Help with Night Long Exposures Please

TurnipFarmer

TurnipFarmer

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Aaron
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I am practising my long exposures at night however when I get past 30 seconds exposures and it goes into bulb mode how will I know how long the exposure has to be? Is there any exposures tables or calculations I should use?

I just want my exposures to be correct, I do have a timer release remote which should help.

:thumbs:
 
Practice.. but night exposures are very forgiving. You just need to remember that the difference between 1 minute and 4 minutes is only 2 stops.. or the same as the difference between 1/250 and 1/1000th of a second.

You can set your ISO to 800 or 1600 or higher and take your meter reading through the camera, maybe even fire off a test shot. Then bring your ISO back down to 100 and add the extra stops back onto the shutter speed.

So.. keeping the maths easy.. at ISO1600 you metered the scene at 5 seconds and a quick test shot looked about right on the lcd screen (for what you had in mind).. you put the ISO back down to 100 and change the shutter speed to 80 seconds (doubling the shutter speed for every halving of ISO on the way from 1600 to 100). You can time the 80 seconds with your watch and use a regular remote shutter, or you can use a remote shutter with a built-in count-down timer for doing bulb exposures. Being bang-on 80 seconds isn't going to be critical.. 5 seconds either way really won't make much difference.
 
Alastair said:
Practice.. but night exposures are very forgiving. You just need to remember that the difference between 1 minute and 4 minutes is only 2 stops.. or the same as the difference between 1/250 and 1/1000th of a second.

You can set your ISO to 800 or 1600 or higher and take your meter reading through the camera, maybe even fire off a test shot. Then bring your ISO back down to 100 and add the extra stops back onto the shutter speed.

So.. keeping the maths easy.. at ISO1600 you metered the scene at 5 seconds and a quick test shot looked about right on the lcd screen (for what you had in mind).. you put the ISO back down to 100 and change the shutter speed to 80 seconds (doubling the shutter speed for every halving of ISO on the way from 1600 to 100). You can time the 80 seconds with your watch and use a regular remote shutter, or you can use a remote shutter with a built-in count-down timer for doing bulb exposures. Being bang-on 80 seconds isn't going to be critical.. 5 seconds either way really won't make much difference.
Click to expand...

My head hurts :bang:
 
Shutter speed works on a halving/doubling scale, twice the time will increase the exposure by one stop, halving the time will reduce the exposure by one stop.

Therefore if a 30 second exposure is showing on the camera meter as 1 stop underexposed, you need to use 60 seconds in bulb mode. :thumbs:
 
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The one stop underexposed etc confuses me, is this shown in the view finder? Im still learning and want to do the long exposures, but need to get my head around it a bit before start doing it, otherwise im going to lose faith.
 
Yeah there should be a scale in the bottom of the viewfinder (looks a little like this <------l------>) each step on the scale indicates 1/3rd of a stop so three steps to the right of the middle would be 1 stop overexposure and 6 steps to the left would be 2 stops underexposure and you can then work out the shutter speed needed from there.
 
cheers guys for the advise, big thank you to Alastair. I think I got the hang of it but alot of it is trial and error. I went out in Scarborough last night so will post some of those night shots up soon and see what you think.

The only other problem that I was having too that you may be able to help with is that in certain night shots, some parts of the image were well over-exposed as they were the brightest part of the photo, no matter what I did with the aperture or the shutter speed it did not correct this problem. Is there a way to balence out the light so the light in the lightest part looks balanced with the rest of the light in the photo, if you get whatI mean??:thinking:
 
Examples help if you could post some (and it's easier to suggest things you can change if we see the ones that didn't work quite the way you wanted and the settings you used).. but in general if there's any source of bright light in a night scene (artificial light, the moon) it will tend to over-expose unless you choose to expose for that area.. but that may mean that other areas are completely under-exposed. This creates circumstances where it's impossible to get all the elements of the shot exposed the way you want them.. in that case you have no option but to take more than one shot and composite the final image.

Here's an example..



Ignore the fireworks.. but in this shot it's not possible to get the moon and the quayside exposed in a useful way in the same shot, exposing for the moon would under-expose the quayside, exposing for the quayside over-exposes the moon (and leaves it as an elongated blob, because the moon moves faster across the sky than you think).. so leaving the camera on the tripod the scene was exposed twice (once for the moon and once for the quay) and the two shots composited. Keeping the composition and the focus identical means that the moon remains the right size and in the right position in the sky.

Here's one where I didn't composite the moon.. there's areas of the shot under-exposed but the moon is completely blown (and the clouds reflecting it's light around it).



Shooting RAW also helps a lot with night shots (it's compulsory in my opinion).. you've got more detail to play with and a bit more leeway for balancing the shadows and highlights in post.
 
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