Using 'bulb' mode... Snip - and now discussing Noise Reduction

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April 2008
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Just wondering, is there any way of knowing how long you can/cant expose for, for any given aperture?

Or do you just run off a test shot at say 60" and take it from there depending on what the screen/histogram shows?
 
Either that or use a lightmeter and a stopwatch...
 
I normally fire a test shot and see how it comes out... Then adjust.
 
i make an educated guess from seeing what aperture allows a 30s exposure. then adjust from there.
 
33L said:
i make an educated guess from seeing what aperture allows a 30s exposure. then adjust from there.
Click to expand...

Ah, that sounds like a goood idea. :thumbs:
 
I usually just take a stab at it when shooting on bulb, it seems hard to overexpose some nights. Also, I make sure my long exposure noise reduction is switched off as it is bad enough waiting for the exposure to be finished as it is. I do the noise reduction in DPP afterwards.
 
To be honest i find once over 30seconds it all becomes less critical as one stop is double the exposure time so if you have desire to have shutter open for 5 minutes and you shut it at 7 minutes that isn't even half a stop over and you will get that back if shooting raw anyway and it becomes even less critical the longer your exposures become. Noise is your enemy though ;)
 
Erm, surely you can just use the exposure display in the viewfinder? When the indicator is in the middle it's correctly exposed. Or should be. :p
 
Claire said:
Erm, surely you can just use the exposure display in the viewfinder? When the indicator is in the middle it's correctly exposed. Or should be. :p
Click to expand...

Except that the camera doesn't know how long you intend to keep the shutter open in bulb mode, so it will be unable to give you a correct reading.

Problem I find is that if I set the shutter speed to 60" (Not using bulb in this instance), unless it is very dark I cannot close the aperture enough and the shot will still be overexposed. If only I could set the ISO to a minus figure. ;)
 
ND filter?
 
The ND comment relates to Fabs post :)

I use the trial and error technique for most of my shots too. :D
 
best way, if not most frustrating way to learn! :lol:
 
In fact, generally when I'm using Bulb mode, I want the shot to be as long as possible up to the limits of the mountings under the camera. I also use as wide an aperture as possible and as high an ISO setting as I can get away with.
 
There was a comment earlier in this thread about long exposure noise reduction.

I know there's something I can turn on in the custom functions. But what does it do? And why not have it on all the time? And does it work on RAW files, or just jpegs?
 
Noise reduction in camera usually takes a second exposure of equal length to your actual exposure, ie if you take a pic of 5mins, the camera will then spend another 5 mins doing the noise reduction. For really long exposures this is a royal pain in the arse. Who wants to wait 2 hours for a 1 hour exposure!

AFAIK, this is essentially a dark frame which is then used to remove the noise. The noise reduction exposure is taken with the shutter closed, so any noise shows up as bright spots.

I'm no expert though, so expect a better explanation soon!
 
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