There’s been an online trend that I’ve seen evolve through the years that has amateur and professional photographers alike trying to out “shallow depth of field” one another. There are actually websites popping up that are dedicated to how thin the plane of focus one can garner. It’s pretty strange because, from personal experience, having a depth of field that’s too thin just isn’t a good thing. Hardly anything shows up in focus. I face this sort of thing when I use my magnifying lenses. Those filters really cut down the sharp areas of a photo. They end up being hardly even there.
That said, if you’re looking for a shallow depth of field, prime lenses are the way to go. In many cases, you simply can’t open the aperture of a zoom lens up enough to be anywhere near comparable to how wide you can make the aperture of a prime lens. I’ve seen prime lenses with apertures that go all the way down to f/1 and more commonly, f/1.2. Compare that with the average zoom lens’ widest aperture of f/4. If you remember, every time a camera goes down or up a stop, it’s either letting in half as much or twice as much light. There’s a big difference between f/1.2 and f.4. Creative difference.
When dealing with video, shallow depth of field can offer ultra creative and unique results, but it can also get in the way. Think about the “plane of focus” as a big sheet of glass. If two people were holding that glass up in front of you, as if you were looking out a window, the thickness of the glass could be considered your depth of field (the plane that’s sharp in an image). If you were shooting at f/1.2, the glass would be very thin. Maybe a few inches thick, depending on how far away you were standing from it. If you were shooting with f/4 or f/5.6, the glass would be much thicker. So if your subject was somehow trapped inside that thickness of glass, that’s what would be in focus.
If you think about taking video, working with a shallow depth of field can make your footage stand out. Picture something moving slowly from an area that’s out of focus to an area that’s in focus. That’s some interesting video right there. But now think about interviewing someone or walking through a house while taking video. Would you really want a very shallow depth of field? Can you imagine how distracting that would be? Imagine capturing someone on video while they’re sitting in a chair. Their face is in focus one moment, but then it’s completely out of focus the moment they lean back. That’s definitely not an ideal situation.
There are many times you’d want to open your prime lens up all the way while capturing video. Product footage is a good time. If you’ve got product sitting on a table and you’re moving from one item to the next, it may be perfectly fine to have the items that aren’t being featured at the moment to go out of focus. It’s actually quite common for that to occur because it allows the emphasis to be placed squarely on the item that’s being featured. But like I said above, when you’ve got moving objects, people or pets that are supposed to be in focus the entire time, keep your eye on that aperture. Remember, just because you’ve got a sweet prime lens that can open up crazy wide, it doesn’t mean that you need to take advantage of that feature when it’s not appropriate. I know, easier said than done.
So here’s a question for you. What if you’re taking video and your scene calls for a deeper depth of field? You need more sharpness in your area of activity. What can you do about that? Well, the first thing I would do is go up a few stops with my aperture size. So if I was shooting at f/2, I would try to bump that up to f/4 or f/5.6, so my depth of field widens a fair amount. I know not nearly as much light will be let in due to this setting change, but to counter that, I could always compensate by adjusting my ISO the same number of stops. Or, I could add more light to the scene. You know, physical light. It’s not always about making trade offs inside of the camera. We can just as well alter the physical environment as well.
The great thing about prime lenses when it comes to video is that they offer tons of flexibility. If you need a wide aperture, it’s there. If you need to close it up some, you can do that too. And again, if you need to close it up, you can always compensate with either a higher ISO value or more physical light. Just some thoughts for today.
What do you have to say about this topic? Do you like shooting video with prime lenses? How do you deal with lighting and depth of field? What’s your go-to setting combination? I’d love to know. Thanks!