What Is ISO In Photography? Camera ISO Settings Guide

Jeff Picoult

By Jeff Picoult

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ISO in Camera

Some advanced skills may seem overwhelming for beginners, but we will get there eventually as you gain experience. For now, let’s start easy with a closer look into ISO meaning in photography, one of the three pillars of the Exposure Triangle.

What Does ISO Stand For Photography

ISO settings refer to the camera’s light sensitivity controls and are not an acronym for any specific phrase. 

Some might mistake it for the International Organization for Standardization (ISO), an independent, non-governmental body that sets international standards for a wide range of products, services, and systems. 

However, ISO camera settings likely originated from a 1974 combination of earlier naming conventions for film speed, particularly DIN and ASA. By the time ISO (the organization) became prominent, the term ISO (meaning camera) had already been established in photography.

1. Base ISO

Sometimes referred to as native ISO, Base ISO refers to the lowest ISO setting on your camera that produces the cleanest image with the least amount of noise

ISO in phootography

In simpler terms, it’s the sweet spot for your camera’s sensitivity. The sensor operates with minimal amplification to produce images with the highest quality, which translates to sharp, clear photos with accurate colors. There’s no electronic manipulation to boost the signals. 

2. Common Values

Some common values you’ll encounter on most digital cameras:

ISO level
  • ISO 100 (Base ISO): This is typically the lowest native ISO setting (though some cameras might go as low as 25 or 50) and produces the cleanest images with minimal noise. It’s ideal for bright outdoor conditions.
  • ISO 200: Another common base ISO on some cameras, ISO 200 offers a good balance between image quality and low-light performance.
  • ISO 400: ISO 400 works great for moderately lit environments, such as indoor spaces with decent lighting or outdoor shade. Compared to lower ISOs, you might see a slight increase in noise here.
  • ISO 800: As lighting gets dimmer, ISO 800 becomes a good option for capturing handheld images without a flash. Noise becomes more noticeable but remains manageable for everyday photos.
  • ISO 1600: This ISO setting is often used for low-light situations or nighttime photography. Significant noise increase is inevitable, but it allows you to capture images without a flash or very slow shutter speeds that could cause blur.
  • ISO 3200 and Above: These extreme ISOs are common only in very dark environments where capturing the scene is much more important than maintaining pristine image quality. Noise will be quite prominent, so prepare yourself!

3. Why It’s So Important

Too-high ISOs (bright) introduce visible grain or noise to your image, which appears as random colored speckles in darker areas of the photo and significantly degrade image quality. In severe cases, it obscures all the fine details and textures, giving the image a blurry, muddy look!

On the contrary, a very low ISO (dark) in low-light situations results in an underexposed image that appears too dark and lacks detail. 

Recovering it in post-processing software is challenging, especially if significant shadow details have been lost. To compensate for a low ISO in dim lighting, you might need to use a wider aperture (reducing depth of field) or a slower shutter speed (causing motion blur) – the other two elements of the Triangle. 

What Is The Relationship Between ISO and Other Elements?

1. ISO and Shutter Speeds

The two have a reciprocal relationship, meaning increasing one setting allows you to decrease the other while maintaining the same overall exposure. Let us explain in more detail: 

As said, ISO controls the sensor’s light sensitivity, and a higher ISO makes the sensor more receptive to light. 

Meanwhile, shutter speed determines the duration of time the camera sensor is exposed to light. A slower shutter speed lets in more light but can blur moving subjects. A faster shutter speed lets in less light but freezes motion.

Let’s say you’re pouring water into the cup. The amount of water (exposure) depends on the duration of flowing; a longer pour lets in more water and vice versa. ISO works similarly, acting like a pressure control on the water source:

  • Low ISO (low pressure) requires a longer shutter speed (longer pour) to get enough water (correct exposure) in the cup, which is suitable for bright conditions.
  • High ISO (high pressure) allows you to use a faster shutter speed (shorter pour) to achieve the same amount of water (correct exposure) even in dim light. However, the water flow might become uneven (noise) at high pressure.

Here’s a reference chart to put things in perspective:

ISO SensitivityShutter Speed
1001/60 sec
2001/125 sec
4001/250 sec
800 1/500 sec
16001/1000 sec
32001/2000 sec

2. ISO and Aperture

shutter speed ISO Aperture

Aperture refers to the opening of the lens iris, similar to the pupil of an eye, to determine the amount of light that can enter the camera at a given shutter speed. 

A wider aperture (lower f-number) allows more light to create a shallow depth of field where only a small area is in focus. Conversely, narrower apertures (higher f-number) let in less light for a deeper depth of field, allowing more of the scene to appear sharp.

Together with ISO, it influences your image’s exposure (brightness). Let’s return to our previous water example, but this time with a cup and a faucet. 

The amount of water in the cup (exposure) depends on two factors: 

  • Faucet opening (Aperture): A wider opening allows more water to flow quickly (more light).
  • Water pressure (ISO): Higher pressure pushes more water through even with a narrow opening (increased sensor sensitivity).

Hence, in bright conditions, photographers often use a lower ISO (clean image) and a narrower aperture (deeper depth of field) for landscapes or group photos. 

Low-light settings, on the other hand, call for a higher ISO and a wider aperture (shallow depth of field) to capture the scene. Shutter speed can also be adjusted to achieve the desired balance.

ISO SensitivityAperture

How To Choose The Right ISO For Your Photos

1. Low versus High ISO 

Let us confirm the basic difference between low and high ISO here.

With low ISO, the image appears clear and sharp, with very minimal noise and well-preserved details and textures. Colors are vibrant yet accurate, and smooth transitions between tones can be seen. The wider range of tones captured (from highlights to shadows) offers more flexibility for post-processing. 

On the other hand, high ISOs make noise (colored speckles, to be more specific) look more apparent, and the colors might seem slightly dull with less vibrancy than images with lower ISO. Plus, since the dynamic range is compressed, the highlights may be blown out (appearing pure white), and shadows lose certain details.

Daytime (Ideal ISO: 100 to 200)

Bright sunshine already provides ample light for the shoot; thus, you can use a low ISO for the best possible image quality – specifically, sharp photos with minimal noise, accurate colors, and a wider dynamic range that captures more details from highlights to shadows.

For example, when photographing a vast landscape on a clear day, we often use ISO 100 to ensure natural clarity for crisper details in mountains, trees, and distant objects. 

However, for portraits outdoors with diffused sunlight (e.g., under shade from trees), we increase the ISO slightly to 200. This maintains the image quality while still allowing us to control the aperture for a desired depth of field (how much of the background is in focus).

Rainy Day (Ideal ISO: 200-400)

Overcast skies naturally reduce light compared to a bright day. If the rain is pretty light and still lets some sunlight filter through, ISO 200 should do for basic portraits and street scenes without losing color accuracy. 

However, in the case of denser rain or heavy clouds, we believe ISO 400 is a must to compensate for the lack of lighting and guarantee a well-exposed outcome. You must also consider shutter speed and aperture, depending on whether you want to freeze raindrops (faster shutter speed) or capture a more atmospheric feel (slower shutter speed).

Nighttime (Ideal ISO: 800+)

Needless to say, the amount of natural light drops drastically during nighttime. 

For photographers who want to capture a cityscape at night (which often involves light trails from cars or illuminated buildings), 800 to 1600 should allow for a great balance between those elements and some background details. Of course, expect some post-processing for the visible noise. 

How about faint stars or the Milky Way? Long exposure times are necessary in that case, and a high ISO like 3200 (or even higher, if required) will compensate for the darkness while the shutter remains open for an extended period. 

Significant noise is clearly inevitable, but you can trust post-processing software to mitigate it to an acceptable extent.

Some Special Cases

Action Photography (ISO 400-800)

ISO 400 maintains good image quality for good lighting conditions while allowing a faster shutter speed to freeze the action. On the other hand, indoor sports or fast-moving subjects in low light require some balance, so ISO 800 is a better choice to freeze motion and achieve a faster shutter speed. 

Professional Astrophotography (ISO 1600 and Above):

Frankly, there’s no clear-cut answer here; it depends on numerous factors we cannot predict, namely the specific night sky object, light pollution levels, and desired exposure time. 

So experimentation is key. Start with a higher ISO (e.g., ISO 1600) and play around to find the sweet spot that captures the stars with allowable noise levels.

2. ISO Priority Mode

Most cameras (except Pentax) do not have “ISO Priority” modes, though the Program Mode does offer some semblance of one. 

With this Program Mode, you don’t directly control the aperture and shutter speed. You only need to adjust the image’s overall brightness (ISO), and the camera will automatically choose a combination of aperture and shutter speed that achieves a good exposure (well-lit scenes) for that particular ISO setting. 

For those who want the ISO to be adjusted automatically, here are some great semi-automatic modes: 

  • Aperture Priority Mode (Av or A Mode):  In this mode, you set the aperture, and the camera automatically adjusts shutter speed and ISO to achieve a correct exposure. This mode is useful for controlling the depth of field (background blur), though we must say the camera’s chosen ISO might not always be ideal, especially in low light.
  • Shutter Priority Mode (Tv or S Mode): You set the shutter speed here and leave the camera to adjust the aperture and ISO, which is great for capturing motion blur or freezing action. However, like Aperture Priority, the automated ISO is not always optimal. 

Common Myths About ISO

Myth 1: ISO just brightens photos.

Fact: False. 

As we already discussed, increasing ISO does make an image appear brighter. However, this setting is not simply a brightness control. It involves the sensor’s sensitivity to light, meaning a heightened sensitivity level comes at the cost of introducing visible noise (grain) in the image.

Myth 2: ISO is part of exposure.

Fact: True and not true. 

While ISO is indeed one of the pillars of the Exposure Triangle, the truth is that only the aperture and shutter Speed directly control the physical amount of light reaching the sensor. 

On the other hand, ISO is an electronic amplification process, meaning it doesn’t physically change the amount of light captured by the sensor. Instead, it only amplifies the signal from the sensor (after the light has already been captured). 

How To Change ISO? Extra Tips To Use It Effectively

Most cameras have an ISO button, often labeled “ISO.” It might be located on the top of the camera body or near the shutter release button. 

Once you press the ISO button, the current ISO setting will be displayed in the viewfinder or on the camera’s LCD screen. Use the dial or buttons (usually the up/down arrows) to adjust the ISO value to your desired level.

Bonus tips:

  • Consult your camera’s manual or online reviews to understand how it handles noise at different ISO values. Some cameras perform better at higher ISOs than others.
  • A tripod helps you use slower shutter speeds more effectively to capture light in dark conditions.
  • Embrace the noise (sometimes) because, in certain situations, the grainy look does add a sense of atmosphere or urgency to the overall vibe. 


At first glance, ISO definition photography simply means darkening or brightening the image, but there’s actually so much more work involved than that. We have tried our best to break down the concept for fresh beginners, but feel free to contact us if you still feel stuck.

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Jeff Picoult

Jeff Picoult


Jeff Picoult is a seasoned photographer, who blends artistry and innovation. With a humble approach, he captures moments resonating with depth and emotion, from nature's beauty to the energy of sports.

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