File Size Question

OK - this may be a much asked/answered question - but I searched and
couldn't find an answer.

I just went from a pocket digicam to a Nikon D40x - and if I am taking
pictures at the highest resolution setting - what size files should I
expect. (Note - not trying to start a flame war, but I am shooting in
jpg mode by choice.)

Over a couple hundred shots I see file sizes ranging from 3.0 to 5.0
MP. Does that seem right? I expected to see larger file sizes.

Thanks in advance.

Tom - Chicago wrote:

> I just went from a pocket digicam to a Nikon D40x - and if I am taking
> pictures at the highest resolution setting - what size files should I
> expect. (Note - not trying to start a flame war, but I am shooting in
> jpg mode by choice.)
>
> Over a couple hundred shots I see file sizes ranging from 3.0 to 5.0
> MP. Does that seem right? I expected to see larger file sizes.
>
3.0 to 5.0 Megabytes (MB) sounds about right for fine quality (low
compression) JPEG files from a 10 Megapixel (MP) camera such as the D40x,
depending on the level of detail in the scene.

"Tom - Chicago" <tob323@gmail.com> skrev i en meddelelse
news:1178313188.263468.224980@h2g2000hsg.googlegro ups.com...
> OK - this may be a much asked/answered question - but I searched and
> couldn't find an answer.
>
> I just went from a pocket digicam to a Nikon D40x - and if I am taking
> pictures at the highest resolution setting - what size files should I
> expect. (Note - not trying to start a flame war, but I am shooting in
> jpg mode by choice.)

I have a D200 and the size off the files in best jpg resolution is about 4
MB, so i think it´s ok

Ole

Tom - Chicago wrote:

> OK - this may be a much asked/answered question - but I searched and
> couldn't find an answer.
>
> I just went from a pocket digicam to a Nikon D40x - and if I am taking
> pictures at the highest resolution setting - what size files should I
> expect. (Note - not trying to start a flame war, but I am shooting in
> jpg mode by choice.)
>
> Over a couple hundred shots I see file sizes ranging from 3.0 to 5.0
> MP. Does that seem right? I expected to see larger file sizes.


In 8 bit JPEG format, it takes 3 bytes to represent one pixel. So
your 10 Megapixel camera makes IMAGES that are around 30 Megabytes.

JPEG uses highly efficient lossey compression. When your 30 Megabyte
IMAGES are stored as FILES, the 30 Megabytes gets squeezed down to
3 - 5 Megabytes. Images with high detail don't compress as well as
lower detail images, so they are bigger.

Your 3 MB FILES get uncompressed back to 30 Megabyte IMAGES when you
open them to view or edit. To prove this, open an image in your favourite
editor and then use 'save as' to save it in an uncompressed format like TIFF.
You'll see your images are really are 30 Megabytes.... It's the efficiency
of the JPEG compression that makes them as small as they are.

"Tom - Chicago" <tob323@gmail.com> wrote in message
news:1178313188.263468.224980@h2g2000hsg.googlegro ups.com...
> OK - this may be a much asked/answered question - but I searched and
> couldn't find an answer.
>
> I just went from a pocket digicam to a Nikon D40x - and if I am taking
> pictures at the highest resolution setting - what size files should I
> expect. (Note - not trying to start a flame war, but I am shooting in
> jpg mode by choice.)
>
> Over a couple hundred shots I see file sizes ranging from 3.0 to 5.0
> MP. Does that seem right? I expected to see larger file sizes.
>
> Thanks in advance.
>
Save the files as tiff. Then you should see really big file sizes.
Jim

In article <133nicmbmt4e16f@news.supernews.com>,
Jim Townsend <not@real.address> wrote:

> Tom - Chicago wrote:
>
> > OK - this may be a much asked/answered question - but I searched and
> > couldn't find an answer.
> >
> > I just went from a pocket digicam to a Nikon D40x - and if I am taking
> > pictures at the highest resolution setting - what size files should I
> > expect. (Note - not trying to start a flame war, but I am shooting in
> > jpg mode by choice.)
> >
> > Over a couple hundred shots I see file sizes ranging from 3.0 to 5.0
> > MP. Does that seem right? I expected to see larger file sizes.
>
>
> In 8 bit JPEG format, it takes 3 bytes to represent one pixel. So
> your 10 Megapixel camera makes IMAGES that are around 30 Megabytes.
>
> JPEG uses highly efficient lossey compression. When your 30 Megabyte
> IMAGES are stored as FILES, the 30 Megabytes gets squeezed down to
> 3 - 5 Megabytes. Images with high detail don't compress as well as
> lower detail images, so they are bigger.
>
> Your 3 MB FILES get uncompressed back to 30 Megabyte IMAGES when you
> open them to view or edit. To prove this, open an image in your favourite
> editor and then use 'save as' to save it in an uncompressed format like TIFF.
>
> You'll see your images are really are 30 Megabytes.... It's the efficiency
> of the JPEG compression that makes them as small as they are.

JPEG isn't 3 bytes per pixel. There's one byte of luminance per pixel
but the color saturation and color hue are almost always downsampled to
smaller bitmaps. Not needing 3 bytes per pixel is the first step of the
compression. The second step is converting the bitmaps to frequency
data and discarding frequencies that contribute little to the
appearance. The third step is simple loss-less compression.

Most RAW files aren't 3 bytes per pixel either. They're usually 12 bits
per pixel with each pixel corresponding to one of three colors. The
exact format depends on how the sensor is built. The RAW file goes
through simple loss-less compression.