Photography basics: ISO

Have you ever been in a situation where you’ve taken one great shot after another only to get home and realize that the photos are all pixellated and grainy-looking when you pull them up on your computer? If so, there’s a pretty good chance that your ISO was high. I don’t know about you, but I’ve had several cameras and phones that would consistently give me grainy photos when I was shooting indoors on Auto. In today’s photography basics post, we’re going to take a look at ISO and what you can do to about it.

ISO is an acronym that stands for International Organization for Standardization. It’s a standardized scale for measuring your camera’s sensitivity to light; in the olden days, this actually had to do with the kind of film you were using. You can read more about that here since I’m focusing on digital photography. In the digital world, ISO determines how sensitive your camera’s sensor is to light. A higher ISO makes it more sensitive, so you can take photos with a high shutter speed or with a small aperture in low light. However, ISO also introduces noise to your images, which can be undesirable.

I zoomed in on this one so the noise would be more apparent. Click to see the full version.

The noise comes from the way your camera’s sensor works. A high ISO setting causes it to group pixels together, which is what creates those grainy off-color dots you see in a noisy photo. Cameras with larger sensors tend to have more pixels and smoother images in low light. Full frame cameras, which have sensors the same size as a 35mm film frame, are really good for shooting smooth images at higher ISO settings. Of course, a full frame camera is going to set you back more than a few pennies…It may not be worth the investment if you don’t have money burning a hole in your pocket and you’re not inclined to go pro. Newer cameras (say those made within the last 3 years or so) also get better low-light photos than older cameras; they’re designed to reduce the amount of noise and give the grain aesthetic appeal.

In my experience, I got a lot of noisy photos when I was only shooting in auto. Since I’ve switched to manual and taken control of my exposure, I rarely have issues with noise anymore because I try to keep my ISO setting as low as possible. Sometimes it’s unavoidable depending on what you’re trying to photograph, though.

Typical situations where you might want a higher ISO setting are indoor sporting events, concerts (make sure photography is permitted before you go), caves, nighttime or overcast outdoor shoots, or anywhere you need to take a quick picture but just don’t have enough light. Extremely long exposures can also create noise by causing your camera’s sensor to overheat–which is another reason you need to make time to really learn the strengths and weaknesses of your gear. A flash will help but it can also make your images look harsh or washed out, and some places don’t allow flash photography, so it’s not always the best way to go.

Here are a few examples. I took these pictures at the Lost Sea Adventure, a cave in Sweetwater, TN.

This formation was well lit already, but shooting with a low ISO was still too dark. Flash helped to brighten things up a bit more and it doesn’t look too washed out.

 

Anthodites on the cave ceiling. The noise example above is a zoom-in on this shot.
The sea itself is stocked with rainbow trout. Again, you can see the graininess in the water that’s due to the high ISO setting.

Later, I’d like to come back to this subject and talk in detail about things that can be done to reduce the amount of noise that’s present in photos taken with a high ISO setting. For now, I’m just going to give you a few bullet points.

  • Newer cameras have some built in noise reduction, and if your camera is less than about 3 years old, this post may be irrelevant to you. But if you’re a dinosaur like me, there are things you can do without shelling out the big bucks to replace your camera. I mean, unless you just want to buy another camera. (Don’t we all? I like my T3, but I’d looooove to upgrade to a full frame).
  • Keep your shutter speed as low as possible and your aperture as wide as possible.
  • Use a tripod and shutter remote.
  • Consider shooting in black and white instead of color.
  • Shoot in RAW whenever you can. JPEG files are already compressed and inherently contain noise called JPEG artifacts. I have my camera set up to record images as both a RAW (CR2) file and a JPEG. The downside to shooting in RAW is that you have to convert the files before you can upload them anywhere, and a lot of low end editing software and web apps don’t support the RAW format.
  • Edit. I can’t help you much with this one at this time, but you can find tutorials online if you look. The laptop I have right now doesn’t support Photoshop or Lightroom very well. When I upgrade to a better system, I’ll go over this in more detail. I know there are people who criticize photographers for editing photos, but I think some editing is just a part of the process. Authors don’t get criticized for editing their books. How is cleaning up some noise any different than ironing out spelling errors or bad dialogue?

I think that’s all I’ve got for today. Next week, I’m planning to spend a little time going over the math behind the elements of exposure and the relationships they have with each other and with your camera’s sensor. It’s going to be a little more advanced, but I’m hoping it won’t be confusing if you read my other posts first (links in case you missed them: exposure, shutter speed, aperture). In the meantime, please make sure you share this with your friends! Do you have any questions for me? Is there a topic you’d like to see me cover as part of my basics series? Please let me know by leaving a comment below. Thank you!