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DPChallenge Forums >> Hardware and Software >> AF "searching"
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 01/25/2005 06:22:17 PM · #1
recently it seems that my Canon75-300IS has been "searching" for a focal point - going all the way to near focus and then back out. Is there a way to stop this?
 01/25/2005 06:37:13 PM · #2
Manual focus.
 01/25/2005 06:40:13 PM · #3
What are you trying to take a photo of? If it's something with very little contrast, like snow, AF can have a difficult time. Or the obvious question, is there enough light?
 01/25/2005 06:41:23 PM · #4
Originally posted by Discraft:
Manual focus.


ain't there no other way? I seem to remember a discussion about this a while back.
 01/25/2005 06:43:27 PM · #5
Originally posted by rscorp:
What are you trying to take a photo of? If it's something with very little contrast, like snow, AF can have a difficult time. Or the obvious question, is there enough light?


It was polar bears...wonder if there was insufficient contrast?
 01/25/2005 07:06:14 PM · #6
Originally posted by jemison:

It was polar bears...wonder if there was insufficient contrast?


Probably. Try painting them different colours - that might help with the contrast problem. ;-)
 01/25/2005 07:07:18 PM · #7
Why do you need to focus on bears anyway? Doesn't infinity work?
 01/25/2005 07:11:03 PM · #8
with manual focus the AF points still blink, or beep when focus is hit - the more advanced autofocus becomes, the less i like it...


01/25/2005 07:14:08 PM · #9
Originally posted by xion:
Why do you need to focus on bears anyway? Doesn't infinity work?


Oh, infinity works...just not if I want the bear in focus - they are from 20ft to 60 ft away or so.
 01/25/2005 07:15:24 PM · #10
whats the fstop you're using?

Message edited by author 2005-01-25 19:15:36.
 01/25/2005 07:23:08 PM · #11
Originally posted by jemison:
recently it seems that my Canon75-300IS has been "searching" for a focal point - going all the way to near focus and then back out. Is there a way to stop this?


You are going to have that problem in low contrast shots with almost any lens, but more so with a lens with wider zoom capabilities and variable max aperture. Your lens has both so with this lens you have will have more hunt on a given subject then if it was taken with a lens with shorter zoom range and a fixed max aperture like say the 70-200 f/4.

Message edited by author 2005-01-25 19:46:17.
 01/25/2005 07:25:16 PM · #12
Originally posted by soup:
whats the fstop you're using?


5.0 - 5.6
 01/25/2005 07:28:53 PM · #13
Try finding the focus on the bears nose or something more auto of the normal colors... Like as if evrything is so white try something black on the bears.
try choosing the focus on the center of the viewfinder and not the 7 points of focus i guess thats how many the rebel has... i'm not sure but thosn't matter choose the center one.

Message edited by author 2005-01-25 19:30:17.
 01/25/2005 07:37:53 PM · #14
Originally posted by Discraft:
Try finding the focus on the bears nose or something more auto of the normal colors... Like as if evrything is so white try something black on the bears.
try choosing the focus on the center of the viewfinder and not the 7 points of focus i guess thats how many the rebel has... i'm not sure but thosn't matter choose the center one.


What I found annoying was that after getting one shot focused, when I tried another, the camera would search all the way back and then back out. It had no trouble finding focus when it "got there". Maybe I'll just chalk it up to "strange" conditions.

I'll remember the tips, though. Thanks.
 01/26/2005 12:03:07 AM · #15
Finding the place that has some contrast is the big trial. Between the bear's foot and the ground (unless on snow), the nose as pointed out, along the outline of the bear somewhere. And ya may have to use a larger smaller aperture---8 or so?
Alot of times I will flick the camera to manual focus after it does get a good focus--as long as the subject isn't moving much that is.

Message edited by author 2005-01-26 00:05:47.
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