Assume a lens or a camera body is poorly calibrated for autofocus, resulting in consistent front or backfocusing.

Will it have any effect on the accuracy of the focus confirmation signal when manual focusing? I'm guessing not. I'm guessing the confirmation signal is always accurate, and it's the focus motors are usually out of sync. But I just want confirmation on the reliability of the... errr... confirmation.

That would be an incorrect assumption IME.

EB

Heck no. The AF confirmation blinking of the AF sensor icon will happen when the camera thinks it's in focus; if the camera AF is in need of adjustment, then it'll blink at the wrong time. OTOH, if the camera is OK but the response of AF lens focus motor is off, then the focus-confirmation blink will be OK.

jcolwell wrote:
Heck no. The AF confirmation blinking of the AF sensor icon will happen when the camera thinks it's in focus; if the camera AF is in need of adjustment, then it'll blink at the wrong time.

I agree with that...

OTOH, if the camera is OK but the response of AF lens focus motor is off, then the focus-confirmation blink will be OK.

... but not this. The lens motor has nothing to do with it because the focus confirmation only works in One Shot mode and only if the camera detects actual focus has already been achieved. The AF motor on the lens is irrelevant because the user has done the focus manually.

- Alan

When the auto focus light blinks in your viewfinder during manual focus your auto focus system is saying "I COULD OF DONE THAT!" any issues with front/backfocusing will still be present.

Alan321 wrote:
jcolwell wrote:
Heck no. The AF confirmation blinking of the AF sensor icon will happen when the camera thinks it's in focus; if the camera AF is in need of adjustment, then it'll blink at the wrong time.

I agree with that...

OTOH, if the camera is OK but the response of AF lens focus motor is off, then the focus-confirmation blink will be OK.

... but not this. The lens motor has nothing to do with it because the focus confirmation only works in One Shot mode and only if the camera detects actual focus has already been achieved. The AF motor on the lens is irrelevant because the user has done the focus manually.

- Alan

Give me a break. I know that the performance of an AF lens motor isn't relevant to a MF lens. I was explaining how the AF focus confirmation could be off for reasons associated with the body and/or the lens. Sheesh!

EB-1 wrote:
That would be an incorrect assumption IME.

Grrr... I need to stop making ASSumptions for myself



jcolwell wrote:
The AF confirmation blinking of the AF sensor icon will happen when the camera thinks it's in focus; if the camera is OK but the response of AF lens focus motor is off, then the focus-confirmation blink will be OK.


So if the Camera body has been calibrated properly, then the AF confirmation in manual focus will be accurate, regardless of the lens? That sounds logical to me.

Yes.

Interesting discussion. Next time I'm calibrating a lens (using the moire/LCD method) I think I'll try hitting perfect focus using the confirmation beep and see if it's consistent in hitting perfect focus. My suspicion is there will be some variation with shorter focal length lenses even with perfect calibration. No reason you couldn't test it yourself though using this technique even if you don't have a body with microadjustment.

http://www.northlight-images.co.uk/article_pages/cameras/1ds3_af_micoadjustment.html#af_microadjustment