Anyone here doing long exposure using black glass? This evening I went down to the sea using a .9 and a 1.8 ND filters (first try). This reduced my light about 9 stops but I never could get my exposure over 4 seconds. Wasn't all that bright. I am reading on the internet about 10 minute exposures using a 3.0 filter (10 stops) mid day, how is this possible? My ND value I wasn't that far off, or so I thought. What am I missing? Hoya makes a 2.7 (9 stops) filter which I thought I'd buy if I can't make this combination work.

I set the camera manually using the light meter in camera, centered not under exposed or over exposed. My photos turned out under exposed. I'd guess the white surf might have had something to do with this although it was really grey and not white like snow. I might have to add some shutter time to fix that, not sure about how much? I wasn't happy with what I shot. Does anyone have some insight? If you have some examples please post them.

camera is a 5D with 27-70 f2.8 lens. these RAW photos were taken at ISO 100, F16, 3.2 seconds at 24mm, .9 and 1.8 ND filter on together, 9 stops, manual exposure, cable release. I'd like a longer exposure creating softer water.

Well, I owe you an apology. I saw bulb as a mean to add light via a 'bulb flash', the old magnesium filament burned to create an intense light (replaced by modern flashes). I did not think of it as keeping the mirror up.

You mean to say...they don't still use flash powder! I don't know how long you have been around. Shortly after we were married 41 years ago, we move to CA so I could continue my education. I was working in a camera store and was cleaning out a back room and found some #11 flash bulbs, the kind with a standard light screw base. Clever me I took one home and put it in a light socket in the bedroom. Well my wife turned on the light that night...you might say the room was well lit...for a second. Funny how I was the only one who thought it was funny. Bathtubs weren't made for sleeping.

Doesn't matter that it is mid day, overcast,ND filters, there is still too much light for a really long exposure. Early morning before the sun comes up or in the evening before dark is a good time for long exposure photography. The less light the longer the exposure needs to be. Try photographing the scene at night using the full moon as your only light source ( moon not included in the photo ). With lens stopped down to f16, try exposing for 8-10 minutes. Use this time as a starting point. Make sure your batteries are fully charged.

What he said. Here's an example of a morning shot before sun came over the horizon, I was pointing toward the west, away from the sun. I Used f/9 ISO 100 30second exposure and No ND filters. 30 seconds gave the clouds and waves a nice ghostly look. Not the best shot but just an example before sun rises.