The photographer’s dance

It’s easy to view photography as a purely artistic discipline especially when we view photographs by the likes of Brassai. He captures the atmosphere of Paris at night with such evocative care that it’s easy to imagine being there. And it’s true that composition, how you frame a shot whether by changing your position or zooming in or out or cropping in the edit, is far more important than gear. No-one looks back at Brassai and says, ‘Well, I would like his photos, but what resolution was he shooting at?’ The technology supports the composition of the photo. However, paired with both the composition and technology is a dance that every photographer must engage in: depth of field. It’s been the technique I’ve found it most difficult to get a handle on.

To understand depth of field, remember that while photographs are two dimensional, what was photographed is three dimensional. So while there are x and y axes to represent width and height, we also have z axis to represent depth. Depth of field is the amount of space in the z axis that’s in focus. If the depth of field is narrow, then what’s in front of that z axis space and beyond it will be out of focus. Precisely what’s in focus is itself a creative choice. For example, the wildlife photographer Simon d'Entremont will typically get his subjects in focus and be happy to let the background be out of focus. Particularly where backgrounds are complex, letting the backgrounds become blurred removes potential distractions from the subject. So for him, depth of field can be wafer-thin, so long as all of the subject is in focus. And yes, getting the whole of a subject in focus can sometimes be harder than you might expect. Just look at this first shot of a flower and compare it to the following shot taken of Marlborough Tower and Maison de la Reine.

Both photos are shot at F6.4 with the flower at 36mm and Hameau de la Reine at 27mm. Both were shot in good weather a few minutes walk from each other. So the two have been taken using very similar settings in the same location. Yet if you look closely, you’ll see that parts of the flower are out of focus despite being shallow while the other scene is at least acceptably sharp front to back despite being a very deep scene. Why? The catch is that depth of field isn’t consistent across all settings, compositions or scenarios.

Reduces depth of field

Increasing aperature (lower F numbers)

Higher focal lengths (higher mm numbers)

Moving closer to the subject

Expands depth of field

Reducing aperture (higher F numbers)

Lower focal lengths (lower mm numbers)

Moving further away from the subject

So this means that depth of field is always moving based upon choices that you make in terms of composing and taking the shot. Change just one of the above and your depth of field will be changed. Whether that change is beneficial or not depends upon what you’re trying to achieve creatively. If you want a bokeh effect where the subject is in focus and everything else is out of focus, then a reduction in depth of field can be beneficial so long as it isn’t reduced to such a degree that only part of the subject is in focus. This explains why the flower is partially out of focus while the scene with the tower is in focus: the distance from the lens to the flower is a matter of inches while the distance from the lens to Marlboroguh Tower is almost three hundred feet. That distance expands the depth of field to such a degree that the entire scene is at least acceptably sharp.

But how can you keep track of depth of field? Perhaps, the most technically correct option is to use an application or website that calculates this for you based upon the data you enter. One example is Photopills where you can enter your camera, distance from the subject, aperture, and focal length. The app will immediately give you details on how far from the camera you need to focus along with the distance in front of the subject and beyond the subject that will be in focus.

Above are two screenshots from Photopills to illustrate. What I’ve entered in the first screenshot is that I’m shooting at 25 mm F8 and that my subject is 5 metres away. For the second shot the only thing I’ve changed is the focal length (zoom) which I’ve increased to 50 mm. The key number to focus on is the hyperfocal distance, the point at which we need to focus for everything to be acceptably sharp. By zooming in twice as far to the same subject, we can see that the hyperfocal point is four times greater. So one simple change, how far you’ve zoomed in, can have a marked effect on your shot. But digging out Photopills to enter all the numbers may not be practical if there isn’t time due to the scene changing or subject moving, for example.

Thankfully, there’s a quick and dirty option. In the settings for my Fuji camera is an option called focus peaking. If you look at the manual for your camera, you should be able to find what it’s called for your camera. There are nuances to how this can be set, but fundamentally it will create speckles in red in the viewfinder or on the screen around the areas of the shot that are in focus. No speckles, no focus. Few speckles, iffy focus. Many speckles, in focus. You can then play with aperture or consider changing focal length or distance from the subject, if composition or the location allows, to adjust depth of field.

Is it precise? No. Should you rely upon it when you absolutely must get the shot perfect correct in all regards? No. But it’s a quick option that will allow you to see how you can change depth of field without putting your camera down. Keeping your camera in your hand while you make changes may also help enhance your practical understanding of how you can manipulate depth of field to best support your photography.