This report has grown rather large. If you get bored with the details, skip to the end.
The following measurements were done on only one sample. I have no way of knowing if they are typical until I have the opportunity to measure more cameras.
Test condition: All tests were done with a Tamron 28-200mm/ 3.8-5.6 Macro lens (the new model) but in manual focus mode to avoid focusing current drain to affect the setup. The lens current was measured in the Tamron and also in a 60mm /2.8 Micro Nikkor. In both lenses the current drain is approximately only 1% of the camera's current drain and can therefore be ignored. During auto focus, the current drain is on the average twice as much as the normal camera drain but the actual time that the focusing motor run is very short, typically 0.1 to 0.2 seconds and therefor it does not significantly affect the battery life. A 128 MB MicroTech CF was used. All photo data was taken at 1/125second.
The current drain was evaluated at different battery voltages and, as is normal with a switching supply load, the current drain increases as the battery discharges. The following data was taken at 7.5 V, a typical average value at room temperature. In the conclusions, I have used the nominal value of 2000 mAh (milliAmpere-Hours) as battery capacity. I have not verified it and usually battery capacity varies versus load but it is a useful practical number to help us understand the camera.
I have about four pages of data of the D1 operating in a variety of modes and resolutions but to summarize it in a practical way I have condensed the information as follows:
1. Camera turned off: The mechanical switch is turned off.
2. Camera sleeping: Switch turned on but it timed out and went to sleep.
3. Camera awake & ready: The shutter button was half way pushed and it woke up or the On-Off switch was turned on. Custom setting # 15 controls the awake time. All measurements were taken with it set to 6 seconds.
4. Taking picture: The shutter was pushed all the way and a picture was taken.
5. LCD Monitor on: Self explanatory.
6. PC Mode: Connected to a PC via FireWire.
I have evaluated another six modes but the above ones will cover the practical functions.
1. Camera off: The drain in off mode is extremely low, 0.17mA. By dividing the 2000mAh battery capacity with the current drain we will get approximate hours of use. 2000/0.17= 11,760 hours= 490 days! Of course, the battery will selfdischarge in the meantime but the "Off" drain is absolutely insignificant.
2. Sleeping: This was a big surprise! The current measured 0.21mA. An insignificant change from the Off mode! Doing the same calculations as above, it would last 397 days. In other words, the practical reasons to turn the camera off is to prevent accidental exposures and auto focusing.
3. Camera awake: As soon as it wakes up, it will use 590 mA continuously until it falls asleep again in six seconds if that setting is used. If continuously used, it would last 3 hours and 23 minutes. Theoretically, one would get 2000 "wake-ups" on one battery charge. This is very significant! If the camera is woken up four times for each picture taken, we are down to 500 wake-ups even before a picture power drain is included.
4. Picture taking: This was the second surprise. There is a large, very short current spike as the mirror closes but then it basically drops back to the typical 590 mA current drain. The current spike is so short that it does not use any significant power. This is independent of the resolution mode. After the picture is taken, which takes a fraction of a second, the camera processes the picture and saves it to the CF. (Actually, if long time exposures are done, the current drain while the shutter is open is 1200 mA and will affect the battery life if very long exposures are made)
It is the processing/saving time that is significant. In order of increasing resolution that time is approximately, 0.5s, 1.0s, 1.5s and 8.5s. The only reason that we are getting fewer NEFs than JPGs pictures is the actual time the camera is awake. I do not know why the NEFs take such a long time to process since no compression is done. JPGs should require a significant amount of calculations for the compression although the final size is smaller. I also do not know if the time depends on the brand of CF. Faster saving directly translates to more pictures. Since I do not have a microdrive, I could not measure one.
Also note, waking up the camera and taking a JPG almost uses as much energy as just waking up the camera, about 7 seconds vs 6 seconds.
5. LCD monitor: The current drain is 50% more while it is on; 900 mA. The problem is that it often further adds to the time that the camera is awake.
6. PC Mode: The same typical 590 mA drain here also. The problem
or thing to watch out for is the long time that the camera might be on,
since it does not time out in 4 or 6 seconds.
NEF, 8sec timeout, 4 second LCD/picture, 4 extra wake-ups: Equivalent to 51s/picture which gives about 290 pictures.
This would be further degraded by a slower microdrive and the focusing current for the lens.
Please do not pick on these numbers, they are calculated based on Nikon's claim for the battery which might not be applicable in this mode and there are many variables that I have not included in this report to try to keep it simple. It does show, how some persons can get 900 pictures and others just a few hundred.