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I've a Sony DSC-F828 and when I shoot in raw it takes a lot of time to write to the card. Is this only because the file has much more data? Will connecting the camera to a PC reduce the time it takes to write one photo to disk? Or using a buffer?

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There are three factors that determine how long it takes to save a photo to the memory card:

  1. The time it takes to compress the data into a file.
  2. The size of file.
  3. The I/O speed.

The time to compress to JPEG and to compress to RAW should be roughly the same, and it's the smaller part of the process, so it's the file size and I/O speed that are the main factors for the time to save the photo.

An USB connection is generally slower than the memory card, so it's not likely that downloading directly to a PC would be faster.

One thing that could speed up the process would be to get a faster memory card, but that would depend on whether the camera could actually make any use of the faster card. Different cameras and different memory cards gives varying performance, so you would look for testemonials of what other users of your exact camera model experience with different memory cards.

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  • \$\begingroup\$ Thanks a lot, very useful! But are Raw data compressed? I thought that raw data are the sensor's data as they are,I'm wrong? \$\endgroup\$
    – G M
    Commented Jul 13, 2013 at 20:06
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    \$\begingroup\$ @GM: How the raw data is stored depends on the camera, as there are a lot of different RAW formats. Often there is a lossless compression applied to the raw data, which about halves the file size. You can easily determine by the file sizes whether the RAW files are compressed, as the file sizes would always be exactly the same if they are not compressed. \$\endgroup\$
    – Guffa
    Commented Jul 13, 2013 at 20:13
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RAW files contain more data than JPEGs so saving/moving the files takes more time. The RAW and JPEG files should be the same resolution, but per pixel there is more data.

Connecting to a PC isn't going to make it take less time; it may actually take longer because the speed of writing to the SD or CF card is probably faster than the USB connection to the PC.

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This F828 is a very old camera and at the time these were limited in I/O bandwidth to the memory card, so the larger file-size causes very long access time. You will notice that if you set your camera to output TIFF, which also produces large files, it takes about the same amount of time.

Of course, even then, there were cameras which shot RAW faster but they cost much more because they has much faster processors and bandwidth to the memory card. As with product design, part of limitations is dictated by the desired feature set and target price.

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