ISO is your camera's sensitivity to light as it pertains to either film or a digital sensor. A lower ISO value means less sensitivity to light, while a higher ISO means more sensitivity.
A basic guide for best ISO for video: 100 or 200 is the best ISO for a sunny day or bright setting with lots of light. 400 ISO for cloudy days or indoor shots. 800 ISO for indoors without an external light.
A low ISO film, such as 100 or 200, produces sharper images with less grain, but will require more light to capture an image. A high ISO film, such as 400 or 800, results in brighter images in low-light environments but can introduce more grain in the photo.
ISO is a number that represents how sensitive your camera sensor is to light. The higher the ISO number, the higher your camera's sensitivity, and the less light you need to take a picture. The trade-off is that higher ISOs can lead to degraded image quality and cause your photos to be grainy or "noisy."
A high ISO means that the camera's sensor is very sensitive to light (for example, 800 or 1600). As the sensor becomes more light-sensitive, it takes less time to scan the image from the lens. So, for example, when shooting at night, it is worth setting a high value to reduce shutter speed and improve image quality.
A lower ISO value means less sensitivity to light, while a higher ISO means more sensitivity. It's one element of photography's exposure triangle — along with aperture and shutter speed — and plays an essential role in the quality of your photos.
The "normal" range of camera ISO is about 200 to 1600. With today's digital cameras you can sometimes go as low as 50 or as high as over three million, depending upon the camera model.
When you have enough light for a good exposure with your chosen aperture and/or shutter speed – you should choose the lowest ISO value. This makes the camera's sensor the least sensitive to light it can be.
You'll get a better result (i.e. less noise) shooting at ISO 6400 and getting a good exposure, then shooting at ISO 1600 or 3200, underexposing, then making the photo brighter. The second is to minimize the shadows and dark tones in your photo.
ISO is what measures your camera's sensitivity to light. More specifically, how sensitive the digital sensor is to light, (it also measures the film's sensitivity, if using a traditional camera). It is represented in numbers such as 50, 100, 200, 400, 800, 1600, 3200, etc.
ISO. For the majority of long exposure photography, especially in the day, you will want to shoot with as low an ISO as possible – most cameras will have a low ISO setting of 100 or 200. This will produce the cleanest image with little noise.
High ISO Performance
Each ISO corresponds to a stop of light; ISO 100 is often where digital cameras “start”, and ISO 200 is one stop brighter, ISO 400 is another stop brighter, and then ISO 800, 1600, 3200, 6400, 12800, …and so on and so forth.
Normally, we shoot at a very low ISO, like ISO-200, to make sure our photos are as crisp as possible. However, for night photography the ISO is our best friend as it allows more light sensitivity to capture more light without requiring a longer shutter speed. ISO becomes incredibly useful for night sky photography!
So what is the best ISO setting for indoor photography? In general, ISO 100 or 200 can work well if you are using a tripod and you have enough brightness. If you are shooting from your hand, you have to raise your ISO to 800 or 1000. Sometimes even higher, as you will notice from my camera settings below.
The key to a great outdoor portrait is considering how bright it is outside. In full daylight, use a lower ISO setting, between 100 and 400, while later in the day or at night you'll have to pick a much higher setting. Playing around with the ISO settings can produce fantastic results — just don't go overboard.
For low light photography, try setting your ISO to 800 and adjust accordingly. If you end up capturing a photo you love but it includes a lot of image noise, all is not lost!
If you are using a relatively low ISO number, but still seeing grain in your photos, it's highly probable that you aren't getting your exposure correct in camera. Under-exposing in camera is the BIGGEST reason for having excessive noise in your photos, even at relatively low ISO numbers.
If you meter off of a brighter area in a scene, your photo will be darker. You can increase the exposure of dark photos in Lightroom, but doing so will add noise to your photo. If you increase the exposure in Lightroom, you will get a noisier image as if you had used a higher ISO when taking the photograph.
By increasing your ISO, your camera sensor will be more sensitive to the available light, meaning that it will need a shorter amount of time to obtain the correct exposure. This minimises the period during which camera shake and movement can have an effect on the shot.
Adjusting your ISO settings.
In brighter lighting, lower ISO is best — low ISO values are better in well-lit scenarios. Conversely, when less light is available, you need a higher ISO to compensate. High ISO increases your camera's light sensitivity, which is ideal for low-light situations.
Instead of bumping up the ISO, use slower shutter speeds and wider apertures, instead. ISO 100 may be impractical for night photography, but ISO 400, 800, or even ISO 1600 should be enough in most situations.
So, raising the ISO setting will increase noise levels for most cameras in most circumstances. But generally speaking, the benefit of raising the ISO setting is greater than the risk of noise, in terms of being able to ensure a fast enough shutter speed to avoid motion blur or not having enough depth of field.
ISO is not a variable of exposure because it doesn't affect the amount of light the image sensor receives. Instead, ISO settings determine how brightly the camera renders a picture given the exposure you have set using the aperture and shutter speed.
The ISO setting determines the camera's sensitivity to light. The lower the ISO number, the more light is needed to properly expose the image. The higher the ISO number, the less light is needed. ISO 200 requires much more light than ISO 6400.
A well-known disadvantage to low ISO speeds is camera shake while hand-holding the camera. When you use low this and shoot photographs in anything other than than bright conditions, you will realize that the shutter speed is slow. When the shutter speed is slower, it will blur out moving subjects of your photographs.