Setting Resolution Preference?

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Posted By
paulsen1
Oct 15, 2003
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483
Replies
12
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Closed
I just upgraded from Photoshop 6 to Photoshop 7, use it exclusively to work on images I download from a digital camera and prep for Web publishing.
Until the current upgrade, all of my images were shown with 72ppi default resolution, exactly what I need for Web publishing. Now the default is 144ppi, meaning once I change the resolution in "Image Size," the image shrinks to half the size: too small. I can of course use the "resample image" option, on every image, but that’s not only inconvenient, but hurts the quality as well. I therefore would like to have all my images displayed with 72ppi, as before, but can’t find a way to set these. How can I do that?
Thank you,
Bernard
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Peace_Pipe
Oct 15, 2003
if you have a 2cmx2cm 144dpi image, convert to 72dpi 1cmxc1cm.. You could set up a action to convert images to 72dpi, and image size 50%, then convert all your images in one go.

To start a new image at 72dpi, start a new page, enter your size and dpi at the begining stage. then from that point on, all new images will start at 72dpi by default.
CW
Colin_Walls
Oct 15, 2003
Resolution is irrelevant for Web images!
Just view at 100% [actual pixels] and you will see what the image will look like on the Web. All the 72ppi stuff is a total myth. Don’t waste your time even thinking about it.
TK
Tomaz_Klinc
Oct 15, 2003
Colin, I don’t think my phone bill is a myth, and I do think hi ppi images only add to it.
CW
Colin_Walls
Oct 15, 2003
Tomaz:

PPI only has any effect when you print something.

If an image is 100×100 pixels, that is the number of pixels that appear on the screen. The size will only vary with the [actual physical] resolution of the screen [which will be somewhere in the range of 70-100ppi].

If the file is 100ppi, it would print as a 1 inch square. If it is 50ppi, it would print as a 2 inch square. The file size will not change.

Try it. Take an image and change the ppi [without resampling]. The pixel dimensions don’t change and neither does the file size [and neither will your phone bill!].
JW
John_Waller
Oct 15, 2003
I don’t think my phone bill is a myth, and I do think hi ppi images only
add to it.

Hi-res images do generate bigger file sizes (MB/printed inch) compared to low-res images but hi-res files are required for high quality printing not screen viewing; dpi resolution is irrelevant for the web.

Compare a 100×100 JPG at 72 dpi with a 100x100JPG at 300dpi and you will find both files are exactly the same file size on disk because both contain 10,000 pixels of info.

A 100×100 pixel image will still appear at 100×100 pixels on a website regardless of dpi settings since dpi is a unit of measure for printing. One pixel on a screen is the same dimensions (w x h) for 72dpi as for 300dpi.

When printed, the 72dpi image will be larger but lower quality than the 300dpi image which will be smaller but higher quality (more visible detail).

Hence, to print a 10"x8" high quality image you need a high dpi file = higher KB on disk.

But to view on a web page (monitor), you just refer to width x height (in pixels) and ignore the rest.

—
Regards

John Waller
CW
Colin_Walls
Oct 15, 2003
You my wish to read this: <http://www.earthboundlight.com/phototips/20020317.html>
P
paulsen1
Oct 15, 2003
Colin:

Thank you for this response. Although I am still a bit in the dark about the connections of image size, display size, print size and their relationship to pixels, I followed your suggesting and started experienting around and feel that I’m, thanks to you, on the right track now.

See, if I take images with my digital camera, let’s say in a small resolution of 640 x 480, download them, display them for the first time in Photoshop, and they are 640 pixels wide, with a default of 144ppi resolution, change the resolution to 72ppi manually without resampling the images, the images are then only 320 pixels wide, which is already too small.
If I do resample the images at the same time, the quality suffers (although I only work in PSD format while editing).

If I understand you correctly, I should not have to worry about a display resolution of 144 for Web publishing. The 640 x 480 images will be displayed with 72 (to 92) ppi on the computer screen only (which ultimately determines their size) but basically in the correct size, not shrunk to half the size. The size of the images also is not higher as if I convert them to 72ppi and resample them.

Did I get this correctly? Is your advice therefore to ignore the 144ppi setting and work with it?

Finally, how about I have a large digital image, let’s say (to simplify) 2000×1000 pixels, and want to send it out to be printed. Should I then raise the solution before starting editing? What happens to the quality then (in a case where size doesn’t matter)?

Again, thank you, and anybody responding and helping me out learning the mysteries of Photoshop.

With kind regards,

Bernard
CW
Colin_Walls
Oct 15, 2003
Bernard:

Changing the resolution from 144ppi to 72ppi, with no resampling will have no effect on the number of pixels.

If you want to send out something to be printed, you need a reasonable ppi setting [typically 200-300]. So, set the ppi and look at the resulting size [in inches] or vice versa. Only if that doesn’t work out do you need to need to consider some [modest] up-sampling.
P
paulsen1
Oct 15, 2003
Colin:

I think I got it. Just let me know if I pass my homework assigment, if you will.

1) For Web publishing, the resolution doesn’t matter, as long as it is at least 72ppi. It is determined by the ability of the monitor, which is between 72 and (on high end units) 96 pixels.

2) What matters in Web publishing is the image size in pixels (width x height), which won’t change without resampling, no matter what resolution is set. Thus, I can take an 640×480 digital image, change the resolution from 144 to 300, and it won’t have ANY effect on the Web, not in file size, not in image size.

3) If I have a digital photo that shall be professionally printed, raising the ppi will make the image smaller but of higher quality, whereas lowering the resolution will make the image larger but of lower quality. The amount of pixels contained in an image remains the same. What has to be determined is how large I could go, without losing too much quality due to the low amount of pixels per square inch.
DM
dave_milbut
Oct 15, 2003
Colin, I don’t think my phone bill is a myth, and I do think hi ppi images only add to it.

nope.

Hi-res images do generate bigger file sizes (MB/printed inch) compared to low-res images

nope.

see the following:

<http://aikodude.tripod.com/difResTest.html>

the top image is 72ppi, the bottom is 300ppi. check the properties. same pixel dimentions (800×600). download the files. same size. PPI (resolution) has absolutely no bearing on file size or web viewing. It only affects printing density. ONLY the total # of pixels counts on the web.

dave
CW
Colin_Walls
Oct 15, 2003
Bernard:

(1) – almost; resolution doesn’t matter – period.

(2) – correct

(3) – correct

You pass. 🙂
JW
John_Waller
Oct 15, 2003
To reiterate Colin:

1) For Web publishing, the resolution doesn’t matter

Correct. Finish the sentence there.

2) What matters in Web publishing is the image size in pixels (width x
height),

Correct.

3)

Correct.

—
Regards

John Waller

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