As will all commodities, the quality varies. Some shots look great, others only look okay. Oftentimes you don’t know which until you buy the shot and can look at the full resolution files. The challenge is to make it look as good as possible.In some cases, the resolution might not match your sequence resolution. If it’s shot well and there are only a few shots like that, you can usually get away with it. If not, it might be appropriate to have a serious conversation about the resolution of the final piece. Does it really need to be 4K UHD or 1920×1080, or can you deliver 1280×720?
Resolution differences are an obvious problem. If you edit in HD and the shots are 4K, there won’t really be an issue. Just cut the shots into the sequence, scale them down, and move on.
But there can be some less obvious problems with stock footage, such as differing frame rates. Do a search on any stock library and you’ll see myriad frame rates listed: 23.976 (or 23.98), 24, 25, 29.97, 30, 59.94 and 60. Of course, you assume that the frame rate listed for a file is an accurate specification. Usually it is. But there’s no guarantee that the frame rate is the frame rate of the original shot.
I recently received a shot of a young girl running through a field of wheat. The shot was in slow motion and the specs said it was 29.97. But when I stepped through the shot frame by frame, every 5th frame was repeated. When played back it was a nice slo-mo shot, but with a small stutter. Most people wouldn’t have noticed it, but if you paid attention to the wheat, the repeated frame became just enough of a distraction to take away from the shot.
Here’s what I think happened. First, the original scene was captured at high speed, resulting in high-quality slow motion. The alternative would be to shoot at normal speed and slow down the scene in post. While there are some great algorithms for this approach, high-speed capture looks better to me. So, the intent of the cinematographer was there. High-speed capture made for a great looking shot.
But then the clip made its way into post and the great looking shot was degraded. I’m pretty sure it was placed into a sequence that wasn’t a multiple of the original. For example (and I’ll round the frame rates), the shot was captured at 48 fps and placed into a 30 fps sequence, not a 24 fps sequence.
You’d have had a problem even if you used a 24 fps shot in a 30 fps sequence. The edit software will repeat some frames so that the 24 fps footage runs at proper speed. If it didn’t, the 24 fps shot would run a little fast.
Why did this happen? Did the submitter think that people searching stock were looking for 29.97 footage? Did it come from a project that had to deliver 29.97 and so it was quickly exported? Was it grouped with other 29.97 footage and then delivered?
I have no idea what happened. Instead, I just remember that for stock footage—or, for that matter, any post-processed shot that doesn’t have true metadata like a camera original—you can’t always trust what’s written You have to trust what you see.