Typically, there are three different images for each 3D orchid; Quicktime detects the speed of your Internet connection and presents you the most appropriate version.
Each of the three versions is at 320 x 240 resolution, unless otherwise indicated. They only differ in amount of compression and in the number of frames contained in them. The higher the compression, the smaller the file and the quicker the image will appear. The number of frames determines how smooth the rotation looks.
The codec used for compression for all versions is H.264, also known as AVC or MPEG-4, Part 10. I am aware that Photo-JPEG gives the best quality, but I chose H.264 for its balance of small file size and good quality.
The "best" images are compressed at "high" quality with 72 frames - i.e., one view every 5 degrees, giving a very smooth rotation. Best images are typically 800 kilobytes to 1.2 megabytes in size.
The "better" images are compressed at "medium" quality with 36 frames - i.e., one view every 10 degrees. The rotation is not as smooth as "best" images, but persistence of vision enables the 3D impression to be maintained. Better images are typically up to 300 kilobytes in size.
The "good" images are compressed at "low" quality with 36 frames, and are typically 150 or so kilobytes in size.