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Author Topic: Stars...how to focus in pitch black...  (Read 2241 times)

davet4

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Stars...how to focus in pitch black...
« on: September 27, 2013, 01:17:21 AM »
i tried some star shots over the weekend with limited results, see two pictures. These were taken with 5DMKIII, 24-105, tripod and 30 sec exposure, 100iso. My questions is how to focus in pitch black :-\ :-\..there is probably a really simple answer about this but i struggled to get any infocus. any advice, suggestions would be great as i want to try again...and hopefully get  better pic's
5d3, 24-105mm, 600EX-RT

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Stars...how to focus in pitch black...
« on: September 27, 2013, 01:17:21 AM »

dswtan

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Re: Stars...how to focus in pitch black...
« Reply #1 on: September 27, 2013, 01:25:44 AM »
Live View. 10x. Use a fast lens. Pick brighter stars. Optionally maximize your ISO, just temporarily to focus. Focus so that you see as many stars as possible. You'll get it!
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Jim Saunders

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Re: Stars...how to focus in pitch black...
« Reply #2 on: September 27, 2013, 01:57:24 AM »
I don't know if 30 seconds is long enough to matter but at some point the (relative) movement of the stars will make them look soft focused or not.

Jim
See what I see: 6500K, 160 cd/m^2, ICC 2, gamma 2.2.

bvukich

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Re: Stars...how to focus in pitch black...
« Reply #3 on: September 27, 2013, 02:23:47 AM »
I don't know if 30 seconds is long enough to matter but at some point the (relative) movement of the stars will make them look soft focused or not.

Jim

The rule of thumb to get star pictures without trails is to divide 600 by the focal length, and use that in seconds for your shutter speed.  e.g. 600/24mm=25sec

bvukich

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Re: Stars...how to focus in pitch black...
« Reply #4 on: September 27, 2013, 02:33:52 AM »
i tried some star shots over the weekend with limited results, see two pictures. These were taken with 5DMKIII, 24-105, tripod and 30 sec exposure, 100iso. My questions is how to focus in pitch black :-\ :-\..there is probably a really simple answer about this but i struggled to get any infocus. any advice, suggestions would be great as i want to try again...and hopefully get  better pic's

The hyperfocal distance at 24mm f/4 is only 15.8 ft, so (greatly simplified) if you focus on anything farther than that, everything behind it will be in focus.  If you have foreground elements you want in focus, as long as they are farther away than that, just focus on them and the stars will be fine.

If you're only worried about the stars, then what I'll usually do is set the lens to infinity, and then back it off just a tiny bit.  Take a test shot, and check for sharpness at 100%.

Sporgon

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Re: Stars...how to focus in pitch black...
« Reply #5 on: October 31, 2013, 04:42:01 PM »
Beginning to play with night shots. Can't believe how far the stars move in 30 seconds. Felt quite dizzy when I'd finished.
Also cocked up the focal point in the dark so there is not enough DOF, but it's made quite a creepy image, suitable for Halloween.

CarlTN

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Re: Stars...how to focus in pitch black...
« Reply #6 on: October 31, 2013, 11:49:52 PM »
i tried some star shots over the weekend with limited results, see two pictures. These were taken with 5DMKIII, 24-105, tripod and 30 sec exposure, 100iso. My questions is how to focus in pitch black :-\ :-\..there is probably a really simple answer about this but i struggled to get any infocus. any advice, suggestions would be great as i want to try again...and hopefully get  better pic's

Magnified live-view and manual focus have always worked for me no matter what lens and body I use.  Especially works great with my 6D and 24-105.  But there are lenses better suited than this one.

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Re: Stars...how to focus in pitch black...
« Reply #6 on: October 31, 2013, 11:49:52 PM »

chilledXpress

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Re: Stars...how to focus in pitch black...
« Reply #7 on: November 01, 2013, 12:23:40 AM »
Stars are very far away... at least a mile or two :D Set for hyperfocal and you don't even need to look through the view finder.

Also, if you're really into this type of work I suggest an Astrotrac mount. You'll never need to worry about star trails, unless you want them. A little pricey but it weighs so little, it's easy to setup and pack for travel... the results are superb! It's also great for time lapse work.

I had a Losmandy Starlapse set up but it weighed a ton and took a bit to set up, eventually sold it and went for the Astrotrac.
« Last Edit: November 01, 2013, 12:29:33 AM by chilledXpress »

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Re: Stars...how to focus in pitch black...
« Reply #7 on: November 01, 2013, 12:23:40 AM »