I’m sitting here trying to learn what differentiates the two video formats so for the sake of clarification I want to explain the details of each in the shortest, simplest way possible. I am no tech expert – merely a consumer with an interest – so don’t take my word as gospel, this is really just me trying to work out these nitpicky differences.

Firstly lets clarify the 1080 bit. 1920×1080 generally means 1920 pixels of width and 1080 pixels of height within the image. The 1080 part means there are 1080 pixels running up the side of the image, such as on your television screen or computer monitor.

1920×1080 Progressive (1080p) is what you could call the simpler video format. If you’re familiar with how video works, you’ll be able to understand this format. It works by taking photographs – otherwise known as Frames – very quickly and playing them back very quickly to create the illusion of moving images. If you’re familiar with video games you’ll recognise that this is how you measure the power of your PC by seeing the number of Frames Per Second the game runs at. The higher the number of Frames, the smoother the moving image seems.

1920×1080 Interlaced (1080i) is the more complicated, however more efficient format. This is where it gets confusing. It does the same as the Progressive format, however it only captures half of each image, known as Fields (rather than Frames). This does not mean it captures the top or bottom half of each frame, rather it captures every other row of pixels. Remember those 1080 pixels running up the side of your TV screen? Each one in this case represents a row of pixels. So just imagine each Field is a full Frame, minus every second row of pixels.

If you paused a video filmed at 1080i, this is what you would see. Notice the two ‘halves’ or Fields that are shown at the same time of this moving car. Source: Wikipedia

This format is shown in a different way to the Progressive format. You already know that Progressive video (1080p) shows lots of images one after another very quickly, however, Interlaced (1080i) shows each Field, while filling the gaps with the next Field.

This presents the main advantage of simply being a more efficient recording format. Rather than recording multiple, full images very fast, the Interlaced format records only half of each image, making the final file much smaller, hence making it easier for transport and transmission. Another advantage is because it shows half of the image the motion seems smoother than the Progressive alternative. It also presents some disadvantages.

Because you’re left with only half of an image with each Field, the ability to slow down or speed up the video is removed, since doing so would make it easier to notice each set of Fields. If you scale the video, the same thing would happen.

So for Television to want to use 1080i as the standard makes sense. The file size is smaller and hence easier to move around the TV station and out to your Television screen.

However for online media this may be different. If you’re looking to appeal to the hardcore gamer audience – which I am in my future ambitions – the use of 1080i may be an issue. A lot of dedicated PC owners have monitors with high refresh rates and no issue with playing back the large format, high resolution Progressive video format. Putting an Interlaced video in this environment may expose it’s inadequacies and cutbacks in the image. I will investigate this as a resolution to my lack of bandwidth.

Funnily enough it seems the definitions for these things are mostly visual, making it very hard to describe them in text. I might still be wrong, but I feel like it makes more sense to me now.