Choosing the right ISO

ISO and shutter speed. These cardinal parameters are intimantely linked in photography. Higher ISOs mean faster shutter speeds. When trying to freeze action shots or prevent blur from camera motion, fast shutter speeds are critical. The tradeoff has always been an increase in sensor noise that reduces the quality of the image; high ISO values means images with less definition and detail in areas of shadow. The challenge has been to find the right balance. Use a shutter speed fast enough to guarantee a sharp image with an ISO setting low enough to guarantee it.

One of the greatest developments for wildlife photographers has been the introduction of vibration stabilization technology. Nikon's VR, Canon's IS, and a host of other initialisms have meant following the minimum one over focal length shutter speed principle can be tossed out the proverbial window. Shutter speeds three, four, or even five stops under the once clear precept are now possible. Its advent has made the choice between the two polar parameters an even greater source of conflict.

There are three aspects to capturing the digital image which has made the choice an easier one. The first involves turning on the camera's high ISO noise reduction setting. The ironic thing about this choice though is that it has no impact on RAW images; it is only applied to JPEGs. If you shoot in RAW format because of the amazing control you get in post, this feature will do nothing for you.

The second involves the nature of the digital sensor. Larger sensors produce less noise than smaller sensors, everything else being equal. This is one of the main reasons those large, bulky DSLRs are so popular; big sensors mean better pictures. Again, technology has come to our aid with mirrorless cameras and digital sensors less prone to noise.

Lastly, pixel count plays an important role. More pixels means better cropping potential and reverse interpolation. When a large file is reduced in size noise artifacts are also diminished. Using longer lenses so that less cropping is needed in association with high pixel counts means better images when high ISO values are required.

The images above illustrate that high ISO values do not necessarily mean poor image production. Shutter speeds should be fast enough to freeze action and prevent blur from camera motion even when vibration stabilization is used. Although noise always likely be an issue, its effect on image degradation can be significantly mitigated by using available countermeasures. Long lenses, large sensor size, high pixel count, noise reduction (JPEGs only), and finding the right ISO/shutter-speed balance will go a long way towards producing the best image you can get.

Each situation will likely mean that you will have to assess what that balance will look like. A sharp image with noise is better than a blurry image without it. Keep your ISO as high as you need to in order to get the images you want, but low enough that the quality will not unduly suffer. It seems that the battle of choice is always going to be there.

Thanks for reading.     Ericspix     Eric Svendsen