Simulate natural vision's selected focus

Conventional wisdom in photography states that to achieve optimum image sharpness it is necessary to stop  the lens down as far as possible (highest f-stop number).  In reality, f 11 or f 16 typically achieves the best results much to the chagrin of the Group f 64 purists, but that's a whole other topic.  The theory is that the higher the f-stop, the greater the depth of field and therefore the greater perception of sharpness.

In most image-making situations this is true. For example, far off subjects like landscapes and group portraits tend to render a more pleasing representation of what the human eye sees if the image is in sharp focus throughout the frame.  In many cases, however, the human eye sees the world with selective focus.  It helps us "focus our attention" on the most important elements of what we are looking at.  By using a very narrow depth of field technique in certain image-making situations, the photographer can often better represent what the human eye naturally sees.  And in some cases, the technique can provide some interesting surprises.

In this exercise, it is best to choose a focal length that best matches with the human eye's field of view.  We typically refer to these lenses of a "normal" focal length lenses as opposed to wide angle or telephoto.  For a 35mm sized image,  a 50 to 55mm lens best matches this field of view.  A good way to test this is with a wide angle to telephoto zoom lens (15mm to 85mm works well) mounted on the camera, then look through the viewfinder and adjust the zoom so it matches up with the perspective of what your eyes see when not looking through the viewfinder.  Typically the zoom should come to rest around the 45 mm to 70mm range.  The image will crop out the peripheral view we experience when viewing a scene through our own eyes.  Discounting that phenomenon, the normal lens will give us the best simulation of our own actual vision.

Our own eyes have a natural depth of field mechanism similar to the camera lenses' f-stop adjusted depth of field.  Not everything in our view is in focus.  The focus plane shifts as we shift the primary subject point.  The closer (and smaller) the subject is, the narrower the depth of field (or acceptable sharpness).  Try looking at a specific item sitting on your desk like your phone or a pen.  Focus on it and then note that items in front, to the side and in back of the item are blurred.  We can exaggerate this phenomenon to even a greater degree in photography by choosing a  very narrow depth of field setting, or low numeric f-stop.  By opening up the lens to a maximum level -- often f 1.2 or 1.4 on most normal lenses -- we can create an effect that simulates the reality of human sight.

At first, viewing a finished image with very narrow depth of field can be a little disconcerting to the viewer.  Initially, the scene actually looks very unnatural.  But the effect is very dramatic and the more you look a the image, the more it looks three-dimensional.

 In this image of a strawberry pierced by a fork (above), the primary focus is on the top portion of the berry and the sharpness falls away.  With a lack of a  background, the berry seems to "pop" out at the viewer. That effect can be even more dramatic as seen in the example below.

Here the Windows 7 decal on the laptop becomes even more prominent because of the separation the extreme narrow depth of field creates. 

Here is another example of how you can make a scene more dramatic by zeroing in a specific item to give it more emphasis.  The key autographs on the ball are sharp and standout while the insignia on the cap, while recognizable, provides a backdrop for the main subject of the image.

And here is a fun example of the technique.  This image of a Elvis look-a-like wiener dog, puts the emphasis on the head, creating a more stunning effect than if the whole dog was in sharp focus.

Play around with the technique to see what circumstances it works best for your intended use.  Remember, the technique is different from using selected focus with a telephoto lens.  This method is intended to simulate the true natural selected focus phenomenon of human vision.  So mount a normal focal length lens on your camera, open it up all the way, and see what you can focus on.

Take a walk to keep your shooting eye sharp

A typical assignent given at photography workshops is to have the participants produce images in what would be a rather mundane setting. It could be a parking lot, the meeting room, or any other normal, everyday location.  The purpose of the exercise is to help the photographer view the world around them with a more critical and creative eye.  Once the photographer obtains the mindset to view everything around them as a potential image, their lives are never the same.

Occasionally I lose my shooter's eye.  I get caught up in the day-to-day activities of living and veer away from the special quality of viewing everything around me as a potential photograph.  It's not that I haven't been doing much image-making lately, it's just that the shooting I have been doing has been with an end result in mind.  For example, on my way to an assignment yesterday I decided to shoot some stock images of a hospital complex nearby.  So I spent a half-hour or so shooting for an end-result: stock architectural images.

There is nothing wrong with that, in fact it is very important to shoot with a result in mind.  But in order to keep the minds-eye sharp and from getting stale, it is a good idea to once in a while pick up the camera with a good all-purpose lens attached (I like the Canon 15-85mm zoom with image stabilization on my EOS 50D) and just start walking.

This morning I did just that.  I needed to pick something up for breakfast so I decided to take a round-about way to get to the store and see what I came upon for subject matter.  Serendipity would need to be my friend in this exercise.  It would prove to be a good pal indeed.




After leaving the house just before 8, I took a right turn and my shadow on a wood fence I walk by everyday during my morning constitutions provided my first image-making opportunity.  I took a few shots holding the camera at my mid-section to get a feel of the angle.  Then I realized I needed something more dynamic to make the picture work so I raised one arm and pointed. "Let's go this way!" 

Serendipity is a funny thing.  A million times every minute a great happen-chance image presents itself but only an infinitesimally small fraction of those events has a photographer waiting with a camera pointed in the right direction. I had taken a handful of bird shots on the half-mile I had walked so far...nothing too exciting but it got me thinking about the subject matter.  Last night I noticed a huge gathering of birds near where I went to pick up dinner.  "Must be migration season," I thought.  I also noticed the setting, waning moon earlier and tried to get it into a couple of compositions.  I was focusing on some birds perched on telephone wires when this flock came out of the north.  I followed the vector through the viewfinder, firing a few frames until the birds passed by the moon.  Serendipity? Yes, but without being in the "observation" game, this would have been one of those moments that would have passed by without capture.  The moral:  Be prepared, be in the game, and serendipitous moments will happen.



Cat tails and rushes by a low-water creek normally wouldn't provide anything to the photographer more than a very mundane image.  But a shaft of sunlight piecing its way through the trees created this dramatic scene.  Photography is highlights and shadows and this shot captures both. 





A picture within a picture -- Sometimes a good  image is hidden within what on the surface looks to be a fairly ordinary photograph.   I was trying to compose a shot of a pet waste receptacle along this walkway hoping for the appearance of a dog and owner to complete the visual  when a man on foot and what appeared to be his two sons on bikes passed me by.  I quickly fired off a couple of frames but the juxtaposition wasn't quite right, and beside, what did bikers and walkers have to do with cleaning up after your pet.  As the trio moved down the pathway, I fired off a couple more long shots with the subjects rather small in the frame.  After getting home and editing the frames, a tighter crop produced a nice backlight image of a universally appealing event.  If you shoot with a high enough resolution, fast enough shutter speed and low enough film speed, you can turn average shots  into more desirable ones. 





Stock photo opportunities can come from anywhere.  After I came out of the grocery store with cinnamon roll makings for breakfast (remember, that was the reason for excursion), I spotted the pumpkin display.  A couple quick exposures and I had a nice seasonal stock shot.



To make an image-making opportunity more successful, a photographer needs to draw on past experiences behind the camera.  This shot is a good example.  With plenty of satisfying shots from my walk already on the CF card all I needed to do was cross over the busy road that separated me from home and a well-deserved breakfast.  Forty-five minutes earlier I had composed a similar shot with the setting moon in the background so I knew how the stop sign could play into a composition.  I have often experimented with shutter speeds and their effect on the representation of speed on moving objects.  A shutter speed of of 1/25th of second did the trick.



Home at last with the goods.