2 x Convertors

[Kev_EJ]

Hi all

I have a Canon 450d with a Canon 70-300 IS USM zoom lens and was wondering if any convertors will work with it. I have looked at the Canon EF convertors but they only seem to support Canon L lenses. Also if they are available would i still be able to use the image stabiliser
Thanks
Kev

[GeoffR]

There are converters that will produce an image at the sensor plane, in fact any Canon fit converter will do that. However, using a converter with what I suspect is a 70-300 f4-f5.6 lens will not be a pleasant or particularly fulfilling experience.

The camera will not auto focus with lenses slower than f5.6, adding a 2x converter will make the effective aperture f11 (a loss of two stops). As discussed elsewhere, focusing manually on a DSLR is difficult at the best of times but with an f11 lens it will be even harder. Finally, unless you have a fully compatible converter, which transfers the electrical signals between camera and lens, you may lose the ability to change the aperture.

Converters only work really well with fast lenses, so a 1.4 x converter on a 70-200 f2.8 produces good results. There is some image degradation but it is generally worth accepting as the price of getting the shot.

There is no substitute for experience so I suggest you take your camera and lens along to your local camera shop and ask to try some 2x converters. You may be pleasantly surprised.

[Kev_EJ]

Thanks for your info.

i had suspected this would be the case maybe i will have to wait a while.

Regards

Kev

[OneTen]

Yes, the Canon EF 1.4 and 2x converters won't attach to your lens. Even eith excellent L glass you'll see a significant drop in quality with the EF 2x converter but it's neglible with the 1.4x. There are third party converters that will fit but the quslity won't be good and like Geoff says, you'll lose AF capability if that matters to you.

[Dorset_Mike]

There are third party converters that will fit but the quslity won't be good and like Geoff says, you'll lose AF capability if that matters to you.

Don't know about using with Canon, but I have a Kenko 1.4X Teleplus Pro 300 which I use on a Minolta 5D with various lenses, (mostly Tamron) and have no problems with AF, IQ is good too.

[GeoffR]

There is a world of difference between a 1.4x converter and a 2x converter in terms of image quality and light loss.

Where a 1.4x will work really well with a slow lens a 2x may well just mot be able to produce acceptable results. Personally I wouldn't use a converter on a lens slower than f2.8. Obviously that option isn't open to every body so if you need the reach, as I said above, give it a try but I think the results are going to be a disappointment.

[beejaybee]

There is a world of difference between a 1.4x converter and a 2x converter in terms of image quality and light loss.

Obviously the "light loss" is an issue (actually you're just spreading the same amount of light over a bigger area) but people keep saying that 2x converters seriously compromise image quality & it's not always true. The mk II Canon 2x tele-extender actually works very well with the lenses it was designed to be used with. Here's an image made with the mk II 2x tele-extender used with the 400mm f/2.8 L IS lens. At full aperture.

[Benchista]

Yup, the weakness of the 2x is much overstated. Even the Mk I Canon 2x is actually pretty capable - I use mine mostly with the 200mm f2.8L and 300mm f4 L. The former becomes a pretty capable and ever so compact 400mm f5.6, the latter is still capable of decent optical quality, although it's out of AF land on my DSLRs. In both cases, it's better than cropping, and technical deficiencies are a lot less visible than camera shake without a decent support.

[OneTen]

Interesting. My 200mm f/2.8 II with 2x II converter combination was awful, not very sharp with very ugly bokeh, it was a noticeable change. Even the 400mm f/5.6 with 2x dropped below a level I was happy with, so I sold the 2x. The 1.4x on the other hand, any drop in quality isn't noticeable in real-life situations even if they do show on a test bench.

[beejaybee]

A tele-extender doesn't have any effect on bokeh, apart from making the "donuts" bigger in proportion to the rest of the image. If you're getting consistently soft images from a lens when using a extender, I wonder if the lens is registered correctly ... on my cameras (5D and 40D) which do not have microfocus adjustment, I get consistently better results focusing manually (using the type S screen and a magnifying angle viewer), with all lenses I've tried except the 24-105 f/4L IS which came with the 5D, the 70-200 f/4L IS which seems to be pretty bombproof, and the Sigma 17-70 f/2.8-4.5 which lives on the 40D when I'm using it as a walkaround camera. My conclusion is that the tolerance allowed in the design and/or construction of the lenses is too much for the autofocus mechanism to cope with properly, at any rate on those cameras that do not have microfocus adjustment. The basic point being that adding an extender gives an extra place for tolerance to be exceeded, as well as doubling the precision necessary for an auto-focussed shot to be as sharp as the lens is capable of.

[GeoffR]

Yup, the weakness of the 2x is much overstated. Even the Mk I Canon 2x is actually pretty capable - I use mine mostly with the 200mm f2.8L and 300mm f4 L. The former becomes a pretty capable and ever so compact 400mm f5.6, the latter is still capable of decent optical quality, although it's out of AF land on my DSLRs. In both cases, it's better than cropping, and technical deficiencies are a lot less visible than camera shake without a decent support.

Where matched converters and those designed for very specific lenses are concerned I whole heartedly agree. However where general converters are concerned the quality is somewhat hit and miss. More accurately the quality produced by the combination of lens and converter can be hit and miss. Some of the converters will be of excellent quality but just not match a specific lens particularly well. So the OPs question, which concerned a 70-300 zoom, really does deserve an answer that contains detail relevant to that lens.

As I said, I wouldn't use a converter on such a lens. 35 years ago I might have but then again I would have been using MF lenses with film where the bigger viewfinder and built in focusing aids would have made it more practical. Though no less prone to camera shake.

Any converter that will fit the OP's lens will be from an independent manufacturer and thus not matched to the lens. A trial might show really good results, but it may not, which is why I suggested taking the camera and lens to a good camera shop and trying what ever they have in stock.