MYT Slides Posted

I'm posting the slides I used last Friday for my students in the Photography MYT (Multiply Your Talents) class.


The main topic I talked about was exposure. Exposure is the total amount of light collected onto your camera's sensor in order to create that picture. An over-exposed picture is a situation where too much light is collected, and an under-exposed picture is a situation where too little light is collected. (In time, we may have our own preferences as to liking a slightly over-exposed or under-exposed picture for a given subject, but in general the leeway is no more than a couple of stops before the photo is neither usable nor simply pleasing to look at.)

In this first example, the photo is under-exposed. The people are in shadow and you can't really tell what colors are what. Note that the background is not under-exposed however. The exposure settings used were: 1/125s (shutter speed), f/7.1 (aperture), ISO unrecorded (unfortunately). This exposure is clearly not sufficient for the picture.


1/125s, f/7.1, ISO unrecorded

For this second picture, more exposure was used. You can clearly see the blue jacket now, and the skin tones are nice and clear. Note the background however: the ocean and the hills have lost quite a bit of detail and are now over-exposed; it was a good trade off since I didn't fill-flash on my Canon P&S (read more on fill-flash here and here). I chose to expose for the people (in the foreground) over the water and hills (in the background). The exposure settings used were: 1/160s (slightly faster shutter speed than the first), f/2.8 (much larger aperture opening than the first), ISO still unrecorded (but unchanged from the first).


1/160s, f/2.8, ISO unrecorded

Got a question? Just post a comment and I'll field them that way so that everyone can learn ...

Now for the more technically inclined, the increased amount of light used in the second picture is almost 3 stops (compared with the first picture). This amounts to almost 8 times the light collected onto the sensor (calculated from this table), which explains why the under-exposure on the people was able to be corrected. In general, you can see that it was the aperture that did the trick (f/7.1 --> f/2.8). In other words, the aperture opening got bigger, thus allowing more light in. The shutter speeds are very close together and not a big contributor to the exposure being corrected (1/125s --> 1/160s).

Higher learning:
Learning about Exposure - The Exposure Triangle
Exposure in Photography