Photography, be it digital or film is part science and part a search for aesthetic gratification. Due to its close relationship with key elements of physics, especially light, one has to have a good understanding of how that element behaves and influences our photographs. A way to understand it is by studying the basic photography terminologies, which we shall discuss today. Additionally, you can also check out this excellent course on the fundamentals of photography.

## Aperture Value

Aperture denotes a small opening at the front of the lens. This opening is frequently compared with the pupil of the eye, the small opening that allows light to pass through and reach the retina. In the case of a camera, the retina is replaced by either the digital sensor or the film.

Aperture can be increased or decreased, much like the pupil, where the iris of the human eye is replaced by the mechanical shutter. Increasing the aperture allows more light to pass through and vice versa. Aperture is expressed as a fraction like this – f/1.4, f/1.8, f/2 and so on. It is also referred to as f-stop.

Progressively changing the aperture from f/1.4 to f/2 would mean that the opening is becoming smaller and thereby allowing less light to pass through. The exact reverse happens when you “open up” the lens from f/2 to f/1.4 and beyond. Interestingly, a big aperture is referred to by a small f-number and vice versa. So, an aperture of f/1.4 is bigger compared to an aperture of f/2. This can be confusing when you start, but slowly you will get the hang of it. Just remember, that if F was an integer then f/2 would have been a bigger fraction than f/4. That way a smaller fraction = smaller aperture and vice versa.

There is an inverse relationship between aperture value and shutter speed. If you use a bigger aperture, you will need to increase the shutter speed and vice versa.

## Shutter Speed

Shutter speed denotes the duration of time for which the lens remain open to collect light. The longer the duration, the greater is the quantity of light that is collected. Resultantly, the final picture quality is better. However, setting the wrong shutter speed in relation to available light can lead to an over or under exposure along with noise and/or image blur. There are several ways both fast and slow shutter speeds can be creatively used in photography.

## ISO

Simply put, ISO refers to the camera’s sensitivity to light. The term ISO is relevant in both film and digital photography. In film photography “speed” of the film is what is referred to by the term. In reality however, it is the sensitivity of the film to light that is being intended. There are films of speeds 100, 200, 400 and so on. Every number is twice or half as sensitive to the immediately previous or next number. The more sensitive the film is to light, the more suitable it is to be used in low light conditions. However, please bear in mind that with higher sensitivity comes the problem of noise.

The same number system is used in digital photography as well. In digital photography, ISO can be changed simply by the flick of a button. It is a lot easier than having to change films in the middle of a shoot or worse still, carry a number of cameras loaded with film of different speeds.

## Exposure

The word is synonymous to taking pictures, but somewhat loosely used in the photography world. Exposure actually denotes the quantity of light that is captured by the sensor or the film. It is imperative that a photographer knows how much exposure is required to create a perfect picture. Keeping the lens open for a longer period of time (using slow shutter speed) on a sunny day will reduce the picture to a white glare with no discernable detail in it.

## Exposure Triangle

Shutter speed, together with aperture value and ISO forms the exposure triangle. They influence each other, meaning if you change the value of one, the values of the other two will change automatically (in Auto or Program mode). In Manual mode you will need to change them manually to get the right exposure. As such it becomes imperative to know how each one of them is related to the other two. Not knowing will most likely result in under or over exposure. The following course we have on photography deals with the topic of exposure triangle in much more detail.

## Exposure Value

The shutter speed and aperture value of an exposure taken together is often referred to as the exposure value or EV. One can use different combinations of the two properties to get the same exposure. We have already discussed that shutter speed and aperture value has an inverse relationship. Let’s say that the camera meters a scene at f/8 and shutter speed of 1/250th of a second. If you change the aperture value to f/5.6 i.e., open it up, you are letting more light in. So, the shutter speed must be reduced to ensure that the exposure is the same. So, in the above example the shutter speed needs to be reduced by one stop in relation to the aperture value going up by a one stop. The desired shutter speed should thus be 1/500th of a second.

### Depth of Field (DOF)

A term that is widely used by landscape photographers, but equally important for most types of photography, Depth of Field (DOF) refers to the extent of the image that is acceptably sharp. It refers to a range within a photo, from a point that is closest to the camera to a point that is farthest, both being acceptably sharp. Landscape photography is one genre of photography where large DOF is preferred. This in-depth course on landscape photography will teach you how to use a small aperture to maximize the DOF.

There is an indirect relationship between DOF and aperture value. DOF increases as the aperture value decreases and vice versa. However, you cannot hope to get a DOF that is infinite. That is something that is optically impossible.

Regardless, all modern DSLR lenses would suffer from the problem of lens diffraction after a while as you go on reducing the aperture. When that happens the overall image becomes blurry.

There is more to digital photography than just the terms that we have learned here. For an in-depth study of the basic terminologies and getting started in digital photography you could check out this course, as well.

Page Last Updated: February 2020