Balancing foreground and background subjects using hyper focal focusing

Kootenay Mountains and the Kootenay River, photographed Aug, 2006

Obtaining a sharp focus on your subjects is always important.  This tends not to be a problem if the subject is strictly in the foreground or background.  Most camera and lens settings will accommodate this with little trouble.  However, when both foreground and background components need to be in focus, more care must be taken.

There are a few variables that you can control to improve the depth of field in an image.  Each of them can be manipulated to maximize what is in focus and what isn't in an image.  I take a moment to explain each one and what you can do to improve the overall depth of field.

1)  Focal length - A lens is defined partly by its focal length, what mm value it has.  We typically think of the three categories:  wide angle, normal, and telephoto.  Wide angle lenses provide more depth of field at any given aperture than normal or telephoto lenses do.  We can explore this further and say that as the focal length decreases, depth of field increases at any given setting.

• What to do - choose a lower mm lens over a higher one (24 mm over 35 mm), ultra-wide angle lenses are even better for this, ranging between 10 and 24 mm (relative focal length).

2)  Aperture - All DSLR and mirrorless cameras have interchangeable lenses equipped with variable apertures.  Low aperture values, like f/4, have less depth of field than higher aperture values, such as f/16.  

• What to do - use the aperture priority mode setting and select a higher aperture value.  You can often go as high as f/22.  If the shutter speed gets too low, you may want to bump up the ISO.

3)  Point of focus - Usually when photographing scenery we use autofocus and have the camera focus on the background.  This isn't a problem if there are no foreground subjects, but if you want lots of depth of field you can improve it by moving the focus point back.  At any given point of focus, there is a before and an after part of the image that is sharp.  If your focal point is in at infinity, you are losing a lot of depth of field.  By manually readjusting your point of focus, you can greatly improve depth of field.

• What to do - back the focus off a bit.  You can do it manually on lenses equipped with full-time manual focus override or you can choose to focus on a point in the scene between far and near and lock the focus in (there are a couple of ways to do this) and then take the photo.  You can also select manual focus.  Focusing closer than infinity gives you more depth of field at any given aperture or focal length.  This is called hyperfocal focusing.

4)  Size of digital sensor - the size of the digital sensor has a large impact on the depth of field in an image.  Cell phones, often using a sensor measuring 1/3", produces an enormous depth of field at any settings you may choose.  Compacts, crop-sensor DSLRs and mirrorless cameras, and full-frame cameras all have larger sensor sizes.  This means that there is more depth of field at any given aperture, focal length (relative), and point of focus as the size of the sensor decreases.

• What to do - for the most part, this is not something you worry about as you have whatever camera you have.  A crop-sensor camera shooting at f/22 (14 mm = 21 mm adjusted) will produce images with more depth of field than full frame cameras using the same relative focal length.

5)  Size of image - The more you enlarge an image the less depth of field there is.  Just look at a photo on the back of your camera, it usually all looks in focus.  However, if you enlarge that on a computer monitor, you will start to see out of focus areas start to appear.  

• What to do - if you find that you are not getting the depth of field you want, do not enlarge a print so much.

6)  Use focus stacking software - You can do something called focus-bracketing.  You take a photo with the lens focused at infinity, move the focus point back a bit and take another shot.  Repeat this several times, each time altering the point of focus a little more so that it is closer to you.  The neat thing about this is that you can use a larger aperture (f/8) which means that the overall shot will be sharper, especially on the edges.  You may have to take 5, 10, 20, or even 30 shots.  The images are then loaded onto a computer where you can use focus stacking software to blend them together.

• What to do - Use a lower aperture and shoot 6 to 10 images and blend them together using FS software.  However, you want everything to be in the same place, so use a tripod, shoot when there is no wind, and shoot when there aren't people wandering through your shots.  I will often do this early in the morning when the light is good, the wind is low, and there are few people around.

You can get some amazing photos using a combination of these techniques.  The above shot was taken with a crop-sensor camera, an 18 mm (27 mm relative) lens, and with an aperture setting of f/14.  If I enlarged the front part of the image (flowers), you may find that they start to look out of focus.

Thanks for reading.

Eric Svendsen     www.ericspix.com