Kenko N-AF 2x Teleplus Pro 300 DGX

[rawill]

I am not sure if I was conned, but while looking at a 500 telephoto lense I was sold the above convertor.

Sadly when using it with my 70-300 the autofocus gets confused when out at max zoom.
It goes in and out of focus.

Did I buy a lemon, and waste my money.

I have got some good shots, as has another person that I loaned it to.
But it is frustrating.

Any comments anyone.

[jeeperman]

If your lens is a 5.6 this may be your issue. This is from the site in the link below...... As there is a loss of two stops with any 2x teleconverter (one stop with a 1.4x teleconverter), Kenko recommends using a lens with a minimum aperture of f/4 (opening of f/4 and bigger, not smaller) to ensure AF will work.

Give me a minute and I will find you a link to info.. http://atinyblip.com/articles/photog...teleconverter/

I realise this was used on a Canon but the principal is the same. Although it can work differently per brand. I do not use one but the Kenko 1.4 is one of the only ones to work with my Sony 4.0-5.6 400mm Even Sony's don't work with it.

[rawill]

Thank you for that.
It seems from the article that I will need to look for a better quality 70-300.
Mine is an Nikon AF Nikkor 70-300, 1:4-5.6G.
Very basic I think.

[jeeperman]

Unfortunately what ever combo you go with the you must not go past a combined f8. This is why your lens focuses ok only patially zoomed out. It remains at F4 until about 135mm or so and starts going up from there, add to that the two stops and you get to f8 quick.
You could go with a 2.8 but they are spendy. You may have better luck returning the 2x and trying a 1.4
If you can afford the 500mm you may be better served and still may be able to use a 1.4

Or you can manual focus what you have now.

[Dave Humphries]

Hi Robin,

I would say this borders on "being conned" if it was;
a) sold to you in a shop by a salesperson
b) that person should have asked what camera body and lens(es) you would use it on and assuming you said the Nikon 70-300mm and D70s
c) they should have advised that combination, AF would be unreliable at longer focal lengths for the reason Paul gave

If you had bought it off the internet, you wouldn't have expected that level of protection and it is buyer beware (i.e. we all need to understand exactly what we're buying, assuming it is accurately described).

If you have all the packaging, it isn't too long after buying and you can visit the store again, I would suggest taking it back for a refund if the above a) - c) were true and makin a noise at a busy time, but only if they are at fault as I describe. If they mentioned it, but you chose to ignore any advice, or didn't fully understand it, that's a different matter.

Good luck,

PS Have you considered a Canon SX50HS?

[rawill]

Hi Dave

Interesting reading, I'd say I was kind of conned!
I was in Hongkong, does that say it all!
I wasn't really looking for a lens, I was just browsing, at a dedicated camera shop.

Anyway refund is out of the question, too long ago, so I will put it down to experience!

I would not have understood the 2 fstop comment even if I was told.
I do now! well a bit anyway.

I also understand that some filters do a similar thing, that is add some f stops, in particular a CPL.
I have a Marumi (a cheap one I imagine, it came with a lens)

[rawill]

Aha, thank you again. I went out this morning with the kenko and 70-300. The light is brighter and on auto the Fstop was about 14, so I set it to A, and worked the lens on zoom in various spots. It seemed to be working, focusing much better.

So I guess that is what you guys and the article have been talking about.

thanks again.

Here is a photo I took with it a few minutes ago.
And a good idea it was too, maybe I have dust on my mirror.!!

[jcuknz]

Just for the record be aware that this problem with f/8 applies to Phase Detection systems. If you have Contrast Detection it is not a problem. My rig is effectively about f/10 and AF snaps into focus just the same as ever.
You will find a CPL cuts down the light by between 1.5 and 2 stops depending on who is writing. One stop equals half the light, two stops a quarter of the light getting through to the sensor.

[rawill]

Hi Robin,

PS Have you considered a Canon SX50HS?

Hi Dave

No I hadn't and probably won't.
BUT!, until I looked up what it was i didn't have a clue.

That is some ZOOM capability.

Good value I think