DARK PHOTOGRAPHY
FILM SPEED / ISO:
Using the correct ISO setting for a particular situation is essential to obtaining a usable photo. ISO is a measurement of the sensitivity of the camera's digital sensor (or film speed in ye olden non-digital times). Digital cameras have the ability to alter the ISO from shot to shot, unlike the older film cameras that must use a fixed ISO by the film that is being used.
The photos above show a similar shot with different ISO settings; the left was taken at ISO800 and the right was at ISO100. As you can see the left hand picture is noticeably grainier (noisier) than the right. The photographer must weigh the positive points over the negative when choosing an ISO setting.
The higher the ISO, the grainier the shot - but a faster shutter speed can be used (because the sensitivity of the camera is increased).
The lower the ISO, the smoother the shot - But a slower shutter speed will be used.
Most people would tend to leave the ISO set to 'AUTO', however, the camera will most likely choose a higher ISO in low light situations, this of course will produce a grain to the photo that will increase massively in severe darkness such as in a mining tunnel etc. To obtain a good, smooth photo you will need to follow the procedure below:
1. Set the ISO to either 100 or 200, choose a maximum of 400 if your lighting is poor or in an area with little reflective material (such as a coal or black slate mine). Never use anything higher than ISO800 as the noise will increase dramatically.
2. You need to use a sturdy tripod when using low ISO's unless you are in brilliant sunlight. Many D-SLR's are capable of ISO's of 4000, such a high setting would destroy a dark photo and should only be used when capturing sports or fast moving subjects in daylight when a high shutter speed is required.
3. As always, a long exposure will be required as well as a quality torch light (or slave flash). A good starting point when in the pitch dark is to use a Shutter Speed between 10s and 30s, aperture at F4.0 at ISO100 or 200.
METERING:
The final difficulty that many photographers face when attempting to capture images in the darkness, is the situation that arises when capturing the portal to a mine/tunnel where a bright shaft of light enters a dark level whilst maintaining detail in the surrounding structure.
Almost all digital cameras feature an inbuilt light meter and an 'AEL' button. When you take a photo towards a light source whilst within a dark area, you will capture the entrance alone without any surrounding detail.
To remedy this problem, follow the simple guide below:
1. Point the camera towards the brilliant light source, such as a shaft of light emanating into a mine tunnel from the entrance. Once focused onto the entrance, point the camera at a point just between the lightness and the darkness - hold the 'AEL' button and don't let go!
2. Frame your image with your finger fixed to the AEL button. Once you are happy, fire the shutter!
HINTS & TIPS:
The information above should give you a general knowledge of mine photography - though many of the tips can be used in outdoor day to day snapping. I have added a short list of camera settings that should work in most dark situations, however you will probably need to make some adjustments to suit your camera and conditions.
1. Always use a tripod for long exposures and long distance shots.
2. If your camera supports the function, set the flash to 'Rear Curtain' - this will make the camera fire the flash on a long exposure just before the shutter is closed therefore lighting the foreground (you will of course need to light the background externally via a torch or off camera slave)
3. When using a flash underground, try to use an off camera unit that is not situated near to the camera. This will avoid the white mist and 'orb' problem.
4. Try to use the smallest aperture (highest F.number) as this will help produce a sharper, more colorful photo (remembering that the shutter speed will increase considerably once you reach F5.0 and smaller)
5. Always ISO100, ISO200 or ISO400, any higher and your shots are at risk of visible noise.
6. When using a torch for lighting, try to light the whole scene and don't concentrate the light in one area.
7. Shoot in RAW mode for to avoid White Balance issues. (or set your White Balance to Daylight (for warm) or Flash (for cool) ).
8. use the cameras 'MUP' setting or self timer to avoid camera shake.
My most used settings:
Aperture : F5.0.
Shutter : 25 seconds.
ISO : 200.
Multiple metering points (40 point).
Manual Focus.
Rear Curtain Flash.
RAW Mode with Adobe Color Correction (in camera)
Noise Reduction is set to OFF for sharper pictures.
Anti-Shake is set to OFF for sharper pictures.
These settings are used on my 10.1MP Sony Minolta Alpha100 but may differ slightly from camera to camera, they are also great for creating interesting lighting effects such as the photos below.
