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 Finding infinite focus in the dark 
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Joined: Mon Oct 15, 2012 6:18 am
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Post Finding infinite focus in the dark
Last weekend I was out doing timelapses of the milky way under a very dark sky. Usually I can find a street lamp near a tree and focus on that, but there wasn't anything around.

I have the Canon 24-70 f/2.8. The infinity focus point is different for shooting at 24mm vs shooting at 70mm, and neither are at the infinity indicator.

How do you guys set the focus on lenses when there isn't anything to focus on? Do you mark your lenses and manually adjust and hope you get it right? I've tried using live view with a high iso and wide open aperture but without light, its tough. I suppose taking an exposure of the stars and zooming in would work, but that could be laborious finding exactly the right focus point.

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Mon Oct 22, 2012 7:01 am
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Joined: Tue Feb 21, 2012 8:33 am
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Post Re: Finding infinite focus in the dark
You can always take exposures of the stars as you said and adjust the focus pic by pic.

Or if the stars are really bright I've managed to focus when in live view!


Mon Oct 22, 2012 7:29 am
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Joined: Fri Jul 23, 2010 6:05 pm
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Location: US Virgin Islands
Post Re: Finding infinite focus in the dark
I use live view and zoom in 10X digitally and us a star to focus. If you're in a area that's so dark that you have nothing to focus on then you should be seeing heaps of stars.


Mon Oct 22, 2012 9:14 am
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Joined: Wed Mar 16, 2011 2:58 pm
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Location: Denver, Colorado
Post Re: Finding infinite focus in the dark
Zigmo wrote:
I use live view and zoom in 10X digitally and us a star to focus. If you're in a area that's so dark that you have nothing to focus on then you should be seeing heaps of stars.



Same here, never had a problem hitting focus with that method.

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Mon Oct 22, 2012 10:05 am
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Joined: Tue Aug 28, 2012 9:29 am
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Location: Seattle, WA
Post Re: Finding infinite focus in the dark
Jack Ripper wrote:
Zigmo wrote:
I use live view and zoom in 10X digitally and us a star to focus. If you're in a area that's so dark that you have nothing to focus on then you should be seeing heaps of stars.


Same here, never had a problem hitting focus with that method.


Yep. Pretty much the way to go.


Mon Oct 22, 2012 11:08 am
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Joined: Fri Apr 03, 2009 6:15 pm
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Location: Middle Earth
Post Re: Finding infinite focus in the dark
You can always go for a walk leaving a LED light 100m away :-)

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Mon Oct 22, 2012 12:51 pm
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Joined: Tue Sep 20, 2011 11:34 am
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Post Re: Finding infinite focus in the dark
I use live view too and zoom in as far as it goes, then take a pic. If it's not sharp enough, I repeat the step until I get it pinpoint sharp.
After that I'm ready to shoot.


Wed Oct 24, 2012 1:31 am
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Joined: Tue May 10, 2011 2:05 pm
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Post Re: Finding infinite focus in the dark
If I know what I want to shoot, I often do the focus during the day and put masking tape on the lens to prevent movement of focus, zoom, auto focus switch, and stabilization switch. When I get to location I am set. If I need to change the zoom, I use the options others describe here.


Fri Oct 26, 2012 2:29 pm
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Joined: Fri Jul 29, 2011 7:36 pm
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Post Re: Finding infinite focus in the dark
This is not the cheapest suggestion but it sure works nice. I bought a Zeis Distagon T* 21mm f2.8 lens. It has an infinity stop. Ie turn the lens to infinity and when it stops you are good to go. Their 50mm, 15mm, and 100mm lenses have infinity stops too. They make them for Canon and Nikon DSLR. The 21mm lens is so sharp you have to wear eye protection to use it. It's a manual focus lens but the electronics in the lens wil tell you when it achieves focus

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Sun Jan 13, 2013 4:47 pm
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Joined: Mon Jul 23, 2012 3:56 am
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Location: Christchurch, New Zealand
Post Re: Finding infinite focus in the dark
I know it's not really very helpful for the OP but I can vouch for that Zeiss 21mm f2.8 lens as well. I have the same one myself, and aside from sharpness and overall fantastic quality, the hard infinity stop was also a reason for me to purchase it.

On my other lenses I also use the live view 10x view on stars. Any focus point should do really, since nailing the infinity focus means everything (within reason) will be sharp anyways.

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Tue Mar 12, 2013 4:12 am
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Joined: Thu Mar 27, 2008 2:15 pm
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Post Re: Finding infinite focus in the dark
Yep, focus on the stars. Crank up ISO and use Live View and 10x zoom. Twist the focus ring until the stars become pinpoints.


Wed Mar 13, 2013 2:03 am
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Post Re: Finding infinite focus in the dark
Mmmmm Distagon aahhhh.....

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Tue Mar 19, 2013 2:58 pm
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