Evaluating An Image

1. 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.

2. 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.

3. Evaluating An Image Using a printer will show how artifacts will print as well as how colors will translate into print.

4. 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

5. Top 8 Imaging Problems Noise: Like grain in film… Not necessarily a bad thing; can create interesting results.

6. Top 8 Imaging Problems Noise: Different cameras produce different amounts of noise, some “prettier” than others.

7. Top 8 Imaging Problems Noise: Typically occurs in darker parts or areas of sky in an image, but can occur anywhere.

8. Top 8 Imaging Problems Color: Different types of color problems can occur in any image.

9. 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.

10. 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.

11. 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.

12. 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

13. 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

14. Top 8 Imaging Problems Chromatic Aberration: Can also happen when a camera sensor “fills up” with too many electrons which overflow into adjacent photosites

15. Top 8 Imaging Problems Detail and Sharpness: The result of several factors… • Camera resolution • Lens quality • The sharpening algorithm your camera uses

16. Top 8 Imaging Problems Detail and Sharpness: Too much detail and sharpness can be a bad thing… An image can look too harsh

17. 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

18. 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)

19. Top 8 Imaging Problems Lens Distortion: Pincushion distortion causes straight lines to bend inward Usually happens at the longer focal lengths

20. Top 8 Imaging Problems Lens Distortion: Barrel distortion causes straight lines to bend outward More common, happens at the shorter, wide angle focal lengths

21. 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?