Dec 7, 2012, 10:53
I've read post here where the photographer is asking about how to improve their photography by improving their focus. I think that in some of the post I've read focus is the issue but in many, sharpness is the issue. When you look at an image and your subject isn't crisp, the first thing that comes to mind is focus but that may not be the problem.
SHARPNESS
Lack of sharpness is usually attributed to camera or subject movement during the exposure. Many of my students (most new photographers actually) go through a learning curve where they learn what can be hand held and what can't. Long lenses and low light are the enemies, shutter speed and ASA settings are your friend when you have to hand hold, tripod or a monopod is your best bet when you can use them. For moving subjects, learn and practice the techniques of panning with your subject or prefocusing at a spot on the ground that You know your subject will pass over.
Modern DSLR cameras have awesome light sensitivity and allow you to shoot in low light levels (at a high ASA) without picking up a lot of noise in the image. Try bumping up your ASA and shooting at a higher shutter speed to counteract camera shake. See if that helps if you're having an issue.
The other factor affecting image sharpness is equipment (lens and sensor) quality. There's a reason pros use expensive glass, the image quality is much better. (among other things) I recommend to my students that are on budgets, that they purchase a cheaper camera body and spend most of their money on lenses. As far as the sensor, the general rule of thumb is bigger is better. a small sensor can be bumped up mathematically to give an impressive MP size but the image quality just isn't there.
FOCUS
Two parts to the focus discussion, Focus and Depth of Field. Focus is a mandatory part of the image and DOF is a design element (with an exception for moving objects). Your subject or the part of your subject you want to emphasize must be tack sharp. In a portrait it's the eyes, in a head a shoulders shot you might want all the subject in focus. In these same examples DOF is used in conjunction with focus to control how your final shot will look. A shallow depth of field will enhance your subject by making it pop. A deep depth of field will keep everything in focus which may or may not be a good thing.
Focus is critical and the ability to do it well is somewhat controlled by the equipment you use. A nice bright viewfinder on your camera is necessary to help you see what's going on and in the case of an auto focus, what your camera is actually focusing on. A dark viewfinder or trying to use an lcd viewfinder on the back of a camera to determine sharp focus is a recipe for disaster.
DEPTH OF FIELD
The 3 main variables in depth of field:
Focal length of the lens (The longer the FL the shallower the DOF)
Distance to the subject (The closer you are the shallower the DOF)
Aperture (The smaller the aperture, the shallower the DOF)
A 4th variable is sensor size. Smaller sensor cameras tend to have a greater DOF (but less sharpness).
As I mentioned earlier, DOF should generally be used as a design element and not as a focus tool. What I'm trying to say is that you shouldn't be trying to shoot using setting that provide a large DOF with the hope that your subject will be in focus. Focus first and then control the DOF to give yourself the shot you want. Use the concept of pre-visualization. [undefined=undefined]See the shot in your head and use the camera as the tool to make it happen.[/undefined]
There's a lot more that goes on in the discussion of the subjects that's beyond the scope of of a simple forum post but these are the basics... I hope this helps!
Kevin Whitcomb
SHARPNESS
Lack of sharpness is usually attributed to camera or subject movement during the exposure. Many of my students (most new photographers actually) go through a learning curve where they learn what can be hand held and what can't. Long lenses and low light are the enemies, shutter speed and ASA settings are your friend when you have to hand hold, tripod or a monopod is your best bet when you can use them. For moving subjects, learn and practice the techniques of panning with your subject or prefocusing at a spot on the ground that You know your subject will pass over.
Modern DSLR cameras have awesome light sensitivity and allow you to shoot in low light levels (at a high ASA) without picking up a lot of noise in the image. Try bumping up your ASA and shooting at a higher shutter speed to counteract camera shake. See if that helps if you're having an issue.
The other factor affecting image sharpness is equipment (lens and sensor) quality. There's a reason pros use expensive glass, the image quality is much better. (among other things) I recommend to my students that are on budgets, that they purchase a cheaper camera body and spend most of their money on lenses. As far as the sensor, the general rule of thumb is bigger is better. a small sensor can be bumped up mathematically to give an impressive MP size but the image quality just isn't there.
FOCUS
Two parts to the focus discussion, Focus and Depth of Field. Focus is a mandatory part of the image and DOF is a design element (with an exception for moving objects). Your subject or the part of your subject you want to emphasize must be tack sharp. In a portrait it's the eyes, in a head a shoulders shot you might want all the subject in focus. In these same examples DOF is used in conjunction with focus to control how your final shot will look. A shallow depth of field will enhance your subject by making it pop. A deep depth of field will keep everything in focus which may or may not be a good thing.
Focus is critical and the ability to do it well is somewhat controlled by the equipment you use. A nice bright viewfinder on your camera is necessary to help you see what's going on and in the case of an auto focus, what your camera is actually focusing on. A dark viewfinder or trying to use an lcd viewfinder on the back of a camera to determine sharp focus is a recipe for disaster.
DEPTH OF FIELD
The 3 main variables in depth of field:
Focal length of the lens (The longer the FL the shallower the DOF)
Distance to the subject (The closer you are the shallower the DOF)
Aperture (The smaller the aperture, the shallower the DOF)
A 4th variable is sensor size. Smaller sensor cameras tend to have a greater DOF (but less sharpness).
As I mentioned earlier, DOF should generally be used as a design element and not as a focus tool. What I'm trying to say is that you shouldn't be trying to shoot using setting that provide a large DOF with the hope that your subject will be in focus. Focus first and then control the DOF to give yourself the shot you want. Use the concept of pre-visualization. [undefined=undefined]See the shot in your head and use the camera as the tool to make it happen.[/undefined]
There's a lot more that goes on in the discussion of the subjects that's beyond the scope of of a simple forum post but these are the basics... I hope this helps!
Kevin Whitcomb
