EF lenses that can be used with extenders

[peter_szwed]

I am looking to purchase a telephoto zoom and an extender to use with

my EOS 3. I am trying to keep my EOS system down to two lenses and an

extender for some extra reach. I think Canons chart for their

extenders may be out of date. Does the EF 70-300 DO work with Canons

EF extenders? What are the drawbacks? What other lenses will work with

EF extenders? Thanks, Pete.

[steve_dunn2]

<p>No, it does not. Officially, only a subset of L lenses work with Canon's TCs: all L telephoto primes 135mm or longer, the 100-400, and all three 70-200 zooms. Unofficially, there are a few other lenses which work, including at least some of the tilt/shift lenses.</p>

 

<p>Few of the non-L zooms are physically compatible with the TCs; both the current and previous models of both the 1.4x and 2x have protruding front elements, and most non-L zooms don't have room for the TC's front element. Even those which do often have issues; for example, my 1.4x will fit into the rear of my 28-135 if the lens is zoomed out towards its long end, but if you were to try that and then zoom towards the wide end without first removing the TC, you'd end up hearing two pieces of glass colliding, and that wouldn't be a good thing.</p>

 

<p>Looking at a block diagram of the 70-300 DO, there clearly isn't room for a TC with the lens at its 70mm setting; I don't have a block diagram of it at 300mm so I don't know if the TC will fit. But you really don't want to get into a situation where an accidental turn of the zoom ring will make the rear element of your lens smash into the front element of the TC. Some third-party TCs also have protruding front elements, and won't fit this lens; some do not, and will fit on any lens. It's debatable whether you'd want to add a TC to this lens anyway; <a href="http://www.photo.net/photo/nature/telezoom_tc.html">telephoto zooms and TCs generally make for poor results</a> unless the zoom is of very high quality.</p>

 

<p>Drawbacks of using teleconverters are that the lens becomes slower and the optics get degraded, more so with a 2x than with a 1.4x. Even a high-quality 2x like Canon's one can't help but cause a reduction in sharpness, and not all TCs are high quality. As is usually the case with lenses, the saying "you get what you pay for" isn't 100% accurate but it's mostly true.</p>

[steve_dunn2]

<p>One other drawback, which is a consequence of the lens becoming slower: you should expect AF performance to be hampered. The body won't know there's a TC there*, so it will try to focus with all 45 points, but since your lens will be slower than the f/5.6 which 44 of those points are designed to require, you may find that they either don't work at all or are erratic. The central AF point is good to f/8, which would be what you'd get with a 1.4x TC; with a 2x TC, your lens will be f/11, and even the central AF point will probably have problems. I don't have an EOS 3 so I don't know how much margin there is around the f/5.6 and f/8 limits; I know that my Elan 7E was generally unable to acquire focus with an f/8 lens and that my EOS 20D's AF, while somewhat better, is still pretty unreliable at f/8 (both of these bodies are designed to require f/5.6 or faster for AF).</p>

 

<p>*: The officially-compatible lenses have extra pins on them which communicate with genuine Canon TCs, so that the lens is aware of the presence of the TC. It can then tell the body its focal length and aperture, as adjusted by the TC. The non-compatible lenses lack these extra pins, as do many (all?) third-party TCs, so neither the lens nor the body will know about the TC. The body will still think you have a 70-300/4.5-5.6, even though what you have would be longer and slower.</p>

[akajohndoe]

Practically every one of the EF lenses can ce used with the tele-extenders if a 12mm extension tube is placed between the lens and the extender.

 

Yes, this does make infinity focus impossible (in most cases). Yes, a tele-extender does reduce the "speed" of the lens (with or without the extension tube).

 

Would this work in every situation? Of course not. But good info nonetheless.

[peter_szwed]

Thanks for the input. I guess I will have to go with the 100-400 IS lens. I know I can extend that if I need to. 1.4x will give me better then f8 at 560mm. Maybe the new 24-105 f4 L as a second lens. I like the flexibility the EOS 3 gives me. But, until I can afford the new lenses, I'll have to use an F or A series Canon and FD lenses. I like to manual focus a lot of my shots anyway and I have glass from 20mm to 300mm. Almost sounds like sour grapes.