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Excellent  |
| Minolta
Dimage 7Hi, Built-in Zoom @ 50mm Macro mode w/flash ISO 100, 1/1800s, f/3.4 |
Consider this very unscientific explanation:
Without conscious thought, your eye quickly focuses on whatever you look at, whether near or far.
It is the same when you look at a photograph, your eye expects to be able to bring out the sharp edges on some part of the image. When edges are blurry, your eye is confused and you will feel a bit disoriented.
If people are distracted by fuzzy edges when they view your photos, they won't be able to appreciate your photographic works.
The image at the right is sharp as a tack - literally!
In this case, it's the tip of a carpet tack.
"Tack sharpness" is an essential skill for the best looking images.
Photo Sharpness and Image Size
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Nikon
D300, 50mm f/1.4 Nikkor lens mounted in reverse
ISO
200, 1/60s, f/11
Flash with blue gel |
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But that same image will show focus problems when printed in a large size, as in this detail of the same push-pin at the left.
Here, the depth of field was not great enough to pull the whole tip of the pin into focus, even at a reasonably small f-stop of f/11.
Key Techniques for Photo Sharpness
To acheive the best photo sharpness in your digital photography, look at the three factors that impact image sharpnes: focus, subject motion, and camera motion.Much like a 3-legged stool - or a photographers tripod! - these factors are equally important at supporting photo sharpness. For each factor, there are techniques to learn and specific equipment considerations.
At a high level, there are several considerations for each of these factors. Your critical eye should be on the lookout for the following:
- "In focus". What does it
mean to be in focus? What is depth of field? What about the out of
focus areas, how should they look?
- Using your auto-focus system.
How do you focus your lens? Does your camera have a fixed or movable
focus point?
- Manual focus. Does your camera
offer manual focus? If so, when should you use it, and how?
- Lens factors. How does lens
quality affect image quality? How does aperture affect focus?
Then, learn about the mechanics of focus at Photo Sharpness: Focusing Your Camera.
Subject Motion
- Freezing your subject. How do
shutter speed, aperture, and ISO work together to hold your subject
steady?
- Not enough light! How do you
use your flash to freeze motion?
Camera Motion
- Minimum shutter speed.
How fast does the shutter have to be to assure that camera motion won't
show in the image? How do I hold the camera to minimize camera shake?
- Rock solid camera mounts. How
do I use tripods and monopods to get steady photographs?
- Overcoming camera vibration.
How can I make my camera absolutely still when I take a picture?
- Vibration reduction. How
effective is vibration reduction (also called image stabilization or
optical stabilization)? Which is better, stabilization in
the lens or in the body?
Exceptions
There are many reasons You may not always want to achieve perfect photo sharpness. You may want to:- Emphasize subject motion by blurring
- Soften focus for a more appealing portrait
- Create other specialized artistic impact
For example, a popular motion effect is to blur the water in a waterfall by using a long shutter speed.
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Nikon
D300, 18-200mm VR @ 32mm
ISO
400, 1/6s, f/16
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For best impact, the other two legs of the sharpenss equation must be kept intact - you still need to have the most interesting part of the waterfall in focus, and you need to use a tripod so that camera movement doesn't blur the the stationary rocks in the river or the trees on the banks.
Now, having tackled photo composition and photo sharpness, it's time to move forward to photo exposure to learn how to put more punch in your images.
