Auto or instant focus. Which is better? Why?

[Bruce Pelley]

This concerns the A1:

Gents,

At times during the last few shoots, I have had considerable and unexpected focus issues with an A1 in a location (and from roughly the same spot) that previously did not have any problems whatsoever!

Currently I am at a loss to explain or justify it as it unpredictably occurs on and off. The focus drifts while shooting live with no hands on the camcorder. Now the focus is unreliable.

I have the focus set to I.F because between church segments I barely have time to be at the right place at the same time, frame the subject and press the record button nevermind adjust the focus manually each and every time. This state of affairs need to be resolved. Please, I need your help. I hope something isn't gone wrong with the optics system!

Which leads me to my questions:

1) What are the pros and cons of each when using auto focus versus "instant" focus?

2) Which is the most/more appropriate mode given the situation/circumstances and setting as stated above?

What would you try to resolve the problem?

Should I switch to auto mode and what possible ramifications would that have other than to presumably focus a tad slower?

All responses, suggestions, input and thoughts on the matter are welcomed.

Thanks in advance

[Chris Soucy]

Originally Posted by Bruce Pelley

1) What are the pros and cons of each when using auto focus versus "instant" focus?

"NORMAL AF" only uses the TTL system for focus, which is slower and can have issues with very bright or low light surroundings.

"INSTANT AF" uses not only the TTL system but the external focus sensor bolted to the 9 o'clock position on the side of the lens.

It is faster, more accurate and better suited for bright or low light siuations.

2) Which is the most/more appropriate mode given the situation/circumstances and setting as stated above?

"INSTANT AF" wins every time.

3) What would you try to resolve the problem?

Detach the lens hood, check that the external sensor aperture in the hood is clear and that the sensor lens is nice and clean, the combination is a crud collector of amazing sophistication.

Should I switch to auto mode and what possible ramifications would that have other than to presumably focus a tad slower?

I presume you mean "NORMAL AF"? If you're having problems with "INSTANT", "NORMAL" will probably be worse.

If my suggestion in 3) doesn't sort it, there's gotta be something else going on, but 3) is usually the problem/ solution.



CS

[Mark Fry]

Auto focus (of any sort) may start to drift (or worse) if the image doesn't have much contrast, sharp lines, etc. This often happens in poor light, such as when shooting indoors. If the scenes you are shooting are fairly static, then try this: switch to manual focus, then press the Instant AF button. The lens will hold that focus until you either press Instant AF again, adjust the focus ring, or switch back to auto-focus. Another thing that helps is to stop the lens down a bit for greater depth of field. For this you need more light, less ND, a slower shutter speed, a "brighter" custom preset or (if all else fails) more gain.

One of the nice things about a "serious" camera like the XHA1 is the ability to combine auto and manual modes to get the best of both worlds.

[Bruce Pelley]

Thanks gentlemen for greatly increasing my understanding and options.

I appreciate and value your informative responses and will use them to try and improve my focusing experience going forwards.

On the positive side, The A1 that I borrow from my local cable station just recently returned from being serviced & repaired (onboard mic would not work) at Jamesburg.

It caused me major focusing issues during the month prior to it being sent back for factory attention. So I think in part it needed a little help from Canon itself as focusing in the 2 weeks since it's return has improved significantly.

Please take care.