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!
![[No title]](/data/xfmg/thumbnail/39/39476-6e232ea205145ad1a1da0690d7617642.jpg?1734173571)
