Verify my math computing capacity in a CF card
/forum/topic/1141459/0



redbarn
Registered: Mar 20, 2011
Total Posts: 136
Country: United States

I would like to get a confirmation or verification in trying to figuring out how many images can an 8G Sandisk 30/mb would hold.

I shoot only RAW no JPEG I am using a 40D body, shooting mostly day shots, and try to staying within 100-200 ISO. The average file size is about 12mg.

1G = 1,000mg < > 1000 / 12.50 = 80 images x 8G = 640 images

Is this about right????



Monito
Registered: Jan 28, 2005
Total Posts: 10097
Country: Canada

mg is a British sports car. Perhaps you mean MB (MegaByte).

Assuming you mean 8 GB (GigaByte) by "8G", that is 8,000 MB. Divide that by 12.5 MB per image and you get 640 images as an estimate.

Image file size depends on detail. A shot of sky will be much smaller than a distant shot of a mass of vegetation.



redbarn
Registered: Mar 20, 2011
Total Posts: 136
Country: United States

Absolutely MG a great sports car . I'm sorry for the mix up

Oh your math gave me more storage than my own computation

Yes. I'm aware that the size of the file can change to several
factors ,ie., ISO, details from the subject, etc. I was just trying to
get an idea how many shots I could shoot with the mem card
I'm taking



Monito
Registered: Jan 28, 2005
Total Posts: 10097
Country: Canada

redbarn wrote: Oh your math gave me more storage than my own computation

Funny, I thought 640 = 640.

redbarn wrote: 1G = 1,000mg < > 1000 / 12.50 = 80 images x 8G = 640 images

Monito wrote: 8 GB (GigaByte) by "8G", that is 8,000 MB. Divide that by 12.5 MB per image and you get 640 images as an estimate.



redbarn
Registered: Mar 20, 2011
Total Posts: 136
Country: United States

Monito

Lol I had forgotten my own math
Yes you had confirmed and agreed with my
math but look what Sandisk told me
Incredible



Monito
Registered: Jan 28, 2005
Total Posts: 10097
Country: Canada

redbarn wrote: look what Sandisk told me

I have no idea what Sandisk told you. It hasn't been stated in this thread. What did Sandisk tell you?



redbarn
Registered: Mar 20, 2011
Total Posts: 136
Country: United States

This is what Sandisk told me I presented the same question as I did on this forum

Thanks for emailing SanDisk Technical Support. It is our goal to make sure you have all the resources you need to get the most from your product.

I am sorry you feel this way sir. As in the previous email you received the link answers your question, I thought my reply was adequate.

As it stated in the link I sent you, the number of Raw files on a 8GB card with your Canos EOS 40D which shoots 10.1 mega pixels are 228

Does this answer your question?



DTOB
Registered: Oct 07, 2010
Total Posts: 1359
Country: Canada

To confuse matters, 8gb cards are not actually 8gb cards, in that you do not actually get 8192MB worth of space.

It works out to be closer to 7.6gb, because 1gb is not 1000mb, but in fact 1024mb and 1mb is not 1000kb, but rather 1024kb.

On top of that, once you format the card, the camera might have some space reserved for god knows what. Usable space will likely be around 7.4-7.6gb.

Ever notice that that 1tb hard drive you just installed actually only gives you around 930gb of actual storage? There is a reason for that...



mdude85
Registered: Apr 12, 2004
Total Posts: 4402
Country: United States

The math is pretty simple:

8000 megabytes per card / 12 megabytes per photo = 666 photos per card

As noted by the above poster, an 8GB card has theoretical capacity of 8,192 MB (about 682 photos per card) but sometimes space has been allocated or is not otherwise writeable. So 8000 megabytes makes a decent estimate.

Also... why is this in the Pro Digital Forum? There is a forum specifically for CF cards called "General Gear Talk". http://www.fredmiranda.com/forum/board/54



DTOB
Registered: Oct 07, 2010
Total Posts: 1359
Country: Canada

mdude85 wrote:
The math is pretty simple:

8000 megabytes per card / 12 megabytes per photo = 666 photos per card

As noted by the above poster, an 8GB card has theoretical capacity of 8,192 MB (about 682 photos per card) but sometimes space has been allocated or is not otherwise writeable. So 8000 megabytes makes a decent estimate.


Actually it is the other way around.

A card that is advertised as 8gb actually has 8.000.000.000 bytes. For "simplicity", the manufacturers devide this number by 1000 three times, but in actual fact, they should be deviding by 1024.

SO:

8000000000 bytes / 1024 = 7812500 Kilo bytes
7812500 Kilo bytes / 1024 = 7629.39 Mega bytes
7629.39 Mega bytes / 1024 = 7.45 Giga bytes

Clear as mud I know, and my 'in head' calculation of 7.6gb is also wrong. A card advertised as 8gb will only give 7629.39mb, or 7.45gb of actual storage, minus of course any space that is used up by the cameras file system.



mdude85
Registered: Apr 12, 2004
Total Posts: 4402
Country: United States

Thanks! I did not know that they basically "round up".

Either way, if you want to know the approximate number of photos your card can handle, just divide the total capacity by the size of the photo. Voila!