[GSVJase]

I've tried reading on the web about these and have confused myself even more

What I want to do is get a new lens that will take me up to 300mm. I would also like to know if the 1.4 and 2x convertors in effect multiply the whole range of a 70-300 lense. For arguments sake a 70-300 sigma lens on a 300D become a 140 - 600 by using a 2x convertor? Or are there any limitations with types of lenses that the canon convertor will be compatible with?

Although I'd love a nice 600mm lens I think the wife would kill me if I even suggested paying that sort of money!!!

[Liberalis]

I think you loose one stop on a 1.4, and 2 stops on a x2, and there is some issues with AF at some point but I forget where.

If the 300D is the same as the 10D .... a 70 - 300mm lens is actually a 112 - 480mm, so with a x2 Extension, you'll have a 224mm - 960mm lens in theory!

I could be talking out my butt, I do that at times, lol

[MyPix]

you are perfectly correct young sir,
the idea is u multiply the magnification on a normal 35mm film lens ( which will work on your particular camera ) by 1.6, this gives the actual lens power for the size of the sensor in your camera ( which is smaller than 35mm format )

i just got a 70-300G lens for my Nikon, that gives me 112 - 480, which is a very powerfull lens, with a 2x converter this will double the power to 960, which would ba almost impossible to hold still without the aid of a tripod,

be warned tho, the more glass u have in front of the sensor the less light will reach it, so puting up exposure times and slowing Fstops ( less light ) by a lot,
so get the best quality you can afford

MyPix

[Steve]

What has been said above is correct, with a 1.4x converter you’ll loose 1 full stop and with a 2x converter you loose 2 stops. Auto focus is slightly different, if you use a Canon converter with a recommended Canon lens and you have enough light (read contrast) AF will function correctly. However if you use the Canon with a Canon lens that’s is slower (has a higher f stop than f4 for the 2x) they say AF wont work, but there is a small work around to activate it. By taping up three of the 10 contacts on the converter it allows correct communication and fools the camera and lens to thinking AF should still function. Obviously it all still depends on the available light.

Tele converters from other manufactures are a little more of a tricky area, the Canon ones are expensive but of excellent quality. Third party offerings can be found at a fraction of the cost and if you know what to get it’s a very good area to save some pennies. Look out for the Tamron converters which are supposed to be good, or better still are the Kenko pro 300 converters. I have the latter in a 1.4x version and have shot side by side with the canon 1.4x and returned almost un-distinguishable results. The best bit of it is that if you are willing to buy from eBay it can be had for about £90 which is a massive saving over the price of the Canon. Even if you prefer to buy from a UK retailer, they can be had for about £139 (try warehouse express) BTW I have read that the glass in the Kenko is actually made by Hoya, although I cant actually confirm that myself.

[silkstone]

Just a word of caution... A 300mm lens is a 300mm lens whatever camera you fit it to. On an APS-C format camera like the 300D etc, the sensor is smaller than a 35mm frame. A standard lens throws an image circle large enough for a 35mm frame, but on the 300D the outer part of this circle is wasted because of the smaller sensor. The effect is an enforced crop which gives the appearance of greater magnification relative to the frame size. The same lens fitted to a full frame camera would give the same 'magnification', but you would get more in the viewfinder and in the actual photo.

Regarding teleconverters, whether they will still allow AF with a particular lens depends on the maximum aperture of the lens and the number of pins/contacts on the lens. Most Canon lenses have 7 pins, but some (especially L-Series) have 10. For 7-pin lenses, a 1.4x TC should be OK with lenses that have a maximum aperture of f/5.6 and faster. A 2x TC should work with f/4 and faster. For the 10-pin lenses, the required apertures are f/4 and f/2.8 respectively.

As already mentioned, a 1.4x TC has the effect of reducing the maximum aperture by 1 stop, and a 2x by 2 stops. This can be important because, even if AF still theoretically works, it may struggle in low light at a max effective aperture of f/8.

Hope that all makes sense! The TC info applies to a Kenko Pro300, and also I believe to Canon's own TCs which are much dearer and allegedly no better.

EDIT/ I was writing this while Steve posted his - so I hope we've both said the same.

[MyPix]

the wise man above is correct,
i didnt make myself clear when stating the power of a lens on a digital camera, it is an efective power on the sensor as stated,
300 is still a 300 ( but we all know what i mean 8) )

MyPix

[Matt]

The Canon Tele converters only work with the 'L' series lenses.

I have used the 1.4x with the 100-400L on the 10D. At the short end of the lens you get full autofocus, as the lens is at f5.6 (this is the maximum f-stop you can use auto on TC's with the 10D). At the long end you need to use manual focus.
I have tried the tape senario and it does work if you have enough light, but once the light drops the lens will start to hunt.

If you wish to take the third party root Tamron and Kenko both make their own Tele Converters (I'm lead to believe they actually come from the same factory).
The Pro versions are the only ones you should consider as the glass is of higher quality, and will help reduce cromatic aberation.







The above TC's are autofocus compatible, and should work with most canon lenses.
If anyone is looking for a TC for a Nikon lens please check that it is compatible, as Nikon use different mounts on their lens range.