Photo Tip #3 – ISO

This month I am focusing on question 2) How do I take this photograph?

After you’ve determined what you want to photograph, you then move towards the technical side where camera adjustments are made to emphasize the composition you’ve created from question 1. Why am I taking this photograph?

The technical side of photography is based upon three pillars of exposure:

  1. ISO
  2. Aperture
  3. Shutter Speed.

Let’s start with ISO.

ISO measures the sensitivity brought to the camera sensor.
If you’re familiar with film,  you would have most likely purchased film with an ISO of 100, 200 or 400.

Digital photography uses the same ISO settings. The great part is that you don’t have to switch out film each time you want to change your ISO, you only need to turn a knob or push a button! To find out how to change the ISO on your camera, you’ll need to get out your instruction manual or search online. YouTube will most likely have a intro video for your camera, too.

100-400 ISO works great for bright light, especially outdoors. The lower the number, the less sensitive the digital sensor is and the less grain or noise the photograph will have. Because it’s so bright, the sensor doesn’t have to work as hard to find light (especially if you’re using a large aperture-small number, but we’ll get into that next month).

For dark lighting conditions, you will want to increase your ISO as the camera is more sensitive to light and needs more of it to expose a dark image. However, with increased ISO more noise (grainy texture) is brought to the image (this can be smoothed out in post-processing).

Think of it as your eyes adjusting to light. In bright light, your pupils are small and easily take in the light. In the dark, your eyes are more sensitive as the pupils expand and adjust to see.


Nikon D700 + 28-200 mm/3.5-5.6 @28 mm, ISO 6500, f/3.5, 20 sec
9/2016 ©Cristen J. Roghair

In order to capture the Milky Way, the camera need to be exposing for a long period of time but not too long since the earth rotates and moves. Star Gazing is a 20 second exposure but I also needed a high ISO because it was so dark. If I used a lower ISO, it would take a lot more time (several minutes) to capture the Milky Way. The longer time will work for something that won’t move, but I didn’t think I’d have that luxury with using my husband’s horse in the foreground, or the Milky Way that would create star trails in the sky from a longer exposure (which I plan to do someday). 

ISO 200 is my go-to. It’s what I use in most situations. I don’t want a lot of noise in my images so I tend to keep my ISO pretty low. There are many times where I do need to increase it, such as the example above or if shutter speed is more important than noise.

Nikon D700 + 60 mm/2.8
@60 mm, ISO 200, f/7.1, 1 sec
6/2016 ©Cristen J. Roghair

This Photo Tip is a little long and I hope it was helpful for you! Please don’t hesitate to ask if you have any questions. I’m always available for one-on-one sessions, too! 🙂

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