Digital Photography in the Wilderness — the challenges and the solutions, by Jean-François Maïon
The above was a very interesting discussing, by Maion where he took his 10D high to some of the highest peaks and brought back beautiful images.
He did not touch on one subject, however, which needs to be addressed as a "caveat" for others of like mind. If you read the specs on the new Sony F828 you will find some distinct altitude limitations. At first blush, it may seem that this warning may be intended because of the possibility of using a microdrive as the media of choice. Microdrives, of course have altitude limits because the head floats upon a thin layer or "cushion" of air. As the air thins with altitude, the probability of a head crash and subsequent catastrophic failure increases. At altitudes over 10,000 feet, depending on temperature, this issue becomes a serious concern.
But if the issue is not the media, they why the altitude limitation? Stay tuned and let me relate my own experience with my 1DS earlier last year.
I took several of my cameras including my 1D, 1DS,10D and a couple fixed lens digicams to the summit of Mount Evans in Colorado. Mount Evans, at an altitude of 14,268 feet is easily reached by driving a paved road to within a couple hundred feet of the summit and following an easy trail to the peak.
While on the peak, I took a few shots with each of my cameras and checked the results on the LCD. After the first few shots with my 1DS, I noticed a very strange, dark grid pattern in the LCD. I took several more shots at different ISO and aperture settings with identical results. Images from my other cameras looked perfectly normal.
After driving down the road to an altitude of about 12,000 feet, I took a few more images with my 1DS which looked normal. I went home to an altitude of about 6,000 feet and everything seemed normal. The following day, I decided to repeat the experiment and returned to the summit of Mt. Evans. This time, the 1DS immediately failed in the identical manner and did not return to normal!
After thinking about this for a couple days, I reasoned that air trapped between the antialiasing filter (which is bonded to the sensor) at assembly time at near sea level had expanded and "warped" the sensor, and the grid pattern I was seeing was the result of light passing through the now misplaced AA filter thus shadowing the grid pattern upon the image.
I returned the camera to Canon's repair facility in Irvine, California where indeed the sensor was replaced under warranty and all was well once again. Canon's factory service rep's told me it "shouldn't" have happened, and that there had been instances of the camera successfully being used at even higher altitudes in Nepal or Tibet. However, I believe that there may have been production changes made so that the bonding is now not continuous on the AA filter.
On the day I took the camera to 14,268 feet the ambient temperature was near 80 degrees F, making the "density altitude" above 18,000 feet. I now notice that Sony has placed an altitude warning on the F828 and I'm a bit nervous about trusting any of my digitals at serious altitudes with the exception of my Kodak DCS-760 which has a removable AA filter and I can be certain there is no bonding trapping air.
Just a caveat to warn others that this can and may be a consideration to make before embarking on a high altitude trek with your digital. There indeed may be risks which you may or may not want to take.
Lin
