ISO is a term that was originally used in film cameras, which represented the sensitivity of film to light (or iso speed). ISO divided the scale of film to be sensitive to different levels of light.
So, the film itself was more or less sensitive to light - meaning the more sensitive it was, the brighter the picture would be once developed.
I'm sure you can see the inconvenience of this. This took skill and experience with different film - you had to know how the film would react to any given scene. You also had to change film if you needed a scene brighter or darker(if shutter speed and aperture couldn't get you there).
Well, digital photography completely changed everything.
First off, ISO is one of the three points of the exposure triangle. What that means is ISO, when used correctly, will help you make a well-exposed photo (which is the goal of photography).
ISO stands for International Standards Organization (or international organization for standardization), and it's an international standard that each country has adapted to. It represents the sensitivity of a digital cameras sensor to light.
Basically, the higher the ISO number - like 1600 - or 25600 for some cameras these days, means that a camera sensor is more sensitive to low-light situations (like indoors with little to no natural lighting).
This also means you're going to have a brighter picture in those environments because your sensor is now more sensitive to the light that is hitting it.
From an understanding standpoint - ISO is one of the easiest points on the exposure triangle, to understand!
Let's dive a little deeper into how it actually works.
ISO is entirely digital (we're taking a photo with a digital sensor, right?). What I mean by that is, aperture and shutter speed (the other 2 points of the triangle) are mechanical or effect actual light.
ISO on the other hand amplifies light that hits the sensor. It does this by increasing the exposure reading (and voltage to the sensor) based on your ISO setting.
So, if you take a shot at ISO 100 and another right after at ISO 800 (with the exact same lighting conditions), the ISO 800 shot will be much brighter than ISO 100.
Note: ISO increases the brightness of all sources of light. This would include ambient as well as light created by a flash.
Knowing about ISO on your camera is important because it will help you take a well-exposed photo. That means knowing which ISO setting to use for different subjects and scenes.
Too low of an ISO value and the picture will be too dark, too high of an ISO value and the photo will be too bright.
ISO also offers you a great amount of creative control in regards to how you shoot by allowing you to change the brightness of your shot; from getting a brighter picture in darker settings (higher ISO values), or vice versa (lower ISO values).
Don't forget, ISO is one of the 3 points of the exposure triangle... it's essential to know to ensure you'll get the correct exposure in any situation.
And, you'll run into a situation at some point (if you haven't already) that you'll need to use ISO.
Knowing when and how to effectively use it is what we're going to discuss going forward in this article.
It's incredible how far technology has pushed cameras even in the last 10 years.
To bring 10 years ago into reality - the Canon T3i was dominating the market. We're talking about great photos and acceptable video. It was one of the first DSLR cameras that videographers accepted as a camera that would take video worthy of paid work.
As far as ISO goes - its range was 100 to 6400.
But, anything over ISO 800 was pretty much unacceptable.
Fast forward 10 years and companies like Sony and their A7iii can take very acceptable photo and video at ISO 6400 with a max value of 25600 (expandable to 51,200). Although you'd never want to run ISO at 25k - the option is there if you ever need it.
The ISO range of most cameras manufactured today is 50 to 25,600. This can change depending on the camera and the manufacturer - but this is the average range of cameras on the market today.
This is the ISO setting that doesn't require any additional voltage sent to the sensor to increase exposure.
Think of this as the 'base level' ISO setting.
You'll also get the most dynamic range out of your camera at this setting.
Lastly (but surely not the least) - you'll get the least amount of digital noise in your images (we will touch on this more here in a minute).
The 'universal' native ISO setting for most DSLR/mirrorless cameras on the market today is 100.
*The images above were taken at an extended ISO setting of 50 with off camera flash*
Extended ISO is ISO values below 100.
Yes, there are cameras on the market that allow you to go below 100.
This does the opposite of increasing your exposure - extended ISO values decrease (lower) your exposure.
There are claims that photos taken with an iso value below 100 are cleaner and have less noise. I have never been able to confirm this (and I shoot below 100 a lot). I haven't been able to confirm the claim, but maybe you could!
The major benefit of iso values lower than 100 - is shooting with a flash.
Cutting ambient light to create moody photos with flash requires a dark(er) exposure. To get to the correct exposure I want - I normally have to use a 3 stop (or 5 stop) ND filter and cranking the shutter speed to 1/250.
A shutter speed faster than 1/250 would darken ambient light even more - but would reduce the power of my flash significantly (because I would have to enter high-speed sync mode or HSS). Knocking down exposure by using ISO 50 has helped me get to a great exposure - even to the point where I don't have to break out an ND filter.
Other than the instance I just explained (and the claims that have been made) - there isn't any other benefit from extended ISO that I can think of.
Let me know of another benefit if you know one!
Many beginner photographers that I talk to either don't know what ISO is at all or they're afraid to use it.
Not knowing what it is, is completely understandable. But why would they be afraid to use it?
Well, simply put, ISO affects image quality.
The higher your ISO the more digital noise that's created - and I know you've seen digital noise. Digital noise doesn't look good in most situations (some people like it for nostalgia/stylized photos)
With that being said, I live by two thoughts when it comes to ISO...
Let's be honest, there wouldn't be a reason to have ISO as an option if it wasn't a viable way to adjust exposure.
So, don't be afraid to use it.
But, don't overdo it! It's easy to 'go ham' with ISO in low-light environments. But get to know your camera, how it deals with digital noise, and make adjustments from there.
Remember, it's much easier to fix a bit of digital noise than it is to fix a really underexposed image.
Let's start talking about when you should (or have to) use iso to get correct exposure.
Generally speaking, the ultimate 'goal' is to not have to go above iso 100. You get the cleanest looking and the best dynamic range.
But, there are times when you'll have to use high iso. Let's go over a few scenarios now.
If you're capturing fast action (life sports or wildlife) - you're going to have to run a faster shutter speed.
Fast shutter speeds means your images may be underexposed.
Assuming you can't open your aperture any wider (or you want to keep it the same) - you'll be forced to adjust your iso settings.
Increase your iso one step at a time. Meaning, go from 100 to 200 and check your exposure. Trust the exposure meter in your camera and go from there.
This is what's great about digital photography (versus film cameras) - you can see your images right after taking them!
Let's assume you're indoors and have your aperture wide open and your shutter speed is as slow as you can get it without introducing motion blur from camera shake.
You would then have no choice but to increase ISO. Much like the suggestions from the last section, start increasing slowly until your exposure meter tells you it's good.
Trust me, you would have the best image quality by increasing digital iso instead of an even longer shutter speed.
Astrophotography is probably the hardest version of photography when it comes to balancing aperture, shutter speed, and iso.
It's very easy to introduce too much digital iso (esp considering you can't see the outcome till after the photo is taken on a DSLR).
I recommend introducing iso values as a very slow pace (much like the recommendations in previous sections).
Be prepared to take a series of shots that aren't good - but trial and error will lead to great results.
I'm sure you can see the pattern in how to approach the use of ISO and how to manage it.
At this point, you know what iso was, what it is now, and when and how to use it! If you haven't read our other articles on shutter speed and aperture - be sure to check those out as well.
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Thank you all for reading and until next time, be safe and keep learning!
Jeff & Reyna