Auto focus won't focus

[Cahoon38]

Hi all:

I'm just getting into my 70D and like it a lot. One thing that's happened twice lately. I was shooting a signature on a metallic object and the camera wouldn't take the shot. I figured there wasn't enough contrast and went to Manual and manual focus. Same thing, the camera wouldn't focus OR take the shot. BTW, the green dot in the view finder was blinking sigifying no focs. I then tried to overide it again by going to Bulb. Again, the same thing. I eventually fooled the camera by focusing on something close to what I wanted and then moved the camera and took the shot.

My question: how do you overide the AF - or can you?

Thanks to those that answer.

[TTMartin]

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@Cahoon38 wrote:

I meant, when I get into a situation where the camer won't focus, I'll have to resort to "fooling" it.

The thing about this situation that pisses me off is that the camera won't allow a shot to be taken. If the green "out of focus" indicator comes on, then it doesn't allow a shot to be taken. Any camera should allow a shot to be taken even if it's overexposed or underexposed or even out of focus.

However, I have to say that I don't have a lot of experiece with the camera yet - and am comparing it to others I've had.

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When the camera's focus mode is set to 'One Shot' it requires that the camera confirm focus prior to the releasing the shutter.

When the camera is in AIServo mode, it will take the photo even when focus has not been achieved.

There is a AF/MF switch on the lens that allows you to change from Auto Focus (AF) to Manual Focus (MF). When in MF (Manual Focus) you can focus manually and take the photo regardless of the AF mode the camera is set to (i.e. One Shot/AIFocus/AIServo).

Even though you read the manual before, now that you've had some experience with the camera it would be a good idea to go back and read it again.

[Cahoon38]

Thanks much for your replies. I did turn off the AF on the lens before trying to manually focus and had no luck with that.

Actually, I shouldn't have posted a question in the forum before getting more experience with this particular camera.

Againk thanks for your attention.

[ebiggs1]

"Actually, I shouldn't have posted a question in the forum before getting more experience ..."

No actually it is OK to ask questions on this or any forum.  Some folks just don't like to interact I guess.  This forum and others like this are the places where you get the advice to gain the experience.

BTW, what lens is it?  It may have a full time MF feature which means you don't have to 'fool' the camera.  If you should happen to be at MFD that would quickly tell you.

[Cahoon38]

It's a 70D with the kit lens - EFS 18 - 135. I see that some disparage this lens, but in the last few days I've taken some very  detaled pics with it, helped by the mirror lock up feature, which is great.

[ebiggs1]

Yes this is a good lens but certainly not a great lens.  It DOES NOT have full time manual focus.  Therefore do not rotate the focus ring while it is in AF mode.

Its MFD [minimum focusing distance] is 1 1/2 feet or so.  Were you that close?  If yes it could be as Mr. Martin suggested, you were too close.

[Mod note: Added verbiage just to clarify for a new photographer. Thanks for a great response as usual, Ernie! -Stephen]

[Cahoon38]

Ha, minium focus is 1 1/2'. I was a LOT closer than that!. However, this lens will focus at that distances much shorter than 1 1/2', but you gotta have enough contrast.

Anway, I suppose the real problems will start when I get into videos. LOL

[RobertTheFat]

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@Cahoon38 wrote:
 

Ha, minium focus is 1 1/2'. I was a LOT closer than that!. However, this lens will focus at that distances much shorter than 1 1/2', but you gotta have enough contrast.

Anway, I suppose the real problems will start when I get into videos. LOL

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The minimum focusing distance is an absolute limit and is unrelated to contrast or anything else having to do with auto-focus. It is purely a function of optics and the design of the lens.

1½ feet is a pretty short MFD for a zoom kit lens. Usually you have to go to a true macro lens to do much better than that.

[TCampbell]

Focus distance is measured from the image sensor -- not the front of the lens.  There a focus mark on the body (it looks like a circle with a line crossing through it and will be printed on the top,of the camera body.)

If you thought you were closer than the MFD you might have been measuring from the front of the lens.