Luminous Landscape Forum
Equipment & Techniques => Landscape & Nature Photography => Topic started by: sandc on August 10, 2015, 02:05:59 pm
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Hi, I tried to take some shots of stars and star trails at the beach. The result: grainy and dull. The star trail ones I did only one single long exposure shot for 30 min and very low ISO (160-350). I don't understand why so much noise if ISO was low? The ones without the trail I did use high ISO (ISO 2000) but still, If I would wanted to print the picture it wouldn't look good. Way to much noise! Why is that? I used a Canon 50D, Cosina 19mm-35mm lens. Is it the camera? So please take a look at the pictures and let me know your opinion or if you have an advice to give me to avoid so much noise on the picture. I must add that there was some light from nearby houses. It wasn't in the middle of nowhere. Could that affect it? My theory: stars where not as bright because of artificial light coming from the area were I was. So that caused little contrast between stars and dark sky there producing a lot of noise.???
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the last picture (or screen shot) is a close up at 50% of the none star trail shot.
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30 minutes of single exposure is going to be noisier than 30 x 1 minute exposures with 5 second gap between each. The 30 1 minute shots are stacked in photoshop and auto-blended. There are a number of astrophotography books and fora out there - I just bumped a recent LuLa post in this forum up top "books about landscape astrophotography"
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http://starcircleacademy.com/quick-tips/
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Looking at it at 100% on screen makes it seem noticeably more grainy than printing it, even to 13x19" and looking at it at normal viewing distance (and, even close up, as well). Also, use LR to control the noise and sharpening. Increasing Clarity helps, to create the local contrast you may be looking for.
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One device that I like to use is the Triggertrap and app that goes with it: http://www.triggertrap.com/#_l_ui
This puts the tools you need in a convenient app as well as giving access to some tutorials that may be helpful. Also simply Google Star Trails to get great hints.
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There is noise because noise is principally related to the light levels, not what ISO you are using. You tend to associate high noise with high ISOs only because they tend to go together in real life (i.e. when you're taking shots in very low light). It's the light levels that lead to poor signal-to-noise ratios - any ISO on any camera will be comparatively noisy under the conditions you shot in. There are better cameras than yours for low light noise performance but it won't make the difference you expect, I would bet. There's nothing 'wrong' with it as such.
You're right that the foreground is brighter than the background and you could have used a much higher ISO to boost the signal-to-noise ratio of the stars if there wasn't a risk of blowing out the foreground.
I'd suggest two things: 1. Get your aperture right down as low as you can (why use f6.3?) to increase light and hence decrease noise. 2. In lightroom/PS, increase clarity to the max in the star areas, plus bring blacks down and whites up. It should improve it quite a bit.