help needed ,

was using my 1dmkIII today all was going well , but not it cant find focus ,
it just keeps going in and out ,??

One lens? All lenses? Specific focus point, any focus mode? Need more details.

all lenses , i even cleared all settings , re installed firmware , and still no joy ,

on my ef 28-70f2.8 it finds focus as it beeps but it is not in focus at all ??

One thing to look at are the mirrors. Make sure there is no hair or smudge on them. Also, take the bulb blower and on the bottom of the body where the AF sensor lives, give it a good dust off. Other than that, there is little you can do but give Canon a call. It's sort of sounding like the AF sensor died.

ok ill give it a try , thanks for your help ,

Oh no, dont use the blower on the chamber. You'll push dust in it and eventually it'll get onto the sensor. I learned it the hard way. Then spent more money on sensor wipes.

Turn it on and off. Remove battery. Do a factory reset. Get a dry chamber cleaning swab and poke the focusing screen. Dust should stick onto the swab. Make sure you dont touch the swab with your fingers because you'll get finger grease on them.

Good luck!

One other thing to look for is maybe a piece of mirror dampening fuzzy stuff that may have separated and fallen into the AF sensor cavity.

shinyknights wrote in post #14000561
... Get a dry chamber cleaning swab and poke the focusing screen. Dust should stick onto the swab.

The focus screen has nothing to do what so ever with autofocusing. Do not tough the focus screen.

ive noticed that when i look through the view finder that when i press for to focus there is a green light flashing in the right bottom corner ?

I believe the flashing green light in the VF is telling you it cannot AF. Usually it's because it's pointed at something with poor contrast like a wall or something.

i will leave into shop , see what they say ,
needs a good service and censor clean too

The first thing I'd check would be the golden contacts on the body where the lens makes electrical contact. Wipe them down with a microfiber cloth or something similar.

If that doesn't do it, then there probably is a problem somewhere in the focus system.

thanks Jim_T i will give it a try .

no joy

hi might be a stupid question , but a scratched focus screen cause my af to malfunction ?