So I did it...

Finally I bought a Kenko 300 dg pro 1.4x . Everybody told me it was a waist of money, but I had to test it myself. Today , in the best situation (I mean good light), I attached it to my nikkor 80-400 VR, and shot this handheld ( in 560 mm ). I could use the VR, and the AF
I have to say I expected worst resuts..., but at least in this conditions, it's not that bad.... (50% crop)

http://farm4.static.flickr.com/3550/...14f2ee76_o.jpg

<table id="Inbox" cellspacing="0" width="100%"><tbody><tr><td style="font-size: 120%;" width="30%">Cámara:</td> <td style="font-size: 120%;">Nikon D300</td> </tr> <tr> <td style="font-size: 120%;" width="30%">Exposición:</td> <td style="font-size: 120%;">0,001 sec (1/800)</td> </tr> <tr> <td style="font-size: 120%;" width="30%">Aperture:</td> <td style="font-size: 120%;">f/6.3</td> </tr> <tr> <td style="font-size: 120%;" width="30%">Lente:</td> <td style="font-size: 120%;">560 mm</td> </tr> <tr> <td>Velocidad ISO:</td> <td>360</td> </tr> <tr> <td>Tendencia de exposición:</td> <td>0 EV</td> </tr> <tr> <td>Flash:</td> <td>No Flash</td></tr></tbody></table>

I like the pose, eye contact and eye contact. I don't know if it is due to the TC but there seems to be a lack of fine detail in the plumage and would clone out the dark patch in the upper right.

Jose, Nice pose and composition-Congrats on your new purchase!does look a bit soft.

Not bad Jose at all. But since it is a 50% crop according to you, could the softness be attributed to the fact that you may have placed an AF sensor on those flowers? They do seem much sharper than your bird to me. Well done anyway, and practice makes you only better anyway. Look forward to your next image.

Composition of the bird here seems too centered. And also I agree the bird is softer than the front part of the plant. Good effort and with the Kenko 1.4 on the 80-400 lens not bad!

Thanks for your comments. After yesterday and today's tests, I can see this solution is not compatible with quality in most of situations. So I will not use it anymore on my main setting, but I will keep it as a lightweight solution to use on my d40 + nikkor 55-200 VR (wich is gonna be always on my car, as maybe....)