Pixels to inches with digital photos

[EAA Docent]

Does anyone know if there is a way to convert pixels to inches using a
digital camera?
What I am trying to say is, i have as an example a photo that is 286 KB with
a 300 dpi resolution and 2921x2100 pixels.

Some one E-maild a picture as an attachment that was 2.01mb, 180 dpi
resolution and 3264x2448 pixels.

I am trying to understand why their picture 2.01 mb and when I take pictures
I never get over 600kb.

I hope I made some sence out of what I am trying to ask. I am new to
digital cameras and just a casual PC user.

 

[Mark L. Ferguson]

a 'dot' and a 'pixel' are the same thing, and 'DPI' is 'dots per inch' so
your '300 dpi resolution and 2921x2100 pixels'

is an '8 by 10' inch pic.

Their '180 dpi and 3264x2448 pixels' is "3264 divided by 180 " by "2448
divided by 180"

or about '16 by 20' inches

The "286 KB" and the "2.0 MB" are setting made within the camera options,
and usually also determine the DPI and pixel ratio. This is usually referred
to as how many 'megapixels' it takes for one pic.

3264 X 2448 = 7990272 (about 8 megapixels) = 2.0 MB file size
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[Adam Albright]

Does anyone know if there is a way to convert pixels to inches using a
digital camera?
What I am trying to say is, i have as an example a photo that is 286 KB with
a 300 dpi resolution and 2921x2100 pixels.

Some one E-maild a picture as an attachment that was 2.01mb, 180 dpi
resolution and 3264x2448 pixels.

I am trying to understand why their picture 2.01 mb and when I take pictures
I never get over 600kb.

I hope I made some sence out of what I am trying to ask. I am new to
digital cameras and just a casual PC user.

Pixels can be a confusing topic. Many confuse DPI (dots per inch, LP1
(lines per inch), PPI (Pixels per inch) and the color depth or how
many bits make up an image. The last has the most effect on how large
the file will be in MB's or KB's, but is separate that the image's
dimensions. The following should help your understanding.

http://www.michaelfurtman.com/pixels.htm

http://www.hp.com/united-states/con...take_better_photos/tips/photo-resolution.html

http://en.wikipedia.org/wiki/Color_depth

http://en.wikipedia.org/wiki/Color_space

If that isn't confusing enough color space also comes into play
depending on what medium we're talking about. Computers use RGB color
space where that universe is composed of values assigned each of the
three primary colors, Red, Green and Blue while hard copies such as
what you see on a hard copy generated from a printer or your camera is
based on CMYK or inks which have a different color space.

 

[ray]

Does anyone know if there is a way to convert pixels to inches using a
digital camera?
What I am trying to say is, i have as an example a photo that is 286 KB
with a 300 dpi resolution and 2921x2100 pixels.

equals 9.74 inches by 7 inches

Some one E-maild a picture as an attachment that was 2.01mb, 180 dpi
resolution and 3264x2448 pixels.

equals 10.88 inches by 8.16 inches.

I am trying to understand why their picture 2.01 mb and when I take
pictures I never get over 600kb.

I hope I made some sence out of what I am trying to ask. I am new to
digital cameras and just a casual PC user.

Yours gives 2921x2100 = 6mp (roughly)
theirs gives 3264x2448 = 8 mp (roughly).

The difference is most likely due to the difference in the level of jpeg
compression on the two photos, though they do have 1/3 more data. BTW -
this question has nothing to do with MS or vista, and would be more
appropriate in, say, alt.photography or rec.photo.digital.

 

[EAA Docent]

Thanks Mark!

Now at least I have a reasonable understanding.