580 vs 550 power drain ?

[Rob612]

I got today, for a fair good price, a new 550 EX that I was planning to use for shooting small objects with my macro lens and a double flash bracket with the 580+remote shoe on one side (master) and the 550 (slave) on the other.

Everything works fine, albeit I still have to learn how to use correctly such a setup, but I noticed that the battery drain (same batteries, charged the same day) of the 580 is MUCH less of the 550. As a rough indication, after having completely discharged the batteries on the 550, I went with another ~50 shots with the 580 and that unit still has some batteries to go.

Now I am recharging all the battery sets to make some more tests tomorrow, but in the meantime I wondered if anybody else here has notice such a difference in battery usage.

A possibility is that being the 550 the slave it stays on "listening" and so burns more batteries ? Tomorrow I will try also to reverse things and use the 550 as a Master and the 580 as a Slave.

Thanks

[robertwgross]

"Same batteries, charged the same day" does not mean that they are the same.

Try some meter measurements to see if some of the batteries are better than the others.

Ideally, you will get best results with one set of four batteries if they are matched for output. If you have three good ones and one bad one in a set of four, it will make the set look kind of bad.

---Bob Gross---

[Rob612]

Well, they were all brand new (2500 Ma NI-MH) so I did not tried them. Will do it.

[Marty_Oz]

I read an article on dpreview about the power consumption of the 550ex and 580ex. I cant find the article now, but the article basically gave the following explanation.
The 580ex flash is aware of the sensor size for the digital camera you are using. Therefore as the 20D is not a full frame sensor, when you use the flash it will only output enough flash to cover the subject area it has calculated for that sensor.
In the case of the 550ex this flash is not aware of different sensor sizes. So it will output the full amount of flash to cover the subject it calculates from the lens.
So the 580ex uses less power and the batteries will last longer.
This will also help in the refresh rate.
Hope this makes sense and it helps.

[Rob612]

This makes sense to me. I will do some test in the afternoon, but I'll go to search the article right now. Thanks.

[djtowle]

I believe I have read in several places that the 580 is more efficent then the 550 flash. This could be from a variety of reasons: the new sensor aware zoom feature, new electronics, more effiecent flash tube, more battery freindly power supply, etc. A comparison of battery life on flashes used in a group as you have done may not be accurate as not all flashes will be firing at the same lvl. When I am using my (3) 550's spread out in a room, often one is firing at full power while the others are barely ticking.

Note: if your Ni-MH batteries are 'brand' new, I have read they take several charge/discharge cycles to reach their full capacity. I number & date my rechargeables in 4-battery sets, ie: set 1, set 2 etc. and use/charge them together, one old battery with 3 new batterys can seriously degrade your performance.

I believe it was at greenbattery.com I found some useful info on batteries once upon a time.

[Rob612]

Hmmmm... that sounds reasonable. I'll do the same with my batteries. split the in 4 pieces sets (I have 16 batteries in total) and use/charge as whole sets. But you're right, chances are that the set that was in the 550 was too new and on its first or second charge. And I have to try the duration with the 550 only (difficult, because I do not do too much flash pics, I use both flashes with a dual bracket basically for macro shoots, it adds weight to the whole thing if compared to a ringflash, but I tought that in this way at least I have two flashes that I can use for everything).

[tim]

The reason is the one that party posted - the 580EX is aware of the smaller sensor size in the 20D, and doesn't light up as much area. Less light = less power = longer battery life. If you use a diffuser you lose this advantage.