. Lot's of people advise it, but results are usually poor, and or it doesn't work at all.
Worse case scenario, you burn out a focus motor.
At least take this advise, if it hunts, take the tape off sooner rather than later.

Juan Zas wrote in post #2242458
Canon 100-400 is a f/4-5.6. It means that with a x1,4 TC can work in the lowest focal (100 mm) correctly with normal Canon bodies. Only 1-Series cameras work the AF until f/8. SO, unless you buy a 1-Series camera, you can expect problems with the rest of the bodies.

You can tape the 3 pins, it will be able to work, but the performance (speed) of the AF is going to be decreased drastically and with low or dim light is going to hunt a lot.

Another draw back of the Rebel XT is the ONLY 7 AF points and their sensitivity; so you are not able to track in movement a medium/small target in the distance in AI Servo correctly. The 30D as far as I have read has better perfomance in AF and 9 AF points: So it´s an improvement in that aspect.

The 100-400 is an f/4.5~5.6 lens so even at the widest focal length, you will still lose AF on a non-1D camera when a Canon 1.4x tc is used.

CyberDyneSystems wrote in post #2243282
Af performance on the 30D will be better than the AF on the XT, but I don't know of any quantifying tests available to show how much the difference is. My guess it won't be a whole lot, but the 20D/30D AF point selection system and layout was a reasonably noticeable performance boost over the 10D.

Beware the Tape trick. Lot's of people advise it, but results are usually poor, and or it doesn't work at all.
Worse case scenario, you burn out a focus motor.
At least take this advise, if it hunts, take the tape off sooner rather than later.

With my 350 D the performance is worst due to the fact of an inferior AF system related to the 20D/30D (speaking about to work with the TC taped).

And yes, when you press half shutter and the AF system start with the TC taped bruuummm for one side, bruunnn for the other side, no target lock, I am getting scare and I stop. But I did have this twice in very low light conditions and I was aware about to demage the AF motor.

I did use it in other circunstances (always single shot) with no so bad results. Tipical Moon shot, for example with EF300 f/4 + x2 TC.

SO be careful .....

Thanks Cyber and Juan—very good precautionary advice. I don't think I'll even risk taping ... I'll just buy a blind so I can get closer to my wildlife subjects.

csquared63 wrote in post #2244249
Thanks Cyber and Juan—very good precautionary advice. I don't think I'll even risk taping ... I'll just buy a blind so I can get closer to my wildlife subjects.

Carl,

really is nothing wrong if you know what you are doing. You can use the tape in the TC with good light condition without almost not problem (when you need longer focal, and you go single shot). When light is going down and you feel the combo is starting to hang, just take out the TC and try to continue only with the Tele lens. Just common sense.