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Post by john101477 on Oct 6, 2009 23:42:49 GMT -5
With some of the stellar night shots I have seen here lately I decided to get out and do some long exposure shots. this one was a 30 second shot. f/6.3 and ISO 400. no filters Is there anything I could have done to make it better? Attachments:
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OrcaBob
Lead Photographer
Frank Zappa lives
Posts: 394
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Post by OrcaBob on Oct 7, 2009 1:41:51 GMT -5
The tree and the poor light-gathering settings (narrow aperture, low ISO and very short exposure) drown out most of the stars.
The tree picks up well, but if you meant to pick up the sky it didn't work very well.
- Faster lens - Higher ISO, then a tool to handle the resulting noise - Longer exposure, but keep the angle wide so the longer exposure doesn't show the Earth's rotation so much
Ideally, you'd piggyback the camera on a telescope on a properly-aligned equatorial mount. That would allow a much longer exposure while compensating for the Earth's rotation. The mount can be powered or, if you've got the patience, manually guided.
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Post by Steve (FloppyDog) on Oct 7, 2009 7:01:17 GMT -5
It's a good stab at it John. Bob hit the highlights. I'd definately try about double your exposure. Maybe re-compose with your tree off to the side a little to show some more star action.
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Post by john101477 on Oct 7, 2009 10:15:09 GMT -5
I think with the lens I was using this was about as good as it gets except maybe a higher ISO. a longer shutter speed would have given me light trails. I tried it in bulb mode with a min shutter and did not like it. faster glass may do it. I might recompose with the 50mm and see what I get tonight. unfortunately I have a large light that comes on with movement and thats what highlighted the tree so much. how I can keep the tree in focus, no light trails, and still pick up stars with out a ton of noise is my main goal here.
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Post by john101477 on Oct 7, 2009 10:31:51 GMT -5
I had the same issues here but a little more harsh as the camera was in the light (behind me). if you look at the right side there is a street light next to the school which is across the street. Attachments:
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Post by jimhobson on Oct 10, 2009 9:02:27 GMT -5
To prevent star trails use this formula: 600 divided by focal length. 600/50mm = 12 or 12 sec max exposure. If you want star trails go longer. On a full moon night I usually start at f2.8 (critical aperture for 50mm) and ISO of 400.
I have a Sigma 28mm f1.8 lens. The 28mm gives me 21 sec. to work with and the f1.8 gives me extra room to adjust exposure. You can always up or down the ISO also. DOF is good also.
At 12-21 seconds it's short enough not to get bored while shooting.
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Post by Steve (FloppyDog) on Oct 10, 2009 18:33:55 GMT -5
Thanks for sharing this formula Jim!
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Post by john101477 on Oct 10, 2009 20:51:39 GMT -5
That formula might be a good thing to sticky for future reference. Thanks Jim I am gonna have to try that this week.
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Post by jimhobson on Oct 11, 2009 13:15:05 GMT -5
Good luck, post some images. You all welcome.
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Post by jimhobson on Oct 13, 2009 18:02:40 GMT -5
I forgot to mention the lens factor. If you camera has an APS size sensor and you are using a full frame lens, don't forget to convert to your actual focal length first. Sorry. Ex. 50mm x 1.6 = 80mm. 600 / 80 = 7.5 sec. I usually shoot film. Don't have to convert.
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