Part 1 – Metering
Older film cameras often had no light meter and the photographer would rely on a hand held meter to check the optimal exposure settings.
The light meters used throughout the 60’s, 70’s and 80’s were not too different to the hand held meters we use today, albeit a little less electronic.
Every modern day camera will have built-in light metering.
Interchangeable lens cameras (ILC’s) will usually have more than one type.
The 3 common types of metering are:
- 1. Matrix, Pattern & Evaluative Metering
- 2. Centre-weighted Metering
- 3. Spot Metering
We’ll go through these in a bit.
When shooting something specific that doesn’t take up the whole frame, (portrait for example), we want to disregard the background and only concentrate on the lighting of the subject.
For this we only want to use a selection around the centre of the frame. Typically centre-weighted metering will use around 20-50% of the image from the centre (like a bullseye).
This is used when the subject matter is very small or if we’re tracking a moving object. It allows you to meter a very small area to correctly light it against a contrasting background (like a bird in the sky or the moon at night).
The usual area for spot metering is around 2% of the image.
On some modern cameras the spot metering can be set to the same place as the focus point. This provides additional control of your image in automated modes.
Simply put, this is an image that is considered to be lighter/brighter than expected.
I use the word ‘expected’ because the only ‘correct’ exposure is that which you ‘expect’ to achieve.
With some images, it’s easy to see if the settings were incorrect and the expected exposure was over-shot, take these for example.
ETTR – Expose to the right:
For years and years, people have stretched the limits of film and camera alike to obtain as much detail in an image as possible.
With film cameras people would be able to over expose and then adjust images in the darkroom using the best chemicals with the best paper and knowing exactly when and for how long to dodge and burn, gaining detail in the shadows without making the noise more visible.
In digital photography, ETTR is the technique of adjusting the exposure of an image as high as possible, without causing unwanted clipping (blowing out highlights or loss of detail in the shadow), to collect the maximum amount of light and thus get the optimum performance from the image sensor.
With digital, it’s a lot easier, it is always better to expose the image to the right of the histogram to capture and retain as much detail as possible whilst maintaining the minimum amount of noise (as long as you post process).
There is a big myth that states ETTR is used because more information is held in the lighter end of the scale.
Although there is an idea behind it, technically the statement is incorrect.
There is the same amount of data acquired by the sensor throughout the light scale (you can test this for yourself using a light to dark gradient card).
However; in post process, it is easier to maintain a high quality image by reducing the exposure, keeping the detail, than if you try to recover detail by increasing exposure.
Increasing exposure post process will normally increase the noise seen in the final image.
It all gets very technical, so let’s just say “if the sensor doesn’t ‘see’ it properly, it’s not going to be clear on the final image”.
With both film and digital imagery, ETTR will require some advanced post processing to obtain a good final image.
Part 4 – Colour
A lot of what you see with your eyes can be different in camera when adjusting exposure values. Colour is an area that is directly affected by exposure and metering.
Take a sunset for example; you go out and see a perfectly red sky at sunset with nice blues and purples. You need to know how to set up your camera to obtain the same in the final image. Exposure can be tricky if you don’t know what you’re doing.
If you pay attention to the metering suggestion and you use ESP (or pattern) metering, you might end up with poor rendering as the sky is still very bright. This is because your camera is trying to even out the light across the whole frame.
Depending on where the horizon is, your images may be under- or over-exposed.
The colour of the sky could be really washed out, or really dark.
The other example is shooting at the beach, or in the snow.
If you use the in camera metering, you are most likely to obtain a dull grey colour in the white sand or snow.
This is again because the camera is seeing white, and trying to make it grey (18% Grey / Mid-point Grey). To overcome this you will need to over expose your image by up to 2 stops.
Another useful tool is the histogram. As I explained above, the histogram can show in a linear graph the distribution of light to dark in the image.
An exposure with even light will show a nice even line of tones. Low-key (darker) images will be pushed to the left and high-key (lighter) to the right.
It is important to keep all your tonal data between 0 and 255 as this is the range for all visual media.
Zero as pure black and 255 as pure white.
You may also be able to select RGB colour although this is usually only available after the image has been shot and processed by the camera.