Exposing for Bulb mode

[Biomech]

This was in a my photography magazine this month. Maybe it's how everyone does it, but I never though of it before and thought it was quite a good idea.

The bloke shot an atmospheric shot of a power station, looking up with a whispy sky set in black and white. He shot the picture at 60 seconds to get the smoothness in the sky/smoke and he did it like this:

Switched to aperture mode and set the correct, deep, aperture.
Pushed the ISO up to 3200 and took a reading - the camera set the shutter speed at 2 seconds.

Then he counted down the ISO and up the shutter speed (or vice versa depending on your take)

2 seconds @ 3200 became
4 seconds @ 1600
8 seconds @ 800
15 seconds @ 400
30 seconds @ 200 and then ended on
60 seconds @ 100

Which gave the image the correct exposure and minimal noise.

If you have it, it 's in Practical Photography Issue June, P.50

[zona5101]

Do digital image sensors suffer from reciprocity failure? If so then calculating stops doesn't usually work when the exposure times get much longer that 1 min. iirc, reciprocity failure was a function of the film. I suppose I should take my own advice and google it rather than speculate...

[inkista]

Originally Posted by zona5101

Do digital image sensors suffer from reciprocity failure?

Nope. Film-only. One of the really nice things about digital for night-time shooting.

[OsmosisStudios]

I've learned to do stops on my fingers, but it doesn't usually work past a minute or so. With a 10-stop Neutral Density filter, I often end up in the 8-30 minute range, and counting stops rarely works so I end up doing several. Takes foreeeeever.

[zona5101]

Originally Posted by inkista

Nope. Film-only. One of the really nice things about digital for night-time shooting.

i like you soooo much better than google

[ravncat]

If you happen to have an old luna pro light meter lying around - you can also use it to give meter readings down to about 8 hours... which can be handy, should you be interested in measuring for a really long exposure.

It can get difficult to get a reading from your digital camera's meter when you get to very very low light (let alone an accurate one) The ISO trick is certainly good for very low light Thanks for sharing

[SwissJon]

LoL.. You read the same article as me.. Made interesting reading, I hadn't considered using the ISO to make a quick check, although his subject matter left a bit to be desired, but I guess we work with what we have.

I've got a free app on my iPhone called "Longtime" that does the hard work for me, tell it what the reading without filter is, tell it what filter you have, and it does the maths for you.. I do find that an ND10 filter isn't neccesarily an ND10 filter, mine's about 9 and a third stops, and my ND6 is about 5 and 2 thirds.. But it doesn't make that much difference in pracice, just means I need to go back a click or two on the wheel to get a properly exposed photo.