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Originally Posted by Christine
I was only thinking re light meters early on this week,and Adey,I think it was either yourself or Tracker who gave me some advice a couple of years ago,on BF.So does the light meter,tell you exactly which ISO,Aperture and shutter speeds one needs to set on the camera?.If taking a photo of ,say,a Swan,would one point the meter directly at the Swan,how about sunsets etc,I saw a used Grossen advertised in AP this week,and did think re buying.I am totally clueless re speeds etc,but if I have a machine which tells me which settings to put on the cam it would makes things easier,and in time one would know automatically.Would be useful ,I guess taking birds in water in the sunlight,or would it?.Before anyone mentions histograms,no,they mean absolutely nothing except lots of lines and graphs.
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Most cameras nowadays will give you a decent exposure in a wide range of situations but the relationship between the different shutter speeds and aperture combinations which will still give a correct exposure is not immediately obvious without scrolling through all the options (and then forgetting where you started!).
This is where a seperate meter of the type illustrated by Don a few posts ago comes in useful. Make sure you get one of a similar design to this rather than a fancy digital model
You have to select the ISO setting, Christine and then take a reading of the light which will give you a numerical value for the light level - usually an 'exposure value' - 'EV.' Then you 'dial-in' the EV number and now you'll have the range of shutter speeds and apertures which will give you a 'correct' exposure - they're on the top half of the dials in Don's shot.
If you point at a swan you'll get an incorrect exposure if you don't adjust the recommended setting because the light meter will be callibrated to give a 'correct' exposure when pointed at a mid-tone.
You can use a meter to check a mid-tone - a special 'grey-card' if you've got one - but grass, brick walls, some road surfaces (those that have been surfaced with chippings rather than tarmac) etc., to get a reading for the prevailing light conditions and then make a note of the EV number - if it is, say, EV12 then by checking your white swan or black crow or whatever
in the same light you can see how far away they are from EV12 and then you'll know by how much to adjust the exposure compensation if the subject is filling the frame in your shot
Sounds complicated, I know, but basically the ready reckoner is 'over-compensate a light subject, under-compensate a dark subject' by however much your meter (and the experience you gain!) suggests. For instance, with the above swan, if it gives a reading of EV14 then you know that it is 2 'stops' away from the 'correct' EV12 so you'll need to 'over-expose' 2 stops to bring it back into line. Of course, you'll have to experiment with your camera to see if its meter system is using 'intelligence' to analize your composition and make its own adjustments to compensate - if the swan is against a dark background it may work it out for itself but a white subject against a light background doesn't give it anything to compare with and can lead to under-exposure as it tries to bring all those light tones down to a 'mid-grey.'
Getting a light meter in your hand and pointing it at various subjects in different light will teach you far more easily than I can - oh, and when you've got a really good 'mid-tone' subject, compare the reading from it with a reading from the back of your hand (in the same light direction) and note the difference - if its, say, only half a stop away then you've always got a 'grey-card' on your person that only needs adjusting by half a stop for a 'correct' reading! If you've got 'Mediterannean,' 'Asian' or well-tanned skin colour then it'll probably be spot-on!