From: "Shel Belinkoff" <[EMAIL PROTECTED]>
There were some messages a while back about the battery charge warning
indicator on the istDS. Didn't have the camera then so I didn't pay much
attention.
Earlier today I noticed the indicator was at half. Turned off the camera
for a while as I wasn't snapping any pix, about 1/2 hour later turned the
camera on again, indicator was at full. After a few snaps it was at 1/2
again.
Does this behavior suggest that it's time to replace the bats, or
something
else.
Unfortunately the battery indicator on the camera only measures voltage, not
actual capacity. Although we like to think that it is showing us how much
charge is left it is really only measuring voltage - which gives a clue as
to the amount of charge remaining, but not a very good clue unless you
understand what is happening.
When the battery is fully charged and under no load it produces maximum
voltage.
As you draw current from the battery the voltage drops. The voltage of even
a fully charged battery drops significantly if you draw a heavy current (the
more current you draw the more the voltage drops). Once you stop drawing
current the voltage of the battery recovers and eventually reaches it's
maximum voltage again. This new maximum will be a little below the original
maximum because we have used some of the batteries capacity, but the
temporary voltage drop when current is drawn is much greater than the
voltage difference between old maximum and new maximum.
The battery indicator shows 'full', 'half charged' and flashing i.e. 'nearly
empty' (this is onthe D but I guess the DS is similar). Unfortunately the
battery voltage doesn't change much until the battery is pretty much
depleted and 'half charged' usually means about three quarters used. The
voltage sensor is really dumb and doesn't know the difference between
battery types so half charged may actually mean half charged, 75% depleted
or 90% depleted depending on battery type.
Do you remember the MX metering? It shows exposure at 1/2 stop resolution.
However you actually get a 'dim glow' from adjacent indicators as the meter
reading moves off the exact value indicated and hence you actually get a
reading to 1/4 stop or thereabouts (maybe better). Think of the change in
battery indicator as being like this. When the batteries are fully charged
they stay as 'full' all the time. As they get flatter they go from 'full' to
'half' when used heavily, then back to 'full'. Later they go to 'half' with
light use and back. Then Stay at 'half' without going back to 'full'. Then
stay at 'half' but drop to 'flashing' under load etc. At least I think etc.
I have never run mine that low.
Does this matter at all? No, or at least not to me. I just recharge my
NimHs before going out shooting for the day, or in the car on the way if I
have forgotten. Battery life is never an issue for me and I have only seen
the battery indicator go down at all when on vacations and unable to charge
the batteries too easily. I'm probably going to regret saying this, but I
don't even carry a spare set of batteries now, always used too but stopped
the practice as redundant weight about a year ago.
In fact if anyone here shoots portrait a lot and/or wants some battery
capacity for the D I have one of the battery grip thingies that I got along
with my replacement body and will probably never use. I got this camera and
battery grip off ebay so even though I have never used it it will have seen
some (I believe fairly light) use. A nice lens in exchange is always
preferable to money :-)
Rob.
