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Topic: Question on star trails, muiltple time exposures, and photoshop overlay
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Manesero
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Subject:
Question on star trails, muiltple time exposures, and photoshop overlay
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I've read about people who take -10 minute exposures of star trails, and then overlay them on photoshop to merge all of the exposures into one single picture. The reasons for doing this, I suppose, is to eliminate the overexposed sky if the moon is out.
Pretty much what I want to do is, for example, take these two pictures of star trails below, and merge them into one single picture where the star trails are continuous, if you know what I mean.
http://www.flickr.com/photos/37565608@N06/3522546568/
http://www.flickr.com/photos/37565608@N06/3521733431/
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ShalisR
Title: Cao's Haggis Hustler
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Subject:
Question on star trails, muiltple time exposures, and photoshop overlay
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Never tried this before, but I had a quick look, pop them both in to the same PSD file, I put the lighter one as the bottom layer, then set the top layer to "screen". This gives you the continuous effect, though in this example, there was a tiny bit of shift between one photo and the next, so they don't line up perfectly.
I'd use a tripod and a remote, set it up for whatever exposure you want (I liked the 5 mins one from your two) then just sit there and click the remote until you get all the shots you want.
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GhostOfACPast
Title: The Phantom Curmudgeon
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Subject:
Question on star trails, muiltple time exposures, and photoshop overlay
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No, the reason for the multiple exposures is because the camera generates a tremendous amount of noise the longer the shutter is opened. On analog film there is no noise so the shutter can be left open for however long you wish.
For me I wouldn't go longer than 2 mins per frame or 5 mins on one of those 6 grand camera bodies because the noise level would eat you alive.
edit: What camera are you trying to use?
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Manesero
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Subject:
Question on star trails, muiltple time exposures, and photoshop overlay
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Canon XSi
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GhostOfACPast
Title: The Phantom Curmudgeon
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Subject:
Question on star trails, muiltple time exposures, and photoshop overlay
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Manesero posted:
Canon XSi
For that camera I would do at most 3 mins then do 10 shots to make 30 mins of exposure.
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../.\ Support freedom of expression. Aleksandr Sdvizhkov...martyr.
Parks sat so King could walk so Obama could run. Aaaaaaaammmmmmerrrrrika F••• YEAH!
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kashani
Title: A Country Boy Can Survive
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Subject:
Question on star trails, muiltple time exposures, and photoshop overlay
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Ghost is correct. I use a 30D, and even as low as 2 mins the noise at 100 ISO (As low as I can go), is pretty noticeable.
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GhostOfACPast
Title: The Phantom Curmudgeon
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Subject:
Question on star trails, muiltple time exposures, and photoshop overlay
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kashani posted:
Ghost is correct. I use a 30D, and even as low as 2 mins the noise at 100 ISO (As low as I can go), is pretty noticeable.
Yep, on my old Canon the noise was horrible at 30 secs. Basically you need to find your camera's sweet spot and work it out from there. I doubt the XSI will do more than 90 secs to 2 mins before the noise will eat you alive. The thing is the noise will be taken care of better on the newer cameras (it does this right before the image is saved) so you might get 3 mins but if it were me I would be doing 2 min shots or 3 on the outside if the darkness is so low it demands that long of a shot but expect some noise (it isn't a film camera afterall).
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...| <- Drawing of Mohammad doing jumping jacks
...|
../.\ Support freedom of expression. Aleksandr Sdvizhkov...martyr.
Parks sat so King could walk so Obama could run. Aaaaaaaammmmmmerrrrrika F••• YEAH!
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Manesero
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Subject:
Question on star trails, muiltple time exposures, and photoshop overlay
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Here is the result of several 2,3, and 5 minute exposures from last night.
The more I overlayed in photoshop the pictures, the brighter each one got...would that be the noise? or just the way it is.
http://www.flickr.com/photos/37565608@N06/3527952032/
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kashani
Title: A Country Boy Can Survive
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Subject:
Question on star trails, muiltple time exposures, and photoshop overlay
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No,
noise in digital is the same thing as "Grain" in film, and it comes from ISO and or long exposures.
Basically its those lil flecks of color you see at the bottom of the photo, and I suspect its in the sky as well, but the photo is to small to really tell.
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With Guns............We Are ~Citizens~.
Without Guns......We Are ~ Victims~.
For America To Live Political Correctness Must Die
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GhostOfACPast
Title: The Phantom Curmudgeon
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Subject:
Question on star trails, muiltple time exposures, and photoshop overlay
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kashani posted:
No,
noise in digital is the same thing as "Grain" in film, and it comes from ISO and or long exposures.
Basically its those lil flecks of color you see at the bottom of the photo, and I suspect its in the sky as well, but the photo is to small to really tell.
Spot on and the sky has the noise as well.
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.\O/
...| <- Drawing of Mohammad doing jumping jacks
...|
../.\ Support freedom of expression. Aleksandr Sdvizhkov...martyr.
Parks sat so King could walk so Obama could run. Aaaaaaaammmmmmerrrrrika F••• YEAH!
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Manesero
Posts:
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Subject:
Question on star trails, muiltple time exposures, and photoshop overlay
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http://www.flickr.com/photos/37565608@N06/3528812235/
I think your right on the noise. This photo merge was done with the overlay feature "lighten" rather than the overlay feature of "screen"
All the stars are a little blurry, but I know that my focus was set an infinity, any reasons why?
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kashani
Title: A Country Boy Can Survive
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Subject:
Question on star trails, muiltple time exposures, and photoshop overlay
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The earth is revolving, and anytime you are using long shutter speeds, the slightest movement causes blur.
Thats why people have a hard time understanding that to photograph the moon correctly, you don't use slow shutter speeds or open apertures, but tighter apertures and faster shutter speeds.
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Nugent for president 2012
With Guns............We Are ~Citizens~.
Without Guns......We Are ~ Victims~.
For America To Live Political Correctness Must Die
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