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08-28-2015, 03:32 AM   #1
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Where does the camera store the "latest" file number?

I thought maybe it looks at (in my case the K3) both SD cards and picks out the last filename, but that would fail if you put in two fresh cards. So it must save each filename in an EEPROM, or maybe a battery backed up RAM (dodgy... does the K3 even have an internal battery for memory backup?)

08-28-2015, 04:18 AM   #2
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I thought that most most of, not all Pentax DSLR's used a capacitor to power the memory when the battery is dead or out of the camera. As to the file number I don't know the answer to that one. I don't remember the last time I referenced a file number . But If I remember correctly on my DL the file number changed with the card . But my memory may be faulty on that issue.
08-28-2015, 05:26 AM   #3
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must be a type of memory not dependent on the battery. i've seen pictures for a battery inside the k-01, i would assume it's in the k3. my guess is that the battery is for a clock/calendar, not the filename. if i don't use the k01 for a while and the lithium battery is removed, it'll ask me to reset the time and date.
08-28-2015, 06:14 AM   #4
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The clock must be battery backed up, though a capacitor could be used. A state of the art real time clock chip draws about 300nA so you can work out how long a capacitor would last: probably less time than it takes to recharge the main battery.

08-28-2015, 07:41 AM   #5
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Most likely the info is stored in a non-volatile form of memory called eeprom aka e2prom. A similar type of semiconductor technology is used in solid state hard drives. Data is kept without power to the device.

Last edited by Bman; 08-28-2015 at 07:48 AM.
08-28-2015, 04:05 PM   #6
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File number wise, somehow my K5IIS picked up right where my K10D left off? Must be in the SD cards.
08-28-2015, 05:49 PM   #7
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On my K10D if there is already a numbered folder (file number set to date) it will increment the folder number to create a new if the date changes. Otherwise it starts with 100_date. So if there was a 321_date1 then the new folder would be 322_date2.

Actual file number is probably stored in a non-volatile memory buffer. When you turn on the camera it may check to see what the highest number file is on the card and update the NVM buffer accordingly.

Another possiblity is the number is based on the shutter count but if it maintains counts between bodies most likely the above scenario.
08-30-2015, 09:07 AM   #8
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QuoteOriginally posted by Douflytoo Quote
File number wise, somehow my K5IIS picked up right where my K10D left off? Must be in the SD cards.
It will count, unless there are files on the SD card. Then it will orient itself on that and use that number as the basis.

08-30-2015, 11:24 PM   #9
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This is written in the manual for my Sony_NEX_3N:
..This camera has an internal rechargeable battery for maintaining the date and time and other settings regardless of whether the power is on or off, or the battery is installed or not. This rechargeable battery is continually charged as long as you are using the camera. However, if you use the camera for only short periods, it gradually discharges. If you do not use the camera at all for about three months it becomes completely discharged. In this case, be sure to charge this rechargeable battery before using the camera.

However, even if this rechargeable battery is not charged, you can still use the camera as long as you do not record the date and time. If the camera resets to the default settings each time you charge the battery, the internal rechargeable battery may be dead. Consult your Sony dealer or local authorized Sony service facility.

Charging method of the internal rechargeable battery
Insert a charged battery pack into the camera, or connect the camera to a wall outlet (wall socket) using the AC Adaptor (supplied), and leave the camera for 24 hours or more with the power off.
...
Most probably this is the standard also for Pentax - at least for the "older" models. A small internal battery for supplying power to a similar internal EEPROM memory to keep the file number, time / date and all the other individual settings. This has been / is standard for many kinds of similar hardware. Occationally I read this from the Sony manual a few days ago and recharged the NEX_3N for 24 hours - to avoid it to become completely discharged because of minimal use for the last months. Perhaps this is something I should remember to do occationally with my second Pentax camera (K10d) as well.

Or has this, for the latest models, been replaced by a a non-volatile form of memory?

Last edited by Dabola; 08-31-2015 at 02:17 AM.
09-01-2015, 08:35 AM   #10
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A clock chip must have a battery. There is no way to make a clock otherwise. It can be a large capacitor but they tend to not last for more than a few days.

The storage of the "last image number" etc does not need a battery. It can be held in an EEPROM.
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