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Nope, focusing distance stays the same. This can be quite an advantage although I personally am not happy with the 2x on digital. Strange, as it worked well on my film camera. The 1.4 is awesome.

Piper

I have to disagree with you, I have a 2 x converter on my digital camera and the results are perfect, you sometimes need to ajust apeture a few stops but that is logical as a converter makes you loose some light, depending on what converter you use and how big the apeture is, I guess a 2 x will work with some digitals and not so good with others, but it works perfectly with leica.

Thanks for that, Mars123.

Best thing I guess is to really test it before buying if possible. To do this I put mine on a tripod with a 300 2.8 L lens set at F8 and used a remote release cable. The results on my Canon 5D were soft compared to the 1.4 and after worrying about this for a while, I checked out a few well known Photography forums and found other guys were finding the same thing. It probably depends on quite a few factors, but I would hesitate to recommend using the 2x very much. Also it seems to me that it would be better to shoot without it and then crop the sharper image later.

This is an example of the Canon 500mm with 1.4x convertor. If everything (focus, exposure, good light etc) is just right you can get superb results.

Richard

http://www.pbase.com/richardharris/june_2006

hi everyone, i was wondering if anyone could give me some advice on buying a 2x teleconverter for my pentax DSLR??

If anyone has a converter could you please tell me if it in any way has decreased your image quality?
I am not a proffesional photographer but i do like sharp, clear images, especially for taking pics in my favourite place!!

hi odessy - and welcome to the forum!

The issue of 2X converters is a contentious one and you will probably get different answers from different people.
I've used 2X converters in the past with mixed results. I think it depends on the lens you use it with.

On my old Nikon D70 and a Sigma 70-200 F2.8 I had fair results with a Sigma 2X. Wide open was not acceptable to me, but stopped down it was acceptable (though not superb). I used it when necessary, because it still gave more detail than up sizing in photoshop.

I just recently got the Canon 1.4X and 2X converters, I have not done major testing with them, but my first impression is that the 1.4X is slightly sharper than the 2X. The other thing that I have noticed is that both converters perform better (less degrading) when used with high quality prime lenses.

The other factors that you must take into consideration is the loss of light. A 2X converter cost you 2 stop - an f/2.8 lens becomes f/5.6 wide open. This, together with the longer reach, essentially requires you to us 1/4 X the shutter speed than without the converter. e.g if you could use 1/500 sec with your lens wide open, you will need 1/2000 sec with the converter to compensate for camera shake and exposure. This can be done these days by increasing the ISO - but at the cost of noise.

Another important factor is that you may lose the ability to autofocus when you add the 2X converter. I'm not sure about the Pentax, but I have a feeling that it will not autofocus with anything higher than F/5.6.

Overall the 1.4X converters give better image quality and will more easily retain autofocus.

Note to mods - this thread may be more suited to the photography forum.

I concur completely. The problem with converters is that they also magnify the flaws in the lens used. Aside from autofocus, I will never use a 2x converter on my 100-400, unless it's just to identify a bird. But I have seem photos Madach made with a 2x on his 300mm f/2.8 and you really have to look well to see the difference.

However, I do not know what the quality of the converters available for Pentax is like...

Thanks for the help, ill think ill just stick to what i have for now and get a sigma 170-500mm or 50-500mm when i have the money!
one other question:
What lens do you use most frequently while in kruger?? i have a 70-300 mm at the moment but sometimes its just not enough for what i want..

Same as many forumites, the Canon 100-400. The versatility of that lens is great for Kruger where you can have animals very close or a long way off.

About teleconverters, for birds your range is nearly never enough, so I nearly always have the Tamron1.4X on my Canon 400 lens. In the Kruger we found the 70-300DO worked well, but the 400x1.4 was even better.
I have now got myself a Tamron 2x converter, and am a little disappointed, like Texasboer say's image quality is a little degraded, one hardly notices the degradation on the
1.4, but on the 2x I think you can see it. Another disadvantage with the 2x is that autofocus doesn't work very well. Even so I still use the 2x converter, and I've got some good photos with it.
An interesting trick you can do with converters is to stack them, and if I put on both converters I get a focal length corresponding to 1800mm. No autofocus of course
but still (with luck) you can get photos of far-off birds that are fine for an id. and much better than nothing.
I hope to try out the new 2X converter in SA this February. I have some examples of 1.4X , 2X and 1.4+2X from Iceland this summer, I presume I can't post these here but perhaps I can do a set in flickr, and a link?
/Neil

If you have a Canon system and lenses then it makes sense to spend a little more and get the Canon 1.4 convertor. I use the Nikon pro wildlife system and have a 1.4 x convertor which literally lives on my 70-200 f2.8 Nikkor lens ..there is no degradation of Image Quality to this sharpest lens I have ever owned. Luckily Nikon is unique in having a marvellous 1.7x convertor where you only loose 1.5 stops and also no image degradation. I hardly use this convertor and its only use is really to go on the 200-400f4 lens for 680mm f6.3 once in awhile because I am a great believer in getting close to your subject and then closer still. Even with Nikon's superior optics I dont have a 2x convertor as all 2x convertors degrade ..some more than others but I guess its second prize if your system hasnt got a 1.7x and no doubt if I had Brand x I would probably get a same brand 2x convertor never 3rd party as you want as high image quality as possible

Peter, Usually you would be correct, but there is a special case with the canon 400L f5.6. Because it's a f5.6 aperture lens the camera will try and switch off autofocus with a canon teleconverter, there is a rule in the software
that says's autofocus will only work on a lens that is f4.0 or better. The trick with the cheap Tamron is that it doesn't report it's presence to the camera, so the camera will try and do autofocus anyway, and in fact it succeeds really well. So that is the reason to accept the Tamrons marginal drop in image quality for the sake of keeping autofocus. And yes it does sometimes dither around while trying to focus, but if there is a clear sky behind it's still very good.
/Neil

You are correct Neil any lens slower than F4 will not focus AF with a convertor . Secret is to have F4 or faster but in Canon's case the 400 f5.6 is their best 400 any f stop IQ wise it seems..my mates who use this lens get incredibly sharp images and its small and light as well...but they get around AF by taping something (a pin??? I am not technical) and that seems to work

I think I may qualify as one of Pete's "mates" who use the Canon 400 and I occasionally use a 1.4 TC with the third pin taped which causes it to try and auto-focus but I find that manual focussing works better when the TC is attached.

Taping it off is no use at all. I tried it on my 100-400, and not only was the lens hunting like an oscilloscope, very often the focus is not right. (Off by a mile in some cases.)

And there is no trouble with a f/5.6 lens and 1.4 TC combo. I'll have AF no problem whatsoever! At least, as long as I use my EOS 3. The 1D and EOS 3 will AF up to f/8....