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The Basics of Image Resolution

Daniel Hayek
April 5, 2012 by Daniel Hayek Alum

When it comes to making and watching videos, it’s important to know about image resolution, if only because the concept is thrown around so frequently. For example, if you go to an electronics store you'll be bombarded with information about how every gizmo and gadget is HD, Full HD, HD 3D, 480, 1080, etc. You might be a bit fuzzy on what these terms mean, and we’re here to help clarify, so you can make your videos super sharp.

Many factors determine the quality of an image, but for the purpose of this lesson we're going to focus on just one aspect: resolution. At its most basic level, resolution is a measure of how many pixels an image contains. Pixels are the tiny squares that make up a digital image. Each square a piece of a puzzle — by itself it might not mean much, but when combined with other pixels it becomes a critical piece of information that helps to tell a larger visual story.

As an example, let's look at a simple image: the Vimeo icon. You'll see that as we add more pixels to the icon (thereby increasing its resolution), the image gets sharper and more detailed.

Click the image to view a larger version

Typically, resolution is expressed as image length (in pixels) times height (also in pixels). So if you read that a camera records video at 1280 by 720, what that means is it records a rectangular image that is 1,280 pixels wide and 720 pixels tall.

Let's review a few common resolutions that you'll encounter with online video. There's 640x480, commonly referred to as standard definition (or SD). Then there’s 1280x720, which is the minimum for what's called high definition (or HD). And finally there’s 1920x1080, which is sometimes referred to as full HD. (Keep in mind that all of these terms are relative, and that as technology marches on HD will include higher and higher resolutions. So don’t get too attached to these numbers.)

Sometimes, to save time or space, or to seem really pro, a person will refer to an image resolution only by its height. For example, if you overhear someone say "my camera shoots video at 1080," they mean is it records video at 1920x1080 resolution. Below is a chart showing the relative sizes of these common display resolutions (note that the images are not to scale).

Nowadays there's discussion of cameras that shoot at 2k, 4k, and even 8k resolution (k meaning thousand) which will deliver ever higher levels of picture detail. Around 4k resolution you start to run into issues where there are few, if almost no, monitors that can natively display so many pixels, you won't find televisions yet that can show images above 1920 x 1080, so that leaves you with a theater setting to be able to view all those pixels in their vibrant glory. Many modern movie theaters now show movies at 2k resolution and some computer monitors can as well, eventually we'll probably just end up with more pixels than we know what do with and we'll move on to obsessing over some other technical specification.

To further illustrate the differences among some common resolutions, check out these videos by Lernert & Sander, created to compare the relative scale of a single pixel in SD, 720, and 1080 resolutions. Notice how much more information is communicated as the resolution increases:

640 x 320

1280 x 720

1920 x 1080

Again, these are approximations, and showing the differences among various resolutions can get confusing since there are variables like display size and monitor resolution. However, this should give you a general sense of the scale variations seen with different resolutions.

Keep in mind that more pixels doesn't always equal a better video, but being familiar with how they affect resolution and the typical dimensions can help you follow the conversation when the numbers and abbreviations start to fly.


Tim Walker Plus

This is a great demonstration that I plan to use with my students to help with a tough concept.

Joyce Pereira

This is sensational! I will be using these with my high school students! Thanks!!!

AFH Central

OK, I get this now. But why are all the player sizes the same? To design a cover image for my videos, I can pick one of the resolution you mentioned, but they will look smaller or larger than the player.

Lazar Der Gregorian

The best explanation of the topic I have come across. Thank you and well done.

Adam Witton Plus

Thanks so much for this post, really simple and easy to follow. In the 5th paragraph you mention three common resolutions, Standard Definition, Minimum HD and Full HD. My question is what would you use these different resolutions for? For example would SD be good for videos displayed on iPhone but not great for playing on computer monitors?

Thanks again for the article.

Diane Brunet Plus

I am fairly new to Vimeo and I keep getting a warning every time I upload a video - not sure what or how to make adjustments to my movie video which is actually a slideshow of pictures. The warning message that I get is: This video's data rate is 24296 kbit/s, which is pretty high. For HD, we suggest you use a lower date rate, typically 5000 kbit/s. A lower rate means smaller video files and faster uploading. I can't figure out on Vimeo how to adjust to those settings - can anyone help me out?. Thank you.

Steve Chalker Plus

Isn't the caption on the first video incorrect? It says: 640 x 320. That is not a 16:9 size. It should be: 640 x 360.

Olatunde Raphael

Whaooo... This is interesting. Practical follows shortly.

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