A picture is worth a thousand words is the best way to make us understand that the best way to capture an all important moment is take a picture of it. Sometimes the picture looks great and some other times it is kind of hazy.

So what exactly happens that makes the picture great or hazy?

To answer this question, we need to understand the basic elements of a picture.

With the advent of digital cameras, most of us are aware of these basic elements like aperture value, time value, focus and mega pixel but the first and foremost parameter is the amount of light that is captured by any camera to record a picture. More the presence of light and better is the quality of picture. The amount of light entering and falling on the recording surface is controlled by the aperture value. For how long the shutter will be open is decided by the time value and it in turn controls the amount of light as well. Focus is related to the minimum and maximum distance, a camera can take good quality pictures. Mega pixel is a value that defines the clarity of picture and vividity of colours.

Again light, being a natural phenomena, is in analog form or in other words a wave form and in this world of digitization, we record everything in the form of bits and bytes. Analog form needs to be converted in a digital format so that it can be stored and used in the world of computers. This process is known as digitization. A wave form is continuous form and this form while being converted to a digital format gets broken down in small parts. To understand it better, let’s take an example of temperature in a day, which is another natural phenomena. During the day change in temperature is in continuous form but when we record it then we break it in small values like 28⁰ C at 7:00 AM or 36⁰ C at 12:00 PM.

So to record a picture in a computer, we break it down in small dots called pixel or picture element which is the smallest part of any picture. Each pixel can be stored in 8 bits, for a simple black and white picture and go on up to 24 bits per pixel for rich coloured pictures. Now that we have discussed the importance of different elements of a simple digital picture, let’s move on to the core subject that is resolution of an image.

Resolution is simply the number of pixels that are present in per square inch of an image. Simply put, we can have 72 pixels to create one square inch of an image or can use 300 pixels to create the same area of an image. Former is known as an image with a resolution of 72 pixels and latter one is an image with a resolution of 300 pixels. The clarity of an image depends on its resolution. This resolution is always measured in pixels. If the number of pixels per square inch is high, the resolution increases, thereby increasing the picture quality. An image with a resolution of 300 pixels will have more details and thereby give good output at higher zoom levels. Such types of images are very good for printing.

Image Resolution at 72-ppi and 300-ppi; Applied zoom is 200%

Now, while working with an image in Photoshop we need to give lot of importance to the image resolution as well. Before working with the image, we need to understand the purpose of that image. An image with higher resolution will have more information and as a result will require more disk space to save that image. Similarly an image with low resolution will require less amount of storage. Once we are clear with the purpose of the image we are supposed to work with, we can decide on the optimum level of image resolution.

In Photoshop, You can change the resolution of image by choosing predefined path Image->Image Size.

Note:
You should deselect the Resample Image check box if you don’t want to change the image data in your image.

In a simpler approach, an image that is to be used for web pages should ideally be lighter in size so that the web page takes lesser time to load on the person who is opening that web page on his computer. At the same time if that image of importance and has to be displayed with lots of details or has to be shown on higher zoom levels on the web page then it has to be of higher resolution.

Again if we have to edit an image in Photoshop for printing jobs then the image must be of at least 300 pixels. This will increase the size of that image but that is not going to make any impact on the final output which is a printed copy on a piece of paper.

This way we can easily decide on the image resolution that we need to have for the image with respect to its usage and purpose.