One of the most common themes people have questions on during our courses and photo safaris revolve around the sharpness of their images.
We can discuss the answers to those questions and explore the how’s and why’s in future posts but for now I thought we should look at what sharpness actually is. More often than not the same people who ask questions as to how they can get their image sharper struggle to define what it actually is.
Sharpness can be described as the amount of clarity in in the detail of an image or the amount of edge contrast in the image. Therefore, when we increase the sharpness of an image we increase the clarity in the detail or the amount of contrast around the edges in an images.
There are two factors that contribute a role to the sharpness of an image.
Resolution: In today’s digital world the resolution of an image is determined by your camera censor and it’s ability to distinguish and render closely spaced details in the frame.
In the image below the details in the closely spaced whiskers and fur is a result of the resolution of the camera’s censor.
Acutance: This refers to the edge contrast of an image or, in other words, how quickly one tone transitions to the next where they meet in an image. When you sharpen your image during post-processing, you are increasing the acutance in the image and therefore the perceived sharpness.
In the image below, the circle on the right is as sharp as it can possibly be from a resolution point of view, as where they meet the lighter grey transitions instantaneously to darker grey, however the circle on the left looks sharper as the acutance has been artificially increased through sharpening.
When sharpening an image, the acutance is therefore increased by a darker pixel(s) being added to the dark side of the edge, and a lighter pixel(s) being added to the light side of the edge, which then enhances the overall perceived sharpness of the image.
In order for an image to be seen as sharp, it needs both a high resolution and high acutance which, when thinking of the questions people ask about sharpness, means that good camera technique and decent post-processing is required.
With regards to resolution, some of the factors that will influence the sharpness of your images include:
- Good camera technique: How you hold your camera when photographing.
- Tripod: A tripod, or other form of support, will always be useful.
- Shutter speed: A fast enough shutter speed is necessary to not get camera shake.
With regards to the acutance, the quality and quantity of sharpening that you apply to your images will influence the final perceived sharpness of your images.
In a future post I will discuss how to effectively sharpen your images by looking at programs such as Lightroom, Photoshop and Nik filters and also, in another post, digital noise and it’s role in image quality and sharpness.
Until next time.