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I bought a cheap toy camera to do lomography, the konica pop. I am trying it out now with an expired fp4 film to see what I get. I am curious though as to how I will know when the battery has run out. I suppose the flash won't charge. The 2 AA batteries feed the flash and adjust the aperture automatically. I guess that the flash, since it demands more power, will be the first to fail. My fear is that the flash will still show like its charged but the intensity of the light will be diminished as the battery runs out, resulting in my pictures being underexposed. Any ideas as to whether I am being paranoid?

Also, does anyone have experience with this camera and with the average life of the batteries?

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2 Answers 2

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The key thing here is that the flash isn't powered directly from the batteries. The strobe needs a burst of very high voltage — much more than that delivered by the batteries. So: the batteries charge a capacitor, and it's the capacitor discharge that makes the flash pulse.

This means that as the batteries drain, the flash pulse will still be basically the same, but the time to charge the capacitor between flashes will increase. So, your fear is basically nothing to worry about.

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Great! Thank you guys for those really useful comments! I'll let you know how it went... –  chango Oct 29 '12 at 14:01

Short:

If you put two new Alkaline AA batteries in the camera it should easily supply the flash well enough for one 24 or 36 exposure film. I would be extremely surprised if it didn't. Note - use Alkaline batteries - not "Heavy Duty" or whatever. Super high price exorbitant profit Lithium batteries are not needed. (If you have a vanishingly rare* optional 4 shot FP4 film pack you may be out of luck.)

  • Alkaline identification: FWIW - you can tell that an AA batery IS an Alkaline by measuring the new open circuit voltage. It should be 1.6V or more. Long shlef stored Alkalines MAY fall to nearer 1.55V but anything under 1.55V is not a new Alakline. Battery weigt should be 22.5+ grams. (About 0.8 Ounce)

Flashes cycle to full power and then light a "ready" indicator. The level of flash output is relatively constant regardless of battery state across much of the battery range. I have found that with the Sony 3600 flash the output definitely falls at the very tail end of battery life, "ready indicator" or no, but it's OK across 90% +.

Flash charging time is a good indicator of battery state. If you roughly measure the charging time with new batteries then as long as it does not increase by a factor of 2 to 3 times you are liable to be OK. The especially paranoid could take a number of flash shots with no film and time and plot the recycle times. {It's the sort of thing that I might do]. The downside is the wear on camera and flash on a bottom end toy may just possibly prove fatal if its well used. This is unlikely but worth mentioning.


Longer:

I sometimes use 4 x AA batteries in a guide number 56 flash. Under high use conditions my memory says that I get 100+ flashes. Energy use increases with the square of guide number soi, even allowing for probable variations in flash power supply efficincy, if you flash guide number was around 18 or less (and it may be much lower than that not be that high) then you'd get about (56/19)^2 guide numbers x 100 my flashes x 2/4 batteries ~~~~= 400+ flashes.

A random stranger here suggests guide number = 14.

This Konica C35 manual - which may or may not be directly equivalent, says

  • The guide number is 90 with ASA 80 to 125 for flash cubes and 45 for the MONICA Electronic Flash X-14.

How your flash relates to the X-14 is uncertain, but it gives an indication what Konica thought was useful. That may be feet rather than metres - which converts to a more sensible GN = 15.

A Sony NEX-7 internal flash has a GN of 6 metres ! That's for the camera with the finest still image quality of any APS-C camera, bar noneaccording to DPREVIEW so KM might be expected to have something somewhat lesss capable on the POP.

AA Alkaline batteries are cheap compared to the value of your time and expectations.

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Any reason to not recommend NiMH low-self-discharge (Eneloop) in this case? –  mattdm Oct 29 '12 at 13:11
    
Also, I know you know more about batteries than I do, but in my experience in many devices, the lithium non-rechargeables cost twice as much but last three times as long, making them a pretty good value.... –  mattdm Oct 29 '12 at 13:25
1  
@mattdm - Eneloop are great batteries, but more than what is needed here for a near 'throwaway' application. They would work well. A reputable brand of AA Alkaline batteries actually has more energy content than an AA Eneloop and a longer shelf life - but not vastly so, especially with the new version one (has a Crown logo) that have vastly extended the shelf life. The Eneloop is of course rechargeable and the Alkaline is not. –  Russell McMahon Oct 29 '12 at 16:07
    
@mattdm - Lithium batteries may last substantially longer in some applications and not in others. If I got 3 x as many flashes for 2x the dollar I'd be happy - but I usually buy a good brand of Alkalines in 40 packs at vastly below Lithium proices. I use NimH in my flashes usually and Alkalines when I'm going to want a very rapid swap over and no need to worry about losing the exxhausted cells. in very heavy use they come out of the flash so hot you can't handle them and finding a place that they can go in safely can lose a photo opportunity. –  Russell McMahon Oct 29 '12 at 16:10
    
Thanks Russell! –  mattdm Oct 29 '12 at 16:20

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