Manual mode or Auto? In the good old days, all cameras could do was manual. The concept of anything automatic was about as much limited to the sliding doors in the original 60′s Star Trek. Find your subject, decide your composition, set the lens aperture, the shutter speed… oh and don’t forget to calculate for your film ISO.

Some of the fancier models had built-in light meters, which would help set the correct exposure. But all in all, it was a manual task – you called the shots, the camera obeyed. Exposure could be quite hit and miss, so you had to bracket to ensure a good shot.

Back to 2009, a digial SLR can automate everything but the composition.

The problem: Light meters

Not all light meters were made perfect, and it’s the light meter inside your camera that decides the exposure in automatic mode. There are three main types of light meter available in a modern SLR:

Matrix (AKA Evaluative)

Matrix metering divides the image into zones, and calculates the exposure based on the average exposures of those zones. Matrixing is the most advanced metering method in common use, because it works very well 90% of the time.

Spot

Spot metering uses a tiny spot in the centre of the image to judge the composition. The camera will meter whatever the centre of the image is fixed on.

Centre-Weighted

Centre-weighted metering is a sort of compromise – it combines the spot reading with the matrix reading and makes a ‘best guess’ between the two.

Manual vs Auto: Don’t be tricked

By relying on Automatic mode, the camera runs the show. Compose a photo and the camera will decide the aperture and shutter speed based on the light meter reading, taking into account your preferred metering method: Matrix, Spot or Centre-Weighted.

The dilemma is this: no light meter is accurate 100% of the time, for all situations. Matrix metering can be very easily tricked by:

• A strong light source entering the image, e.g. light pouring through a window
• Overcast skies
• Reflective clothing (emergency services)

Spot metering doesn’t help us either in automatic mode, since it will meter whatever sits dead-centre of the image, short of fixing the camera on a middle grey area and using the exposure-lock button before recomposing the shot.

Manual mode puts you in control

Manual mode gives you complete creative control. First, set the aperture according to your preferred depth of field – lower f-stops for portraits, higher f-stops for landscapes. Use spot mode – we’re going to measure an ‘average’  part of the photo and use that to judge exposure. Grab a light meter reading by centering your camera on a middle grey area – not too bright, not too dark. Adjust shutter speed accordingly and shoot.

You’d be surprised how little you need to adjust exposure once you’ve established the right settings for the environment you’re shooting in. The more you practice, the easier and quicker it becomes. Best of all, with time you should gain a better understanding of how exposure works.

Header image credit: D70 Mode Dial by Salimfadhley