ISO : Understanding Exposure in Digital Photography

In today’s editorial, we’ll be looking at ISO as the third primary factor which plays a contributory role in capturing a perfectly exposed image. The first we discussed was Aperture, next we looked at Shutter Speed, and now we’ll be looking at ISO as it relates to Exposure in Digital Photography.

What is ISO?

DSLR Camera sensors have a way of interpreting/responding to light. Their response to light, however, determines how bright or dark the image captured is. This mode or response can be referred to as ISO. ISO is measured in values such as 100,200,400,800 etc and can be controlled automatically or manually via the camera settings.

ISO VALUES EXPLAINED.

Like we mentioned earlier, ISO can be used to control the brightness of an image. The higher ISO values you apply, the brighter your image is. But it gets to a certain value where you begin to notice grains on the image; otherwise known as noise. This noise is acceptable by some photographers while some don’t like it. Personally, I don’t like noise in my images. I love them clear and crisp.

ISO Understanding Exposure in Digital Photography
ISO Understanding Exposure in Digital Photography Aperture f/9 Exposure time 1/160 sec ISO 100, Focal length 50mm

To achieve the highest image quality from your DSLR camera, it’s advisable to stick to the Base ISO. The base ISO here is the lowest ISO value your DSLR camera has. Unfortunately, we can’t always stick to this value at all times due to the conditions in which we’re shooting especially in low-light conditions.

What ISO value is best for you?

Pick up your camera and start experimenting. Set your Aperture to around F4 and your shutter speed to about 1/160th sec and ISO set to your base ISO. Start taking pictures with varying ISO values until you get to a point where the noise/grains are unacceptable. That would then give you an idea of the best acceptable ISO value for you to shoot at using your DSLR camera.

Conclusion

This is just a basic knowledge of ISO as related to Exposure in Digital Photography. We’ll go deeper into how it can be controlled when we discuss the Exposure Triangle.

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APERTURE : Understanding Exposure in Digital Photography

On our series of demystifying photography, we’ll be looking at one of the three cardinal factors that determine exposure in photography; which is Aperture. The other two are ISO and Shutter speed. Before we go ahead, it’s advisable we have a good knowledge of the structure of a DSLR camera

What Is Aperture

Aperture can be defined as an opening in a lens through which information in form of light travels into the camera body/structure. This could vary in size. The larger it is, the more light that gets into the camera.

Aperture Size

The size of the aperture can be controlled by the Iris. In Digital Photography, the aperture is measured in f-numbers (for example f/8). The f-numbers or f-stops can be used to describe how wide or narrow the aperture is. A smaller f-stop means a larger aperture while a larger f-stop translates to a smaller aperture. This is another area photographers find confusing but once you understand the ideology, it sticks.

Below a graphic representation of Aperture.

Aperture Explained
Aperture Explained

Depth Of Field.

We can hardly discuss Aperture without making reference to Depth of Field. Depth of Field can be defined as the amount of your shot that is in focus. A large Depth of Field means that most of your image would be in focus. This can be produced using a small aperture (large f-number/f-stop) such as f/16.

Large Depth of Field
Large Depth of Field (Large F-number/Small Aperture) F-stop f/13 Exposure time 1/160secs ISO 160

A small or shallow Depth of Field can be seen as an image with only a portion of it in focus while the rest of it remains blurry or fuzzy.

Shallow Depth Of Field
Shallow Depth of Field (Small F-number/Large Aperture) The image was taken at the LetstalkphotographyPH meeting f-stop f/1.8 Exposure Time 1/200 secs, ISO 1600 Focal Length 50mm Subject Distance 2.5m Metering Mode Centre Weighted Average No Flash

DSLR Lenses are manufactured to have specific values on how wide or narrow the aperture can get. The lens specifications usually state the largest f-stop and the smallest f-stop. A lens with a maximum f-stop of f/1.2 is considered to be a fast lens because it allows more light to pass through compared to a lens with a maximum aperture of f/4.0

Here's a brief video produced by Olufemii Tutorials that also explains Aperture

We tried to keep things as simple as possible while explaining Aperture as it relates to Exposure in Digital Photography. Feel free to share your thoughts in the comments section below.

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Understanding Exposure in Digital Photography

As simple as the title of this editorial sounds, many “Professional Photographers” are yet to have a grip on what Exposure in Digital Photography really means. Learning is a continuous process and so This is would be the first in a series of editorials where we’ll be taking an in-depth look at Exposure and how it can be demystified. Kindly attempt to read our introductory Editorials to this series which talks about what photography is and a detailed explanation of the DSLR Camera.

Definition of Exposure in Digital Photography

Exposure could be seen as how bright or dark your image would be. It’s imperative that we capture our images with the perfect exposure; meaning it shouldn’t be too dark or too bright.

For us to capture a perfect exposure, we must correctly and creatively combine the three cardinal factors which play a contributing role towards achieving a well-exposed image. They are Aperture, Shutter Speed, and ISO. A simple guide to achieving a perfect exposure is the use of the exposure meter. This could be seen when you look into the viewfinder of your camera.

Light meter scale as seen inside the viewfinder
Light meter scale as seen inside the viewfinder

If it tends towards the right, there’s a tendency for the image to be over-exposed; if it tends towards the left, there’s a tendency for the image to be under-exposed. Having the mark at the at the dead center tends to give a perfectly exposed image. The outcome may vary under certain situations but it’s good we have this as our guiding principle.

We’ll be looking at the three cardinal factors {Aperture, Shutter Speed and ISO} and how they individually and collectively {Exposure Triangle} contribute towards producing a perfectly exposed Image.

Did you find this tutorial helpful, please share your thoughts in the comment section below?

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