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FORUMS Photography Talk by Genre General Photography Talk 
Thread started 01 Jun 2009 (Monday) 12:12
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Long Exposure Focus Issues...

 
32ANA
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Jun 01, 2009 12:12 |  #1

Hi guys

I am using a 5D and 24-70L 2.8 and 15mm fisheye lenses on my tripod to do some long exposure shots at night while I am traveling.

The majority of my long exposure experience so far has been of areas with plenty of light around them, so focussing has never been an issue.

Now I am visiting places that are extremely dark and am working by moonlight, so getting focus is near impossible.

When I am unable to get focus by using the centre focus point, does anyone have any suggestions as to how I can gain focus? Going manual has proved far too hit-and-miss. I really am out in the pitch black darkness!

I am wondering if taking a torch/flashlight with me to shine on a nearby object to get a focus point is practical or likely to work out decently?

Can't think of anything else to try! Any suggestions welcome :)

Thanks.


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hollis_f
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Jun 01, 2009 12:19 |  #2

A green laser pointer produces an excellent target for the AF system. Just make sure it don't go anywhere near eyes - and watch out for reflective surfaces.


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Johan ­ Groenewald
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Jun 01, 2009 12:47 |  #3

I do a lot of these very dark long exposures for star trails, I use my 4cell maglite to focus with on the subject, normaly a building or tree. I then use the maglite also to colour in the suject.


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Nighthound
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Jun 01, 2009 16:17 |  #4

A quick way to get focused to infinity with your lens:

• Find the brightest star in the sky.
• Set camera to "M" manual.
• Set lens to "AF"
• Point at brightest star.
• Position the flashing focus sensor box on the bright star until you see the lens snap to focus.
• Carefully Switch the lens to "M"
• CAREFULLY point the camera to the portion of the sky you want to image and compose your shot. Be careful not to touch the lens while doing this so you don't knock focus off.
• Shoot away


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32ANA
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Jun 01, 2009 17:42 |  #5

Hmmm thanks for your comment, however some of the shots i'm doing dont have any sky in them at all, so focussing on a star isnt possible. And since its pitch black out here there really arent even any stars to focus on even if i wanted to!
It's so dark that i cant even focus on rocks or things that are only a few feet away.
Help! :)


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Nighthound
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Jun 01, 2009 18:49 |  #6

32ANA wrote in post #8030720 (external link)
Hmmm thanks for your comment, however some of the shots i'm doing dont have any sky in them at all, so focussing on a star isnt possible. And since its pitch black out here there really arent even any stars to focus on even if i wanted to!
It's so dark that i cant even focus on rocks or things that are only a few feet away.
Help! :)

My apologies, I misread/misinterpreted your question. I was thinking that you were trying to include the sky and wanted focus at infinity.

I'm confused on how a place could be so dark that there are no stars however. The sky should be plastered with stars on Moonless nights. In turn there should be quite a bit of starlight illumination. For myself as an astrophotogapher, the darker the skies for imaging the better but I can certainly understand how it could make focusing landscapes a challenge.

A location that dark sounds like a dream spot to do some deep sky imaging.


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aram535
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Jun 01, 2009 19:01 |  #7

A small flashlight is all you need, any will do. You just need to light enough for the AF to kick in and switch to M.


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32ANA
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Jun 02, 2009 02:51 |  #8

Thanks a lot for the comments everyone, much appreciated :)


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Long Exposure Focus Issues...
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