In this article I explain how depth of field (DOF) and an out of focus (OOF) background are independent of each other. It is possible to have a front to back subject sharpness in a portrait yet have an out of focus background and it is equally possible to have a shallow depth of field and a fairly well rendered background.
Glossary
Depth of field or DOF is a phrase that refers to the distance about the focal plane that appears to be acceptably sharp. Large apertures and tend to cause a small depth of field or a shallow focus while small apertures tend to cause a large depth of field or deep focus.
Bokeh refers to the aesthetic quality of the blur produced in the out of focus parts of a photograph and is not a measure of quantity. You can’t have more bokeh but you can have swirly bokeh or calm bokeh.
The relationship between depth of field and out of focus backgrounds
- The depth of field in the subject is fixed for a given aperture irrespective of the focal length used. That it, If I shot a head and shoulders portrait with the XF 23mm lens at f/2 from close up and matched the head and shoulders framing with the XF 56mm lens at the same f/2 from further back the depth of field in the subject will be the same. It might just happen to be from the tip of the persons nose to just in front of their ears but it will be the same for both lenses.
- The perceived out of focusness (new word 🙂 ) of the background is different however for the two shots in example 1. The picture taken using the XF23mm lens will include more background due to the wider angle of view and the background will be easily identifiable. The XF 56mm lens shot will include far less background because of its narrow angle of view of view and it will appear more blurred giving more separation from subject to background.
- When I shoot a fashion collection like these Barristers gowns, I need enough depth of field to show the garments in sharp focus from front to back but I still want an out of focus background. I therefore set an aperture of f/4 on the GF 250mm lens. The long focal length takes care of the background while the f/4 aperture gives me about 50cm of depth of field to work with.
1. Click on the picture to see the top left shot full size (Then pinch to zoom in). In that shot you can see a depth of field of about 1m that encompasses both barristers yet the background is nicely out of focus. Top left, right and bottom left: GF 250mm lens at f/4 on the GFX50s. Middle right: I shot this interior with the wider yet still telephoto GF 110mm lens to include a bit of the background. It needed to be clearly discernible yet not competing with the principle subject. The shallow depth of field in this shot is not an issue because the narrative is more important than the detail.
To tell a story or set the scene in a portrait use a short focal length or wide lens. In its extreme I use very wide lenses to include all the space that I’m in.
2. This portrait was shot using the XF 14mm lens on an X-T1. Notice how it pulls in the complete room for effect. The depth of field is quite shallow and although the background is out of focus it is clearly adding to the picture.
To isolate a portrait from its background use a long focal length or tight lens.
3. These shots taken with the XF 90mm lens at f/2 could have been taken anywhere, in a studio or on location. With a long focal length it is possible to completely isolate a background. Early in my career as a wedding photographer when I shot weddings in less than beautiful locations I used a long lens for almost every shot. You can’t go wrong with the long lens. Left: Notice the shallow depth of field that f/2 gives. One eye is in focus and the other not. I think I got away with this one but it’s not a look I particularly like. Top right: Close up shots have less depth of field than far away shots so expect to need a smaller aperture if you want your subject sharp front to back. Bottom right: I’m not a fan of out of focus foregrounds but I don’t mind a mirror shot like this where it’s part of my principal subject that is out of focus.
4. The GF 110mm f/2 lens at f/2 has a very narrow depth of field of about 1cm when used close up like this. I should have stopped the lens down to f/5.6 for this shot to get Mischkah’s nose, lips and chin in focus too. There is nothing in the background to ruin the shot. The thing is, it’s all subjective and some people live razor thin DOF.
5. These shots were both taken with the XF 50-140mm lens set to 140mm and f/2.8. Top: I just had a small amount of beach hut wall to work with as a background so I opted to use a long focal length lens. Bottom: I chose to create an abstract background for this shot taken in a woodland in France.
So when someone asks “What’s the best lens for portraits”? You can explain it depends upon how much background blur they want in their images coupled with how much intimacy and narrative. The truth is nearly all lenses are suitable for portraiture of some kind but each will have a certain characteristic.
Summary
Long focal lengths deliver tighter out of focus backgrounds and that makes them the easiest to use. If you have good light you can literally shoot a portrait with a long focus lens anywhere. The XF 50-140mm f/2.8 zoom lens makes shooting portraits easy.
Short focal length or wide lenses include more background so are perfect for environmental portraits where the background is relevant to the narrative. They also have more intimacy due to the closer perspective. Shooting portraits with a wide angle lens is hard because the background composition needs careful consideration as well as the connection/ intimacy. When they’re done well, wide angle portraits are amazing.
6. This shot was taken with the wonderful XF 50-200mm lens at 200mm using f/4.8. I love the child that’s hiding 🙂 The background is suitably out of focus and there is enough depth of field to make the shot work.
Standard lenses are often overlooked and I think they are often just what’s needed for portraits. The Rolleiflex twin lens reflex with a fixed ‘standard’ lens was the portrait photographers camera of choice for a decade before the Hasselblad with its 80mm planar came on the scene. Take a look at these portraits I have taken with the fabulous XF 35mm f/1.4 lens.
The quest for lenses with a larger aperture, faster lenses is often misguided. An f/1 lens will give such shallow depth of field wide open that only a tiny part of a close up portrait will be in focus. Yes the background will be blurred but the portrait will suffer (in my opinion). Often the compromise is to use a lens like the amazing XF 90mm f/2 lens. Pop that on an X-H1 with its IBIS and you are in portrait heaven.
