How Much Depth of Field Do You Need?

How Much Depth of Field Do You Need?

Depth of Field, or a lack thereof, has become a buzzword of sorts in photography circles. Many times the term is used as a blanket nomenclature to cover anything to do with how much or little of a subject is in focus. What we often fail to consider is why. Why are we choosing to use as much or as little depth as we do? It's time to look past aesthetics and really think about depth of field in relation to our subjects.

What is Depth of Field?

Depth of field is a measurement. It's a definable distance. It is the total region of "acceptable" focus around a given point. If your autofocus locks on to a point, that point is not the only distance of acceptable focus. Depending on a variety of factors, there is a certain distance both in front and behind that point that yields adequate focus. As your aperture gets smaller, that distance becomes greater and greater, all other factors remaining equal. The distance from your subject, focal length, and sensor or film size also all come into play in calculating your total depth of field. But, how does that help us as portrait photographers?

Sometimes even a bare, ugly room can bring focus to your subject.

Using Depth of Field as a Tool

Because we know that depth of field is a clear, definable number, we can use it as a reliable tool. Say I'm on assignment and need to do a portrait of someone in a very tight space that isn't conducive to the look I want. I probably want to eliminate as much of that background as possible. By knowing how much of that background is in focus ahead of time, I can begin to make decisions about which lens I want to use, what aperture I want to shoot at, and how much of my subject I want in the frame. Too many times, we grab a lens because we like it and not because it's the best for the job. If you're shooting in an opulent ballroom and want to get as much of the room in the photo as possible, why are you shooting at f/1.4? Environmental portraits that completely ignore the environment have become a bit of a plague with photographers. I bet I know why.

No doubt, using shallow depth of field can be useful. Just make sure it's purposeful!

The "Bokeh" Trap

The term bokeh, aka the word that won't die, has become ubiquitous in the portrait community. I've made no secret of my ambivalence for it in the past. However, depth of field goes far beyond bokeh. What is bokeh? Thousands upon thousands of articles across the interwebs have been devoted to it, but, in essence, it's the quality of the out of focus area of a photograph. Bokeh is not depth of field. Bokeh has probably made lens manufacturers more money than sharpness ever could. It's also caused many, myself included, to create photographs that didn't utilize nearly as much of the environment as they should have. Bokeh, in the grand scheme, is trivial. Depth of field, on the other hand, can truly make or break a photo. If you photograph a bridal party and the "bokeh balls" have a cats-eye shape, 99.9% of people won't notice or care. If half the groomsmen are out of focus, someone is going to be pissed. There's nothing wrong with appreciating bokeh. Just don't let your love for it screw up your priorities.

Subject Separation: Don't Be a One Trick Pony

When you ask a photographer why they're using a shallow depth of field, more than likely the answer will be subject separation. They need to separate the subject from the background to make clear what or who the photo is all about. That's a totally valid answer. Just make sure that it's not to the detriment of the rest of the image. There are many ways to achieve subject separation. You can light the subject. You can use the surroundings in an interesting way. The composition can draw the eye where you want it. The answer to "How do I isolate my subject?" isn't always "use shallow depth of field." You're better than that. Think about your options before you habitually break out that 85mm and lose the scene. 

Controlling depth allows you to showcase the environment without it taking over your subject.

The Best Tool For Nailing Your Depth of Field

During the time of manual focus lenses, most lenses came equipped with scales to easily read the depth of your shot at a given aperture and focus. Although many lenses do still have distance scales, most are so small or general that they are basically useless. My favorite way to check my depth of field is with an app! There are a few apps on both iOS and Android that will quickly and easily give you your depth of field. If you don't want to use an app, you can find a great website here. Just enter in some approximate distances, the focal length of the lens you're using, and your sensor size and it'll spit out your depth of field. For example, you're shooting a corporate group photo. You can guestimate that you need to cover about 3 feet of depth between the front and back rows of people. You plug in the numbers and the app tells you that at your current f/4 setting your depth is 2 feet. You know that you need to stop down, move back, or switch lenses. Simple. Your LCD will lie to you. You'll be in a rush and think you've got the shot when you don't. That's what makes depth of field so handy. It doesn't lie. Bokeh is subjective. Focus is not.

Knowing your depth of field can also reveal flaws in your technique. If according to the numbers your subject should be in acceptable focus and it isn't, something else could be wrong. What you think is missed focus could be motion blur. Perhaps you need to get on a tripod. A lot of photographers think they can hand-hold a shot when they're not nearly as stable as they think they are. I know that as I've gotten a bit older, I need to reach for my tripod more and more often. There's no shame in it. Get the shot. Don't worry about your ego. 

Do any of you have tips for managing depth of field? We'd love to hear them!

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12 Comments

JetCity Ninja's picture

i use DOF purely to create the look i desire for a certain composition. shallow, deep or somewhere in between, it depends on what i'm trying to achieve. occasionally, it's because i didn't have the tools with me to facilitate the shot, be it light or stability.

either way, to try and stipulate when and where is simply a vain attempt to control another person's creative vision. however, there are a lot of people out there who have little or no creative vision... i may be one of them.

Good subject discussion here. I own a few 1.4 primes but only in super low light will I ever go that low. I tend to default to F4 or F16 with natural light. F4 will usually get the whole face of a one subject portrait in focus with a little wiggle room and create enough focal separation with the background to still allow it to register in an environmental portrait. F16 if you have the light and just want to effin go for broke and get it all sharp haha F1.4 or 1.8 is just madness, in a fast paced editorial setting where the subject could move or you could move just a little bit and the cam misses af tracking, you're limited on time and then miss a ton of useable shots. No do-overs haha.

I tend to think of F1.4 in these terms, if you look up old shots of musicians like the Rolling Stones back stage, back then, film was slow, 3200 for b&w or maybe 6400 if you really wanted to push it. Fast lenses were the only way to really get shutter speed at the sacrifice of sharpness overall and depth of field. But saying that, subject and composition still reigned despite the potential for technical errors. There is a shot that comes to mind, of the above situation, the photo is of Mick backstage in super low light, I believe and most of the photo is not sharp, even mick is slightly out of focus and something in the foreground is, you can tell the photog missed focus but the photo still worked and ran due to mick's expression I think. So that's the way I think about fast lenses, when it's an acceptable aesthetic choice that you can be okay with the technical error of the focus.

Chris Rogers's picture

This. I almost never shoot wide open any more. Unless my subject is standing straight on in front of my camera I'm only ever going to get maaaybe one eye in focus. f4 is rock bottom unless i'm shooting in ridiculously low light for an event or something.

I loved this article! You rule!

I think where the fixation on bokeh often takes a wrong turn is confusing background separation with complete obliteration. Obliteration has its uses, like transforming the background into something abstract, but I don't really consider that to be necessary (or even appropriate) for an environmental portrait. But I do think that, in a lot of cases, some amount of blur is useful for environmental portraits. Again, not to conceal the background, but to subtly separate your subject from it it. I see it as a difference.

Understanding that difference is helpful when evaluating the whole f/1.4 obsession, especially when you factor in focal length. Are you looking for separation or obliteration? You don't need f/1.4 on an 85mm lens to get separation. Want obliteration? You're not going to get if you're shooting 24/35mm either way. On the flip side, you can get plenty of separation with an 85 f/1.8 but probably none at 24mm with anything less (more, whatever) than f/1.4.

Basically, unless you actually care about obliteration, you're better off saving your money on the widest apertures at longer focal lengths and investing it into wider apertures on shorter focal lengths. Are you a landscape photographer? Heck, you can rack that 70-200 f/4 out to 200mm and get plenty of separation.

My two cents anyway.

David Moore's picture

I am super guilty of just locking s%^$ down to wide open and going from there. I really need to get out of that habit. I actually got rid of my 50/35mm 1.4's to try to stop the habit lol.

Paul Lindqvist's picture

Nice article and important subject for sure! I think most of us been guilty of using lenses wide open just to get a blurry background, especially when we started out. :-)

Korey Napier's picture

Excellent article, Hans! I just recorded a video for YouTube posing the question of how much shallow depth of field is too much. Like you mentioned in the article, context to the scene of environmental portraits makes much more sense than obliterating the background (what's the point of an environmental portrait at that point?). Like you also mentioned, shallow depth of field isn't the only tool for subject isolation. I've really been trying to use light and harsh shadows as of late to put emphasis on my subject. Often times, that makes for a more compelling image than interesting "bokeh" does.

Pedro Pulido's picture

How much DoF do you need?
the answer is simple. As much/little as you want/need.
no 2 photographers are alike and that is why photography still exists. Otherwise, we'd all be shooting the same.
isn't it great?! we get to shoot what we enjoy and see other people's perspectives!

Cool article, I specially liked "Bokeh is subjective. Focus is not."

Steven Gotz's picture

DOF is a huge consideration for me because I am a Zootographer. I shoot through a lot of fencing or wire mesh. So the more shallow the DOF, the better my chance is to have the fencing melt away. There are other factors, but that is the primary issue.

I have to make decisions like, do I shoot the 70-200mm f/2.8 wide open at 200mm and crop, or do I shoot the 200-500mm f/5.6 wide open at 500mm and not get the entire animal in the shot. (Hint: it is some of each depending on what I am after at that moment.)

But then I get over to an area where there is no fencing between me and the animal, just a moat that allows me to use any setting I want. Do I try to blur the background, or am I shooting two or more animals in an area where the background is a grassy hill and I need to stop the aperture down to get all of the lions, or tigers, or bears (Oh my!) in the same shot and all in focus?

As you might imagine, the best solution would be to have a 500-1200mm f/1.4 and shoot it at a nice sharp f/2.8 but that is a dream that will never be realized. If only because it might be too heavy for me to lift on to the tripod without assistance.

Great article. I think your point about using lighting as a method to separate (or focus on) the subject can't be overstated. Look at the power of using a pinch of vignetting in LR et al, INSTANT focal point creation.

Thanks for highlighting the nonsense surrounding the 'Bokeh wars' thing, sad...