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PostPosted: Mon Nov 17, 2008 8:29 am 
I just registered and posting my first thread!
I am new to DSLR. I have been taking night shots.
However, it is just impossible to take sharp images. For some reason, most of my pictures are always out of focus.
Someone told me to
1. increase f number for large DOF,
2. set the focus to MF
but I failed to get sharp images. I read about hyperfocal distance. It pretty much said high f number doesn't neccessarily mean deep DOF.
I just have no idea how to take clear pictures at night at the beach

People repeated talk about setting the focus to infinity for these type of shots, but I am really lost on this subject and very frustrated.
:(

Also, for aperture, higher it is, the more light it will take. So for night shots, it make sense to set the aperture high with reasonable shutter speed for nondark image, but then, DOF is shallow. However, if the focus is infinity, there can't be DOF since there is no focus to have DOF? Then why not take these pictures with high aperture(low f number)?

I think I am not completely understanding each concept when it comes to infinite focus.

Sorry for a long post and please help me~!
thanks[/img][/code]


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PostPosted: Mon Nov 17, 2008 9:09 am 
what camera are you using?


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PostPosted: Mon Nov 17, 2008 4:00 pm 
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Joined: Fri Oct 24, 2008 8:08 pm
Posts: 1626
Location: New York, US
It's because your focus ring will go beyond infinity and you need to actually focus on a distant object. What I do is I find the furthest illuminated object possible (usually a street light) and auto focus on it, then I switch my lens to manual focus and start taking shots like that.

Also when I'm doing night shots and I need a long exposure it's a good thing to close down the aperture or you won't be able to get that long exposure you're after, there will just be too much light entering the lens.

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PostPosted: Tue Nov 18, 2008 5:56 am 
Gregory.Rotter wrote:
what camera are you using?


I have Canon XTI with EFS 17-55mm


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PostPosted: Tue Nov 18, 2008 11:32 pm 
If those photos weren't taken on a tripod, it would also be motion blur instead of out-of-focus blur. The mininum shutter speed is guided by the Rule of Thumb. (ex: for 30mm focal length (film equiv) you are advised to use a shutter speed of at least 1/30s.)

Quote:
However, if the focus is infinity, there can't be DOF since there is no focus to have DOF? Then why not take these pictures with high aperture(low f number)?


You are correct! But if the camera is on a tripod, smaller aperture is still more desirable because most lenses have a sweet point (sharpest images) at about f8.

Hope it helps a little..


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