Understanding Image Resolution

The image resolution is a confusing term that crops up repeatedly in the photo industry. Sometimes it makes new photographers scratching their heads. Beginner photographers are often confused about DPI & PPI. Even they complain, why is their 300dpi image blurry? What points are they missing? Why is the term image resolution so confusing?

In this article, I will explain everything. I think this guide will help you understand it if you are a beginner. You don’t have to be confused again about image resolution.

What is Image Resolution?

The image resolution is the detail in an image. It applies to raster images, film images, and other types of digital images. The higher the resolution, the more detail an image can hold.

Resolution is the number of megapixels produced by an image sensor in a digital camera. Which means it corresponds to the amount of detail a camera can capture. If your camera packs 12 MP (megapixels), it captures less detail than a camera with 24 MP. So, a camera with 40 MP can capture more detail than 24MP. But are you confusing about pixels or megapixels? Let’s see what pixels are and how they affect your photos.

What are Megapixels?

Before knowing megapixels, you have to understand what a pixel is. A pixel is a physical point in a raster image or the smallest element of all points. So, the term megapixel came from the pixel. According to standard measurement, a megapixel is equal to 1,048,576 pixels. But camera & display manufacturers round this number to 1,000,000. And the round figure is easier to understand for the general people.

Suppose your camera captures 16-megapixel images. It is around 16,000,000 pixels per image. But to understand pixel, it is not enough information. This only describes the total number of pixels that make up the image.

Let’s assume the dimension of your RAW images is 4672 x 3104 pixels. To get the actual number of pixels, you need to multiply the number of pixels along the image width & height. Thus, the actual number of pixels of your RAW image will be 4672 x 3104 = 14,501,888. We may call it 14.5-megapixels. But the display or camera manufacturers round this up to 14.6-megapixels.

In a word, a pixel is a single photo element. A pixel can only be one color & an image consists of a grid of thousands of pixels.

In an image, you can check camera information & image details. Many image editing software contains this feature. To check camera data in Adobe Photoshop, open the image & choose File > File Info > Camera Data. It will open up a dialog box that shows the image details like size, dimension, megapixels, etc.

DPI vs PPI

DPI & PPI are two important terms in image resolution. They are both used to measure the resolution or clarity of an image. But each one of them refers to separate media resolution like digital vs. print.

DPI (Dot Per Inch) describes the amount of ink dots on a printed image. On the other hand, PPI (Pixels Per Inch) describes the resolution in a digital image’s pixels. PPI mainly refers to the digital display, but it also affects the print size of your design. There is nothing DPI can do digitally. Its only concern is print.

Higher PPI tends to be higher quality images as it contains a greater pixel density. If you increase the PPI it increases the size of your file. You may want to use a high PPI only when it is needed.

The pixel density of your screen is fixed. So, PPI does not really matter for distribution on the web. A 300 PPI image & a 72 PPI image will appear the same on your display.

Image Size

A higher resolution means a sharper image. It would be true if all images were the same size. The high or low quality of an image depends on the relationship between pixel density and image size. If you change one, the other fact changes with it.

If you increase the image size, it will result in a lower DPI. Which means there are fewer pixels to make up each square inch. So, the pixels will become bigger to fill the space.

You can understand this with the flaccid balloon’s example. Keep some balloons in a small box. Then again, keep the same number of balloons in a larger box. Now, look at the two boxes carefully. What do you understand from this? you can only fill the box by inflating the balloons. The size of the balloons increases even their number remains the same.

Resizing Image in Photoshop

In Adobe Photoshop, you will see two different dialog boxes for image resolution and size. One is Image > Canvas Size, and the other one is Image > Image Size. We use Canvas Size to change the ultimate size of the canvas. It never alters the image size other than to crop it. On the other hand, the Image Size box is the key to controlling the image’s resolution and dimensions.

In the above image, you can see the image size box. It contains three key options for changing image size. They are Width, Height, and image Resolution. All of them are linked with each other. So, if you change one, the others will change proportionally. You can also see the file size at the top of the box, which is necessary when trying to reduce the image size. The dialog box also shows your desired resolution when you change it.

Image Resolution: Resampling

The resampling option in the dialog box allows you to change the pixel dimensions. You can do that by adding or deleting pixels. Turning on the resampling option, you can set a new resolution without changing the image size. In this case, Photoshop will fill in the missing pixels.

Conclusion

There is a myth about a megapixel that says you need more and more megapixels for great images. But it is just a marketing strategy for selling cameras. The latest cameras have over 10 megapixels nowadays, which is more than enough.

If you have enjoyed this guide, you may want to read more new content. Read about Kit Lens, Aperture, & ISO to be an expert in photography. Also, let us know if you have anything to say about image resolution.