The shallow depth of field effect is very trendy and popular right now. It has always been effective, long before digital arrived. Some photographers have been confused why it is stronger some times than others and with some lens it does not work. So here are the tricks to getting the most effective background blur and how to control it.
To get the shallow depth of field effect it’s a combination of f-stop, lens choice and background/foreground distance.
You will want the aperture, the f-stop, to be as wide open as possible. The smaller your f-stop is, the more striking the effect will be. This is one of the reasons pros seek out the more expensive wider aperture glass. The f2.8, f1.5 and lower can get the stronger effect without much effort.
It might take a few steps to get your f-stop down there if it’s a bright day. You can set your ISO to its lowest setting, I live as close as I can to 100 ISO at all times. Going up as needed rather than down. Now that still might not be enough so the next trick is to use neutral density filters. You can get these in either plastic from manufactures like Roscoe or buy actual glass ND filters to go on the lens. They come in different strengths, rated by f-stop. A polarizing lens can act like a variable ND filter. Be prepared for a loss in the light through your viewfinder or your LCD screen. It’s a bit trickier to focus. You could turn your LCD screen up to compensate.
The next consideration is your choice of lens. The longer the lens the more pronounced the effect. You will want to select the largest mm lens you have. The effect of a wide-angle lens is not really noticeable. The longer lenses like the 200mm are really dramatic. One of my favorite lenses for this effect is my 100 Tamron continuous focus macro lens. Experiment with different lenses to see the effect.
The last consideration is distance. The distance you are from the subject and the distance the subject is from the background.
The closer you are to the subject the more striking the effect is, or more noticeable. The depth of field becomes shallower the closer you are to your subject. You need to be careful though; it narrows for both foreground as well as the background. What to watch for is if you are doing a face is the nose, which can go out of focus and look odd.
If you are not dead on with the face but shoot down, then you can get the effect of the eyes zone being in focus but the going down gets softly blurry as well as up. I use this effect a lot; my clients love it.
The other distance is the distance of the background from your subject. The shallow depth of field gets blurrier the further back it goes, a natural fall off the focus plane. This means if your background is sharper than you want, just move your subject away from it.
The characteristic of a shallow depth of field created by a camera is very different than that created by a blur effect or most third party software. It is more natural with the camera, which can see the plans of focus, the “real” depth of the scene. With the camera you will see octagonal shapes appear, noticeably in the highlights. You are actually seeing the aperture of the lens.
You can take advantage of this by placing cutout shapes in front of the lenses, like heart shapes or initials. This shape will be replicated in al the highlights in the scene. This effect is known commonly as Bokeh. The bonus of lens mask is it lowers the light coming into the camera so the reaching your low f-stop is achieved.
Once you have achieved a shallow depth of field, don’t waste it on just straight on shots. Get up high, shoot at angles, or get down low. Work the drama the effect creates. Think of it as a thin strip of focus on a plane that you can move around at will.
For example, you could shoot down a guitar neck to a wedding ring the strings hold in place. With the shallow depth of field you have blurring leading lines to the very sharp diamond with the guitar neck receding behind into a progressively falling of focus until its an indistinct color blob at the end.
Have fun with this it’s really powerful for focusing your image viewer’s attention to what you want them looking at.
Mark Laurie map, spa, FellowPPOC
Mark is a photographer, instructor and writer. His 35 yr old Calgary based studio specializes in photographing women. Mark has had his own TV show, written 3 books plus 4 limited edition books. His Revealing Venus experience workshops run out of Italy.