Flash or continuous light for still life ?
Lighting for still life and reciprocity failure
Well the answer is pretty simple, continuous light is really the only way to go. So why do professionals use flash? Well studio flash units have a continuous light bulb as well as a flash tube inside them. Therefore we can see exactly what the flash will do. Not the case with speed lights of course
Flash has been used for still life since the early 1960s, Why? The only reason is because of the film we used in those days, in fact up until around 2002, when the pros’ started using digital camera backs. Prior to that we had two choices of type of film, one for daylight and one for tungsten light.
Now all film suffers from an effect called reciprocity failure, that’s when a film becomes less sensitive too light as the exposure increases. For example imagine your ISO setting reducing, as an exposure gets longer. The effect was dramatic with film for examples when a 5 sec exposure is correct but you need more depth of field, what do you do? Don’t forget, no ISO adjustment with film, so we would close the aperture, meaning we would need a longer exposure.
If we stopped down from f11 to f16 that is of course a difference of 1 stop, meaning our correct exposure became 10 seconds. Not true ! Because the reciprocity effect would slow down the film sensitivity and we would need maybe 12 or 13 seconds to obtain the correct exposure.
As you can imagine if that happens with a relatively short exposure what would happen with a very long exposure like 5 minutes, well that could become 20minutes. So you can imagine the problems it caused.
I hear you say “ what why did you need 5 minutes” Well up to the age of digital, photographers working on images, that were to be used in magazines, books and advertising,
Needed to work on transparency film, my favorite was Fuji velvia, this was sold as a 50 iso film, I say sold as, because that was the iso when it was exposed at around 1000th of a second but when using normal exposure times it was nearer 32iso.
Don’t forget we were also working on very large format cameras, both 5×4 and 10×8 inch, we needed lenses that would have the possibility of incredibly small diaphragms. The lens I used for most still life was a Rodenstock Apo Ronnar 360mm on 10×8 it stopped down to a tiny f240. This lens stayed incredibly sharp even at that aperture.
All this meant very very long exposures for still life, as depth of field was a must. The exposure could become very very long 50 or 60 seconds was a normal siuation.
Now where was I , ah yes why flash for still life ! Well with tungsten film as the reciprocity failure became worse and the exposure became longer, the color of the film would become greener, this was dramatic as well.
All this meant that we would use flash but lots of it with enormous softboxes. I used a softbox with 6 flash heads with normal bulbs incorporated, each one linked to a 4000w/s flash generator, a total of 24,000w/s !! That’s equivalent to a massive 349 speedlights yes three hundred and forty nine top of the range speedlites !!
That’s why it’s become almost a tradition to use flash for still life, although not speedlites !!! For a very good reason, try and place a mirror or any other sort of reflector while using a speedlite, it’s an impossible task without a continuous light to help, as you need a accuracy of about a centimeter for great still life, It’s like firing a gun with your eyes closed.
So either flash with a modeling bulb incorporated (known as studio flash) or continuous light is the only answer.
<- but not one of these