question on focus lock

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scoobychief

Senior Member
just been outside and took my first nightish shot in manual mode but I left the focuscing in auto mode my question is I moved my focus onto a subject and then locked it, I use the back button ae/l I find this easier and then kind of pointed it at the moon but I noticed that when I let go of the ae/l focus button and then pressed the shutter button to take the picture it wouldn't take the pic, any reason why that is? is there a way to do this, so I had to keep my finger on the focus button and then press the cable realese button but that will defo cause the camera to not be still even tho its on a tripod. any suggestions?.
 

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480sparky

Senior Member
scoobychief said:
Just been outside and took my first nightish shot in manual mode. But I left the focusing in auto mode. My question is: I moved my focus onto a subject and then locked it. I use the back button AE/L. I find this easier. I then kind of pointed it at the moon but I noticed that when I let go of the AE/L focus button and then pressed the shutter button to take the picture it wouldn't take the pic. Any reason why that is? Is there a way to do this? So I had to keep my finger on the focus button and then press the cable release button. But that will defocus cause the camera to not be still even though it's on a tripod. Any suggestions?.
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Proper spelling, punctuation and capitalization makes a difference between "Helping my uncle, Jack, off his horse." and "Helping my uncle jack off his horse." Now that I've cleaned up your post:

You're using back-button focus, with the AE/L button to focus? If so, is the camera actually acquiring focus according to the camera? It may not be, since it's so dark and low contrast it cannot find focus.
 
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scoobychief

Senior Member
during the day if I focus on an object after it has focused and I hear the bleeps I can take my fingers off the focus lock and recompose and take my shot, so why cant I do this in this case it wasn't actually pitch black I did have focus but when I recomposed and tried to take the shot no joy.
 
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Blacktop

Senior Member
In that case, it would be, "Helping my Uncle Jack off his horse."
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If you are going to start a tutorial on spelling, grammar and punctuation, please do it in the "off topic forum".
This must be very distracting to the OP.
 
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DraganDL

Senior Member
Check the AF mode and the shutter mode too (it looks like your camera is set in a way that shutter can be released only if AF is achieved). If you think you know what you're doing, set the shutter button's behavior in such a manner that it is independent from AF (shutter can be actuated even if no AF has been achieved).
 
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480sparky

Senior Member
Blacktop said:


If you are going to start a tutorial on spelling, grammar and punctuation, please do it in the "off topic forum".
This must be very distracting to the OP.
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What's even more distracting is to have to spend 5 minutes trying to decipher the question to begin with. I'm not the OP's buddy or girlfriend, and we're not texting over the phone. Maybe I'm too old-fashioned, but learning how to compose a question properly tends to attract more help.
 
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kluisi

Senior Member
Does the D3100 have the ability to set AF-C to shutter priority instead of focus priority? If so, that may be what the OP needs to do.

Off topic: Try the picture again with a faster shutter speed or smaller aperature (which ever you choose, keep the other the same). That will give you a better chance to properly expose the moon. You might still be able to pull the shadows up in post.
 
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