slow shutter speeds and exposure.

[HTCahHTC]

hello everyone!

I am wondering...
how do people take long exposures (like, really long... 2 mins, 15 mins etc...) knowing when to close the shutter? been seeing some perfectly exposed pictures which one had a shutter speed of 384 secs.
so maybe someone could teach or enlighten me?

 

[gymak90]

hello everyone!

I am wondering...
how do people take long exposures (like, really long... 2 mins, 15 mins etc...) knowing when to close the shutter? been seeing some perfectly exposed pictures which one had a shutter speed of 384 secs.
so maybe someone could teach or enlighten me?

Bulb mode. With/without shutter release cable.

 

[HTCahHTC]

Bulb mode. With/without shutter release cable.

yup yup, this i know.
was trying to ask, how do they know whether the pic is undexposed/overexposed?

is like, i'm shooting in Bulb for already 2 mins, how do i know whether i've exposed enough/too much?

 

[zcf]

the oldest way, trial, error and speculation :sweat:

 

[foxtwo]

1. Set mode to Aperture Priority.
2. Set ISO to highest available, example 1600.
3. Set aperture to any choosing, example f5.6.
4. Note shutter speed, example 10s
5. Do mental sums.
- if ISO=100, then shutter speed=160s (1600 --- 10s, 800 --- 20s, 400 --- 40s, 200 --- 80s, 100 --- 160s)
and
- when aperture=f8, then shutter speed=320s (f5.6 --- 160s, f8 --- 320s)
6. Enter final settings into camera, ISO 100 F8 320s

Points to note:
1. At long time exposures, there is little to no difference in mere seconds. A shutter speed of 320s and 325s have little bearing compared to 5s and 10s.
2. It is vital you understand the relation of 1stop=2xAmount of light

 

[night86mare]

yup yup, this i know.
was trying to ask, how do they know whether the pic is undexposed/overexposed?

is like, i'm shooting in Bulb for already 2 mins, how do i know whether i've exposed enough/too much?

not that hard.

shoot wide open, get the exposure, then use stops and all that to adjust accordingly.

if you are talking about extremely, extremely long exposure then i can't help you there. it's all up to guestimation and experience. i suppose for things like star trails it doesn't really matter, since you will be at a location where you will find it hardpressed to end up overexposing. the only problem is underexposure.

 

[gymak90]

For me, I do trial and error.

I don't think a light meter will work at night.

So start off with a rough shot and get some values. Then compensate accordingly by the number of stops.
Basically at night, it is near impossible to get an overexposed shots, except when you have lights. Thus again, adjust accordingly until you're satisfied.

 

[catchlights]

for digital, unlike film, you need not to bother about the reciprocity failure.

 

[HTCahHTC]

hey.
thanks for all the replies and inputs.
will try out someday.
once again, thanks!

 

[attap seed]

for long exposure, there is no need to be very accurate.

eg, 1 sec and 2 sec is ONE stop difference.

5 min (300sec) and 10min (600sec) is also ONE stop difference.

so, its perfectly alright to plus minus 1 or 2 dozen seconds, and end up w essentially the same exposure.

 

[HTCahHTC]

for long exposure, there is no need to be very accurate.

eg, 1 sec and 2 sec is ONE stop difference.

5 min (300sec) and 10min (600sec) is also ONE stop difference.

so, its perfectly alright to plus minus 1 or 2 dozen seconds, and end up w essentially the same exposure.

really? :bsmilie:
didn't know that. thanks dude.

 

[night86mare]

really? :bsmilie:
didn't know that. thanks dude.

every stop approximately double

so for example, 60 seconds is one stop more than 30. etc etc etc