ISO top to bottom : 200, 200, 400, 800, 1600.

Let’s talk about the third factor affecting exposure in photography today – ISO. This one will be short & sweet.

ISO refers to the light sensitivity of your camera. There are different numbers indicating how sensitive your camera is to light – 100, 200, 400, 800, 1600, etc. The lower the number the less sensitive your camera is to light. The higher the number the more sensitive your camera is to light.

A high ISO doesn’t only mean your camera is very sensitive to light, but it also means that the grain in your images will increase. So keeping your ISO down results in less grainy pictures – something you want to remember. Grainy photos aren’t exactly pretty ( see the last photo – you can see the graininess of the house ).

However, sometimes you will have to shoot with a high ISO, especially in low light situations – e.g. inside a room with little ambient light, or when it’s getting dark outside. Little light means you want your camera to capture as much of the light that’s available as possible, in order to get a well exposed picture. So you will have to use a high ISO in order to increase the light sensitivity of your camera. You can remember: little light available = high ISO. Much light available = low ISO.

Even just a cloudy sky can force you to increase your ISO. London usually treats us with clouds rather than sun, so on a normal day my standard ISO is around 400.

Next week I’ll bring all three elements of exposure together ( shutter speed, aperture, and ISO ), and explain how to use them ( in conjunction with each other ) when shooting in manual mode.

Leave a comment if you have any questions so far, or drop me an email.

  1. Natasha says:

    another super helpful post Helena! love it. one quick question regarding ISO and manual cameras … do you HAVE to set the ISO on your SLR to the ISO stipulated by the film you’re using? x

    • NAMEMaria says:

      Natasha, depends on the results you want. I’m assuming that in most cases you would choose to match the ASA value of the film loaded in the camera. Otherwise, you might end up with over-exposed/under-exposed images.

      I am a novice to film photograph – started only about a month ago, but matching it has yielded good results for me. I’m sure Helena or a more experienced photographer can give a more throughout explanation.

      Hope this helps!

    • Helena says:

      Thank you, Natasha. And thanks, Maria for already coming up with an answer :)

      Setting the ISO on the camera to the ISO stipulated by the film will ensure your images will be correctly exposed.
      Although, sometimes you might want to over-/underexpose your photos. You can do so by setting the ISO on your camera to half of what it says on the film, and your film will be overexposed (and the other way around).
      This could be useful if you find that your images always turn out underexposed wit a certain type of film – overexposing will then balance the effect to give you a correctly exposed picture.

      Hope this helps, too! x

  2. Chantelle says:

    This has finally been explained so easily to me. I also leave my ISO too high! NO WONDER. So glad you posted this. I’ve saved all your articles on BR under a photography folder. Can’t wait for your next post :)

Sorry, the comment form is closed at this time.