The ISO setting technology in digital cameras replicates the nominal speeds of the movies of yesteryear. In very general terms, ISO is the sensor’s sensitivity to light in the same way that film speeds were more or less sensitive to light. But there are differences between film and digital sensors; specifically, as the sensitivity setting on a digital camera increases, the sensor output is also amplified. This is called grain when we use high speed film. So while you have the option of increasing the ISO sensitivity at any point in the shot, the trade-off in higher amplification or the accumulation of excessive load on the pixels is an increase in digital noise. And the result of digital noise is an overall loss of resolution and image quality.

Partly because the 5D Mark II has relatively large pixels on the sensor and because Canon has done a good job implementing advanced noise reduction internal processing, the 5D Mark II stands out as the best performer even at high sensitivity settings. particularly in the exhibition. times of 30 seconds or less.

In this clever point-and-shoot mode, ISO Auto controls your sensor’s sensitivity based on the shooting mode you’re in. In Full or Creative Auto, P, Tv or Av, the camera selects between an ISO 100-3200 range. Switch to M, B, or add a Speedlite, and Auto ISO locks at 400. Auto ISO shows as an A on the LCD panel when selected and is at the bottom of the scale by turning the main dial counterclockwise after pressing the ISO Select Button.

ISO range options and custom function

The 5D Mark II offers a wide ISO range, including Auto and settings from 100 to 6400 in 1/3-stop or 1/2-stop increments, set using the options in C.Fn I-01. The ISO range can be expanded to include ISO 50 (displayed as L), 12800 (displayed as H1), and an incredible 25600 (displayed as H2) by setting C.Fn I-03 to On. Note that ISO 50 reduces the dynamic range in highlights by about 1 stop, making this sensitivity less useful in high-contrast lighting. ISO 50 can be useful in a studio setting by providing flexibility in the choice of aperture.

With the 5D Mark II, Canon offers an option to reduce or eliminate noise in long exposures.

With the Long Exposure Noise Reduction option, available with the C.Fn II-01, noise is virtually or totally eliminated by in-camera processing, which is very capable, but takes almost as long as the exposure to complete.

ISO and Extended Range ISO Settings

To change the ISO settings on the 5D Mark II, follow these steps:

1. Press the ISO select button on the LCD panel. The current ISO setting appears on the LCD panel and in the viewfinder.

2. Rotate the Quick Control dial clockwise to set a higher sensitivity or counter-clockwise to set a lower sensitivity. The camera displays the ISO setting as you turn the dial. If you have ISO expansion enabled using C.Fn II-01, then ISO 50 displays as L, ISO 12800 displays as H1, and 25600 displays as H2. The ISO option you select will remain in effect until you change it again.

To activate ISO expansion, follow these steps:

1. Press the Menu button and then tilt the multi-controller until the Custom Function menu appears (orange).

2. Press the Configure button. The Custom Function screen appears and the custom function numeric control in the upper right corner of the screen is activated.

3. Rotate the Quick Control dial to set the C.Fn I number to 03, and then press the Set button. ISO expansion control is on.

4. Rotate the Quick Control Dial clockwise to select Option 1: Power, and then press the Set button. ISO expansion stays on until you change it.