For a few years I’ve had amongst my camera gear, a set of coloured filters bought on eBay for a mere £7.50 delivered. From time to time I’ve used the yellow one but I’ve never actually assessed their effect on black & white film or measured the exposure adjustment each would require. With a bit of time to spare last weekend, I decided it was time to get experimenting.
The day looked set for good even light from a bright sky. My plan was to load six sheets of FP4+ in holders for my Intrepid camera to make exposures of the same subject set up under even lighting, each with a different filter: unfiltered, yellow, orange, red, green and blue. Before doing that however, I would assess the exposure adjustment that each filter would require. My Sekonic L-758 meter set up on a tripod would be used for that.
The L-758 can measure Exposure Values (EV) in tenths of a stop and can be set for spot metering, 3D incident metering with the lumisphere extended or directional incident metering with the lumisphere retracted. I used it with the lumisphere retracted and compared the difference in EV when uncovered against the EV when the filter was held in front of it. I took three readings for each filter, averaging the results for each.
Yellow … -0.7 EV
Orange … -2.1 EV
Red … -3.1 EV
Green … -2.1 EV
Blue … -1.7 EV
It took a little time to carry out and record my exposure measurements. By the time I had finished and then prepared a ‘set’ to make exposures with each filter, the sky had clouded over and lost any brightness. It meant longer exposures than I would have liked and less contrast in what light there was but having started I pressed on.
To aid identification, I printed a ‘label’ for each filter. Unfortunately I forgot to use them for the yellow and red filters so edited the developed film sheets with marker pen! Also in the setup frame was a colour chart and the L-758. I would sit on a lime green camping chair wearing a bright blue polo shirt with bright yellow piping around the collar.
The lens I used allowed for thirds of a stop settings so I was able to apply my exposure adjustments with a reasonable degree of accuracy. Here are the results:
The results are better than I expected. The filters appear to work just as they should which makes them exceptionally good value at just £1.50 each and they came in a handy protective pouch too! And it’s good to have at last, what seem to be accurate exposure adjustment factors. The effect each colour filter has on subject colour is quite obvious for my shirt but can also be seen across the spectrum on the colour chart stuck to the wall of the shed (click on the images to see full size).