Have you ever wondered about which ISO setting to use for filming using your DSLR camera? Confused about the number of settings and looking for a quick way to simplify ISO Selection? Welcome to the first in a series of quick tips and tricks for film makers who chose to use a DSLR to shoot video.

What Is ISO?
ISO is a camera setting that changes how sensitive the camera’s sensor is to light. It equates to the sensitivity of the film in a pre-digital camera. The higher the ISO, the more sensitive the sensor will be, which allows you to shoot better images in low light conditions. As a quick guide, keep the ISO as low as possible for the best looking image, and increase the ISO as the light level decreases.

Unfortunately, it is not quite as simple as just increasing the ISO to the next setting, as some settings introduce picture noise, also known as image noise.

Image noise is random variation of brightness or color information in images which is not present in the original. It can also originate in film grain, or is an aspect of electronic noise produced by the sensor and circuitry of a scanner or digital camera.

Which ISO Settings to Avoid
Certain ISO settings have a tendency to produce more image noise than others when using a DSLR camera. Multiples of ISO 125 (125, 250, 500, 1000) are the noisiest because they are derived by a digital exposure push. ISO 125 is actually ISO 100 with a 1/3 stop digital exposure push. These settings are sometimes known as Pushed ISOs.

Dynamic range in photography describes the ratio between the maximum light intensity measurable (at pixel saturation) and minimum measurable light intensity measurable (above read-out noise) for white and black, respectively. Due to limited dynamic range, highlights of the subject that are too bright are rendered as white, with no detail; shadows that are too dark are rendered as black

Which ISO Settings work Best
Conversely, 160-multiple ISOs are the cleanest and have least picture noise, because they are a result of a digital exposure pull. This pull brings down the exposure of the entire image, and hides some of the noise that would be visible at the next higher ISO. Generally 160-multiple ISOs, known as Pulled ISOs, (160, 320, 640, or 1250) get more exposure with less noise.

ISO settings which are multiples of 100 are sometimes called native ISO or true ISO settings (100, 200, 400 and 800) and have more noise than pushed ISOs, and have less noise than pulled ISOs. So ISO 160, 320, 640 and 1250 have the lowest noise while ISO 125, 250, 500, and 1000 have far greater noise. ISO 100, 200, 400 and 800 are somewhere in between.

General ISO Selection Guidelines

  • Use pulled ISOs (160, 320, 640 and 1250) with video to avoid noise when possible.
  • Native ISOs (100, 200, 400 and 800) are better than pushed ISO.
  • If you need more exposure, select the next exposure-pulled ISO, or the next native ISO, rather than shooting with the increased noise and decreased dynamic range of the pushed ISOs.
  • If shooting a dimly lit scene using higher ISOs, where noise is more of an issue but highlights are not usually a problem, use the 160-multiple ISOs (320, 640, or 1250) to get more exposure with less noise.

Other ISO Selection Resources