Canon EF: weak batteries and meter reading

<p>I was using this camera recently (only for the second time or so!) and realized when I was into half the film that its battery was dead. Shutter, of course, worked (it is mechanical from 1/2 s to 1/1000 s). The meter also appeared to be working. I was not using the lens in auto aperture mode (for which the battery is required).</p>

<p>When I realized the batteries were weak, I changed them and continue shooting, while recalling that the camera eats batteries while ON. So I was then careful to switch it ON only during the metering and shooting instance, and to switch it off immediately afterwords.</p>

<p>My questions is, in the weak battery situation I described above, how reliable is the meter reading?</p>

<p>Thanks.</p>

 

<p>HS - I have 3 EFs, and you're right, they eat batteries. Luckily they can take the 1.5v button cell because of internal bridging circuitry. Having said that, I have found that if the batteries are dead/low, the meter will not function at all. Thus, if the needle is moving I would surmise that you had accurate readings.</p>

<p>Aha! Thanks for the confirmation.</p>

<p>As I mentioned earlier, I was not using the auto-aperture mode, so the batteries were not that critical, as long as the meter worked I was happy.</p>

<p>I have given the film for processing and will pick it up in a day or two. I will know then how it went, more or less. I will have to wait till I scan it during this weekend to know for sure.</p>

<p>Regards.</p>

<p> </p>

<p>The batteries in my EF last for about a year if I only use them when actually shooting. If you leave new batteries turned on in about 4 days they will be worthless. </p>

<p>Think of the EF like a flashlite and you will be fine.</p>

<p>I have two EFs.<br>

In August 2009 I fitted two new silver oxide batteries to each of them.<br>

After six months they had only had taken a couple of films each and were switched off when not in use. However while the batteries in one of them were OK (and are still OK) the batteries in the other were not working. When I checked the non-working batteries one was low but the other was OK.<br>

Given that there are two or three different EF circuits, does one use up batteries faster than the other and if so does it use up one battery rather than the other or is there something wrong with one of my EFs?</p>

<p>Interesting question, Richard. I have also found that my different EFs eat batteries at different rates. I read elsewhere that one battery controls the slow speeds of the shutter (below 1/2 s) and the other controls the meter. But my experience is that they are not independent and both batteries must be viable for the meter to function at all. Given that the EF takes the 1.5v button cell (I can pick thenm up for 5/$1 at my local dollar-store) I don't really worry about the battery drain issue too much.</p>

<p> </p>

<p>Capita Q, as far as I know, the two batteries are in series (the camera works on 3 volts, with two 1.5 V batteries). So I don't think each powers a separate circuit.</p>

<p>How do I know which circuit version my Canon EF has?</p>

<p> </p>

<p>HS, I know for a fact that the two batteries are used for different functions except the battery check would check the total voltage for 2.5V or higher. That's why one battery may be eaten more than the other.</p>

<p>Another interesting fact is that in one of my EFs, the two battery compartments are shorted and I need only one battery for the camera to function normally, only except the battery check light will never be on (metering and low speeds are fine)</p>

<p>Here is some more info.</p>

<p>If I use the depleted batteries (as reported by the battery check function), I get good metering (comparable to metering with good batteries) and I get slower speeds as well. But the battery check function does not make the LED glow and thus reports dead batteries. A voltmeter reads 1.45 V on both batteries under no load conditions.</p>

<p>With good batteries, the LED flashes rapidly during battery check function, metering works and slower speeds all work (as expected).</p>

<p>John, I tried using one battery at a time. Nothing works in the camera; meter LED is off, slowest speed is 1/2 s (the slowest mechanical speed). So I am not sure if both batteries are used separately. I recall reading a hand written note in Canon EF's service manual that the two batteries were in series. I could be mistaken, of course. Could you tell me how you know each powers a separate circuit.</p>

<p> </p>

<p>The EF service manual has the circuit diagrams in it. <br>

It is downloadable from several sites on the net including this one: <a href="http://camera-care.com/repair_manuals.htm">http://cameracare.com/repair_manuals.htm</a></p>

<p>Richard, I checked the service manual. Yes, the two batteries do power parts of the circuit. For example, the CAT system appears to be work on one of the batteries.</p>

<p>Thank you, and also John, for pointing out this interesting fact.</p>

<p>Regards.</p>

<p> </p>

<p>I think I didn't clarify this fully. The circuit for the CAT system is the part that takes power from one of the batteries. Rest of the circuit uses both the batteries in series (so 2 * 1.35 V or so).</p>

<p>Thus as long as the CAT-Normal switch is on Normal, the camera system is working on two batteries in series. In CAT mode, if I understand this right, the "Normal" camera system still works on two batteries in series and only the CAT part works on one of the batteries.</p>

<p> </p>

<p>Hey Everyone - I was just given an EF body and The meter does not seem to work, nor the speeds below 1/2 second. Could you guys recommend someone who still works on these?</p>

<p>Thanks!</p>

<p>Aris, your battery is more than likely dead. As the camera needs the battery to function the light meter and shutter speeds below 1/2s this is more than likely the reasoning. The batteries are very easy to come by and can be picked up from any standard electronics store. Best Buy or even Radio Shack or something should be fine.</p>

<p>hope this helps,</p>

<p>Josh</p>

My latest EF purchase (my third - the first was an expendable alternative to my T90 for a trip back in '94) is showing weird metering behaviour. It seems to be working as ISO 200 when set to ISO 12... I suspect it may be that the batteries are drained - Does this sound feasible?

OK, answered it myself, by default. I was using some old Wein cells and they do say it takes 30 mins to get up to speed which is clearly correct as the meter and long shutter speeds now work properly.

 

Now time to get some film and go for a work-out with this chunk of heavy metal.

Edited August 25, 2019 by barryreid