lengthenenening exposures
Discussion
a noob question if ever there was one... I presume I need a filter of some description to lengthen exposures, what do I need, and what do I need to take into consideration?! I was trying to capture some light streams a few days ago, but was maxed out on exposure time and they were still way too short.
I've seen some people use a 10 stop ND filter to get very long exposures during daylight hours.
Most DSLRs also have a bulb setting that you can use, which gives you full control over when the shutter opens and closes - giving you the option to have exposures running into many minutes or even hours.
Most DSLRs also have a bulb setting that you can use, which gives you full control over when the shutter opens and closes - giving you the option to have exposures running into many minutes or even hours.
If you've already got the ISO at the lowest it will go to, and the lens's aperture as small (big f numbers) as you want want to go to, then you need a neutral density (ND) filter: basically just a grey filter that blocks out some of the light.
These come in various levels that filter out progressively more f stops of light out. I.e. a one f stop ND filter halves the amount of light getting to the sensor and doubles your exposure time, a two f stop quarters it and quadruples your exposure time and so on. They're marked either by the number of f stops the filter out, or with another system where 0.3 is one stop, 0.6 two stops, 0.9 three stops etc.
They come in either square types that you slot into a special holder that goes on the front of your lens (made by Cokin, LEE, Formatt) or circular ones that go screw straight on (made by Hoya, B+W and others).
ETA: I may have misunderstood you. Are you saying that you've already got to the maximum exposure time your camera will allow (probably 30 seconds or thereabouts), or that you can't increase the exposure time to cause blurryness because there's too much light? If the former, bulb mode is what you need; if the latter, an ND filter is what you need.
These come in various levels that filter out progressively more f stops of light out. I.e. a one f stop ND filter halves the amount of light getting to the sensor and doubles your exposure time, a two f stop quarters it and quadruples your exposure time and so on. They're marked either by the number of f stops the filter out, or with another system where 0.3 is one stop, 0.6 two stops, 0.9 three stops etc.
They come in either square types that you slot into a special holder that goes on the front of your lens (made by Cokin, LEE, Formatt) or circular ones that go screw straight on (made by Hoya, B+W and others).
ETA: I may have misunderstood you. Are you saying that you've already got to the maximum exposure time your camera will allow (probably 30 seconds or thereabouts), or that you can't increase the exposure time to cause blurryness because there's too much light? If the former, bulb mode is what you need; if the latter, an ND filter is what you need.
Edited by SamHH on Monday 21st September 11:09
SamHH said:
If you've already got the ISO at the lowest it will go to, and the lens's aperture as small (big f numbers) as you want want to go to, then you need a neutral density (ND) filter: basically just a grey filter that blocks out some of the light.
That was exactly it Sam - my apologies to all it was a bit vague wasn't it! Yes basically with the aperture full wound and ISO at it's lowest, it was overexposing if I manually increased exposure to try and lengthen the light streams. Off for some ND filters I go 
Klankie said:
There's a new fad doing the rounds, using a glass out of a welders mask to increase exposure time, its to avoid shelling out £££ for a 10-stop ND filter.
I've yet to try it as I have a limitless supply of said glasses, but not much time!
Hardly Neutral Density though, is it? I've yet to try it as I have a limitless supply of said glasses, but not much time!
Most welding glasses/helmets I've seen have green glass.
Ravell said:
Klankie said:
There's a new fad doing the rounds, using a glass out of a welders mask to increase exposure time, its to avoid shelling out £££ for a 10-stop ND filter.
I've yet to try it as I have a limitless supply of said glasses, but not much time!
Hardly Neutral Density though, is it? I've yet to try it as I have a limitless supply of said glasses, but not much time!
Most welding glasses/helmets I've seen have green glass.
There's a whole thread on another forum about it, is one aLlowed to link to other forums?
If so I'll find it and post a link.
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