# Star trail photography.. PROBLEM!



## D-B-J (Oct 10, 2010)

So i took my first star trail photo last night, at 45 minutes, iso 100, f8.  The stars are a little dark so i am going to retry tonight.  Problem is, the corners are a light pink.  I dont have the image cause this isnt my computer and it cant read or convert the raw files.  But around the corners and edges are a faint pink.  Is this light leaking in from the viewfinder?  My viewfinder cover is at home, so should i tape over it? Or is my sensor screwy?>?

Thanks!


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## KmH (Oct 10, 2010)

It may just be ambient light. Were you at a dark site, or in town?

Today the hot set-up for doing star trails is doing a bunch of exposures at 30 seconds or so, and then stacking them.

Did you try using the forums search feature: http://www.thephotoforum.com/forum/beyond-basics/216787-stair-trail-using-slow-exposure.html

Did you do what Sw1tchFx recommended in your other thread: http://www.thephotoforum.com/forum/...otographing-night-star-trails-lightening.html


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## DerekMellott (Oct 10, 2010)

KmH said:


> It may just be ambient light. Were you at a dark site, or in town?
> 
> Today the hot set-up for doing star trails is doing a bunch of exposures at 30 seconds or so, and then stacking them.
> 
> ...




You will not get any movement in 30 secs unless you are zoomed in. the earth moves about a degree a minute so you do need to have a long exposure. try 5-10 min exposures and stack them, also up your iso.

The good thing about short exposures is you can see the results more often and make correction to get a better image.


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## prodigy2k7 (Oct 10, 2010)

DerekMellott said:


> KmH said:
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> > It may just be ambient light. Were you at a dark site, or in town?
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I agreed with everything until you said that. Why up ISO? This will just increase the noise that you already get.


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## DerekMellott (Oct 11, 2010)

prodigy2k7 said:


> DerekMellott said:
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He said the stars were dim, up the ISO, try 200, 400, 800 see what you get the picture is free to take, play around.

I do my night shooting at 800 with no noise, but I rarely do multi minute exposures.

Keep it at iso 100 but go to your widest f stop, f8 is too small


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## prodigy2k7 (Oct 11, 2010)

DerekMellott said:


> prodigy2k7 said:
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Im sure you get some noise in the dark like that at ISO 800?
Yes use ISO 100, open your aperture more, use longer shutter speeds.  Or get a film camera and leave it open all night.


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## DerekMellott (Oct 11, 2010)

prodigy2k7 said:


> DerekMellott said:
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any noise is only in lit areas the sky is black, but this is with 20-30 sec not 5 to 10 mins.

I have not done star trails since I used my Nikon fm10 12 years ago, good old film. even then I used iso 400.


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## DerekMellott (Oct 11, 2010)

I took a bunch of images I shot for a time lapse and stacked them to see how it looks.
These are 20 sec f3.5 iso 800, the exposures were taken about 10 seconds apart and I stacked about 70 of them.

The lights are from a police officer who was wondering what I was up to.


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## prodigy2k7 (Oct 11, 2010)

I can see plenty of noise.


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## DerekMellott (Oct 11, 2010)

prodigy2k7 said:


> I can see plenty of noise.



Yes in the lit areas as I previously stated. I didn't post it as an example of noise it was an example of technique ie. the topic of the thread.


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## John Mc (Oct 11, 2010)

I like the image,im not sure what it is about it,but i actually like it


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## nemopaice (Oct 11, 2010)

.


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## Sw1tchFX (Oct 11, 2010)

There are two main ways of doing star trails, you can do what most people do, which is what DerekMellott does by shooting a series of short exposures and stacking them, or do it the old fashioned way and do it in a single exposure. Both have pros and cons.

The purple or magenta clouding you're getting in the corners is called amp noise. Film has what's called reciprocity failure, where if there's not enough light, film loses sensitivity. Digital doesn't have this. digital has a constant amplifier which turns up the volume on the signal the sensor picks up. The problem with this, and it's mostly with cameras with CCD sensors (like your D200) is the amplifier heats up the sensor so much, you start having purple and magenta clouds on the edges of the sensor where it's the hottest. CMOS sensors do this too, but aren't nearly as much. 

The easiest way to get star trails is to get outside of the city. take a drive, go at least 50 miles out of the big city if possible. Light pollution is ridiculous in the U.S. especially around metro areas. 





The best way in my experiences so far shooting at night digitally is this:

Put the camera on a tripod with manual expsoure and Kelvin WB, compose the picture and focus.

If you have a camera that can do it, use contrast detect AF in live view. If you have a lens like the 24, 35, 50, or 85 1.4, you can set the lens to f/1.4, and use Contrast AF in Live View to focus on a bright star, if it doesn't catch, which it usually does for me, you can manually focus. Once you've done that, flip the lens to MF so it won't try and reacquire. Reason I do this is so that I know focus is perfect beyond shadow of a doubt.

Than set your WB to something cool, i usually start at about 2500ish and go up from there if needed.

Crank the ISO to 25600, you'll have to use 3200 (Hi 1).

Set your shutter speed between 5-30 seconds, you don't want to go too long, and it's ok if the stars blow out. The key here is to get the ambient exposure correct.

I usually leave the aperture close to wide open, if not wide open.



Now bear in mind, the first shot's going to look like dogsh*t, but that's ok. We just want to get our ballpark exposure without waiting 15 minutes, just to find out we got it wrong.

SO, with that in mind, here's a shot of mine, the initial exposure was ISO 25600, 4 seconds, f/2:





PERFECT! It's noisy as all hell, but that's ok. Now we know it's pretty dark, so we'll compensate for that no problem.

So now that we have our base exposure of 4 seconds ISO 25k, f/2, now we just have to crunch the numbers down to the same exposure at ISO 200, adjust our shutter speed a couple stops and stop the lens down a little more!

Easy.

about 32 minutes, ISO 200, f/2.8. Rack it off:




SWEET!

That's right on! 

So now just bring it into lightroom and do some post and you'll have this:







Basically, just do a rough, high ISO shot, get your general exposure, than crunch the numbers down to the equivalent exposure at ISO 100. 

It's pretty easy after you do it a few times. This is also why alot of photographers are interested in really fast glass and mega aperture primes. 

On the D2x, D200, D40(x), D50, D60, D70, D80, and D3000 Nikon's, you MUST turn on Long Exp Noise Reduction. FF cameras like the D3s and D700 don't need this, but the CCD partial frame sensor cameras do. What it does is after say a 30 second long exposure, the camera takes _another_ 30 second exposure of nothing and subtracts the noise from that exposure from the one you composed. This is how you get rid of that purple clouding. The D200 is OK at it, my D70 was atrocious. It can't do anything longer than a couple minutes. My E-P1 is also just terrible, 4/3rds really can't go past 60 seconds without starting to fall apart.

Now you can also do what's called stacking. Stacking is taking a bunch of shorter exposures where it's just enough to see stars, than "stacking" them all in Photoshop. This is a good method because it's possible to capture more stars, but at the expense of ambient light if you're way outside of the city. I prefer the single exposure method. 

Some Nikons can actually do the stacking _for you_ so you can skip the step in photoshop. It's great because along with stacking the exposures for you immediately, it also suppresses noise by averaging it out. On the D700, you can shoot 10 ISO 1600 shots, have the camera stack them, and the image will have noise characteristics of an ISO 200 shot. It's pretty remarkable to be honest. having the D700 stack the exposures at low ISO's like 100 or 200 yield the purest files i've ever seen from any SLR by anyone. Problem is, depending on the camera, the limit is 3-10 pictures. 

hope that helps!


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## sam_justice (Oct 11, 2010)

Sw1tchFX said:


> There are two main ways of doing star trails, you can do what most people do, which is what DerekMellott does by shooting a series of short exposures and stacking them, or do it the old fashioned way and do it in a single exposure. Both have pros and cons.
> 
> The purple or magenta clouding you're getting in the corners is called amp noise. Film has what's called reciprocity failure, where if there's not enough light, film loses sensitivity. Digital doesn't have this. digital has a constant amplifier which turns up the volume on the signal the sensor picks up. The problem with this, and it's mostly with cameras with CCD sensors (like your D200) is the amplifier heats up the sensor so much, you start having purple and magenta clouds on the edges of the sensor where it's the hottest. CMOS sensors do this too, but aren't nearly as much.
> 
> ...



:EDIT: DUMB QUESTION PLEASE IGNORE:EDIT:
Nice shot


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## DerekMellott (Oct 11, 2010)

John Mc said:


> I like the image,im not sure what it is about it,but i actually like it



Thanks, this was not the intended use of these shots, they were shot for use as a time lapse but I didn't like it and they were in the garbage pile.
I just did this to try out the stacking technique for star trails and they were the only images I had on hand.

P.S. i used cropped and resized lower res images, I'm sure if I went back and started at the raw file it would look a bit better.


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## McNugget801 (Oct 11, 2010)

stacking stacking stacking

Stacking, High ISO, Short Exposure, and Wide Aperture

Its rare for me to shoot trails under ISO1600 these days.

When stacking I ALWAYS light paint the foreground 3 or 4 different ways around ISO400 - F5.6 - 20sec exposure.  This way I have a few options to work with in post.

some of my recent trails

30sec - F2.8 - ISO1600
Camp Trails - Capitol Reef 5.29.2010 | Flickr - Photo Sharing!






Star Trails at the Point Reyes | Flickr - Photo Sharing!





http://www.flickr.com/photos/summit42/5057122852/


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## DerekMellott (Oct 11, 2010)

McNugget801 said:


> stacking stacking stacking
> 
> Stacking, High ISO, Short Exposure, and Wide Aperture
> 
> ...



Nice! These are great, thanks for sharing!


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## D-B-J (Oct 11, 2010)

I'm still not sure how to reduce the pink corners..

And how are you supposed to stack them?


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## Sw1tchFX (Oct 12, 2010)

D-B-J said:


> I'm still not sure how to reduce the pink corners..


turn on long exposure noise reduction on the camera


D-B-J said:


> And how are you supposed to stack them?


use Photoshop and overlay them


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## D-B-J (Oct 12, 2010)

Sw1tchFX said:


> D-B-J said:
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> > I'm still not sure how to reduce the pink corners..
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I's there a simple way to over lay them?


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## McNugget801 (Oct 12, 2010)

Sw1tchFX said:


> turn on long exposure noise reduction on the camera



Careful with that one....
When noise reduction is enabled in a lot of SLRS is can cause a bit of a delay in the shutter release between images. If you get even a two second delay your trails will have little gaps and bee worthless.
My XSi would keep up fine until it got a few images in then the camera would lag a bit when trying to keep up with the noise reduction and back to back firing.





D-B-J said:


> I's there a simple way to over lay them?



startrails.exe


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## Sw1tchFX (Oct 12, 2010)

McNugget801 said:


> Sw1tchFX said:
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ahhh good point..didn't think of that.


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## softball29 (Dec 3, 2010)

McNugget801 said:


> stacking stacking stacking
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> Stacking, High ISO, Short Exposure, and Wide Aperture
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> ...



Wow.

I'm just starting to try my hand at star trails and have been researching, but these are simply incredible. 

I need to learn about stacking as I have no clue. There's a couple of covered bridges in my area and I'd like to use those for the star trails and I think the stacking might do best being there might be some light here and there etc. 

These are inspiration, though. Simply awesome.


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## timlair (Dec 3, 2010)

D-B-J said:


> Sw1tchFX said:
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There are a few free (and paid) programs out there on the net that does the stacking for you. Google it. Not hard to find.


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