A Beginner's Guide to Photography - Part 1: Intro & ISO

By Dimitrios Zavos

So you've been bitten...

You now are (or have for some time been) carrying the Photography bug. You have been admiring those stunning photos on photography websites or magazines, and you have been wishing you could have taken similar ones yourself. Dreamy landscapes that take you on a journey, action shots sharp as a razor and wildlife so colourful and crisp it looks like it could jump out of your screen at any time.

And so you made your mind up...

You took the plunge and purchased your first Digital Single Lens Reflex (DSLR) camera and a zoom lens to go with it. And now you're good to go! All set! The editors of Nat Geo must surely have reserved some prime space in next month's issue for your best images. No doubt about it.

So why is it that the first shots out of your pricey DSLR look so similar to the ones you used to take with your mobile phone? And the next ones too...? Something's not right here... Is it the lens? Is it the camera?? Oh why did you have to waste all that money on an impulse...? Again...!

And then it starts to dawn on you...

Canon 5D Mark III Body

You don't really know what all those buttons and switches around your live view screen are for, right? What do all the acronyms and signs on the back of your camera mean? What do all the numbers on that small LCD screen at the top measure? And finally, why would anyone place a joystick or a wheel on a DSLR camera body?

Well, if you've made it all the way here it means that you already belong to a minority. The minority that wasn't disheartened by that first blow, placed that brand new camera back in its box and stored it for future generations. You are here because you want to learn! Because you want to know how to do it right and be proud of the results. You have been looking for a way to express your imagination and creativity and you know you have found it through your lens.

So please allow me to assist you further in your quest. Through a series of tutorials in the Tips & Techniques section of my website I will attempt to take you through the basics of Digital Photography and make sure you start-off on the right foot. Once you get the basics down, then the sky is your limit.


One of the first concepts you will need to understand in some considerable depth is Exposure. Now, one could get all technical about it, but as this is the first part of my Beginner's Guide I will try to simplify it as much as possible.

An image's Exposure establishes how light or dark the image will appear after it has been captured by your camera.

Exposure is determined by the following three elements, which are known as the "Exposure Triangle": Post 1-2Exposure TriangleExposure Triangle

  • ISO – an indicator of a camera sensor’s sensitivity to light

  • Aperture – the size of the lens' opening when a picture is taken

  • Shutter Speed – the length of time the shutter remains open

Each of the elements of the "Exposure Triangle" relates to how light enters and interacts with the camera and any change to one of them will have an impact on the others. Therefore, understanding their interdependence and mastering their use is essential in order to progress any further in Photography.

The image to the right visually represents the concept of the "Exposure Triangle" and shows that the intersection of the influence of each of the three elements is where the image’s perfect exposure is worked out.

So, without further ado, let's begin with examining each of the three elements of Exposure in detail. First stop: the concept of ISO.

ISO in Digital Photography

In digital photography the ISO rating indicates the level of the camera sensor's sensitivity to light. The higher the selected ISO, the higher the sensor's sensitivity.

In most DSLR cameras the lowest ISO setting you can select is ISO 100 (some can go as low as ISO 50). From there the sensitivity can be increased to 200, 400, 800 and even more than 100000 in the latest high-end DSLRs. Increased sensitivity means that your shutter remains open for a shorter period and yet the same "amount" of light is captured by your sensor. Therefore, a faster shutter speed makes it possible to capture photos of moving subjects in low-light conditions without motion blur and even without the use of flash.

So why not use a high ISO setting all the time then?

Well, I hate to be the bearer of bad news, but the increase in sensitivity comes at a cost: The dreaded Digital Noise a.k.a. Grain.

Take the following image as an example:

Post 1-3ISO setting comparisonComparison of digital noise levels created by different ISO settings

For all three samples the Noise Reduction (NR) setting in the camera has been disabled. In the first photo, which was shot at ISO 100, there is hardly any noticeable digital noise (or grain), but the more the ISO increases the grainier the image becomes, until it is almost unusable.

So how do photographers manage to take crystal clear photos in very low light conditions or even in the middle of the night? What is their secret?

Well it isn't really a secret, as such, but it is definitely the most essential piece of gear every self-respecting photographer should own in order to maximise the picture quality of his/her images. It is the humble tripod.

By mounting the camera on a sturdy tripod a photographer can turn the ISO setting down to very low values, as the camera is guaranteed to remain motionless for as long as the shutter remains open. The end result should be a crystal clear image with minimal digital noise.

The following night shot of the Seoul Tower and Pagoda is a 6-second exposure, captured at ISO 100. On the right, you can see a 100% crop of the same photo exhibiting the almost total lack of digital noise and an image sharpness only achievable through the use of a tripod (or anything that can keep the camera motionless for that matter).

Post 1-4Example of minimal digital noiseExample of minimal digital noise during a long exposure at night

Now that you have taken your first step towards understanding the basics of Digital Photography, I suggest that you grab your camera and test the different ISO settings on it. Trial and error is the only real way to master the abstract concepts of photography.

On Part 2 of my Beginner's Guide we'll be discussing the concept of Aperture and its impact on Depth of Field and establishing why understanding its mechanics is so crucial to achieving stunning results from Macro to Portrait and Landscape photography.

Until then, keep practicing and have fun!


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