The Exposure Triangle: Understanding The Basics

What is The Exposure Triangle?

Before now, we discussed the three primary factors that determine the exposure of a photograph; which are the Aperture, Shutter Speed and ISO. (These factors as stated here have clickable links that would take us to the previous posts where we discussed them in detail just in case we need to refresh our memory).

Now Exposure Triangle is the act of striking a balance between these three variables so as to produce a perfectly exposed image.

APERTURE

The Aperture can be defined as the diameter of the channel through which light passes to get into the image sensor. The Aperture is measured in f-stops. So an Aperture value of f/1.8 has a wide opening while an Aperture value of f/22 has a small opening.

With Aperture comes Depth of Field. The depth of Field here refers to how much of your image is in focus. So shooting with a wider aperture makes less of the image be in sharp focus while shooting with a smaller aperture makes more of the image be in sharp focus.

SHUTTER SPEED

Shutter speed refers to the length of time the shutter is open. So if you’re shooting with a fast shutter speed, for example, 1/1000th of a second, less light gets into the image sensor compared to when you’re shooting with a slow shutter speed of 1/10th of a second which allows more light into the image sensor.

When shooting with a wide aperture, your shutter speed will need to be fast to compensate for the amount of light entering the camera otherwise you’ll most likely end up with an over-exposed image. Same applies if you’re shooting with a small aperture, your shutter speed will need to move slower to enable more light into the camera otherwise you’ll most likely end up with a grossly under-exposed image.

Your shutter speed can also be used to freeze motion. So if you’re taking a photograph of a moving car or a waterfall, using a fast shutter speed freezes the movement. A slower shutter speed will produce a blurry image of the car and a creamy look of the waterfall. These outcomes are not necessarily bad if done creatively.

ISO

This refers to the way your camera interprets light; This is also known as the Image sensor’s sensitivity to light. This sensitivity is measured in figures like 100,200,400,800 etc.

So a camera with a base ISO of 100 means that the best picture quality is to be taken at this setting and this requires enough light and excellent conditions for it to perform. A camera with an ISO setting of 4000 would require less light to take a bright image but this could be at the expense of the quality of the image as there could be the existence of image noise or grainy pixels in the picture.

If you’re taking a photograph in a dimly lit room, you can introduce an external light source like a Speedlite and still operate at a low ISO to ensure the digital noise is kept at it’s barest minimum.

CONCLUSION

In summary, this is an idea of what the exposure triangle is all about. Effective utilization of these three variables; Aperture, Shutter Speed and ISO to produce a perfectly exposed image. So it’s time to pick up our cameras and get practising. You could share your images in the comments section below or on our community lets all learn.

If you have any questions or contributions to make, kindly share your thoughts in the comments section below.

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SHUTTER SPEED : Understanding Exposure in Digital Photography

The next important factor to be considered while trying to achieve a perfect exposure in digital photography is shutter speed. Like I mentioned earlier, the other two are Aperture and ISO. Firstly, we’ll give a brief introduction to what the shutter is in a DSLR camera, what it comprises of, how it works before we finally go into discussing shutter speed and features associated with it.

What is a shutter in a DSLR camera?

In photography, a shutter is a device that allows light to pass for a pre-determined period, exposing photographic film or a light-sensitive electronic sensor to light in order to capture a permanent image of a scene. The shutter is constructed such that it automatically closes after a certain required time interval. Operation of the shutter is triggered by a button called the shutter button or shutter-release button.

What is a shutter button?

In photography, the shutter button or shutter-release button is a button located mostly on the right-hand side of the DSLR camera body. When the button is pushed, the shutter opens for a pre-defined length of time; allowing light into the image sensor. During this process, an image is captured and the shutter closes afterward.

How does the shutter work in a DSLR camera?

Looking at a typical DSLR camera, the shutter comprises of 3 primary mechanisms; namely the mirror box, the bottom door and the top door. When the shutter button is pressed, the reflex mirror is tilted backward allowing light further into the camera. When the mirror flips upwards/tilts backward, a small door slides open from top to bottom, exposing the image sensor beneath. After that, another door slides down, covering the entire sensor. This process usually varies in time depending on the length of your exposure (shutter speed). After the second door closes, your reflex mirror falls back into place. The doors would then assume their default positions and technically, this process is known as Actuation. A typical DSLR camera can withstand close to 100,000 actuations in its lifetime.

shutter speed-How the shutter operates
How the shutter operates courtesy premiumbeat.com

What is shutter speed?

In Photography, shutter speed or exposure time is defined as the length of time the shutter remains open allowing light to get to the image sensor; also allowing the camera to take a photograph.

Features associated with shutter speed.

  • Shutter speed controls exposure – It is used to control the brightness of an image. The longer the shutter speed, the brighter the image. This is possible because the shutter is open for a considerable length of time to allow the image sensor to gather more light.
  • Shutter speed is measured in seconds – This could be full seconds (i.e 1 second, 5 seconds, 10 seconds etc) or fractions of a second (i.e 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8 etc). The larger the denominator, the faster the shutter speed; the lower the denominator the slower the shutter speed. for example; 1/500 is faster than 1/30.
  • Shutter speed is used to freeze movement in an image – By using a very fast shutter speed, motion is frozen. For example, using the featured image above, the image taken at 1/1000 sec freezes motion.
  • Shutter speed is used to capture motion in an image – By using a very slow shutter speed, motion is captured. For example, using the featured image above, the image taken at 1/80 sec captures motion.
  • Shutter speed and focal length – As a rule of thumb, always use shutter speeds with a denominator greater than the focal length. This helps to prevent camera shake especially in situations where image stabilization is absent

Conclusion

So while making things as simple as possible, we’ve been able to analyze the shutter speed as regards to digital photography and how it plays a significant role to achieve a perfect exposure while capturing an image. We have looked at Aperture, Shutter speed, next would be ISO.

Kindly share your thoughts in the comment section below.

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The DSLR Camera

The term DSLR is an acronym which stands for Digital Single-Lens Reflex. So a DSLR Camera is a digital camera that combines the mechanics of a single-lens reflex camera with a Digital Imaging sensor; as opposed to a photographic film.

The primary difference between the DSLR and the non-reflex single-lens digital camera is that the viewfinder of a DSLR presents an image that is almost equal to what’s captured by the camera’s sensor and not being captured by the camera’s image sensor and displayed on a digital screen.

  1. Lens
  2. Reflex Mirror
  3. Shutter
  4. Image Sensor
  5. Focusing Screen
  6. Condenser Lens
  7. Pentaprism
  8. Eyepiece/Viewfinder

OPERATIONAL DYNAMICS OF DSLR CAMERA’S

The Eyepiece/Viewfinder <8> is situated at the back of the camera. When you look through it, what you see is a reflection of information that has passed through the lens <1>; which means there’s a 100% chance of capturing what you see.

Information in form of light passes through the lens <1> and hits the Reflex Mirror <2> which is positioned at a 45 degrees angle inside the camera structure. This light is then directed vertically to a chamber called the Pentaprism <7>. This light is again re-directed by two mirrors into the viewfinder <8>.

When you take a picture by pressing the shutter button, the Reflex Mirror <2> bends backward, allowing light into the camera. The Shutter <3> remains open for as long as it’s been programmed to. This enables information to get to the Image Sensor <4> which then records the image and then the Shutter <3> closes and reflex Mirror <2> returns to its original position of 45 degrees thereby re-directing light back to the viewfinder <8>.

Once the process ends, the camera then processes information from the Image Sensor (4) and converts it into a pre-defined image format and writes it onto the memory card. This process takes less than a second and in most cases, some DSLR Camera’s can replicate this process of writing images more than 10 times within a second.

This is at best a summary of how your DSLR Camera works.

For an expanded view of how it works, you could follow this link and read more on Wikipedia

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