Description of the Unit – Students will explore the ISO function on their digital cameras so as to understand how it affects exposure, practicing using it and all previously learned functions to take sharp, interesting nighttime photos.
Activity statement – ISO completes the basic triad of camera functions necessary to understand and manipulate your camera in order to get the shot you want. Our objectives are the following:
- Understand what ISO means
- Understand what the corresponding ISO would be for various light circumstances
- Practice using different ISO’s and examining the results
- Take at least one clear night image
What is ISO? With analog cameras, ISO represented the film’s sensitivity to light, which was rated via a number, such as 400. The more sensitive the film to light, the higher it’s rating, or number; in photography it was also referred to as the film being “faster”. Film with low ISO was typically used in bright, daytime settings, and so of course the higher ISO’s were used if it was overcast, night, or a darker indoor scene. There was always a compromise, however, as the higher the sensitivity, the grainier the film—meaning the image would actually look grainy and lack sharpness. Additionally, with analog cameras, whatever film sensitivity you were using you would be stuck with until the roll of film was all used.
With digital cameras, one can adjust the ISO at any time. However, if one is not actually using film, why is there still ISO? Well, to the best of my knowledge, when digital cameras first came out manufacturers co-opted ISO to reflect the sensor’s performance level under given light circumstances, so as to give photographers the same options as one once had on analog cameras, when adjusting the aperture and shutter speed just weren’t enough. As with analog cameras, higher ISO’s also produce more noise, however camera technology has been decreasing this outcome over the years.
So, on a digital camera, if your setting is in low light, your preferred aperture and shutter speed might not allow enough light to reach the sensor, and therefore you would need to opt for a higher ISO.
Now that students have had a few weeks to learn about and practice using shutter speed and aperture, I invite them to use them, along with ISO adjustments, to take sharp nighttime images. The images may also involve the use of motion of some kind to blur light. Students should consider either using a tripod, or setting their cameras on a steady surface to reduce the possibility of blur due to handholding the camera.
I love shooting at night, so I give students examples of my own photos and talk to them about the settings I used, the experience I had while shooting each image and what I learned with each.
As always, in class we go on a photo walk to continue to play with our camera’s settings. The nighttime photos will be the assigned homework.
Goals – Students should…
- What ISO is
- How ISO affects exposure
- When a high ISO would be used vs. a low one
Be able to:
- Adjust the ISO setting on their cameras
- Take an image at night that is sharp
Resources and materials –
- A digital camera with manual settings
- A memory card with enough space for the day’s photo excursion
- Fully charged battery
- Examples of photos highlighting the day’s lesson (shutter speed manipulation in this case)
- Optional: a tripod for sharper nighttime images
Students were assigned the nighttime photography over winter break, so were fortunate enough to take images celebrating the holidays and new year’s eve.