I have a Panasonic DMC-TZ5 which, per the manufacturer’s documentation, set to maximum resolution (~9MP) and maximum .jpg quality can store about 860 photos on a 4GB SD card (and which the in-camera display showing the number of available shots left on an empty card basically confirms).
I was looking at the documentation for a Canon G12, which states it can store about 1471 images of ~10MP at its highest .jpg quality setting size on a 4GB card.
Why the large discrepancy, with the Canon able to store 70%+ more images of slightly larger size on the same sized card? Does it just come down the the amount of .jpg compression applied?
The difference in the amount of compression is the most likely reason. My Sony NEX-3 claims 618 fine compression images at 14 meg on a 4 gig card.
Compare the number of RAW or TIFF format images that can be stored on the card. These are uncompressed and should be a closer number.
I don’t know if there’s a standard image used for the number of images available. For example an image with a lot of clear blue sky will compress much better than a “busy” image filled with detail.
There are myriad factors involved, not the least of which is the actual size of the sensor that those millions of pixels are sitting on. Not every 10MP P&S camera has the same size sensor; the OP’s Panasonic DMC-TZ5 has a 9MP sensor that measures 6.16mm x 4.62mm, the Canon G12 at 10MP sports a larger, 7.6mm x 5.7mm sensor.
Factor this in, along with vastly different processors, and the fact that even uncompressed files will vary in size depending on the amount of detail in the scene, and it’s easy to understand the difference in amounts.
Besides, anyone who carries 800 or 1400 images on a single card isn’t doing themselves any favors.
I’m wondering what the sensor size has to do with the file size for an image of a given number of pixels?
For example the specs for a Canon 40D, with a much larger APS-C sensor than either of the above, claims 1096 pics of ~10MB on a 4GB card - somewhere between the two.
(I understand that real world file sizes vary depending on subject matter etc., the pros and cons of raw vs jpg, the risk of card failure, etc., but am just curious about what could account for the large difference in theoretical number of files per GB claimed by the manufacturers for the different cameras, other than the typical amount of jpg compression applied).
I don’t think so. UNcompressed files represent the RGB values of each dot as a number. A dot doesn’t know if it is unique or the same as every other dot around it. To store 10 8-bit values takes 10 bytes every time.
It’s only if compression is applied that the data size varies, and only if lossy compression is applied can it vary greatly.
Uh, yes, but two sensors of identical pixel count with different physical sizes will still record the same amount of data per photo (uncompressed), and given identical compression algorithms, will generate the same compressed size per photo on average. The number of pixels, not the size of the sensor, determines the digital size of the image.
Uncompressed files will not vary in size based on detail. Losslessly compressed ones might, but generally that’s not an option found in cameras.
The correct answer to the OP’s question is simply: ‘varying compression.’