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Old May 25, 2003, 5:27 PM   #1
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Default Mystery With 5 Megapixel Resolution of only 72 Pixels/Inch


All of my images are shot at the highest settings on my Sony DCS F717 5 Megapixel camera, yet at the very bottom left of the Photoshop Elements 2.0 screen where it shows Width, Height, Channels and Resolution... it shows only 72 dpi... even though the JPEG file is over 2 megapixels! The prints look fantastic on my Canon I950 Printer so I know I'm somehow truly getting great photo resolution...

but the confusion with this mysteriously low resolution number is driving me nuts.

Even shots I am sent from other people who have much lesser cameras or basic, small images I download from the web show the magical 300 dpi I seek when I load them into Photoshop Elements.

What is MY dpi referring to at 72 dpi whereas other people's photos are at 300 dpi?

Thanks so much!

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Old May 25, 2003, 6:08 PM   #2
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I don't use Elements but what you are seeing is the editor resizing for your PC monitor which is about 72dpi. You don't have as many pix on a monitor as in a camera, so to get the pic the right size to view, the image copy in graphics memory is re-sized.

However, this does not mean the original file itself is being changed, only the 'Preview' copy held in your graphics card memory. When you hit save or print, you will keep the original file size unless you deliberately re-sample a copy to a lower resolution e.g for web publishing.
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Old May 25, 2003, 10:26 PM   #3
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Photoshop uses 72 dpi as the default for displaying your pictures on the screen... has nothing to do with actual file size.
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Old May 26, 2003, 12:22 AM   #4
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The megapixels is only the horizontal resolution x vertical resolution:

1600x1200=1920000 or 1.92mp.

At 72dpi that equals 22.222" by 16.666".

At 300dpi that equals 5.333" by 4.0".

But the filesize remains the SAME...the only thing I did was tell how many dots per inch I want, and the photo program recalculated the picture dimensions.
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Old May 26, 2003, 2:11 AM   #5
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No if I look at the EXIF info on pics from my 5050 it shows them as 72 dpi before I even open up a viewer or editor.
Anyone know why??
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Old May 26, 2003, 5:16 AM   #6
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Here is what an expert on the Adobe Photoshop Elements forum helpfully and athoritatively answered as help to me:

Sean, welcome!
You're seeing one of the most confusing aspects of Elements: that Image
Size/Resolution screen. A few key points:
1. There is nothing wrong with your camera! If you look at the top of the
Image Size screen when you first open your picture, you should see Pixel
Dimensions - for your images, they should be 2560 pixels by 1920 pixels (or
thereabouts) if you've taken a high-resolution picture. The pixel
dimensions are what Elements really sees in your image.
2. In the Document size section, you see three numbers: width, height, and
resolution. The three are linked to the pixel dimensions, i.e., they show
you how big a printed image you could have (width and height) at the default
resolution (in your case, 72 pixels per inch). You'd never print at 72 ppi,
but if you did, you'd have a picture more than 36 inches by 26 inches.
3. VERY IMPORTANT! Before you go changing the resolution from 72 to a
number more like what you'd want to print (300 ppi is good, although you can
get away with numbers in the 240 range), make certain that the box at the
bottom ("Resample Image") is unchecked. If you don't, the Image Size box
will add a bunch of pixels to your image to maintain the 36 inch by 26 inch
size at 300 ppi. The results a huge file with a very unsatisfactory image.
4. With Resample unchecked, change the value in the resolution box to 300.
You'll see that the document size dimensions will change to more reasonable
numbers, like 8.5 inches by 6.4 inches; at the same time, you'll see that
your original pixel dimensions are unchanged at 2560x1920. This is what you
5. Again with resample unchecked, you can change the linear dimensions
instead and let the resolution in ppi be calculated for you. If, for
instance, you put 10 inches in the long dimension, the short dimension will
come out to 7.5 inches and the resolution will be something like 256 ppi -
which is fine for printing.
Let's stop there and see if that helps - or just confuses more. Just
remember: keep resample unchecked to avoid image degradation.
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Old May 26, 2003, 6:51 AM   #7
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You have to remember the digital camera is a convergence device, combining still video, computer with the ability to connect to a computer, with the feel of a regular camera. I mentioned those features in that order for these reasons:

1) The first electronic still video cameras were video based devices, recording pictures in analog video format with the only output being to TV...they only had standard TV resolutions (NTSC or PAL, interlaced or not).

2) Later cameras encorporated a computer interface (either you could plug the camera into the computer, or more likely you had to take out the CF card and put it into a reader) so they had computer related resolutions; 240x180, 320x240, and 640x480 max, all at 72dpi to match the monitor resolution.

3) Only in the last couple of years we are seeing more regular film camera influences with the inclusion of shutter speeds, F-stops, ISO, plus the resolution is starting to approach the resolution of film, and people are more interested in seeing standard photographic resolutions (4x5, 8x10, etc.) and with them you will see those settings right in the camera and they should set the dpi accordingly.
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Old May 27, 2003, 11:37 AM   #8
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Resolution (dimensions in pixels) and dpi are completely independent.

the resolution (pixels) is the number of dots that make up the image. This determines its quality and detail.

The dpi is just a number that is stored along with the photo that tells a printer how big to print out the photo (ie how many dots per inch to print). The dpi doesn't change anything about the photo itself, and chaning the dpi doesn't change the resolution.

People keep making the mistake that dpi is important when you're looking at an image on a screen. It doesn't make any difference whatsoever. I'm a web designer and I never need to think about dpi because I only deal with on screen images.

It's only when you'r printing something out that you may need to consider the dpi, for example if you know that you want your photo to be no less than 150dpi when you print it out, then you would divide the number of pixels across by 150 and that would tell you the biggest you could print it (in inches).
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