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Click on the image to the left to start downloading a 22 second long, 720 x 576 pixels sized, time-lapsed film clip of the auroral display of 23 December 2000. The 910 MB clip is compressed to 2.5 MB with DivX which is an Mpeg4 format. The media player that is needed to fully see the clip can be downloaded from www.divx.com or via a direct download from download.divx.com. You can download the clip to your harddisk by right-clicking on the image and then choosing "save target to". |
| How this movie was made: The frames were shot on a Nikon F3 with a 250 exposure back filled with 35 mm Kodak Vision 800T motion picture film and a 16 mm f/3.5 full frame fish eye lens. Each frame was exposed for three minutes with an intervalometer. An interval of 10 seconds between frames was used to check for condense on the lens. The exposure sequence started on 23 December 2000 at 00.45 UT and ended at 02.50 UT. Near the end the sequence was interrupted twice for ice removal from the lens. This accounts for the two "missing" frames that occur near the end of the clip. Normally the lens is heated but this night the heater was used on the still camera that recorded startrails. With a temperature of minus five degrees Celsius and a mild northern wind coming in over the warm North sea, the air was saturated with moisture and the film sequence was abruptly halted when thick icy fog rolled in. A total of 31 frames were shot. After developing the frames were digitized using a negative scanner and registered with PictureWindow 3.0. The image of a far away street light near azimuth 360 on the horizon was removed from all 31 frames. Also dust particles and small scratches were removed. Apparently not all dust particles were removed; these show as guest stars that appear sometimes in the clip. The 31 frame sequence was then imported in Adobe Premiere 6.0 where first the fish eye image was warped to get a straight horizon and also some color corrections were made. Mainly a lot of blue was filtered out since Vision T800 is an indoors Tungsten film with enhanced blue sensitivity as compared to Daylight film. The length of the 31 frames clip was then doubled to 62 frames and this sequence was superimposed with itself, whereby the clip with 50% transparance was shifted one frame. This process was repeated another three times until a sequence of 248 frames with smooth movement was made. Viewed with a speed of 25 frames per second (PAL), this 10 second clip was still moving fast and therefore the length of the clip was doubled to 20 seconds. Including fading in and out at the begin and end, the clip now contained 574 TIF frames with a screen size of 720 x 576 pixels and a file size of 1.6 MB per frame. The total size of the clip at that stage was 910 MB. Using the DivX codec this was finally compressed to a 2.5 MB file size with a viewing fame rate of 12.5 fps. A side effect of the superimposing technique of cross fading single frames is that moving star images are blended with either dark sky or aurora, making them appear weaker than in the original frames. |
