For a 9x9" black and white aerial photograph at a map scale of 1:12,000, the following table gives an idea of the trade-off between file size and resolution.
| DPI (click for sample) |
File Size | 1 pixel side equals how many inches on the ground |
| 100x100 | 757 K | 120 inches |
| 200x200 | 3 Meg | 60 inches |
| 300x300 | 6.8 Meg | 40 inches |
| 400x400 | 11.8 Meg | 30 inches |
| Therefore, a 1:12,000 image scanned at 400 DPI will be 11.8 Megabytes but you should be able to discern items on the photograph which are greater than 30 inches in the real world. For example, if you were interested in looking at shrubs in a photograph, you would want to scan at a resolution greater than 100 DPI because most shrubs are smaller than 120 inches across.
There is also a trade-off between different image formats and the software that can use them. |
