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What is ISO? As fast as possible!

Getting into Photography also means getting into that grand mission of ‘perfect exposure’ every time.

And, getting perfect or ‘desired’ exposure every time is challenging in ‘auto’ mode.

That’s the reason camera manufacturers include a manual mode option in every DSLR camera which allows Photographers to manually adjust the exposure, depth of field & shutter speed.

Manual Mode may take some learnings and understandings to master it.

And, being familiar with terms like Aperture, ISO & Shutter Speed will help you alot as they are the main players in manual mode or more professionally, manual photography.

In this article, I’ll be explaining you about ISO, as fast & as clearly as possible.

Let’s jump into it.

In the early days of Photography, a film was used in the camera & that film came in different ISO speeds.

ISO mostly varied between 100 – 400. 

In that case, ISO number was used as the light sensitivity scale of the film.

But, in modern cameras the sensor of camera is capable enough to vary its aperture from 100 to 6400 in basically every DSLR & upto 102400 in high-end DSLRs.

In short, ISO is just a standardization of camera’s sensor that refers how sensitive the sensor of the camera becomes with the light.

Basically, lower the number, lesser sensitive the sensor gets with the light and vice-versa.

Lower ISO number (100 – 400) becomes helpful in daylights or at any situation where enough light is available.

In same manner, higher ISO number means it’s gonna help in low-light situations.

Look at this picture as it would make more sense.

As you can see, lower ISO means darker image and higher ISO means brighter image.

In night shots and bad day photography sessions, ISO always becomes our best buddy.

Because, even in some uneven situations or environments, playing around with ISO will give you pretty impressive shots.

That means, in daylight situations ISO 100-300 would work.

And in medium exposure situations like in cloudy day, you can jump to 400-800 range.

I won’t recommend you to go above ISO 800 as it would start producing something called ‘digital noise’ in your image.

Which means, image would start looking grainy & overall the quality will fall.

You may have noticed in the picture above that, picture with ISO 1600 has shown up some digital noise in it.

Here’s the closer look to compare.

That’s the only downside of selecting high ISO speed.

So, that’s pretty much everything you need to know about the ISO.

Let’s quickly recap the whole thing.

ISO is simply a standardization of camera’s sensor sensitivity that determines how the sensor reacts with light.

Lower ISO means darker but cleaner image & higher ISO means brighter but noisy (digital noise) image.

Here’s a graphics of whole issue that may help you.

For productivity and learning purpose you can save this chart, copy paste this article in your notepad or just bookmark it.

Also, share it to your friends who are new to photography or just if you think they need to know about ISO.


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  1. Osaka

    Its so interesting to know about ISO..being non photographer I was unknown about ISO and its effect on photo..thank you for your article!! I want to have training with you soon!

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