tele converters

[nickt]

Does anyone have any experience using teleconverters. Can they be used on zoom lenses or just prime lenses? If they cam be used on zoom lenses, I was thinking of using a x2 on my Nikon 70-300mm. Do the apertures remain the same? ie; when the 70mm end becomes 140mm, does it have an f/3.5? Conversly when the 300mm end becomes 600mm, does the aperture remain at f/5.6. I would imagine you'd have to allow for a couple of stops of light. Thanks in advance.
Nick 

[Mick]

Hi Nick,

I don't have any tele converters myself, but I believe you'll lose one stop with a 1.4x tele, and 2 stops with a 2x tele.   They can be used on zoom lenses / prime lenses /and even macro lenses.

Most people seem to go for a 1.4x tele so it doesn't impact the image quality and speed.  Also I believe that some of the longer lenses won't autofocus with a 2x. (not sure what combination this applies to though).

As I said, I don't use them, but I dare say someone will come along and advise. 

[bones615]

Hi Nick

I use one on my canon 70-210 f4, cant complain about picture quality but i have never used it in poor light. I think I read somewhere that a x2 doubles the f no. ie my f4 becomes an f8. Its the best way to get a long lens without huge expense but i guess it will magnify any problems within the original lens.
There is a pic in my gallery of an aeroplane taken using a x2 teleplus converter, it was moving at quite some speed, the autofocus kept up but it was in good light.

Simon

[Colin]

You will loose 2 stops with a x2 converter. The theory is that your lens won't auto focus beyond 5.6. In good light it will auto focus as Simon says (and I have found) but if the light starts to fall you will have to manually focus. The other thing to bear in mind is that the optical quality of the converters is generally not as good as that of your lens so it is likely you will loose some image quality.

[nickt]

Thanks for your answers. Oh dear... I don't know what to do. I use the 70-300mm for my son's rugby games and just wanted a little more pull. I usually shoot at the lowest f number for the focal point at iso 400. ISO 800-1600 shouldn't be a problem as I've got a d300 and its not bad at high ISOs. Should I go for the x2 or x1.4? I plan to shoot at Twickenham at the Internationals (albeit I will be in the stands) and that's why I wanted to get the converter. Can't really justify a 400mm lens! I think I might go the shop and try one out at different focal/ISO settings and see what happens.
Thanks again.
Nick

[Oldboy]

Does anyone have any experience using teleconverters. Can they be used on zoom lenses or just prime lenses? If they cam be used on zoom lenses, I was thinking of using a x2 on my Nikon 70-300mm. Do the apertures remain the same? ie; when the 70mm end becomes 140mm, does it have an f/3.5? Conversly when the 300mm end becomes 600mm, does the aperture remain at f/5.6. I would imagine you'd have to allow for a couple of stops of light. Thanks in advance.
Nick  

Sorry, but the Nikon converters won't work on that lens. As a general rule the lens needs to be at least a F4. Check out Nikon's website for what converters work with which lens. I use the Nikon 1.4 and 2x converters on my Nikon 70-200mm F2.8 VR, 300mm F4, 105mm F2.8 Macro and 400mm F2.8. Can't use on my Nikon 60mm F2.8 Macro. Autofocus stops on anything below F6.3 for most cameras and F8 for top cameras. When light levels are low you may struggle to get a decent image unless you can push the ISO to 6,400. In bright light they work well and I'd have had some cracking shots with mine.  
You could use a Kenko converter with that lens, but might not be worth the effort.  

[nickt]

Thanks for that OldBoy. I think I'll knock the converters on the head!
Nick

[bones615]

Nick
Just put a pic of the dog in my album using 2x converter, relativley low light (8pm) autofocus ok at f4.

[nickt]

Nick
Just put a pic of the dog in my album using 2x converter, relativley low light (8pm) autofocus ok at f4.

Bones, that looks quite bright. I might look at the Kenko range.
Nick

[bones615]

Its actually a jessops one (looks identical to the kenko) that I got on ebay for £25, can't lose just resell if its no good.

Simon

[nickt]

Just had a quick look at the Kenko site. They state that AF is only possible at f/4 or faster, as OldBoy said .If I'm using one on the 70-300mm, the max aperture will change from 3.5 to whatever ie will get smaller, especially at 300mm. AF will be quite important as I'll be using it for sports. I think I'll find it difficult to manually focus on a rugby player in full flight! I may go to a shop just to try it and satisfy myself.
Thanks again for your advice.
Nick

[Oldboy]

Nick
Just put a pic of the dog in my album using 2x converter, relativley low light (8pm) autofocus ok at f4.

Your lens is F4, with the converter on it's F8, but the converter doesn't tell the camera this. If you used the Canon extender it would show as F8.