What is Iso in Photography ?

ISO is the unit of measurement for light sensitivity of digital sensors.

It is also one of the three parameters to be considered when making exposures, such as aperture value and shutter speed.

Today’s digital cameras are capable of raising the iso sensitivity by generating little digital noise, but it is not necessary to use extreme values depending on the type of picture you want to take.

What is digital noise? It is simply the amplification of the digital signal generated on the sensor.

50 isos, 100 isos, 200 isos, 400 isos, 800 isos, 1600 isos, 3200 isos, 6400 isos, 12800 isos, 25600 isos, 51200 isos Simply put, the higher the iso sensitivity, the more sensitive your camera will be to light and vice versa.

Unfortunately, this increase in sensitivity has a consequence on the image quality and causes what is called digital noise, an unsightly color blur visible on the image.

The more noise is present, the finer the details.

Conversely, if you make an image with low sensitivity, noise will be almost non-existent and therefore the quality of your photo will be better.

You can notice that the quality is gradually deteriorating.

You should know that the quality of light plays a very important role in the final rendering of a photo according to the selected iso sensitivity.

A photo taken indoors under artificial light conditions with high sensitivities will have a lower quality rendering than a photo taken outdoors in daylight with the same iso sensitivity.

How do you reasonably choose the sensitivity on your camera?

You will choose the lowest ISO values as often as possible when there is enough light, i.e.

on sunny or cloudy but bright days.

100 isos, 200 isos, 400 isos You will get a quality image with almost no noise at the lowest values.

When sunlight decreases, you can use sensitivities higher than 400 isos to ensure sufficient shutter speed and avoid blurred images.

The other solution is to use a tripod.

As for the high sensitivities, they should be used sparingly because the higher you increase these values, the more digital noise your camera’s sensor will generate.

You’ll get a lower quality image, with less detail and blander colors (contrary to what I’ve heard on blogs about learning how to take pictures).

Switching from one iso sensitivity to another will change the aperture value or shutter speed depending on the semi-automatic mode you have chosen to finally get the correct exposure.

An ISO button on the camera allows you to change the value in the semi-automatic modes which areAorAV,TV,PetM.

I refer you to the manuals of your respective devices.

The ISO sensitivity can also be changed automatically on some cameras.

This auto iso mode will adapt itself according to the light conditions to choose the right iso sensitivity, while favouring the lowest possible iso sensitivity.

The advantage is that you no longer have to worry about setting the sensitivity value.

Some proponents of this feature find it a considerable advantage, since they no longer have to change the iso value manually.

For my part, I’m not a fan of iso auto sensitivity, because I always like to control what I do.

If you want to have low sensitivity to give priority to image quality over speed You don’t have to worry about the shutter speed because your camera is on a tripod, so you can do it.

In auto iso mode, your camera does not know your intentions, so the sensitivity may not be at the value you want.

So, if you’re new to photography, I wouldn’t recommend this automatic function, which must remain manual until you have mastered the exposure triangle perfectly.

Increasing iso sensitivity for more speed

Gray, gloomy weather, a dimly lit room, will certainly force you to increase the iso sensitivity.

The reverse is not a necessity but can help you to get a fast speed for subjects that the ask.

If for example I want to photograph a surfer in very cloudy but bright weather.

I need speed to freeze the action but given the light conditions, my camera’s light meter shows me a shutter speed much too slow (example 1/60th of seconds).

I complicate things by using a 300mm telephoto lens that opens at F/5.6 and doesn’t have a stabilizer.

My only solution will be to increase the iso sensitivity of my sensor in order to get closer to my safety speed and to take my pictures with peace of mind.

In this case, in relation to the focal length of my lens, I need a shutter speed of at least 1/250th of a second or more.

This is also valid for a landscape when I need a small aperture to maximize the depth of field on my final photo.

How to remove digital noise?

There are two different ways of doing this.

The first one may already be on your camera, as there is indeed a digital noise smoothing option.

It can be set to low, medium or high.

It’s not that I don’t trust the camera, but I like to fine-tune my photos for the little ones.

onions, as some people say.

Feel free to use this denoising option, but I do not recommend it, as you will not master the smoothing of your final photo.

The other way to reduce noise is to do it during post-processing using your favorite development software.

then sharpen the image to restore contrast and sharpness.

Indeed, a photo taken with high sensitivity in very difficult light conditions will undoubtedly affect details and colours.

The sharpness and micro-contrast of the image will also be degraded, which is why you need to rework your photos (especially if they were taken in RAW format).

You need to smoothly remove this digital noise while adding micro-contrast to achieve usable quality.

Beware of noise smoothing on your photos! Avoid pushing the noise sliders in your software so as not to remove details from your images.

Remember that a noisy photo does not mean a smoothed photo at all, i.e.

no micro contrast.

For example, the “wax doll” effect is synonymous with “smoothed photo”, when referring to the excessive denoising of a portrait.

Deliberately adding digital noise

You can also give an artistic and dramatic effect to your photo by deliberately adding noise in any shooting condition, always thinking about the rendering it will give on the final image, especially for black and white photos.


Now Your Turn

Now I would like to know, do you have any question ?

Or maybe do you have some information to add ?

Either way, let me know in the comments below

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