What is an ISO or light sensitivity in photography ?

Many amateur might not know what is iso in photography? well don’t worry, this article is made right for you
The ISO in photography and manages the sensitivity of the camera to light, which is the third component of exposure (the other two components are aperture and shutter speed). Which offers him to set exposure to light.

When we need to increase or decrease exposure after adjusting the first two elements (aperture and shutter speed), we resort to controlling the iso light sensitivity of the camera sensor. So we change the ISO number in the camera to make the sensor more sensitive to light or less according to the value we want.

And raising the ISO sensitivity level has consequences An image captured too high from ISO will appear blurry or grainy. Therefore, image brightness across ISO is always a trade off. We only have to raise your ISO when we cannot lighten the image via the shutter speed or aperture.

Also Read: what is Exposure in photography ? the rules of EXPOSURE

What is the meaning of ISO?

The ISO symbol is an acronym for “International Organization for Standardization”. However, the camera’s ISO does not directly refer to the organization that creates various technical and product standards. Since two film standards called ASA and DIN were incorporated into the ISO standards in 1974 (later revised for both film photography and digital photography).

And they were referred to as one “ISO” from that point onwards. Although ISO initially specified only movie sensitivity. It was later adopted by digital camera manufacturers with the purpose of maintaining similar brightness levels to film.

Common ISO values

Every camera has a different range of ISO values ​​(sometimes called ISO speeds) that you can use. The common group is as follows:

• ISO 100 (low ISO)
• ISO 200
• ISO 400
• ISO 800
• ISO 1600
• ISO 3200
• ISO 6400 (High ISO)

To put it simply, when you double your ISO, you are doubling the brightness of the image. Therefore, the image at ISO 400 will be 2 times brighter than ISO 200, which will be 2 times brighter than ISO 100.

What is the ISO rule in photography?

The lowest basic ISO in the camera is the “base ISO”. This is a very important setting, as it gives you the ability to produce the highest image quality, minimizing the visibility of noise as possible. Some older DSLRs and a number of modern cameras, such as Fuji X-T2 have a base ISO of 200, while most modern digital cameras have a base ISO of 100. Optimally, you should always try to adhere to the basic ISO for the highest quality For the image. However, it is not always possible to do this, especially when working in low-light conditions.

Low vs High ISO Noise Visibility

To give an example of two photos taken at different ISO values, take a look at the comparison below. Pay attention to the noise level (grain, color, spots) in the images:

The difference is clear – the image at ISO 3200 has more noise than the image at ISO 200 (which I lit up at a long shutter speed instead). This is why you should avoid high ISO as much as possible, unless circumstances require you to use it.

When to use low ISO?

You should always try to stick to the lowest ISO (rule of ISO) your camera, which is usually ISO 100 or 200, whenever you can. If there is a lot of light, you are free to use low ISO and reduce the appearance of noise as much as possible.

Even in dim or dark environments, you can still use low ISO. For example, if the camera is on a tripod or you are seated entirely at the table. In this case, you can safely use a low ISO and brighten your photo at a long shutter speed instead, since you won’t be displaying camera shake.

Also, try using a wide lens like 50mm f1.4 in a dark environment in order to take advantage of its wide aperture to bring in light and avoid raising the ISO as much as possible. With variable aperture lenses, for example, with a wide focal length lens, with an 18-55 lens, try shooting at 18 so that you get an f3.5 aperture instead of f5.6 at 55.

When to use High ISO?

Although it is ideal to use low ISO values, there will be a lot of times when a high ISO will be necessary to capture a good photo in the first place. The simple reason is that you often fight against motion blur, and you’ll need to choose between a sharp image at high ISO, or a blurry image at low ISO. See the picture below:

I took this photo of the birds with a shutter speed of 1/2000 of a second and ISO 800. Here, it took my camera 1/2000 of a second to completely freeze the birds in flight. What would have happened if I had set ISO 100 on my camera instead? I would need a shutter speed of 1 / 250th of a second to take a bright photo. In this setting, there was a lot of unwanted motion blur in the image because the birds were moving so fast. In short, I would have ruined the image.

The bottom line is that you should increase the ISO when there isn’t enough lighting for the camera to take a sharp and bright photo any other way. When I shoot indoor handheld photos without flash, I always set the ISO to a higher number to capture the moment without introducing blur. Or, when photographing ultra-fast motion like in the bird image above, raising your ISO is often necessary.

On most cameras there is a setting of Auto ISO, which works great in low-light environments. The benefit of this setting is that you are entering the maximum ISO that you want to use, so that the camera does not exceed this limit. Personally, if I wanted to reduce the amount of noise in an image, I’d set the maximum ISO to something like ISO 800, 1600, or 3200. The downside is that the camera would start to use progressively longer shutter speeds if it reached the ISO these limits. It leads to more motion blur. Everything is here at the expense of the other.

Firas Ghraoui