On Thu, 11 Apr 2013 19:56:08 -0400, nospam
wrote:

In article , Jennifer
Murphy wrote:

I think digital photography is beyond my mental capacities (sigh).

i think you're trying to make it more complicated than it needs to be.

It wouldn't be the first time...

I have several photos that were saved both as raw image files and as
jpgs. For many of them, the jpg file reports more pixels than the raw
image file. How can that be?

i don't know where you're getting the raw files but they're not
straight from the cameras. the numbers are wrong.

I have a couple of friends with cameras that are better than mine. I
asked them for the "raw" files and that's what I got.

also keep in mind that a jpeg can be resized to anything you want.

And once resized, the number of pixels as reported by IrfanView could be
anything, right?

if you are going to compare raw versus jpeg, they must be unmodified
out of the camera, with the settings set to maximum resolution.

I'm starting to think that my friends may not know as much about how
their cameras work as I thought they did.

I thought a jpg file was a compressed
version of the raw image file. So the number of pixels should be at most
the same, and I would have thought somewhat lower.

it should be the same, unless the jpeg has been resized, cropped or
otherwise modified.

Here are a couple of examples:


Camera: Canon 5D Mark I with Canon EF 24-70mm f/2.8L lens

Filetype: CR2 (raw file)
Pixels: 2496 x 1664 Pixels (4.15 MPixels) (3:2)
Print Size: 21.1 x 14.1 cm; 8.3 x 5.5 inches (at 300 dpi)
Colors: 16,7 Millions (24 BitsPerPixel)
Disk Size: 12.92 MB (13,550,637 Bytes)

Filetype: JPG
Pixels: 3156 x 2678 Pixels (8.45 MPixels) (1.18)
Print Size: 26.7 x 22.7 cm; 10.5 x 8.9 inches (at 300 dpi)
Colors: 16,7 Millions (24 BitsPerPixel)
Disk Size: 7.07 MB (7,418,412 Bytes)

The JPG also has a quite different aspect ratio (1.18 vs 1.5).

i don't know where you got that raw file but it's not from a canon 5d.
a canon 5d (mark i) has 4368 x 2912 pixels, for 12.7 megapixels, not 4
megapixels. the aspect ratio on a 5d is 3:2, so the jpeg was cropped.

I was told by the owner that it was the raw camera file. (sigh)

Camera: Panasonic DMC-G1 with a 14-45 zoom lens

Filetype: RW2 (raw file)
Pixels: 1920 x 1440 Pixels (2.76 MPixels) (4:3)
Print Size: 16.3 x 12.2 cm; 6.4 x 4.8 inches (at 300 dpi)
Colors: 16,7 Millions (24 BitsPerPixel)
Disk Size: 13.99 MB (14,665,216 Bytes)

Filetype: JPG
Pixels: 2816 x 2112 Pixels (5.95 MPixels) (4:3)
Print Size: 23.8 x 17.9 cm; 9.4 x 7.0 inches (at 300 dpi)
Colors: 16,7 Millions (24 BitsPerPixel)
Disk Size: 2.61 MB (2,736,853 Bytes)

something is wrong there too. the dmc-g1 has 12 megapixels, not 2.76 mp.

Again, I asked for the raw camera file and that's what I was given.

Camera: Nikon D700 with a 24-120 mm zoom lens

Filetype: PSD (raw file)
Pixels: 2910 x 2435 Pixels (7.09 MPixels) (1.20)
Print Size: 24.6 x 20.6 cm; 9.7 x 8.1 inches (at 300 dpi)
Colors: 16,7 Millions (24 BitsPerPixel)
Disk Size: 81.14 MB (85,081,048 Bytes)

Filetype: JPG
Pixels: 2910 x 2435 Pixels (7.09 MPixels) (1.20)
Print Size: 24.6 x 20.6 cm; 9.7 x 8.1 inches (at 300 dpi)
Colors: 16,7 Millions (24 BitsPerPixel)
Disk Size: 4.25 MB (4,455,756 Bytes)

For this pair, the number of pixels and the aspect ratio are the same,
but the size of the file shrank by almost 20:1.

psd is photoshop, not raw, and a nikon d700 has 12 megapixels, not 7.

This is very disappointing. I am reluctant to go back to my friends and
suggest that they con't know what the heck they are doing.

is that the one your friend adjusted the perspective? if so, that
explains why it's 7 mp and why it's a photoshop file. it was resized
and cropped in photoshop to fix the perspective distortion.

There is one that she cropped in PS, but the one that is 130MB (.psd)
was supposed to be a raw camera file.

Maybe I need to hire a professional photographer to do it right. I've
spent sop much time trying to get a good shoot, what I could have paid
for it several times over.

Thanks for the patient instruction.