How to Adjust ISO in Manual Mode

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  By Kim Suarez
How to Adjust ISO in Manual Mode

Becoming a good photographer takes practice, but also requires immense technical understanding. Among the 3 basic pillars to master, along with Aperture and Shutter, is ISO. As a beginner, you most like are shooting in Auto ISO. This is a great starting point to get right out and shoot. After some practice, you’ll want to begin experimenting in full manual mode. This will allow complete control and understanding of your equipment. Even if you plan to shoot in Auto all the time, you’ll want to understand how it works.

On a sunny day, you can shoot ISO 100, shutter speed at 1/100 – 1/125 and f16. This is referred to as the Sunny 16 rule

How Does ISO Work?

ISO controls the amount of sensitivity to light your camera displays. This can range from 100 (least sensitive) up to 25,000+ depending on your camera. The settings increase in powers of two, meaning from 100 to 200, 200 to 400, 400 to 800, and so on. Each increase of the setting is doubling the sensitivity of your sensor. Which means the higher the ISO, the better it will perform in low lighting. Lower ISOs are better for higher amounts of light. It also means the higher the ISO, the more grain you’ll see in your images. But more on that later.

There are a handful of common ISO values, which you can fall back on when shooting in manual mode:

On a sunny day, you’ll want to shoot at or around ISO 100.
On a cloudy day, you’ll want to shoot at or around ISO 400.
If you are inside, you’ll want to start around ISO 800 and work your way up if needed.

In concert photography, I am usually shooting at ISO 1600 – 3200, higher if needed.

Remember, this is all based on your camera’s sensor. Some are more sensitive than others. You’ll need to experiment to see what works best for the image you are capturing. Above is a general starting point to follow when learning manual mode. Use these values as a guide and adjust from there if needed.

This scene is more cloudy than the one above. Here, you should adjust to ISO 400, while adjusting shutter and aperture accordingly to achieve the desired effect.

How Does ISO Work With Aperture and Shutter Speed?

It’s important to understand how ISO relates to Aperture and Shutter Speed. All three interconnect and a change to one affects the others. You’ll need to understand when to change ISO and how to adjust Aperture or Shutter to compensate.

The larger the ISO value means the smaller the shutter speed needed for the image. This means: When in ISO 100, your camera sensor needs 1 second to capture the image. But as you increase ISO, your camera sensor will need less time to get the shot. It increases by a power of two, so from 100 to 200. 200 t0 400, 400 to 800 etc. As this doubles, the required shutter speed halves. So at an ISO of 1600, you’ll need 1/16th of a second to get the same shot as ISO 100 at 1 second.

So, say you are shooting outside at ISO 100 and 1 second and are happy with the image. But, the clouds start to roll in. You’ll need to adjust ISO, but you want to maintain the same image. Increase ISO to 400 and increase the shutter speed to 1/4. You’ll achieve the same image as before, but now you’ve exposed for the clouds. All while keeping aperture the same for both images.

Increasing aperture lets in less light. This means if shutter and ISO stay constant, but aperture increase from, say, 3.5 to 8, the image will be dark. This is because less light is coming in through the lens. If you want to increase your aperture to allow more of the image in focus, you’ll need to increase your ISO. Because you increase your ISO, you’ll need to decrease your shutter. If you want to maintain the same image exposure and focus.

To figure out the correct settings, begin with identifying the desired outcome. Are you in low lighting? Or are you outside looking to freeze the subject? Identifying that outcome will confirm which pillar (ISO, aperture, shutter speed) to set first. If you are shooting low light, you’ll want to start with a low aperture and high ISO. Then you can determine shutter speed. If you are attempting to freeze motion, set a high shutter speed. From there, determine ISO and aperture needed.

If you are unsure which ISO you need, follow the general guideline above. It’s always best to start low and increase as needed. If your shutter and aperture are at an acceptable value, but the image is still too dark, turn up your ISO.

This is a low light image, shot at night. You’ll need to increase ISO, start at 1600 and adjust from there. You’ll need a tripod here, as this will mean slow shutter speeds to maintain the exposure and open aperture.

ISO in Manual Mode and Noise

When you take a picture and notice a lot of grain in the image, that is the noise. You will see noise in your image if you are using too high of an ISO setting for the light required; however, too low ISO values don’t always guarantee proper illumination, which can translate into blurry images. For example, the below image, taken at ISO 200, has a lot of imperfections, as the lighting was too dim to allow for a proper exposure under such ISO values. The same image, if taken at ISO 800, looks much better. As I adjusted ISO, I also adjusted shutter and aperture to allow for the same exposure.

Noise can be subjective based on the photographer and the type of image they are creating. In some instances, a gritty image is what you are looking for. And you may adjust your ISO for this. It will all depend on your desired outcome. This is another example of why understanding this pillar is important. In auto ISO, your camera will adjust for the perfect exposure. If you do not want perfect exposure, you need to know how to get there. How to manipulate ISO to achieve this more or less noise is a great skill set to have as a photographer.

The process of manual ISO control will take time. But you will gain a better understanding of your camera. It is important to work towards having complete control over your images. This way, you will understand the appropriate adjustments to make, to get the image you want.

Because of the extremely low lighting, I had to shoot at ISO 6400. Because of the limitations of my camera, I could only shoot at f4 and therefore 1/50 shutter. You can still see a lot of noise in the image, but given the subject, it seems to work ok

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Kim Suarez

I am a self-taught travel photographer and writer from San Francisco, though currently based in Ventura, CA. Working in the outdoor apparel industry allows me another outlet for my creativity, as well as access to the outdoor industry. In my free time, I love running, biking, surfing, camping, anything outside.

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