What is a good exposure and its Importance
Basic Photography
Pixean
September 21, 2018

When we are starting out on our photography journeys, we tend to run after the perfect exposure. What is perfect exposure? It is hypothetical. Perfect exposure doesn’t exist. There are several ways to photograph the same scene. What may seem to be perfect exposure for me may not be the same for someone else. The perspective is what matters in this kind of a scenario.

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Let us analyze what a good exposure is…

A photograph is exposed properly if it is neither too dark nor too bright. Having said that, there are several exceptions too which we will come to over the course of this blog. For starters, a well exposed image is one in which the histogram seems well placed. A histogram is a graphical representation of the various aspects of the photograph like the highlights, shadows and mid tones. A histogram is said to be well placed when the entire curve fits within the two extreme lines and is pushed a little towards the right side. A right heavy histogram actually means that the image has been exposed for the highlights. The dark areas may appear a little darker but they can be managed in post processing. However when you lose data in the highlights, they cannot be recovered. Once you have taken a shot, take a look at the histogram to analyze whether the image is properly exposed or not. You cannot judge the exposure of the image by seeing the image on the LCD screen.

The basic exposure triangle parameters:

1)   Aperture:

This is the opening of the lens. The wider the opening, the more amount of light will be able to enter the camera sensor. Aperture is denoted by f stops. For example, f/2.8 is a wider aperture and lets in more light than f/11. Wider apertures result in shallower depth of fields whereas narrow apertures have very large depth of fields.

2)   Shutter speed:

Shutter speed is the time duration for which the camera shutter remains open while clicking an image. The lower the shutter speed, the more amount of time the shutter will be open for and hence more amount of light. For example, a shutter speed of 1/250th of a second will let in much more light than 1/1000th of a second. A fast shutter speed is required to freeze the motion whereas a slow shutter speed is used to capture the motion blur.

3)   ISO:

ISO is an international standard term which measures the sensor’s sensitivity to light. More the ISO, the more sensitive your camera sensor will be and hence more the light. This is an electronic aspect of our camera bodies. For example, ISO 3200 will be much more sensitive to light than ISO 400. High ISO values tend to introduce digital noise into the images.

Camera metering: Metering is the way by which the camera internally decides the amount of exposure of the image. There are quite a few types of camera metering techniques like spot metering, evaluative metering etc.

1)   Spot metering:

This metering mode is used to meter the entire image based on a single spot. This spot is mostly the center focusing point of the camera. The camera analyses the exposure of that particular spot and exposes the image as a whole based on that.

2)   Evaluative metering:

This metering mode is used to meter the entire image based on the entire frame. All the pixels of the entire frame are analyzed and the resulting image is exposed according to that.

Camera metering techniques must be learnt in order to analyze correct exposures. The assisted modes like aperture priority and shutter priority are relatively easier to use than the manual mode. But once you are thorough with the manual mode, you will understand the operation of the exposure triangle parameters with ease.

Operating in Manual mode to learn exposure settings:

Now that we have already learnt about the three exposure triangle parameters, it is time to operate the camera in full manual mode to understand the process of achieving proper exposure.

Let us take an example of the following scene where there is a landscape with a few people moving around in the foreground and a number of trees in the backdrop. Assuming the following settings are giving us a proper exposure, let’s see how we can tweak those settings for different purposes without changing the overall exposure.

f/8 ;; 1/125 sec ;; ISO 200 – Proper exposure settings (just an example). The shutter speed used is not very fast and might have failed to freeze the motions. To do that we need to increase the shutter speed to around 1/500th of a second. This means that the shutter speed increased by 2 full stops. 1/125 -> 1/250 -> 1/500. The exposure of the image will come down by 2 full stops of light. To compensate for this, we can increase the ISO by 2 full stops. 200 -> 400 -> 800. Thus f/8 ;; 1/500 sec ;; ISO 800 will give us the same exposure as f/8 ;; 1/125 sec ;; ISO 200. Similarly if the aperture needs to be changed to increase the depth of field in the image, you can adjust the shutter speed or ISO to compensate for the same. If we increase the aperture by a stop to f/11, we need to increase the ISO by a stop to 400 to actually retain the same exposure. Hence f/8 ;; 1/125 sec ;; ISO 200 is the same as f/11 ;; 1/125 sec ;; ISO 400.

So we have gone through the entire set of exposure triangle parameters, the use of each of the parameters and how we can change each parameter to achieve the result we are striving for. You need to learn to operate the camera in full manual mode in order to understand the entire dependency factor in the exposure triangle. Remember, there is nothing called perfect exposure. You as a photographer need to decide what the perfect exposure for the particular scene is. 

Basic Photography
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Pixean
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