Photoshop CS3 - Raw Jpeq Question

[PIC]

Why is it that the same image of Jami when shot in Raw + Jpeq is ...

JPEQ - 32.444 width by 48.667 height inches and 72 pixels per inch {2336 by 3504 pixels}
and
RAW - 9.733 width by 14.6 height inches and 240 pixels per inch {2336 by 3504 pixels}



Slow days make me Wonder ...

EL

[Shane Jennings]

You have the same number of pixels (2336 by 3504), but the JPEG is set at 72 PPI and the RAW is at 240 PPI. When you spread the pixels out to 72/sq inch for the JPEG, they cover more inches. The resolution at full size would be much more grainy for the JPEG at those settings.

(I didn't stay at Holiday Inn last night, but I've been helping my daughter with math a lot lately.)

[PIC]

Originally Posted by Shane Jennings

You have the same number of pixels (2336 by 3504), but the JPEG is set at 72 PPI and the RAW is at 240 PPI. When you spread the pixels out to 72/sq inch for the JPEG, they cover more inches. The resolution at full size would be much more grainy for the JPEG at those settings.

(I didn't stay at Holiday Inn last night, but I've been helping my daughter with math a lot lately.)

Daaa, We know the math ,,,
why is one big and one small inquiring minds want to know ... does any one know ???
why is the sky blu and sun yellow ???

[Patti Edens]

I think maybe we (at least Shane and I) are not understanding what you are asking. Because it seems to me that he answered your question.

If you take the short side for example and look at the fact that it is

2336 pixels divided by 72 pixels per inch, you get 32.444 inches for the jpeg
and
2336 pixels divided by 240 pixels per inch, you get 9.733 inches for the RAW file - which is smaller

The reason is because for the three variables, the pixels stay the same and the resolution changes. So, the other variable, the size, has to change.

But, I think you already know all this. So, what are we missing in your question?



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This reminds me of a joke my BIL likes to tell. He will ask if you have noticed that when geese fly in their v-shaped pattern, one side is always longer than the other. When you say "Yes, I have noticed that.", he asks if you know why. When you are thinking that it must have something to do with aerodynamics or something scientific and finally admit that you don't know, he says, "Well, because there are more geese on that side.

I suspect that we are telling you the obvious answer, that there are more geese on that side but that's not really what you are asking.

[erisian pope]

I think the question is more "why did the camera makers choose to save the JPG at 72dpi as opposed to any other setting?" And to contrast, "why did the camera makers choose to save the RAW at 240dpi?"

I think monitors display at 72dpi (approximately, some are more like 75 or other similar numbers) so perhaps the JPG is being saved at "video screen" resolution since it is hardcoded into pixels. From what I understand (and I have no sense of certainty here), in the RAW your pixels are not entirely saved yet (when you adjust the colors, etc you are adjusting how the pixels will be encoded when you convert into another format) so perhaps there is some benefit to saving this "not quite in pixels yet" image format at a higher pixel depth.

I am more comfortable with the first half of my answer (the part about 72dpi) than the second, but both are stuff I made up based on what teeny bits of the technology I understand.

I sure hope someone with better knowledge than I have comes in and sets us straight.



EDIT: I did a little googling and found one site that mentions 72dpi as an estimate of the actual DPI of your monitor like I was guessing, and they point out that if your monitor is at 72dpi and your image is at 72dpi than 1-inch of your image will actually appear as 1-inch long on the monitor. So you see it in "actual size" on your monitor.

[PIC]

Originally Posted by erisian pope

I think the question is more "why did the camera makers choose to save the JPG at 72dpi as opposed to any other setting?" And to contrast, "why did the camera makers choose to save the RAW at 240dpi?"

Exactly !!
Most Browsers are at 72DPI so JPEG at 72 DPI might make sense to the Gods who set this. But Raw at 240 is an odd duck.
If it was 310 or 5 x 72 that night make sense to those Gods but at 240 thats 3.33333333... x 72 DPI.
or why not have JPEG at the Higher DPI than RAW ???
or why not have JPEG at 69 DPI and RAW at 666 or etc etc ???
There must or should be some reasoning to the maddness.
But is it "really" the Camera Makers and not as Adobe opens it ???
I am not so sure ...
Perhaps this is like asking Why to God {???}
God Please answer ...

EL

[erisian pope]

I believe it is the camera maker, as you can view the EXIF data on the image straight from the SD or CF memory card and that includes resolution and DPI (I just checked several of mine). In Windows you can do this by right-clicking on the image, choosing "properties" then clicking the "summary" tab then clicking the "advanced" button. My straight-from-camera JPG images are all 72dpi and they have never been opened in Photoshop.

[Shane Jennings]

Ahhh....I see your question. It's just like some of my kids' "why" questions. Here is the answer that God gave me to give to them:

That's just the way it is. Deal with it.

[PIC]

Originally Posted by erisian pope

I believe it is the camera maker, as you can view the EXIF data on the image straight from the SD or CF memory card and that includes resolution and DPI (I just checked several of mine). In Windows you can do this by right-clicking on the image, choosing "properties" then clicking the "summary" tab then clicking the "advanced" button. My straight-from-camera JPG images are all 72dpi and they have never been opened in Photoshop.

I have also seen this in Non Adobe software.
But are all camera makers the same - we both shoot w Canon 20D,
I wonder about things like Nikon Neff, Phase One P45, or 1DSIII but dont loose any sleep.
If all cameras are the same then that is support for God's Law of Camera Format Creation.

EL

[d2creative]

240 dpi is one of the graphics industry standards for printing.
300 dpi is usually what I shoot for when commercially printing an image but 240 dpi acceptable. Anything lower and the image starts to degrade.

If i took the image as a jpg and it imported at 32.444 width by 48.667 height inches and 72dpi, i would need to change it to it's 240dpi (or 300dpi) equivalent. And then down-size from there if needed. If I really needed the image to be 32" wide... I'd be screwed.

72dpi for screen. 240dpi for print.