Resolution is a word that is bounced around in discussion of video cameras and projection systems, but often the impact of resolution on the image is not actually understood. No matter how good the resolution of the video system is, the image that is being displayed or recorded will suffer if the level of detail in the image approaches the available pixel size, or the the limits of the video resolution. Here is an example of an image with type size that ranges between very small to quite large. Note that the actual font size is not as relevant as the font size compared to the pixel size. The smaller fonts in this image have each letter being roughly equal to the pixel size, so the letters turn to little grey blobs. As the letters get larger and are made up of increasing numbers of pixels, the letters have more integrity, and are more legible.
Let's blow that up a bit...
Most people assume this is just a matter of buying a higher resolution display. Consider a video projector with 640x480 resolution versus a projector with 1280 x 1024 resolution. One projector certainly has higher resolution than the other, but despite that, it would still be possible to replicate the fuzzy font image to the right with either projector. This image is a blown up section of the one above (like walking closer to the screen). If the choice of font size or original image size is inappropriate for the detail that has to be presented, then the video display system will fail to present that detail. This is a typical problem with images such as architectural drawings and maps, where it is necessary to have the whole image shown to see the relationships between various areas, and then it is necessary to resolve the fine detail like street names or small text.
Consider that this same situation occurs for the human eye as well. If you want to see the "big picture" of a large map or drawing you stand back until it fills your field of vision, and then when you want to read the tiny details, you move closer to the object until the small details can be seen. It is necessary to have this process replicated in the video display system as well. This can be done by zooming in on the image with a camera if it is a document or drawing, or it would be necessary to zoom the display in an Autocad application to show the area of interest at a larger scale. Note that this is a source resolution issue and not a problem with the display resolution. It is important to determine the range of detail that must be presented and provide suitable source resolution.
Video sources can only scale the resolution by zooming in so that features and details are made up of enough pixels to resolve the detail. The number of pixels needed per detail will vary with the kind of detail. Let's look at a map image.
The monitor you are viewing has a resolution of between 72-96dpi (dots per inch), the pixel dot pitch on computer monitors varies between 0.28mm to 0.26mm, hence 96 pixels per 1 inch (25.4mm) of screen. These images are all scanned at 100dpi. Note that the only way to fully resolve the street names is to zoom in. You lose the sense of the neighborhood this street is located in, but you can read the adjacent street names. The source resolution determines how legible the image is, not your display device. If you had a magic computer monitor with 600dpi resolution you would still not be able to read the street names on the map on the upper left, it would be too small for the eye to resolve the text. This same effect scales up to large projected images too. Once the source resolution is determined to be adequate, then it is just a matter of choosing a display resolution equal to, or greater than the source resolution, and having the display be of adequate size for the viewing distance, and your presentation system will deliver the images you need.
Mc Squared System Design Group, Inc
323 - 901 West 3rd Street, North Vancouver, BC. V7P 3P9 Ph 604-986-8181