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I'm thinking of trading in my Canon EOS 650D (DSLR) and buying an EOS M5 (Mirrorless). But apparently mirrorless cameras don't last very long in between recharges.

This would be a problem for me because I'm already frustrated with my current battery life, and there's no battery grip accessory available for Canons mirrorless cameras.

So what causes the mirrorless cameras shorter battery life?

Is it the electronic viewfinder & LCD display? Because I constantly use LiveView anyway. So maybe it won't be too bad (by comparison).

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    Consider turning off your LCD display. Regardless of what type of camera you use, it will greatly improve the amount of time you can get out of a battery. – Mast Jan 14 '18 at 20:44
  • As a side note, if you are already frustrated with the battery life with your 650D, you should try to stop using LiveView. You will also have the added benefit that your AF is much faster. This assumes that you are taking stills, not video. – Robin Jan 15 '18 at 17:47
  • (Just my two cents) If the battery is removeable, you may consider getting replacement batteries. – neverMind9 Oct 25 '18 at 17:00
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  • Using an electronic viewfinder or LCD screen to compose the image uses more battery life than a standard viewfinder
  • Using an LCD screen for the majority of device settings uses more battery life than physical, dedicated buttons
  • Smaller physical devices may, by design, have smaller batteries
  • Using standard viewfinder doesn't use ANY battery. When you take the battery out, viewfinder keeps working. Metering uses battery, but it's closer to "negligible" rather than simply "less". – Agent_L Jan 15 '18 at 10:28
  • @Agent_L Most "standard" viewfinders on modern DSLRs have electronic overlays. They'll use some battery. – Oli Jan 15 '18 at 12:15
  • @oli only while they're displaying something, if you don't half press the shutter to activate the meter, no power usage – Joseph Rogers Jan 25 '18 at 20:34
  • @JosephRogers, not so. Both the grid and low battery overlays on my Nikon D750 are powered features. Even when the camera is off or in standby. You can tell they're powered because when you remove the battery, they vanish. I suspect it's OLED, next-to no power, but not absolutely none. But the broader point is that using your viewfinder probably also means you're using the camera, the viewfinder info "underlay" line and AF widget are probably active. – Oli Jan 25 '18 at 21:09
  • @Oli I stand corrected, for some models at least, the viewfinder displays in my Pentax don't come on until I ask them to with a half press, having anything in there on when the camera is off seems a very strange design, as you say, presumably very low power draw. Equally however, the guide lines on my camera are drawn onto the (interchangeable) viewfinder screen, I have no reason to activate the display unless I need metering or AF – Joseph Rogers Jan 25 '18 at 22:36
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The main reason is because the batteries for MILCs are almost universally smaller than DSLR batteries.

Some mirrorless batteries:

  • The LP-E17 battery for the Canon EOS M5 has a 1050 mAh (milliamp-hour) charge storage.
  • The NP-FW50 for the Sony a7R II has 1020 mAh.

DSLR batteries:

  • Nikon's EN-EL15 battery (for D500, D600, D610, D7000, D7100, D750, D800, D800E, D810, and Nikon 1 V1 cameras) has 1950 mAh.
  • Canon's LP-E6N battery (for EOS 7D Mark II, 7D, 5D Mark II, 5D Mark III, 5D Mark IV, 5DS, 5DS R, 60D, 60Da, 70D, 6D, and 6D Mark II cameras) has 1865 mAh.

So really, the question becomes, "why are DSLR batteries about twice the capacity of mirrorless camera batteries?"

The answer there probably simply has to do with size of the camera body (you can't make a 1900 mAh battery any smaller, so it won't fit into the the smaller grip of the mirrorless camera).

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    That doesn't really answer the question though, as it would incorrectly imply that a mirrorless with a larger battery would last longer. However it isn't likely that it will outlast a DSLR. As to energy usage: a Canon G7 X battery is rated for something like 230 images on one charge - I managed to get over 500 images out of it on one day. How? - Quickly taking photos, using Eco mode to not waste energy on the screen and basically not waste energy looking at images/the screen. LCD screens are a huge waste of power.... – DetlevCM Jan 13 '18 at 9:39
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    ...which makes me think back to the 5D MK II: The difference between the rated number of photos with and without Live View is huge too, on the same battery. Add to that, besides running the LCD, you also need to keep the sensor powered, the image processing... - And all of that needs power, a lot of it. – DetlevCM Jan 13 '18 at 9:40
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    @DetlevCM Actually, it answers the question perfectly. The asker says they always use live view on their DSLR, so they're effectively using the DSLR as a mirrorless camera. Of course, the points you make are all correct and answer the question of why DSLRs get better battery life in general. – David Richerby Jan 13 '18 at 13:55
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    @DetlevCM - The biggest difference is that quoted battery-life includes 50% flash use. Not using the flash makes a huge difference to get above quoted battery-life (unless you have one of those cameras without a built-in flash which makes their numbers really really high). – Itai Jan 13 '18 at 14:56
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A mirrorless camera consumes more power mostly because the circuitry is constantly running. Both the sensor and EVF or LCD have to be powered continuously in order to maintain the Live-View which is necessary for framing.

In contrast, a DSLR can even be used to frame while powered off. The viewfinder requires no power at all and the status line below the view is made of segmented displays which consume virtually no power. An EVF on the other hand with millions of pixels requires much more power to operate and refresh at a sufficiently high rate.

For the EVF or LCD to be fed, the sensor which is essentially a fairly large chip must be also read at a sufficient rate. This is highly power consuming. The sensor on a DSLR on the other hand only needs to be powered to read the exposure off of it.

ADDENDUM

When you use Live-View on a DSLR, it essentially becomes a large mirrorless, keeping the sensor on constantly and refreshing the LCD screen. Even though, mirrorless are optimized for this case (many DSLR will turn off Live-View after a few minutes or when the sensor reaches a certain temperature), it is often the case that a mirrorless uses a smaller less power battery. This means you will likely suffer even more from battery-life with a mirrorless than with your DSLR.

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