Evaluating An Image
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Evaluating An Image How things look on the screen doesn’t always matter. A full resolution image from a 6 megapixel camera printed on 4” x 6” paper…
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Evaluating An Image. How things look on the screen doesn’t always matter. A full resolution image from a 6 megapixel camera printed on 4” x 6” paper… each pixel is 1/512 of an inch. Evaluating An Image. - PowerPoint PPT Presentation
Transcript of Evaluating An Image
Evaluating An Image
How things look on the screen doesn’t always matter.
A full resolution image from a 6 megapixel camera printed on 4” x 6” paper… each pixel is 1/512 of an inch.
Evaluating An Image
If your prints are going to be printed, evaluate that image to how it looks on the printer you use.
If for viewing on the screen at full resolution, then pixels matter.
Evaluating An Image
Using a printer will show how artifacts will print as well as how colors will translate into print.
Top 8 Imaging Problems
Although there are problems inherent in digital imaging, digital cameras still give better quality images than many point-and-shoot film cameras without any corrections to
the image
Top 8 Imaging Problems
Noise:
Like grain in film… Not necessarily a bad thing; can create interesting results.
Top 8 Imaging Problems
Noise:
Different cameras produce different amounts of noise, some “prettier” than others.
Top 8 Imaging Problems
Noise:
Typically occurs in darker parts or areas of sky in an image, but can occur anywhere.
Top 8 Imaging Problems
Color:
Different types of color problems can occur in any image.
Top 8 Imaging Problems
Color:
Some cameras consistently shoot warmer, others, cooler. Some shoot more or less saturated.
None are wrong, maybe just not to your taste.
Top 8 Imaging Problems
Color:
Some cameras produce a color cast; could be a shift of color in the shadows, but the midtones and highlights are fine.
Color casts aren’t hard to fix.
Top 8 Imaging Problems
Bad White Balance:
Similar to images with color casts, but affect more of an image.
If improperly white balanced, a camera will not be able to accurately produce colors.
Top 8 Imaging Problems
Chromatic Aberration:
Happens with all types of cameras
Known as “purple fringing” in digital cameras
Often appears in high-contrast areas
Top 8 Imaging Problems
Chromatic Aberration:
Can happen when a lens focuses some wavelengths of light more or less than others
More prevalent in wide angle lenses
Top 8 Imaging Problems
Chromatic Aberration:
Can also happen when a camera sensor “fills up” with too many electrons which overflow into adjacent photosites
Top 8 Imaging Problems
Detail and Sharpness:
The result of several factors…
• Camera resolution• Lens quality• The sharpening algorithm your camera uses
Top 8 Imaging Problems
Detail and Sharpness:
Too much detail and sharpness can be a bad thing…
An image can look too harsh
Top 8 Imaging Problems
Detail and Sharpness:
Too much sharpening can cause aliasing, or “jaggies” in
your image.Anti-aliasing can be applied to images
Top 8 Imaging Problems
Exposure Problems:
Camera meters can make mistakes
Be aware of how a camera’s metering and exposure choice can affect detail and overall results. (practice)
Top 8 Imaging Problems
Lens Distortion:
Pincushion distortion causes straight lines to bend inward
Usually happens at the longer focal lengths
Top 8 Imaging Problems
Lens Distortion:
Barrel distortion causes straight lines to bend outward
More common, happens at the shorter, wide angle focal lengths
Are Problems Always A Problem?
An image can have many technical mistakes but still look good. Examine the whole picture. Does it “work” or not?
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