why am I getting inconsistant results?

[CT]

i have had something similair to this when trying to snap a very dark wolf(i think) spider.

just thought it was me being rubbish as normal.

LOL. No it isn't you. Trying to focus on a dark area like that is no different to trying to focus on a piece of blank paper. You'll run the batteries down eventually and you still wont get focus.

 

[oldgit]

Focus works on contrasty edges.

Here's a link that explains it

http://electronics.howstuffworks.com/autofocus3.htm

 

[Cobra]

Although, Chris... didnt you say earlier that in the viewfinder afterwards the red dot that was the focus point in that photo was displayed on the screen?
Mine does that... and if it was on the eye..then surely that is where it would have been focusing at that time? :shrug:

Yep your quite right Janice it did look "bang on" on the screen but I think that CT Proved that it wasn't where I thought it was :shrug:

Also... looking at CT's image with the red lines on it.... if you had focused just above or below the eye...........why would that make the leaves in the far background in focus instead?

I did sharpen the full size image out of curiosity and it looked as though the background was sharper than the bird I guess I missed :shrug:
when I magnified (just to prove it to myself) the image in camera the red dot dissapears ( well I couldn't see a way of retaining it any way)

Cobra, was the focus limiter set to 3m->infinity as opposed to 1.5m->infinity?

1.5 ( I did check )

Focus works on contrasty edges.
Here's a link that explains it
http://electronics.howstuffworks.com/autofocus3.htm

Thanks Paul

 

[tappilappi]

Hi Cobra, I have occasionally had a similar problem, but only sussed it out last week. In my case it was/is dirty contacts on the camera/lens: Sometimes I could hit "perfect" focus in an instant, almost every shot. Other times the focus would hunt and never quite hit the spot. It would still work reasonably well, but not as quick or accurate as normal.

I eventually found the answer when I noticed (during one of these "bad" focus spells) that even with a convertor fitted the aperture was showing as f2.8 instead of f4. I took the lens/convertor off, cleaned all contacts, refitted and YES - f4 and sharp, quick focus.
Not sure if this is your exact problem but this info may help someone with a similar problem.

 

[Techno-Geek]

Could this also be the problem with mine? slow focusing?

DOH

 

[Deleted member 3428]

Chris go manual, I grew up with manual focus and still use it most of the time, all these damn modern trickeries to make us think were not quite as good as we are.

 

[Cobra]

Hi Cobra, I have occasionally had a similar problem, but only sussed it out last week. In my case it was/is dirty contacts on the camera/lens: Sometimes I could hit "perfect" focus in an instant, almost every shot. Other times the focus would hunt and never quite hit the spot. It would still work reasonably well, but not as quick or accurate as normal.

I eventually found the answer when I noticed (during one of these "bad" focus spells) that even with a convertor fitted the aperture was showing as f2.8 instead of f4. I took the lens/convertor off, cleaned all contacts, refitted and YES - f4 and sharp, quick focus.
Not sure if this is your exact problem but this info may help someone with a similar problem.

Good point,I have the camera and lens soaking in turps as we "speak"
disclaimer that was meant to be a joke
I'll give it a try Tappy cheers

Chris go manual, I grew up with manual focus and still use it most of the time, all these damn modern trickeries to make us think were not quite as good as we are.

Alby, Alby,Alby, At my age I need all the help I can get. and that includes "short cuts"
as I have usually forgot what I was doing half way through. Now where did I put that keyboard lawnmower thing :shrug:

 

[frankee]

Hmm sometimes that happens to me with my 55-200 mm and i take the lens out switch the camera off and then put the lens back in and its fine.