Tele convertor

With the air show comming along in July I was thinking of purchasing a tele converter, can someone recomend a useful one as I have no idea what the market is. Also any experience positive or negative re there use. If also anyone has a photo or two with he use of a converter that would be helpful as well.
Ian

Which lens?

The Kenko 1.5x or Tamron 1.4x would be my choice besides the Pentax 1.7 since they work with SDM. Here in the Netherlands only the Kenko is avaible the Tamrons are hard to come by but they are same in design and quality by the looks of it.

Edit: yes which lens is also smart to ask

The lens I have is the Tamron 70/300.
Ian

Personally I wouldn't be using a teleconverter at all unless the lens is f4 or faster but if you must then the Tamron 1.4x or Kenko 1.5x would be your best bet.
You would probably be better using the Tamron and cropping hard.

Thanks Guys Mike Im just wondering if the focal length will be enough as the aircraft are quite a distance from the shaw. My lens is a f4.5.
Ian

Just thought of another question, will the auto focus work through out the full range of the lens.
Ian

Your lens is f4.5 at the short end though isn't it?
What is it at 300mm?

On the box it has Tamron 70-300 F/4-5.6 Di LD Macro so Im thinking 5.6 at 300mm Mike.
Ian

I have the Kenko 1.5 on my Tamron 70-300 permanently only problem it hunts a bit trying to focus in poor light but apart from that I am very happy with it, it is fully automatic with all AF lenses.

I went looking for a photo you can see it here link

Well that's the UK out then

Looks like the Kenko then Ian as the Tamron is nigh on impossible to find and expensive when you do.
I seem to remember someone selling one in the for sale section a few days ago.

Thanks again Mike for your help, Jack thanks for the link to the photo does the autofocus work throught the focal range ?.
Ian

KENKO AF 1.5x Super High Quality Teleplus converter also has genuine Gated Array IC and is compact for light weight and easy handling. Full AF is capable with lenses having a maximum aperture of F/4.5 or brighter. (Manual focusing will be required with lenses of smaller aperture.)

Looks like a no go as the AF will only work correctly at F/4.5 which limits the focal length to around 70mm plus what extra is gained with the converter on the lens.
Ian

Maybe not, look at the Exif in Jacks pic and it says 450mm

It still depends on the light you have and the subject you try to focus on, if it has a lot of contrast it will focus easier but still suspect it will hunt alot.
Maybe you can focus first at the widest range and then zoom in, sometimes it helps if the focus is already very close. In bad light I mostly help the lens to bring the focus very close and let the AF do the fime adjustimg, it works better sometimes.