Power consumption: What drains the camera battery
Depending on use, a camera's battery sometimes lasts for more, sometimes for fewer photos. Test measurements show that the exposure time has hardly any effect on the battery, but the time between photos does.
How you use your camera affects the battery life: Do you take your time when taking photos and is the screen always switched on? Do you often use the flash? Do you use computing-intensive functions?
In order to assess the battery life independently of the person, the industry association CIPA has defined a standardised measurement method. The result is a value that can be used to compare cameras. However, this hardly says anything about how many photos you can actually take with the camera. There are also certain reservations when it comes to camera comparability: Not all cameras have the same requirements.
It would be useful to know how much power a particular camera function requires. If the battery is low, you could adjust your behaviour accordingly.
There are some truisms that nobody doubts:
- The battery lasts for more photos with continuous shooting. Not only does the shutter release require power, but also the operation in between. And this is extremely short with continuous shooting.
- Shots with an internal flash require more power than those without.
- Photographing with a bright screen requires more power
- Videos drain the battery more quickly than photos.
- The autofocus and image stabiliser also require some power; if you switch these off, the battery should last longer.
But how much difference does it make? I investigated this with measurements.
How I measure the power consumption
Normally, I measure the power consumption of an appliance with an electricity meter. But here it doesn't give me any meaningful values. The meter, which hangs between the socket and the camera, always shows around four watts on my Sony RX100, no matter what I'm doing with the camera. My guess: the power meter is too inaccurate for these purposes and reacts too slowly.
I therefore use the camera's recording timer. It takes a photo automatically every few seconds until the battery is empty. I repeat this process with different settings, for example with and without flash, and compare the number of photos.
This is time-consuming. A test run takes several hours and the battery has to be recharged every time. I could only continue using a second battery if it had exactly the same power. That's not the case with any of my cameras.
Sometimes I have only realised afterwards that the test did not run correctly. That means a lot of lost time. Once the memory card was full before the battery was empty. Twice, when looking at the shooting data, it turned out that the camera took much longer between two shots than the interval timer was programmed for. This falsifies the result because the camera is in operation all the time and consumes power.
Why doesn't the camera take pictures at the specified interval? I suspect two reasons. One is the autofocus: if there are no recognisable contours in the focus field, the camera tries to focus for a very long time, which delays the shot. The other problem has to do with the flash. Flashing at full power requires the flash capacitor to be fully charged, which can take a few seconds. My programmed interval was too short for this.
Power consumption with internal flash
My first successful run compares the runtime of the Nikon D7500 with and without flash. During the first test run, the flash is manually set to full brightness so that the flash intensity does not depend on the ambient light. The second time it is deactivated. All other settings are identical. The autofocus always remains deactivated for safety reasons. The shooting interval is 15 seconds in both tests.
Result: With flash, the camera takes 621 photos. Without flash 1271 photos.
With full flash power, the battery only lasts about half as long as without flash. At least with the Nikon D7500. But this is likely to be similar for all cameras.
The CIPA standard procedure uses automatic flash. This is a bit daft, as the power consumption then depends on the lighting situation. When the manufacturers test in bright surroundings, the flash only uses a small fraction of its luminosity and consumes very little power. I don't know whether the manufacturers really do this. But it would be obvious, as this results in better values and at the same time a camera with a built-in flash does not have a major disadvantage compared to a camera without an internal flash.
Power consumption of the screen
The next test is intended to show the influence of the screen on battery life. I'm using the Canon EOS R6 for this. Here I can control whether or not the viewfinder image is displayed between two shots. I can't switch the screen off completely, but I can display only the shooting data instead of the viewfinder image. I also set the screen brightness to maximum for the viewfinder image cycle and to minimum for the test run with just the info display.
The difference is small: 877 photos with viewfinder image and bright screen compared to 956 photos with info image and dark screen.
Unless a fundamentally different screen technology (OLED) is used, the differences will not be particularly large with other cameras either.
Electronic viewfinder versus screen
When shooting via the screen, the battery should last longer with the electronic viewfinder. I have often read this in the specifications. According to the CIPA standard, the Panasonic Lumix G110 can take 250 pictures with a viewfinder and 270 with a monitor.
I check this on this camera. It has a timer recording function that allows me to switch between monitor and viewfinder. The result confirms the manufacturer's specifications:
With viewfinder 7386 photos, with screen at medium brightness 8143 photos.
The very high values in both cases are due to the fact that I took the photos at 1-second intervals. You can only compare these two values with each other. A comparison with the other data in this article is not meaningful.
Why does the viewfinder need more power even though its screen is much smaller? One reason could be the resolution, which is usually significantly higher in the viewfinder. On the Panasonic G110, the viewfinder has 3.7 megapixels and the screen 1.8 megapixels. Higher resolutions require more computing work and therefore probably a little more power. In addition, the viewfinder and screen use different technologies: The viewfinder uses OLED, the screen TFT.
However, these cannot be the only explanations. With the older Sony RX100 III, the difference is still very large: 320 photos with monitor, 230 with viewfinder. This is despite the fact that the 1.4 MP resolution of the viewfinder is not much higher than that of the screen, which has 1.2 MP. With the Sony RX100 VII, the resolution of the viewfinder is more than twice as high as that of the screen. However, the difference in the CIPA test is only 20 photos: 260 with viewfinder, 240 with monitor. It remains completely unclear why the values with the monitor have become worse and worse over the years. Its resolution has not increased.
Image stabiliser of the lens
Back to the Canon camera, where I repeat the test run for the dark screen. All the settings are exactly the same, there's just one difference: the lens image stabiliser is switched off this time. The lens is the RF 70-200mm F2.8.
The difference is tiny. 962 photos compared to 956 photos with image stabiliser. This may also be a random deviation.
Exposure time
Do long exposures really need more power? The previous test used a manually set exposure time of 1/250 second. Now I drain the battery with a shutter speed of 2 seconds. In both cases, the interval is again 15 seconds.
The camera took 981 photos. That's more than with the short exposure time. A longer exposure time therefore does not require more power. The screen remains black during the two seconds. This could be the reason why the longer exposure times actually require slightly less power.
Continuous images
Finally, I want to burn through the battery with continuous shooting. This can't be done using a timer, I have to keep the shutter button pressed the whole time. I use the mechanical shutter. Something physically moves that should actually consume energy.
After 4000 pictures, the camera still shows the battery as full. If the battery were to last even half an hour, that would be enough for 21,600 photos at a continuous shooting speed of 12 fps. With an electronic shutter (20 frames per second) it would even be 36,000 photos. The test seems pointless to me and I cancelled it. It is also so clear: with excessive use of the continuous shooting function, many, many more photos are possible than in single-frame mode.
Summary
I have left out the video function. This is another chapter in itself and would have to be measured in a completely different way. The photo tests on power consumption revealed the following:
- The flash needs a lot of power when it has to light up at full power. However, I rarely use this in everyday life.
- The image stabiliser of the lens seems to consume practically no power at all. It also doesn't matter whether I use a short or long exposure.
- A brighter screen naturally requires more power - but the difference is not too great.
- The viewfinder requires slightly more power than the monitor, although the difference is only small with the latest cameras. This was different five years ago.
- Long intervals between two shots require much more power than short ones. This is the factor that makes the biggest difference.
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David Lee
Senior Editor
David.Lee@digitecgalaxus.chMy interest in IT and writing landed me in tech journalism early on (2000). I want to know how we can use technology without being used. Outside of the office, I’m a keen musician who makes up for lacking talent with excessive enthusiasm.
