need help with star trails

chrismoore

This is my very first attempt at star trails. I want to be able to get it right so when I have a real opportunity somewhere nice I won't mess it up. This is from my backyard. 45 min exposure, f/4.0, ISO 100, bulb mode, canon 5D. The unprocessed image was VERY noisy... is this typical? I used a noise reduction program to reduce it a bit, but the more I reduced it the more the trees lost their definition. I also increased the contrast slightly. Image is still more noisy than the star trail posts I see in Dgrin.
My question for any experts out there- are there different camera settings I should be using? what typically is required in post processing for these type shots? are they always that noisy out of the camera?
Thanks so much for your help.

pyry

chrismoore wrote:

This is my very first attempt at star trails. I want to be able to get it right so when I have a real opportunity somewhere nice I won't mess it up. This is from my backyard. 45 min exposure, f/4.0, ISO 100, bulb mode, canon 5D. The unprocessed image was VERY noisy... is this typical? I used a noise reduction program to reduce it a bit, but the more I reduced it the more the trees lost their definition. I also increased the contrast slightly. Image is still more noisy than the star trail posts I see in Dgrin.
My question for any experts out there- are there different camera settings I should be using? what typically is required in post processing for these type shots? are they always that noisy out of the camera?
Thanks so much for your help.

For exposures that long, yes you do get a lot of noise.

You can get cleaner results if you shoot the trail in shorter bits, I've used two minute exposures, with the help of a programmable cable release. You can stack the parts together in post.

schmoo

Great trails! Yes, with an exposure as long as 45 min (and even less than that) you can get a lot of digital noise. There's a lot of info and examples in this thread here, if you want to see some more chatter about this kind of shooting!

chrismoore

schmoo wrote:

Great trails! Yes, with an exposure as long as 45 min (and even less than that) you can get a lot of digital noise. There's a lot of info and examples in this thread here, if you want to see some more chatter about this kind of shooting!

Thanks Schmoo for pointing me there, don;t know how I missed it. Lots of good stuff in that thread and lots of ideas to try out.

chrismoore

pyry wrote:

For exposures that long, yes you do get a lot of noise.

You can get cleaner results if you shoot the trail in shorter bits, I've used two minute exposures, with the help of a programmable cable release. You can stack the parts together in post.

Thanks. That seems to be the consensus in the thread the shmoo pointed me to. I downloaded that photoshop action and will try it out at some point.

Can you point me to a programmable release? I searched on B&H and amazon with no luck.

pyry

chrismoore wrote:

Thanks. That seems to be the consensus in the thread the shmoo pointed me to. I downloaded that photoshop action and will try it out at some point.

Can you point me to a programmable release? I searched on B&H and amazon with no luck.

For Canon the answer might be the TC-80N3.

chrismoore

pyry wrote:

For Canon the answer might be the TC-80N3.

Thanks!

kdog

Don't forget you get a poor-mans interval timer with just a standard remote by simply setting your shutter speed to 30 seconds, and locking the button down for as long as you want to keep taking them.

chrismoore

kdog wrote:

Don't forget you get a poor-mans interval timer with just a standard remote by simply setting your shutter speed to 30 seconds, and locking the button down for as long as you want to keep taking them.

Yeah, that's probably what I'll end up doing at least for now. I did read on that other thread, however, that it is recommended to pause a short interval between exposures because the heat or whatever can increase the noise. Not sure how significant that is though. But the poor man's timer beats sitting in a chair for 2-3 hours and repeately pressing the shutter every 30 seconds.

pyry

chrismoore wrote:

Yeah, that's probably what I'll end up doing at least for now. I did read on that other thread, however, that it is recommended to pause a short interval between exposures because the heat or whatever can increase the noise. Not sure how significant that is though. But the poor man's timer beats sitting in a chair for 2-3 hours and repeately pressing the shutter every 30 seconds.

Depends on how hot it is outside. I've shot with only one second gaps, without any noise issues, but that was in freezing temps. Pausing for too long will cause visible breaks in the trail, and I'm not certain it would be possible to stop for long enough to produce any meaningful cooling. Something to test then

Besides, I think that when you stack the trails together you will essentially average the background anyway, if the exposures are even. If they're not, it's possible to make an averaged image with no trails (or stars!) and use that as a base to add the trails on for essentially noise free images.