noob help a390 teleconverter problem

Hello im just getting into the world of photography, i have a sony a390 and i decided to pick up a 2x teleconverter. I got a quantaray af x2 one made for minolta that has the 8 pin af connecter. Anyways when i put it on my camera along with the 18-55 sony lens that came with the camera it will not take a picture. The af illumator flashes but no pic is taken. The af is working as you can see the lens adjusting in and out. Also just so you know i have both af switches flicked on, (the one on the camera and lens) I spent $70 for the teleconverter so i hope i didnt get burned, any help will be greatly appreciated, thanks !

The 18-55 f/3.5-5.6 becomes an f/7.1-11 with the 2x TC attached. The AF system will not work with an aperture (officially) smaller than f/5.6 so, even though it is trying to AF, it cannot. It may work at the minimum focal distance with the f/7.1??? - Terry

I thought the AF would still find focus, it just needed to be very bright and solid contrast.

Putting a 2x teleconverter on an 18-55 is a very poor idea.

Hate to say it but yeah, it basically is a waste to have a 2x teleconverter with a slow, wide angle kit lens. Yamahu - what is basically happening is the autofocus mechanism cannot detect the edge transfer with the TC because it makes the view so dim. a TC is better off used with longer, faster lens.

For telephoto work, get the beercan, the 70-210 f/4, or the big beercan, the 75-300 f/4-5.6. The 2x teleconverter should work well for the f/4 beercan. Making for an effective perspective range of 140-420mm at f/8. Puting a 2x on your kit only gives you a very poor quality 36-110.

Quote:

---

Originally Posted by Anbesol

I thought the AF would still find focus, it just needed to be very bright and solid contrast.

---

I believe that the phase detect AF requires a certain distance between the two spots (or the ends of the line) that it uses and a small aperture just doesn't have a large enough circle at the semi-transparent portion of the main mirror. This is why f/2.8 can have special AF - larger circle. - Terry

Thats what I thought before too, but then I tried a 2x TC on my 400mm f/5.6 and it found focus out in bright light, but obviously very dim. I was confused by the fact that it found focus as I thought it was impossible, or, is there some reason I was able to do it on the A700? Maybe it has a smaller narrower opening or something, not sure.. BUUT I wouldn't recommend throwing a 2x TC on an f/5.6 lens anyway, I only did it for curiosity sake.

Quote:

---

Originally Posted by Anbesol

Thats what I thought before too, but then I tried a 2x TC on my 400mm f/5.6 and it found focus out in bright light, but obviously very dim. I was confused by the fact that it found focus as I thought it was impossible, or, is there some reason I was able to do it on the A700? Maybe it has a smaller narrower opening or something, not sure.. BUUT I wouldn't recommend throwing a 2x TC on an f/5.6 lens anyway, I only did it for curiosity sake.

---

The circle is still covering part of the pixel array, so it will at least try if allowed. Is your TC third party? I believe that the Sony/Minolta TCs won't even let it try. - Terry

It wasn't mine, I only got to try it out. It was third party, I forget who it was but not sony or minolta. The AF was useless enough though, I only was curious that it found focus at all.

Yamaha if your having problems using your x2 converter in auto mode you will still be able to use it in manual mode or in aperture priority mode. that way you have not been burnt as you put it.