[Leica] Digital questions . . . .

[grduprey at mchsi.com (grduprey@mchsi.com)]

Alastair,

While I am unfortunately not able to procure a DMR, I do have the Nikon 
D200.  I use the 2GB cards for it, and they do very nicely for me.  If you 
shoot medium ammounts of photos per outing, I would get a couple of them.  
If you plan on shooting tons of photos on a trip, then maybe the 4GB cards 
will be the better choice.  I would just buy one if the cost is not too bad, 
and see if the 4GB card suits your needs.  The 2GB cards are priced pretty 
low these days.

Gene


-------------- Original message from "Alastair Firkin" 
<firkin@ncable.net.au>: -------------- 


> Great explanation: should I therefore NOT buy 4 gb sd cards for the DMR? I 
> believe the firmware is updated to allow this, but has anyone had 
> experience? 
> 
> > The major and meaningful size-problem barrier is at 2GB. 
> > This is because the computer chips inside cameras deal in 
> > 32-bit chunks of information. The 32 bits hold numbers in binary, 
> > and each binary bit doubles the size of the number that it can 
> > hold. 1,2,4,8,16,32,64,128,256,512, and so forth. 
> > 
> > If you start with a 1 and double it 31 times, you get the number 
> > 2,147,483,648 which is 2 giga. 
> > 
> > 2,147,483,647 is the largest number that you can represent in a 
> > 32-bit system without special tricks. The reason you can't double 
> > again to get 4 gig -- 4,294,967,296 -- is that that last bit is 
> > needed to indicate negative numbers. On a regular 32-bit computer 
> > if you take the number 2,147,483,647 and add 1 to it, the answer 
> > will be -2,147,483,648 instead of +2,147,483,648. Bad mojo. 
> > 
> > So if you're going to build a digital system that deals with 
> > /anything/ bigger than 2GB, it needs to be patiently constructed to 
> > use two 32-bit data items to stand for a single number. This is 
> > tedious, error-prone, and slow, so deadline-wracked engineers don't 
> > do it until they have to, and they usually get it wrong the first 
> > couple of times. 
> > 
> > The next size bomb lurking in digital systems is 140 gig, which 
> > is the limit with a 48-bit system. Most computers built before 
> > aboutg 2000 or 2001 can't use hard drives bigger than 140 gig. 
> > 
> > 64-bit systems can deal with numbers up to 9,223,372,036,854,775,807 
> > which is higher than I can count and certainly bigger than any 
> > storage device that's going to be made in my lifetime. So there's 
> > no need when building digital controllers to use more than two 32-bit 
> > items to store one number. This means there won't be a repeat of 
> > the 2GB problem at 4GB or 8GB or 16GB or whatever. If you can deal 
> > with something bigger than 2GB, then you can deal with pretty much 
> > anything. 
> > 
> > 
> > _______________________________________________ 
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> > 
> 
> 
> 
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