If you’ve ever ventured out of AUTO mode, then you are likely familiar with the ISO setting on your camera.. One of the three pillars to the Exposure Triangle, ISO is a vital part to getting the exposure you want.
So what is ISO? And how can you better use this setting to capture better quality exposures?
We begin with the birth of ISO. From there, we cover the basics of this camera function every photographer should know.
An Introduction to ISO
The term ISO stands for International Standards Organization. This term was penned back around the early days of film when a rating system was needed to standardize film speeds.
If you ever shot back in the days of film, then you likely remember purchasing film labeled “sport” or “sunlight” etc. These labels were correlated with different ISO ratings.
These ratings define how sensitive the film is to light.
By creating a standardized system for rating these sensitivity levels, all camera manufacturers could create film and cameras built around the same measures.
Fast forward to the days of digital and there is no film! Rather, there is a single setting you can control to manipulate ‘ISO’. While ISO now works different for digital cameras, the concept is still the same.
ISO is used to control how sensitive your camera is to light and color.
ISO measures not just sensitivity to light, but also color.
How ISO Affects Photographic Exposure
The ISO for most cameras is set to increase by the power of two:
Older cameras typically are confined to these ISO ranges while newer DSLR models allow for ISO’s between these ranges (250, 500, etc).
As ISO numbers rise, so does the sensitivity.
A low ISO of 100 is typically the least sensitive (although some cameras have ISO’s of 50 available). At this ISO, your camera will produce the best color and dynamic range possible.
Moving up the ISO ladder, color and light quality diminish. An ISO of 200, 400, and even 800 is far better than an ISO of 6400.
Higher ISO ratings also increase grain or noise to your image.
As you can see below, ISO 100 to 800 increases grain, although not nearly as noticeable as when you move to an ISO of 1600. Moving to an ISO of 3200 shows a substantial increase in noise.
Notice how the background bokeh rendering is also made more rugged, less smooth as ISO increases.
So why shoot with a higher ISO?
In fact, it’s this reason that many photographers call higher ISO’s ‘fast’ and lower ISO’s ‘slow’.
The Pros and Cons of a Higher ISO
With each step up of ISO, you double your camera’s sensitivity to light. An exposure that takes ¼ of a second with an ISO of 100 can be reduced to 1/60 of a second with an ISO of 1600.
Take a look:
- 100 = 1/4 second
- 200 = 1/8 second
- 400 = 1/15 second
- 800 = 1/30 second
- 1600 = 1/60 second
When you triple the ISO, you also triple the amount of light you can expose with. As covered in the Exposure Triangle, this can allow you to easily capture fast-moving action or low-light scenes.
This can also help with hand-held low light scenarios.
When shooting hand-held, it’s important to follow the shutter and focal length rule (using a shutter speed equal to or faster than your focal length) to avoid camera blur. In low light, this can be nearly impossible though with a lower ISO. Fast ISO’s allow you to bump up available light and get back to more manageable shutter speeds.
Without doing this, you’d likely struggle with either photos underexposed or blurry.
A higher ISO rating allows you to easily…
Reduce blur from handheld camera shake
With an ISO of 100 indoors in the evening, you’ll struggle to get any decent exposures without a flash. A high ISO of 800 or higher can turn this ‘impossible to shoot’ scenario into a seamless occasion.
Capture fast-moving objects
To capture a fast-moving object, you need a shutter speed that moves faster than the subject. The thing is, faster shutter speeds require much more light to work with.
Fortunately, fast ISO’s allow you to add more light to your camera. ISO’s of 800 or higher are common for sports and other fast-action scenes. Combine this with a fast, large aperture lens and you’re set!
To capture extremely quick scenes (bullets, moving insects, etc) pro photographers use advanced flash systems that spray intense amounts of light for fractions of a second. This gives them the needed light to expose an image at lightning fast shutters.
Expand Depth of Field
Many times I’ve found myself without a tripod and needing to use a smaller aperture for an expansive depth of field. The only way to get enough light for these shots was by raising my ISO.
While a fast ISO is a life-saver for scenes when I don’t have a tripod or need to freeze motion, I almost always aim to use the lowest ISO possible.
The Benefits of a Low ISO
Use the lowest ISO on your camera and you’ll ensure you capture images with as much detail and quality as your camera is capable of. ISO’s of 100, 200, and 400 are all considered in the lower range and are great at retaining image quality without the drawback of noise.
To use a lower ISO, however, you need to have more light available to expose with.
The more light you can work with, the lower the ISO you can use.
Bright sunny days are prime examples when a low ISO is no problem to use. The light for these scenarios is often so plentiful you can even use a low ISO with small apertures lik f/16.
Pretty much all other times of day and weather make shooting with the lowest ISO a little more tricky.
These scenes can include:
- Cloudy, overcast days
- Shooting in the shade on a sunny day
- Indoor scenes at all times of the day
- Sunrise and sunset
- Night or other low light scenes
If you plan to use a large aperture of f/5.6 or bigger, you could get away with an ISO of 100. But if you want a smaller aperture and more depth, the reduced light sensitivity will require additional light via increased shutter speed.
This is when a tripod is a must!
Having a tripod around will allow you to never have to worry about boosting up your ISO. You can always just set your tripod up and capture the shot with the lowest, highest quality ISO possible.
Do note that for lower light scenes, an ISO of 100 can require you to use very slow shutter speed exposures. This will, consequently, blur any motion within your frame.
If this is something you don’t want, you’ll have to go with a faster ISO.
I typically try using an ISO under 200 most times and let the exposures go long (unless I’m shooting a fast-motion shot).
The one scenario when I don’t do this is night photography. An ISO of 100 in the dead of night, combined with a small aperture means each shot will take 5-10 minutes to take, at least. Boosting up the ISO speeds up the shooting process in these scenarios.
When it comes to these night shots, sometimes I’ll just boost up the ISO to 1600 or higher and once I find the right composition I like, I’ll drop down the ISO. This speeds up me having to wait 5 minutes to see how the exposure turned out.
ISO Isn’t Everything When It Comes to Grain and Quality
ISO is far from everything that controls image noise and quality. ISO is solely a lever that tells your camera’s digital pixels how sensitive they should be to light.
The quality of your images, ultimately, is determined by the size and quality of the pixels your camera has.
Large pixels mean less noise. Small pixels mean more noise.
This is why DSLRs typically have better image quality than compact cameras. They’re bigger and have bigger pixels built into their bodies.
This is also why a full-frame DSLR will perform better than a crop sensor DSLR, especially in low light scenes.
Limitations of ISO
These days cameras are getting released to the market with the ability to use ISOs as high as 100,000. While this all sounds great on paper, it’s important to know that most ISO levels above 1600 begin to produce a significant amount of noise.
Some higher end DSLRs allow you to get up to 3200 or higher with manageable noise.
Just know that the higher up you go on the scale, the more degradation to image quality you’ll experience.
The key is to know what you’re trying to use the image for. If you’re trying to make a large canvas print, an ISO of 1600 or higher is likely not the best choice.
Smaller image formats are much more forgiving of high ISOs.
Shooting for an Instagram profile? Then a higher ISO may not be as big of a deal.
Overall, if you have to choose between capturing an image with a high ISO or capturing the image with a lower ISO that ends up blurred, go for the higher ISO.
You can minimize noise, not blur.
Getting Control of Your Camera’s ISO
If you’ve shot in AUTO mode the majority of the time, then I absolutely recommend taking a stab at manual or semi-manual modes. These modes allow you to take full control of your ISO.
While AUTO mode does a good job of picking the appropriate ISO for most average scenes, if you are chasing after splendid, dramatic light, you need more control. The more you can control what your camera does, the more your camera can output images that match with your vision.
I find myself changing ISO often to get the ideal settings I need. For small apertures for landscapes or expansive depth, particularly at sunset or low light, I need to adjust ISO often. As the sun continually rises or falls from the horizon, incremental adjustments are made.
If you’re looking to get a stronger grasp of ISO and how it works with the Exposure Triangle, I recommend going through The Exposure Den course. It teaches a unique approach to exposure that’s both easy and effective.
When It Comes to ISO, Remember These Three Things
To close this lesson, think about these three main things when it comes to ISO:
How much light are you shooting with? What time of day is it? What’s the weather like? And what aperture / shutter speed do you plan to use?
All of these will influence how much light you have to work with.
#2. Is a Tripod Available
If you’re stable and have a stable environment, low ISO’s are fine. if not, you’ll have to accept grain to capture images clearly in low light or at long focal lengths.
If you want to blur objects or scenes, a low ISO is both ideal for clarity and getting to slower shutter speeds. If you want to freeze motion, a faster ISO is needed to reach fast shutters with adequate light range.