long exposure, what am i doing wrong?

hi

tried some long exposures w/ my 5d iii but they seem to be kind of noisy. hard to tell from this jpeg but in lightroom it is noticeable. you can see it in the crops better. did i just underexpose these, too high iso? or is this normal? I did not have in camera long exp. nr on, and adjusting the noise reduction sliders in LR helps a little, but still the noise is there. these were straight out of camera, w/ nr 0 in lightroom

30 second exposure @ 4.5, iso 1250

Question: what is the purpose of having your iso at over 1000 for long exposure? I would have set the iso at 100 and then let the shutter take a long as it needs...thereby eliminating the additional noise from high iso

The only disadvantage with a longer exposure is the formation of star-trails, as starting to appear in the last image - Some people deliberately go for this, but unless you are poiting at Polaris the movement of the earth will cause this.
Unfortunately at ISO 1000 you will start to get noise, especially if you you want to capture the atmosphere of a dark setting, but I bet it's not noticable at 'normal' image sizes (i.e. not 100% viewing) or if printed.

vilimo wrote in post #14559106
Question: what is the purpose of having your iso at over 1000 for long exposure? I would have set the iso at 100 and then let the shutter take a long as it needs...thereby eliminating the additional noise from high iso

i didn't have my remote at the time to shoot bulb mode so the longest shutter speed i could get was 30 seconds. i wouldn't have gotten enough light w/ a lower iso and 30 second shutter speed. i will try a lower iso next time and remember my remote trigger

vilimo wrote in post #14559106
Question: what is the purpose of having your iso at over 1000 for long exposure? I would have set the iso at 100 and then let the shutter take a long as it needs...thereby eliminating the additional noise from high iso

Agreed. I try keeping my iso set to 100-200

guess high iso noise is more evident in long exposures? 1000 would be pretty clean on a 'normal' shutter spead

With 5D3, you should be able to use iso 1000 during "normal" shooting condition. However, I don't think long exposure is considered "normal" shooting condition ... Also, as you have mentioned above, it is always good to use the remote trigger for this type of shooting - especially for star trails

john_galt wrote in post #14558825
hi

tried some long exposures w/ my 5d iii but they seem to be kind of noisy. hard to tell from this jpeg but in lightroom it is noticeable. you can see it in the crops better. did i just underexpose these, too high iso? or is this normal? I did not have in camera long exp. nr on, and adjusting the noise reduction sliders in LR helps a little, but still the noise is there. these were straight out of camera, w/ nr 0 in lightroom
30 second exposure @ 4.5, iso 1250
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When doing long exposure you need it to be as Dark as possible.
Keep the iso at the minimum 100, and play with your aperture from 8-20.
Aperture depends on how long you will have your shutter open. (Maybe)
Just remember to keep your iso down low!

Possibly try the long exposure noise reduction, assuming the 5D III has that feature. Just be aware that total time to take an image is essentially doubled. A 30 second exposure would take 30 seconds for the image, then roughtly 30 seconds to process the image and remove the noise.

ISO at 100 for me and then I play with the aperture and shutter to get the effect I want. I always review the histogram too. If shooting in the day I will use filters but a long exposure could be 1 second or minutes.