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09/28/2008 09:13:12 AM · #1 |
| I was just wondering, I see all of these pictures of star trails and long exposures, 30min exposures, 1 hour exposures. I can't seem to wrap my head around it. How do you get your shutter to stay open for a half hour or an hour exposure? |
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09/28/2008 09:23:52 AM · #2 |
| Put you camera to Manual Mode and then set the shutter speed to Bulb. If you have a shutter release cable then it is pretty much a necessity, or a remote for that matter. |
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09/28/2008 11:00:44 AM · #3 |
| When doing very long exposures like that it is also wise to do a high ISO test shot to make sure your exposure is right - you wouldn't want to wait for a 30 minute exposure and then not get the correct exposure. |
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09/28/2008 11:19:37 AM · #4 |
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09/28/2008 11:22:38 AM · #5 |
Originally posted by d56ranger:
Don't forget your tripod |
Handholding a 30 minute exposure - when's the next abstract challenge? :D |
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09/30/2008 09:36:28 PM · #6 |
| Im not so sure about the high ISO for a really long exposure like that. I am willing to bet the image quality would be horrible. |
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09/30/2008 09:40:09 PM · #7 |
Originally posted by darnok:
When doing very long exposures like that it is also wise to do a high ISO test shot to make sure your exposure is right - you wouldn't want to wait for a 30 minute exposure and then not get the correct exposure. |
Typically, for long exposures, you don't want to use high ISO's.
You want to stick to the lowest, or base, ISO your camera has. Like 100, or 200.
If you take a minute long exposure with a high ISO, your results aren't going to be very clean. Noise-wise that is.
There is a brilliant tutorial here on DPChallenge made by Philos, found Here.
Definitely worth reading. |
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09/30/2008 09:45:16 PM · #8 |
| He is talking about testing it at a high ISO so that you test exposure time is shorter. Then after you get the right exposure with the high ISO there is a formula to figure out how long you have to keep the shutter open at 100 iso. Does that clear it up? Your final shot is of course at 100 iso but all your test shots dont have to be 30 minutes you see? |
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09/30/2008 10:29:57 PM · #9 |
Originally posted by Patrick_R:
He is talking about testing it at a high ISO so that you test exposure time is shorter. Then after you get the right exposure with the high ISO there is a formula to figure out how long you have to keep the shutter open at 100 iso. Does that clear it up? Your final shot is of course at 100 iso but all your test shots dont have to be 30 minutes you see? |
Glad you cleared that up. We almost jumped to a confusion.
I knew exactly what was being suggested. It's a good idea if you don't have time to wait all night to get the correct EV.
Tungsten WB will give you nice blue skies in a lot of night shots, esp where there are street lights polluting the night sky.
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10/07/2008 11:19:23 AM · #10 |
It should be mentioned that you must have a bulb shutter setting on your camera in order to take star trails. I have a feeling a good number of digital cameras do not have this.
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10/07/2008 12:09:33 PM · #11 |
Originally posted by Patrick_R:
He is talking about testing it at a high ISO so that you test exposure time is shorter. Then after you get the right exposure with the high ISO there is a formula to figure out how long you have to keep the shutter open at 100 iso. Does that clear it up? Your final shot is of course at 100 iso but all your test shots dont have to be 30 minutes you see? |
That's correct. I should have been more specific about what I meant in my initial post.
This shot is a 15 minute exposure at f/8 (ISO 200). The light meter is pretty useless when it's that dark and if I had been taking my test shots at ISO 200 (used ISO 200 instead of 100 because I didn't want to do a 30 minute exposure) I would have been out in the cold all night long. I knocked up the ISO to 3200 (max on the D200) and opened the aperture to f/4 and took test shots to get the exposure correct. The noise was horrible (even on the small LCD preview) and the colours were bad - but the histogram was correct. I then set my aperture to f/8 (2 stops adjustment) and ISO to 200 (4 stops adjustment) and therefore had to increase my aperture by 6 stops to maintain the same exposure. Working in the other direction now, the correct high ISO exposure will be 14 seconds - much better than waiting around for 15 minutes. This way I only had to take one long exposure - I even put the camera back in my bag as soon as the shutter closed (it still had to do the dark frame noise reduction) and went home because I was freezing.
Originally posted by Dermot:
It should be mentioned that you must have a bulb shutter setting on your camera in order to take star trails. I have a feeling a good number of digital cameras do not have this. |
A cable release that you can lock is also an essential piece of gear for long exposures.
Originally posted by MelonMusketeer:
Tungsten WB will give you nice blue skies in a lot of night shots, esp where there are street lights polluting the night sky. |
For long exposures it's best to shoot RAW, both for the increased dynamic range and signal-to-noise ratio as well as being able to set your white balance. It is very annoying to have the colours of a long exposure come out wrong because you didn't use the correct white balance setting. When standing (in the cold) on concrete blocks in the water you want to spend less time fiddling with camera settings and more time trying not to fall in :D |
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