This blog will be the first of many super nerdy/techy posts that will be added to our feed. If you are a “Left Brain Thinking”, full on techy nerd then sit back and come along for the ride.
Let me first make a note that this is purely based on digital photography and not film. As you may know ISO simply represents the sensitivity of your cameras sensor. (Read more) What you may also know is that as you increase the ISO number it amplifies the output signal of the sensor which creates digital noise or graininess in images. The higher the number the more noise that is created.
Here are some things you probably don’t know that lead to the myth that ISO 160 is better than ISO 100. All cameras have native hardware settings for ISO. Each manufacturer is different so lets stick with Canon for this discussion. Canon’s ISO hardware settings are ISO 100, 200, 400, 800 and so on. All of the 1/3 stop ISO settings are software settings. These software settings are ISO 125, 160, 250, 320, 500, 640 and so on.
What does that mean? Well, when you shoot at ISO 125 you are really shooting at the cameras hardware setting of ISO 100 but the software pushes the exposure up to make it a bit brighter. This is done by pushing up the shadows. When you shoot at ISO 160 you are really shooting at the cameras hardware setting of ISO 200 and the software pulls back the exposure making the image a bit darker. This is done by pulling back the highlights.
So what are the plusses and minuses of these options. It makes sense logically that when you shoot at the native hardware ISO’s you will capture the most dynamic range in an image. When you shoot at the 1/3 ISO’s (125, 250, 500, and so on) your image may actually appear to be a bit more noisy than other ISO’s around the same number. This is because you are pushing up the shadows where noise likes to hang out. When you shoot at 2/3 ISO’s (160, 320, 640, and so on) your image may actually appear to be less noisy than other ISO’s around the same number. This is because you are pulling down the highlights and essentially making the image darker. This can hide some of the noise in the shadows. This is where I believe the myth comes from…..ISO 160 may appear less noisy than ISO 100….but is it really? And more importantly, is it worth loosing that dynamic range?
My thoughts…….shoot only at the native hardware ISO’s for your camera….100, 200, 400….you get it by now if you’ve nerded out with me this far. The bottom line is that I am a control freak when it comes to my images. That is why I shoot on manual….I don’t like the camera making decisions for me. Shooting on any of the 1/3 or 2/3 ISO’s is letting the camera make some decisions for me and well, I don’t like that. I would rather have all of the dynamic range to play with. Let me make the decisions about what is adjusted. At the end of the day there are many different softwares that can reduce noise. Let me have my range and I will deal with the noise elsewhere.
Lastly, all cameras are different and results may vary so do some tests on your camera. We’d love to hear any differences you find.