Photoshop CS3

digital basics

*HSJ\SH[PUN H Z\P[HISL ÄSL ZPaL HUK ZJHUUPUN YLZVS\[PVU Scanning resolution is rarely the same as the resolution you require to print out your image. If you are going to create a print larger than the original you are scanning, the scanning resolution will be greater than the output resolution, e.g. a 35mm negative would have to be scanned at 1200ppi if a 6 × 4 inch commerical print is required. If the print you require is smaller than the original, the scanning resolution will be smaller than the output resolution. The smaller the original the higher the scanning resolution.

1˝

4˝

Magnification × output resolution = scanning resolution scanning resolution = 4 × 300ppi = 1200ppi

To calculate the correct file size and scanning resolution for the job in hand you can: Either: Go to ‘File > New’ in Photoshop, type in the document size, resolution and mode you require and then make a note of the number of megabytes you require from the scanning process. Then adjust the scanning software resolution until the required number of megabytes is captured. Or: Multiply the magnification factor (original size to output size) by the output resolution (as dictated by the output device) to find the scanning resolution (not so difficult as it sounds!).

Output device resolution

Size and mode

100ppi screen

240ppi

300ppi

inkjet

commercial

2.29MB

13.20MB 4.39MB

20.60MB 6.87MB

8 × 10 RGB

781K

8 × 10 Grayscale

1.00MB

5.77MB 1.92MB

9.01MB 3.00MB

5 × 7 RGB

342K

5 × 7 Grayscale

703K 234K

3.96MB 1.32MB

6.18MB 2.06MB

4 × 6 RGB

File size

4 × 6 Grayscale

33