When iStock started offering video files back in 2006, picking the right video size seemed pretty straightforward. You would consider the largest monitor that the project would be presented on and purchase the corresponding file. We might be oversimplifying things a bit — you also needed to know how the file would be prepared for your project (editing, re-compressing, etc.). But by and large, file size was linked to monitor sizes. Big monitors = big files. Small monitors or web-based players = small files.
Standard monitor resolution also made things easier. Back in the day, resizing photos and videos was easy because everything was basically 72 ppi. All you had to do was bring your assets into 72 ppi conformity. Sure, more resolution than that might have been useful to the skilled video editor, but generally speaking, extra resolution was wasted.
Then something happened — people started jamming more pixels into the monitor frame. Slowly, laptops started sporting higher res displays. Soon, point and shoot camera backs followed suit. For a while, the original equation still sort of worked. But not for long.
Today, super high-resolution monitors are everywhere, and frame size is no longer a fool-proof way to judge the size of file required. Increasingly, buyers are making decisions that are more akin to a designer picking the photo size based on projected print resolution.
Consider this. A typical Big Web sized video from iStock measures about 5.5 inches wide and just under 3 inches high on a MacBook Pro. It may be bigger on your monitor. If I hold up my iPhone to the laptop display, I can’t cover the video — there is still lots showing.
But if I take that same video, and play it pixel for pixel on my iPhone with no re-sizing, it wouldn’t even fill the screen. True, the phone would blow the file up to fill the screen, but we all know what up-sizing does to digital images. The only way to get a good quality video picture at the 326 ppi resolution of Apple’s Retina display is to use a file that fits.
So we find ourselves back at the beginning. Remember, I said, “ consider the largest monitor... and purchase the corresponding file.” Except we are now in a world where the "largest" monitor may mean a physically smaller monitor.
So what is the right size? It always comes back to the project. Based on these key questions, you should be able to make a pretty accurate choice.
1. In the life of your project, what is the greatest field of pixels that it will be shown on? Keep in mind that if the project life is long, then the chances that the project will be repurposed down the road at higher resolution is greater.
2. If the look of the project is extremely crisp by design, then purchasing a file one size bigger than is necessary is an editor’s trick to sharpen the look of the file. Conversely, if the look is low-tech by design, then a smaller than normal frame size may be justified.
3. If the project is for cinematic release, or cut together with cinematic footage, you should never use files smaller than 1280 x 720, preferably 1920 x 1080, and only use progressive scan files.
4. If the project is now and always will be a DVD, then a PAL or NTSC file (depending on your region) is just fine. However, iStock has more HD files than SD, and HD files in the hands of a good editor or technician can be made into beautiful SD files.
5. If the project is now and will always be a window in a web site, then the web size files should be perfect.
And in the case of that iPhone 4, the smallest version that will fit that screen is the HD 720 size.
A completely unrelated tip:
When you have found a file you really like, click on the View Portfolio link of the artist. Chances are you will find more files that fit your aesthetic. Perhaps they don’t work for your current project, but if you add them to a lightbox, you will be able to find them when the inspiration hits.