Kenko pro 300 DGX

Bigfatmole

Senior Member
Has anyone tried the Kenco pro 300 DGX x 1.4 on the tamron 150-600 ..

im not sure if it will AF on a D610 or D750

im happy for a slight loss in image Quality but not too much lol

ive found some short eared Owls n could do with just a tad more reach :(
 
Last edited:

Fred Kingston

Senior Member
If will autofocus on lenses that have a max aperture of F4 or less... The Tamron starts at F5 on the low end... chances are, it won't autofocus the Tamron unless you're at the low end 150mm and the sun is blinding out...
 

BeerBelly

Senior Member
Not really true with the above post. The newer bodies have the ability to focus down to f8. From my own personal experience I can say that the D750 will AF with the 150-600 Tamron and the Kenko 300. I tried it and it acquired focus quite decisively. Don't really have any samples with it to show though, but the IQ does degrade a bit.
 

J-see

Senior Member
Not really true with the above post. The newer bodies have the ability to focus down to f8. From my own personal experience I can say that the D750 will AF with the 150-600 Tamron and the Kenko 300. I tried it and it acquired focus quite decisively. Don't really have any samples with it to show though, but the IQ does degrade a bit.

Focus down to f/8 does require including the loss the TC adds. On the D750 I tried the TC2.0 + 70-300mm and it hunts. Nikon mentions f/4 or lower for TCs. It might work at the short end of the Tam when there's enough light but it's doubtful it does anything at the long end.

You'd require f/11 anyways to get decent shots in regards to sharpness.
 
Last edited:

BeerBelly

Senior Member
Focus down to f/8 does require including the loss the TC adds. On the D750 I tried the TC2.0 + 70-300mm and it hunts. Nikon mentions f/4 or lower for TCs. It might work at the short end of the Tam when there's enough light but it's doubtful it does anything at the long end.

You'd require f/11 anyways to get decent shots in regards to sharpness.

I'm aware of the fact you need to include the TC loss in the calculations. I'm also aware of the fact I tried it and it works...Often these long zooms (like the 150-600 or the older 150-500 from Sigma) represent their wide open aparature to the body as f5.6 instead of f6.3 to allow AF on older bodies that do not focus down to f8. This is also the reason AF works with the TC, since 1.4 x 5.6 is f8. The reason why your 2x TC didn't work is because it is a 2x TC...the arithmetic here is f5.6 x 2, getting a number of f11.2 (too low to AF).

Stopping down to achieving sharpness doesn't come into play, since the lens always focuses wide open (to let in the most light possible) and stops down only to take the shot.
 

mikew_RIP

Senior Member
I have read a few bits in different places saying in decent light the Tamron will still auto focus on bodies with f8 capability with a 1.4,not tried it though as i dont have a converter,i borrowed a sigma 1.4 to try with my sigma 120-400 on the D7000 and it would not but i think it was a f5.6 body.
Just remembered some one on here has tried it cant remember who though.
 

J-see

Senior Member
I know I can only get the 70-300mm going at the shortest end IF there is enough light. Else even that doesn't work and she keeps hunting. Manually to get a sharp shot, I need to push it to f/11 at the long end. It's with the TC2.0 but it gives an idea what will be required for the Tam.

The Tam only starts getting sharp at f/6.3 and very good between 7 and 9. If I'd add a TC to that, even if a 1.4, I'd need a whole lot of light, not to mention a very fast shutter. 600*1.4*1.5 for a DX or 600*1.4 for an FX. Minimum.

Tripod maybe it would work reasonable well but for handheld shooting you'd need close to perfect conditions. I know I gave up using the TC on the 70-300mm because my ratio of good shots was depressingly low handheld and that was only at 600mm.
 
Last edited:
Top