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324 posts

Ultimate Geek


# 173560 27-May-2015 17:05
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Hi all

I just bought myself a Canon 70-200mm F4 IS lens, it was second hand, new in 2012.

When I push the shutter button half down the af is constantly searching, sometimes it wont focus at all.
I can use the manual focus ring to get a good shot, but shouldn't it do this itself?

The AF switch is on, image stabiliser is on, stabiliser mode 1
Am I doing it wrong? Or expecting too much?

I have been using the 55-250mm stm up until now.

Apologies if I have any terms wrong, still a beginner!

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  # 1312939 27-May-2015 17:09
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it should be INSTANT. always test them out before buying.




Involuntary autocorrect in operation on mobile device. Apologies in advance.


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  # 1312940 27-May-2015 17:10
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that is one of the fastest focussing lens in the world




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  # 1312942 27-May-2015 17:11
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What focus mode is your camera on? It should be one shot/single shot. Sounds like you may have it on AI servo, which is for moving objects, sports.

Put it on one shot, then somewhere in good light focus on something with good contrast, like the transition between white and black. Take test shots at say 2m (may be too close and won't focus), 10m, 20m, 50m.

Report back.

Or just send it to Canon to be inspected/repaired.

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  # 1312947 27-May-2015 17:14
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good point, mr Pro ;p




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Ultimate Geek


  # 1312952 27-May-2015 17:18
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It's definetly on 1 shot
works better in good lighting,  hardly works at all in muted light, its a bit intermittent 
I don't mind sending it to Canon (I got it super cheap from a retired photographer) but wondered if I was expecting too much

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  # 1312953 27-May-2015 17:19
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how muted light? it won't focus if there is no light!




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  # 1312955 27-May-2015 17:19
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the camera needs contrast (lines) to focus. point it at a smooth black wall it won't focus even at high noon.




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Ultimate Geek


  # 1312959 27-May-2015 17:23
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4.30pm outside (not dark lol) standing 1.5m from a flower it wouldn't do auto focus



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Ultimate Geek


  # 1312962 27-May-2015 17:28
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Click to see full size

Taken at 4.30pm, had to use manual focus

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  # 1312966 27-May-2015 17:39
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it's broken. give it back!




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  # 1312967 27-May-2015 17:40
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it should take approx 0.1s to take that shot in daylight. was there any daylight? what was the ISO?




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  # 1312969 27-May-2015 17:44
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Try what I suggested, report back, I requested specific things for a reason, including minimum focus distance. If you don't want to do that show it to someone experienced, then just send it straight to Canon.

Focus issues are notoriously difficult to diagnose, and sometimes to fix. I went through years of hassle with Canon before I gave up and switched to Nikon. The 70-200 F2.8 L Canon lens was always perfect though.

You pretty much always need to manual focus when you're working at macro distances, or trying to fill the frame with something small.

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  # 1312975 27-May-2015 17:47
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good point. the lens minimum focal distance is not the camera's minimum focus distance. it will not focus within 5-10cm of its rated minimum focus distance, can you try to focus something further away




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Ultimate Geek


  # 1312978 27-May-2015 17:53
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timmmay: Try what I suggested, report back, I requested specific things for a reason, including minimum focus distance. If you don't want to do that show it to someone experienced, then just send it straight to Canon.

Focus issues are notoriously difficult to diagnose, and sometimes to fix. I went through years of hassle with Canon before I gave up and switched to Nikon. The 70-200 F2.8 L Canon lens was always perfect though.

You pretty much always need to manual focus when you're working at macro distances, or trying to fill the frame with something small.


Thanks Timmmay, I'll do it either tomorrow , or tonight (just feeding the kids dinner)



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Ultimate Geek


  # 1312980 27-May-2015 17:55
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joker97: it should take approx 0.1s to take that shot in daylight. was there any daylight? what was the ISO?


Yes there was daylight, just no sun
ISO 3200
1/250
Aperture 5.0

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