Daily Archives: May 4, 2012

Photography 101: Depth of Field & Bokeh

Okay… okay… so I know I haven’t written one of these in like, forever, apologies to those of you who have been patiently waiting… however, I’ve hit several speed-bumps on this one, not least of which was moving home and losing my internet connection for several weeks… but anyway, enough excuses… here is the next in the series of Photography 101 posts (if you haven’t read the others, please do so. I kind of assume you have for the purposes of keeping things simple in here…)

So – my other big roadblock on this post was actually trying to boil this concept down to its essence – trying to keep things simple – making it accessible. If you do a search for either of the terms (DOF/Depth of Field, and bokeh) you’ll find a myriad plethora of hits – all of which go into great depth and detail about things like hyperfocal distances, the circle of confusion, lens diaphragms and aperture diameters….

In all honesty, it’s all crap. YES – knowing the nitty gritty details of the physics of the light as it travels through your lens is interesting, YES – it is good to know that kind of detail if you’re truly trying to understand how and why bokeh occurs, YES – you need to understand focal length and lens settings to properly estimate your depth of field… but NO – you do not need to know that level of detail to control, use and create bokeh and/or the depth of field in your images. So YES – it’s all crap. (Cue massive backlash from the photographic community…)

So first off, what’s the difference? Easy.

Depth of Field/DOF is the term used to describe the area in your image that is “Acceptably Sharp” (read “in focus”).

Bokeh is the term used to describe the out of focus area in an image – however, simply being out of focus is not enough to qualify as bokeh – there must be a ‘uniformity’, a ‘pleasing’ aspect – For an image to have ‘nice bokeh’ (© Flickr) there must be some kind of aesthetic appeal…

See why I had such an issue pinning this one down?

Examples make it easier:

As you can see in the above image, the background is so out of focus that points of light become spherical globes… THIS is what most people mean when they talk about bokeh.

In this shot, however, we see that very narrow area of focus – that small area right in the center, right where the bridge of the glasses is, that is ‘sharp’ – this is a shallow depth of field.

And in this shot, we see everything in focus – there is no fall off of ‘sharpness’ – this shot shows a wide depth of field.




Right, so now you know what we’re talking about, how do we create these effects in our images? Well, it’s actually pretty easy…

Both bokeh and depth of field are hybrids. One denotes the existence of the other. In order to achieve that darling of the flickrverse ‘nice bokeh’, you normally need a shallow depth of field. Conversely, a wide depth of field will, usually, remove any ‘bokeh’ form the frame. Please note the ‘normally’ and ‘usually’ here. These statements are not universal truths handed down from on high, but general rules… guidelines, if you will… and like all rules, there are exceptions.

To control the depth of field, and therefore the bokeh, in any given shot, you need to focus (pun totally intended) on two things – the aperture of the lens you’re shooting with, and the distance between the lens, the subject, and the background.

So, for example, you have a ‘nifty fifty’ (by far the most common ‘bokehlicious’ lens out there) and you’re shooting ‘wide open’ at f/1.4… that wide aperture lends itself to a very shallow depth of field… so when you shoot something/someone, the background is immediately going to be thrown out of focus, and right into ‘bokeh’ territory…

Like so...

However, this only happens because the depth of field at this aperture and focal distance is so shallow… basically, what you’re doing (without all of the technical wizardry that already populates the web on this topic) is placing your subject in that small area of the frame that is ‘in focus’, and allowing the rest of the frame to be blurred. If you took your subject and moved them up against a wall and shot using the same settings, then the wall would be brought into focus too, because you brought it into that shallow area of focus (your depth of field).

Notice how the blades of grass nearest the subject’s face are in focus… This is because they fall within our ‘depth of field’.

So, the distance between your lens, the subject, and the background will have a massive impact on your bokeh and depth of field. As you move further and further away, your area of focus becomes smaller and smaller, throwing anything outside of that area even more out of focus… and this is when points of light, or highlights of any kind, become that sought after circular bokeh. Of course, the shape of the bokeh depends entirely on the shape of your aperture blades… and you can even ‘trick’ the aperture into different shapes using these kits. Or, alternatively, you can Do It Yourself for results like this:

Knowing this, you can try and create bokeh (or at least, an approximation of a shallow depth of field) using any aperture – most lenses will open up to f/3.5 – f/4.5 at the ‘wide end’ and this is still wide enough to play around with bokeh – as long as you remember that distance thing.

Just pull your subject away from the background as much as possible (or, as in the example below, put them against a background that is very distant) and you’ll see that pleasing ‘blur’ kick in – your ‘bokeh’ may not be as defined as it would be using those other, faster, lenses, but you’ll still be able to isolate your subject.

Because the above shot was taken on a sunny, sunny day, shooting wide open would have blown out the sky to near white… in order to get this shot, I had to step down to f/7. Normally this would give the shot a wide depth of field and leave most of the frame within that ‘acceptable sharpness’ range, but because of the massive distance between my subject and the background (those hills are a couple of miles away, at least) you get that blurred, bokeh-y (is that even a word??) feel.

Hopefully, after reading this, you now have a better understanding of how to use your aperture to isolate subjects and create ‘nice bokeh’ in your images!

Have fun with it!


Coming up next time: Adventures with light.



J :)

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