To answer this question, you must know how would like to print your mosaic.
If you work in a pre-press bureau - you may already know this information and may not need read
I can give you a few simple tips:
1. If you want to display your mosaic interactive zoomable image on Web site or local computer:
There are no restrictions for image sizes and for size of tiles. Just keep in mind that it is not good to
make mosaic cell bigger than size of your tile images. e.g. if you assembling the mosaic from small 300
x 300 pictures it will be good to select cell size 300 x 300 or smaller. Otherwise the program will up-scales the pictures that may by not looks nice.
Also it is probably unpractical to make a single mosaic cell bigger than a size of a monitor. If you think
that people will be looking on your mosaic at popular Full HD monitors with 1920 x 1080 resolution it will
be better not to select a single tile size bigger than 1920 x 1080.
Please note that, as obvious, a bigger image will take bigger file size. For example our
33 Gigapixels mosaic
takes about 10 GB on our server. The same picture saved as a single Adobe
Photoshop PSB file takes 90 GB.
2. If you want to display your mosaic on a monitor (or Web site) only:
The size of your mosaic in pixels must be no more than the typical computer screen resolution:
800x600, 1024x768, 1280x1024 or maybe a little more. The majority of Web surfers use 800 x 600
Keep in mind that if you want to display a 30x30 tile mosaic on a screen with a resolution of 1024x768,
every tile will be about 34 pixels in width.
3. If you want to print a mosaic on an ink-jet printer:
Even if you have a "very hi-tech super-duper photo" printer that prints 2400x2400 dpi (so they claim in
the users manual) you usually do not need an image file with a resolution of more than 150 to 200 dpi. If
you want to print an A3-sized mosaic (about 12x17 inches) with a resolution of 200 dpi, you'll need to
have an image file of 2400x3400 pixels.
If that mosaic is 30x30 tiles, every tile must be about 80 x 113 pixels.
4. If you want to make a mosaic suitable for a typography process:
For typography, you'll most likely need a file with a resolution of 250x300 (maybe more) pixels per inch.
Consult with your pre-press bureau manager about file resolution and then calculate the tile size you
need using the examples from the ink-jet printer.
If you want a very high resolution mosaic, be sure that every image you'll want to use as a tile is not less
than the size of a tile you want in the output mosaic.
When making those high resolution mosaics, it is better to render it first using a small output size and
when you are satisfied with the result, render it as big tiff or bmp file. This way you may speed up the
overall process significantly.