Beginner Bulb Mode

taff63

taff63

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Tried to do this today on a river/weir hoping for a long exposure I left shutter open for a min at least
but when I checked all I had was a white screen now I normally use bulb when doing traffic trails with no problems but this has
confused me (not hard) was in manual mode with a 70/130 lens any help/advice really appreciated .

mark
 
If your doing long exposures in daylight you need a strong ND (Neutral Density) filter in front of the lens to dramatically reduce the speed/amount of light reaching the sensor, because you've been unfiltered you've completely burnt out the image...hence why it is just white...what this means is you were completely over exposed the filter reduces the available light so that but a fraction of the available light actually hits the sensor

You can look at welding glass as a cheap alternative to strong NDs but you'll never get the results with welding glass as you will with the real deal filter
 
It was probably dark when you were doing the traffic trails, but daylight when you were by the river..
 
taff63 said:
Tried to do this today on a river/weir hoping for a long exposure I left shutter open for a min at least
but when I checked all I had was a white screen now I normally use bulb when doing traffic trails with no problems but this has
confused me (not hard) was in manual mode with a 70/130 lens any help/advice really appreciated .

mark
Click to expand...


you need to achieve a correct long exposure - what you've basically done is massively overexposed your shot, which is why its white

as matt says the best way to achieve this is to use an ND filter in front of the lens to reduce the amount of light coming in.

If you don't have an ND , the other option is to get as long an exposure as possible from your camera settings - ie if you set your iso as low as it will go (usually 100 but some cameras can go to 50) and set a small aperture like F22 , then you will get a slowish exposure (it still won't be a minute in day light)
 
thank you Mathew will try the welding glass next time I,e in the morning if weather is good as I have a piece already glued to a filter ring
also with welding glass this may sound silly but would I have to compensate exposure I,e up/down
 
taff63 said:
thank you Mathew will try the welding glass next time I,e in the morning if weather is good as I have a piece already glued to a filter ring
also with welding glass this may sound silly but would I have to compensate exposure I,e up/down
Click to expand...

You don't have exposure compensation in bulb, the trouble with welding glass is we don't really know how strong it is (eg how much light it cutting out) I us a B&W ND110 myself which is a 10 stop filter as a result a unfiltered exposure of 1/15th with the filter will become a 1 minute exposure see the chart below

ndchart-jpg.78160


SOURCE
 
also about 'if the weather is good' you can get a longer exposure if the weather is crap because cloud and rain cut the available light (the same applies to shooting in the 'blue hour' after sunset)
 
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