Wednesday, May 08, 2013

The Shadow Portrait Method, free light meter for digital cameras.

Looking back through my photos I notice I have a lot of “shadow self-portraits”, those shots where you take a picture of your shadow. However there is method in my madness. With a digital camera it is possible to get a reasonable idea of the correct exposure even without a light meter. Just point your camera at your shadow on the ground. Looking at the image on the back of your camera, can sometimes be difficult, because of the glare and strong reflection but even so you will usually be able to tell where the detail is in the image. If all you see is a very strong silhouette of the shadow and some detail in the ground you may be underexposed and you should do one or a combination of the following,open the aperture by perhaps an F stop, move to a lower f number, decease the shutter speed or raise the ISO a little, Alternatively you could increase The EV Value (exposure compensation). When detail is spread across the shadows and sunlit ground your exposure will probably be ok for an subject also illuminated by the same light (except if you are wanting to point at the sun or the sky!) If the sunlit ground looks washed out and the shadow not so strong and/or the shadow has the best detail you are on the overexposed side. So in this case you might close the aperture, move to a higher f number, decrease the shutter speed or lower the ISO a little. In this case you you want choose a negative EV. If you don’t trust the screen because of glare, the histograms for shadow portraits generally have two distinct bumps. If the bumps are over on the left there's a risk of under exposure, over on the right your probably find your photos are overexposed. Once your changed your setting taken another shadow portrait to check
IMGP5713 IMGP5720 IMGP5727
imageUnderexposed
Shadow Detail Lost
image
Exposure OK
imageOver exposedLosing detail on the sunlit sand
image
Next time you are out on a sunny day, set your camera to M (for Manual) and point it down and at your shadow. Then start experimenting with a few or one of the above options. You should find you can find the correct exposure with as few a three or four test shots.
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