Eos 7D & 1.4TC question

[Lee O'D]

Can anyone tell me if a 400mm 5.6 lens will auto-focus on a 7D body with a 1.4X TC? I know it won't on the 40D / 50D but I believe the focusing sensors are different on the 7D.

Cheers, Lee.

 

[pete.rush]

Can anyone tell me if a 400mm 5.6 lens will auto-focus on a 7D body with a 1.4X TC? I know it won't on the 40D / 50D but I believe the focusing sensors are different on the 7D.

Cheers, Lee.

Quick answer NO

Only the 1D series camera bodies retain autofocus (centre focus point only upto f8), all other canon bodies will only autofocus upto f5.6 (lens + TC combo) and manual focus above f5.6. The 400mm f5.6 and 1.4x TC combination creates an f8 lens (loses 1 f-stop), so will only manual focus on your 7D

 

[admirable]

What he says

 

[Lee O'D]

Quick answer NO

Only the 1D series camera bodies retain autofocus (centre focus point only upto f8), all other canon bodies will only autofocus upto f5.6 (lens + TC combo) and manual focus above f5.6. The 400mm f5.6 and 1.4x TC combination creates an f8 lens (loses 1 f-stop), so will only manual focus on your 7D

Thanks Pete.

 

[Canon Bob]

But it just might if you use Liveview

Bob

 

[alastairb]

or tape over some pins?

 

[pete.rush]

or tape over some pins?

If you want to damage your lens by burning out the autofocus motor, go straight ahead. Personally I won't recommend it on a £1000s worth of lens.

 

[Orville]

Taped pins with a 1.4x TC and a 100-400mm worked fine on a 40D & 7D for me. AF was pretty fast in normal to good light, but I did notice increased hunting in dimmer conditions. I didn't smell any burning when I used the combo.

 

[pete.rush]

Taping the pins basically makes the TC invisible to the camera, TC doesn't report back to the camera to tell its there, which if you have perfect light conditions ain't a problems, although you'll have exposure problems, however if the light conditions ain't perfect the lens starts to hunt and thats where you do the damage to the focus motor.

 

[artyman]

I wonder how much hunting is a problem since this is what AI Servo is doing all the time with moving objects.

 

[Canon Bob]

If you want to damage your lens by burning out the autofocus motor, go straight ahead. Personally I won't recommend it on a £1000s worth of lens.

You can stick the lens on a 5DII/7D and use AF continuously during a 29 minutes of video recording....it's a fair bet that Canon would have prevented this if it was likely to burn out the USM.

Bob