Canon 180 L Macro + TC 1.4 II ???'s

[sevans16]

I just got my Canon 180 L in and have been doing a little home testing of the lens and combo. I have noticed it will not autofocus closer than .84m with TC on. the lens will go down to .48m. I can manual focus in the .48-.84 range but the autofocus will not work till I manual focus past the .84 point.

Does anyone know if there is a problem with my combo or is this normal?? I am headed off to find the manuals now.

[sevans16]

OK how about reading the manual?? The lens manual states it will only autofocus down to .80m due to effective aperture value limitations. What ever that means? Also if the camera is set to 1/3 stop increments you get max aperture of f5.0 and if set to 1/2 stop increments you get a max aperture of f4.5. That seems odd!!!

[JeffreyG]

I can't answer the 1/3 vs. 1/2 stop bit, but I think the reason you are losing AF with the TC installed below 0.80CM is because the lens is passing less and less light with increasing magnification. This is a normal phenomenon in macro, especially noticeable as you shoot at greater that 1:1 magnification.

Basically there just isn't enough light beyond 1:1 for the AF to work.