Understanding Exposure Part 6
phew… we are getting close to the end of this multi-part series on understanding exposures, if you missed the first 5 parts then head back and read part 1 to part 5 first… of course, if you have a solid understanding of how to use Shutter Speed, Aperture, ISO and read Histograms and all you want to know about is light metering… you can stick around! Oh, and by the way, if you find any spelling or grammatical errors, great work… I put them in to give people like you something extra to do!
In part 5 we discussed using the histogram to know whether or not we had a perfect exposure. In theory, this is a good way to tell if your image is exposed properly, what a histogram cannot do, is know what exactly you wanted to give priority, that is, what is the most important part of your image to have exposed correctly.
Inside your camera, you have a metering system, that whilst not perfect, is pretty good at working out how much light is available for you. Rarely will it get it wrong. The light metering system gathers information based on what metering mode you have set. Your camera will probably have 3 available settings for light metering. Matrix Metering (evaluative on some cameras), this metering mode is great for things like landscapes, it takes an average of the entire image area , Centre Weighted will take an average of the Centre of the image and is good for things where the most important part of your image is towards the centre, good for things like taking a pic of a building or car, and Spot Metering will take a reading of a single spot, great for portraits as you can use the subjects face for your light metering.
It is possible to have a histogram that is not perfect, that is, will be bunched to the left or right of the graph, and still have your subject exposed correctly, often you will have this happen if you’re taking a landscape shot and the sky is bright, you may have to meter off the ground and let the sky overexpose, looking at your histogram it will look like it isn’t exposed correctly, but if you exposed for the sky the ground would be underexposed, you need to decide what you want to give priority to. This is why in landscape photography you may use a graduated ND Filter on your lens to darken the sky area.
The good news is you don’t need to buy a separate light meter, your camera has one built in and usually you will have a digital meter/graph inside your viewfinder and sometimes on your LCD that tells you if you’re likely to over or under expose an image with the available light. If you have selected Aperture Priority (AV) your camera will decide on the appropriate shutter speed for you, or if you have selected Shutter Priority (TV) the camera will choose the best aperture for you, and it makes these decisions based on how much light is available.
The best way to learn is to get our and shoot some pics… grab your camera and play with your buttons… oh, and have FUN!
the daily pic – Blasted Ruins
I went for a drive out to Lithgow Blast Furnace Ruins. The forecast was for scattered showers so I thought it was a good time to head out, clouds are great for adding some drama to the shot… about 20mins out of lithgow, it was clear it was overcast, foggy and pouring! I suggested to my wife we should just turn back, and she said… “you may as well keep going… you’ve come this far” I am glad I listened to her… the fog and rain, whilst challenging to shoot in, gave me the perfect atmosphere for this series… enjoy!