Extension Tubes and Canon 50mm

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Name
Paul
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Hi,

I have been having a play with my extension tubes on my Canon 50mm. Problem is, I cannot get the camera to auto focus. The light just flashes and it wont let me take a picture. It works if I use the 75-300mm lens so not sure why not with the 50mm

Any thoughts?

Thanks
Paul
 
Is it a communication problem with the contacts on the tubes not aligning properly, or perhaps dirty? Give them a wiggle, or clean them carefully with the rubber on the end of a pencil.

But most people don't use AF with macro. It's usually easier to pre-focus the lens, switch to manual, and move gently back and forth so that the image moves in and out of sharp focus.
 
ok - the contacts work fine. The lens is trying to focus but wont give me the "good to go" light.

I can muanll focus no problem, was just wondering why the auto wont work with this lens
 
Since extension tubes are designed to allow you to focus closer than normal you end up unable to focus at infinity while the tubes are fitted. I don't know what the actual cutoff distance is - it might be 10m or 100m or 2m. Are you trying to focus close up or far away?

Also, nifty focusing is not its great strength and tubes do decrease the light hitting the focus sensor. Do you have enough light and contrast on your subject for the AF to function properly?
 
I can get the image in focus if I do it manually so I know my focusing distance is ok... I think it may be a contrast issue as I was inside under artificial light. Maybe I will have a play outside when I get home tonight.
 
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