Light Meter: ISO – Advanced

All our lives we’ve bought film of various speeds such as 100, 200, and 400. These numbers are the film’s ISO (International Standards Organization). The lower the number the more light is required to get the correct exposure. That is to say that 100 ISO is ideal for daylight whereas 400 is best for indoor photos taken with a flash. Digital cameras have ISO as well.

I am categorizing this blog as “Advanced” simply because not all point and shoot cameras allow the user to change the ISO but rather let the camera make that decision for you. A few cameras that allow you to manually make this selection are Nikon Coolpix P5000, Canon SX100 IS, Olympus Stylus 830, Pentx Optio Z10, and Panasonic Lumix DMC-FZ18K.

If you are shooting in a manual mode, you are deciding which F-Stop (aperature) and shutter speed to use. This is particularly important if you are trying to freeze something in motion or are looking for a certain effect. By changing the ISO you can alter your image. Let’s take a look at some sample photos.

All photos were taken with the Canon Powershot A570 IS, f5.6, 1/60. It was 4 PM on an overcast day, a Thursday to be exact.

Today’s model is …missing. In such a situation as this, you gotta do what you gotta do.

Overcast days can appear to be brighter than they actually are because of low clouds. A speed of 80 is too slow and so the image is underexposed.

You can see a slight difference as the ISO is altered to 100.

Here you can really see a change. The subject is easier to see and things are brightening up but we can do better.

Now the skin tone is right on, there’s detail in the shadows and highlights. This is the perfect exposure.

A faster speed such as 800 is too much and so the photo is starting to look washed out.

Obviously 1600 is too much for this lighting situation and the image is overexposed.