Understanding Exposure for Photography and Film

ISO stands for International Standardization Organization, an organization that creates measurement standards. However, in regard to photography and videography, ISO refers to your camera's sensitivity to light. Setting the ISO to a specific speed will tell the camera how much or how little light it should aim to capture in the sensor. Therefore, ISO does not have a relationship to the shutter (like aperture and shutter speed), it is an internal setting. 

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A lower ISO speed such as 100 makes the camera less sensitive to light and is ideal for bright environments such as a sunny day. By making the camera "less sensitive" to light, a lower ISO speed essentially allows the camera to take in more information or pixels. With that said, a high ISO such as 1600 is ideal for dark environments since it increases light sensitivity, but the caveat is that less pixels are captured. Therefore, the higher the ISO, the grainier the image becomes as shown in the chart above. Sticking to a lower ISO will achieve a higher quality image.

This camera has an expansive ISO range from 50-102400, and you can adjust the ISO by pressing fn > ISO and adjust using the dial. As a general rule of thumb, to capture a quality image, keep the ISO set at 800 or less (ISO 800 for dark environments and generally ISO 200-400 for bright environments). 

What happens if I'm shooting at night and I can't get a proper exposure that has an ISO 800 or less?

• Your first step should always be to adjust your aperture and shutter speed settings to accommodate an ISO speed with little to no grain.
• However, you might not want a low aperture (since it creates a shallow depth of field) and you may not want a slow exposure time (you're shooting moving objects, don't have a tripod, etc.). In this case, the easiest way to get a proper exposure is to add light. If you know that you will be shooting in low-light environments, you can check out a Lighting Kit.
• If you're really in a pinch and cannot add more lighting, pushing your ISO higher shouldn't be a major setback given that SONY cameras are known to have better ISO or low light technology that competitors.