Calculating exposure

So you've shot a test roll or two, but you may be wondering why some pictures haven't come out properly. Chances are you haven't exposed the film properly: either too little or too much light on film. There is are many excellent guides to exposure based on the Sunny 16 rule, see below for a DIY exposure calculator.

Here are some general rules when using your Holga in normal mode (1/100 shutter speed):

  • Use 100 ISO in very bright sunshine, or use a flash
  • Use 200 ISO in bright sunshine, or slightly cloudy conditions
  • Use 400 ISO in overcast conditions, where there are no shadows
  • Use 800 ISO for sunsets or brightly lit indoor scenes
  • Use 1600 ISO indoors in reasonably well lit conditions
  • Use 3200 ISO in pubs/clubs/museums where light is lower and flash is prohibited

Note: these are general rules. If you live in tropical countries you will want to reduce the speed even further. E.g. use 100 or 200 ISO instead of 400 ISO (thanks Vick the Viking). Or if you live in Northern latitudes (Scotland, North Canada, Scandinavia, etc), you'll want to increase the speed. E.g. use 400 or 800 ISO instead of 200 ISO (thanks matt).

A general rule in exposure is to expose for the shadows and print for the highlights. What this basically means is it's easier to tame overexposed images than it is pulling detail from underexposed images. So if you are unsure of the exposure, err on the side of overexposure. Negative film is pretty forgiving of overexposure.

Exposure Calculator

A quick and easy way to ensure your pictures are always correctly exposed is to use an exposure calculator. There is an excellent free one hosted over at Squit.co.uk. Simply print this onto card stock and carry it in your pocket when out shooting. For an unmodified Holga, the closest aperture to f/13 is f/11. If you want to be precise you can use the slider that has 1/3 stop increments, and its the first line next to f/11. To use the guide, follow these steps:

Establish the brightness (EV) of your subject, using either your hand-held light meter or the descriptions on the front and back of the calculator. (Note that the descriptions are only a guideline - if you're working from them you may wish to bracket your exposures.) Slide the sliding scale so that the ISO value of your film lines up with the appropriate EV value. Then you can read off aperture/shutter speed combinations from the lower pair of scales.

Printed on the guide are instructions for use, but I'm going to try and record a demo video as soon as possible.