The Web knows nothing about ppi. Calling it 72ppi is just a convenience. It’s all just pixels. Browsers display JPG and GIF files at their full resolution; how big they look is dependent on how big the pixels are on the user’s display. On one display, 72 pixels may be an inch; on another, they may be 3/4 inch… it’s always at 100%.
Just save your file for the web at the width x height (in pixels e.g. 75h x 100w) that you want it to be viewed at.
Resolution of the file is irrelevant for the web and does not affect the file size of the JPG or GIF.
—
Regards
John Waller
r_harvey and John Waller,
I have to disagree with you that the DPI is irrelevant for the web. Save for Web ‘resamples’ the files, reducing it to 72 PPI, so that the file will download more quickly for the user of the web page. You can see the difference in file size when you view the ‘2-Up’ window in Save for Web or Imageready. As far as the quality of display, you are correct, it does not make a difference (as it does in printing).
Also, Mac computers are optimized for 96 PPI while PCs are optimized for 72 PPI (or is it the other way around?).
Jake
Oh boy! Here we go again.
Steve
I have to disagree with you that the DPI is irrelevant for the web.
nope. disagree all you want.
check it out too. top image is 72ppi, bottom is 300. any diff? file size? quality? dimentions? nope. nada. nothing.
Res test page:
<
http://aikodude.tripod.com/difResTest.html>
I have even been caught by this argument in the past…it was Dave’s link that set me straight…thanks Dave.
I know understand that when it comes to web, it is all about the pixel 🙂
Okay, Dave. Please explain why, when you send a file to ‘save for web’ that is 4MB in size (300PPI), let’s say, it is downsampled to 176K (72PPI) in size?
There is no change in pixel dimensions (e.g. the size as it appears on the screen, its width and height). The only change is in the pixels per inch (72. The reason for this is to reduce the size of the file for download/viewing purposes. Save for web DOWNsamples to reduce file size and the extent of that downsampling depends on the quality (low, medium, high) you select.
Try printing that downsampled file and compare it to the original 4MB file (200-300dpi). You will notice a substantial difference. But, as was already pointed out, it makes no difference on the screen because the monitor is optimized to show 72PPI.
By the way, I think you could be a little more diplomatic and less flippant in your responses. I was only trying to help – as most people here are. If I’m wrong, I will admit it but I don’t like having someone I don’t know talk down to me.
Hugs and kisses.
Jake
"I have to disagree with you that the DPI is irrelevant for the web."
DPI is a printing term used to designate the dots per inch that an inkjet printer is rated at, or, in offset printing dots per inch is the screen count for a halftone screen. None of these relates in any way to the web.
<forum programming> It is all about the pixel. </forum programming>
"I don’t like having someone I don’t know talk down to me."
This could be the title of a class that all managers in the world should be required to take before they are allowed to manage employees.
Jake:
I agree that the responses you got were flippant, but I know where they are coming from. Eeven though their tone was wrong, it has its origin in the fact that we hear this again and again and again on this forum.
PPI is irrelevant to screen display – printing is another matter.
SfW will downsample, if you ask it to save at a pixel size smaller than you currently have. Otherwise it won’t.
So, if I have an image, which is 1800×1200 pixels at 300PPI. It will print 6×4 inches. To show as 6×4 on the screen would mean reducing the number of pixels. Something like 432×288 might be good. However, how big it actually is will depnd upon the specific screen and the resolution it is set to.
So the rule:
For screen, think pixels and forget PPI [and DPI which is something else entirely]. For print, PPI does matter, as it tells the printer what to do with the pixels.
Jake,
"Okay, Dave. Please explain why, when you send a file to ‘save for web’ that is 4MB in size (300PPI), let’s say, it is downsampled to 176K (72PPI) in size?"
It is a 4 MB working file that perhaps has multiple layers? the working size in uncompressed. JPG uses lossy compression so it will allow you to compress a file to the point that it shows distortion. the more you compress it (The data not the resolution) the more quality is lost.
If you don’t believe me go to file -> Save as instead and save your file to a JPG with high compression. It will look just as bad as a file highly compressed with SFW yet still open at 300 DPI because the EXIF data is also saved with the file.
The overall dimensions do not change. If the file was 1024×768 it will still be 1024×768 after you Save for Web (Unless you change the size on the "image size" tab).
Pixels are pixels. DPI (or PPI, if you prefer) refers to the rate of pixels within one inch of display (paper or monitor). If you want to guess how many pixels are in one inch of monitor screen real estate, just use math. There are many more pixels in one inch of a 17" monitor running at 1280 x 960 than in the same monitor running 800 x 600. (For example, the live horizontal area of my 17" monitor is approx. 14.25". 1 inch of screen real estate at 1280 x 960 contains approx. 90 pixels, while 1 inch at 800 x 600 contains about 56.) Web browsers will display the pixels at a 1:1 ratio dependent on the individual monitor resolution. When designing for the web, don’t worry about inches, use pixels as your unit of measurement.
Please explain why, when you send a file to ‘save for web’ that is 4MB in size (300PPI), let’s say, it is downsampled to 176K (72PPI) in size?
beacause you’re saving in a lossy format? using compression? turning down quality? all of the abobe? it has NOTHING to do with ppi.
The only change is in the pixels per inch (72).
nope. the change is in stripping exif info and probably applying compression.
and you do know that save for web strips ALL ppi data from the image right? when you see 72 ppi when opening a previously saved for web file, what you’re seeing is the open dialog’s default, not the image files native resolution.
Save for web DOWNsamples to reduce file size and the extent of that downsampling depends on the quality (low, medium, high) you select.
hmmm… well kinda, but you’re confusing terms. downsampling generally means actually creating fewer pixels (ex. 800×600 –> 400×300). the quality you’re speaking of (low, med, high, etc) is generally referred to as the compression ratio. high compression, low quality.
Try printing that downsampled file and compare it to the original 4MB file (200-300dpi). You will notice a substantial difference.
yea. you know why? because you compressed the heck out of it and threw away data. and don’t say downsampled unless you mean you actually changed the image size. you’re confusing people.
By the way, I think you could be a little more diplomatic and less flippant in your responses
huh? i’ve rarely been called flippant. jocular maybe, fecitious somtimes, but not flippant.
I was only trying to help – as most people here are.
me too.
If I’m wrong, I will admit it but I don’t like having someone I don’t know talk down to me.
No problem. Sorry if I sounded that way. I was sneaking in a couple of minutes in the forum while scarfing down a snack. I humbly beg your forgiveness, oh mighty one! 🙂 – ok THAT was flippant! still, sorry, wasn’t trying to piss you off! and I definately wasn’t meaning to talk down to you.
Now remeber, the web has no notion of ppi/dpi/lpi/spi or magnum pi. S4W gets is savings by stripping out the EXIF data and performing compression on an image. For web work, it’s all about the pixels. 😉
Dave,
Thanks. I was just having a bad day at work and nerves were a bit frayed. I know you were being helpful. Thanks for the explanation. THAT makes much more sense to me (e.g. the stripping out of extraneous data, etc.).
Colin and others,
Thanks for the explanations. It tells me I have a lot to learn yet and I appreciate all the insights.
I am the first to admit that pixels, PPI, DPI, etc. confuse the hell out of me. Every time I think I have it down, I realize I don’t. I consider myself an intermediate Photoshop user and always have something to learn. I would never presume to be an expert but I try to help those whose questions I can answer – just as others have so often helped me. And, occasionally, I get it wrong as in this case. Man! If I only had a nickel for each time that’s happened!
I plan to educate myself further on this topic so I can understand it. I will start with the explanations you all have provided and go from there. I can be dense at times, no question. But for now … I am off to experiment with my copy of Photoshop CS that just came today.
Jake
I am the first to admit that pixels, PPI, DPI, etc. confuse the hell out of me
Help is on the way! See this site for helpful, well written (in english) definitions and explination of all the wierd technical terms that get thrown around and confused:
<
http://www.webopedia.com/>
just type your term (for example: ppi) into the keyword box and hit enter and you get: <
http://www.webopedia.com/TERM/p/ppi.html>
I consider myself an intermediate Photoshop user and always have something to learn.
then you’re probably beyond me! 🙂 I’m more of a computer geek and photoshop hack. But I have fun with it and this is the best place I’ve found to learn. I’ve learned more in the last year and a half here than in the previous five using photoshop by myself.
Thanks, Dave. I will try it.
Hey remember me?
Good gravy,,, I did not mean to stick my finger in a hornets nest here :o) I fully respect all your viewpoints but please allow me to re-phrase the question,
Regardless of anyones thoughts on ppi or dpi or dot gain or political beliefs the question is quite simple:
Has anyone seen an option to change the default 72 ppi output of ImageReady to a different setting?
yes, no, maybe, would have been just fine with me thanks.
As for all of the confusion and arguments about graphic imaging terminology it just would not be fair if I did not toss another can of gasoline on your fire for fun.
If you read through the Adobe help files in Photoshop 7.0 you will eventually come to the part where they say,
"In Photoshop, you can change the resolution of an image; in ImageReady, the resolution of an image is always 72 ppi. This is because the ImageReady application is tailored to creating images for online media, not print media."
This paragraph below, also directly from the Photoshop 7.0 help file is a prime example of exactly why this very common argument and
misunderstanding of terminology is kept alive to this very day. I ask you is this from the experts at Adobe or from clueless copy writers ?:
"The number of pixels or dots displayed per unit of length on the monitor, usually measured in dots per inch (dpi).
Monitor resolution depends on the size of the monitor plus its pixel setting. Most new monitors have a resolution of about 96 dpi, while older Mac OS monitors have a resolution of 72 dpi."
Lets dissect that first sentence.
"The number of pixels or dots displayed per unit of length on the monitor, usually measured in dots per inch (dpi)."
They are talking about a monitor, period no question right.
A monitor displays an image by way of pixels (witch is an abbreviation for "picture element") period, a scientific fact.
First they say monitors display with pixels then one second later they say monitors display using dots.
Then they say (per unit of length) and (dots per inch).
The fact is monitor manufactures always use (pixels per inch) as the unit of length to describe monitor resolution.
This is not to be confused with monitor "dot pitch" which is another part of monitor manufactures specifications.
Dots per inch do not and can not be used to refer to a monitors display.
Why?
Because a monitors display is made up of pixels which are activated by an electron beam from three color guns in the back of the picture tube.
Not because there is a printer inside of the picture tube spraying dots of ink on the inside of the glass!
Next they say,
"Monitor resolution depends on the size of the monitor plus its pixel setting."
What they call monitor resolution and pixel setting refer to the same thing (the pixels per inch that a monitor can display).
I have a 22 inch monitor that is built at 96 ppi and a 17 inch monitor also built at 96 ppi. So diaganal monitor size is irrelevant.
Monitor resolution is measured in ppi and is determined by how the manufacturer built the monitor.
And finally as they state in the next sentence,
"Most new monitors have a resolution of about 96 dpi, while older Mac OS monitors have a resolution of 72 dpi."
One more time Adobe boy, please its pixels not dots.
And yes most all new monitors are built to display at 96 ppi (pixels per inch) including the one on my desk.
Also,
Printing presses display images by building up ink "dots" through different line screens for each color.
Ink jet printers display images by spraying out small "dots" of colored ink (very small).
A: The only thing that can display an image using pixels is a monitor or other electronic display tube.
B: The only thing that can display an image using dots is a printer or other mechanical device.
As long as people in the industry and book copy writers keep using three or four totally different terms as if they where one, this confusion will continue.
Another reason people get mixed up is they are using pixels on the monitor and in their graphics programs then when they push the button and send it to the printer it gets converted to dots (dpi) by way of unseen complicated internal software.
Most people dont think about this conversion in their head as they see the printed output.
None the less it is a conversion and it is two different displays with two different terminologies.
Yes you can change the apparent viewing size of a monitors screen (640×480) (800×600) (1024×768) on and on.
However this does not change the factory built-in resolution of the monitor (96 ppi)
They are only narrowing the focus of the picture tube to show an apparent wider view.
========================================================= Hey I almost forgot, there was a point to all of this,,,,
As Adobe correctly stated most all new monitors are built to display at 96 ppi not 72 ppi
That is why I ask to change the default output setting of ImageReady to 96 ppi.
Because 72 ppi is not using my or your monitors full resolution potential.
The extra ppi allows for more image bit depth information not more inches.
one inch is still one inch regardles if there is 96 pixels in that inch or 72 pixels in that inch
And before we get back into that old bar room brawl, yes the image file size measured in bytes (not dots) will increase somewhat)
This is a trade off I would like to have the option of choosing for myself.
Maybe I have a web site where I want to display works of art for sale and I want to use the full potential of everyones monitor to display my inventory.
When people come to my site they want to see a good detailed image before they buy it. They understand it may take longer to load but they want it.
Maybe I have small navigational images on that web site where I could save for web at 72 ppi because thats all it requires to display nicely.
==========================================================
For another can of gas you all could talk about bit depth increasing the file size.
I read last week where the Japanese have prototyped a new kind of flat panel display that can display 10 bit instead of eight bit color depth and they said it will be 15 times the resolution of todays HDTV they even had to build a special video camera just to record 10 minutes of video to display on it for a demo.
As a final note:
Forums in my view are about the friendly exchange of knowledge not arguments and anger.My opinion is just that, (mine) if you check it out and find it correct thats great if not, you can pick out the good parts and toss the rest no harm done.
This is fun, thanks for all your help everyone.
As Adobe correctly stated most all new monitors are built to display at 96 ppi not 72 ppi
No they’re not. Discuss…
That is why I ask to change the default output setting of ImageReady to 96 ppi.
Because 72 ppi is not using my or your monitors full resolution potential.
<sigh>
is there a difference?
<
http://aikodude.tripod.com/difResTest.html>
Re: And yes most all new monitors are built to display at 96 ppi (pixels per inch) including the one on my desk
I disagree. I can set my monitor to 640×480, 800×600, 1024×768 and a couple other dimensions. The ppi is different on each of them, and the resolution is not built to any standard … it is entirely designed to be user-choice.
BTW, I agree with the others … ppi has no bearing on web work, and being able to set resolution for a web image is pointless (and thus Adobe is right in not making it an option in Image Ready).
Why? Because a monitors display is made up of pixels which are activated by an electron beam from three color guns in the back of the picture tube.
Thats called a cartho ray tube.
Did you take a look at Daves link? If you did, you should be able to figure out that the PPI setting is irrelevant to web work. Don is right when he says worrying about PPI in web graphics is pointless. So changing the default "save for web" resolution won’t really accomplish much. I would stick with 72ppi.
In all honesty, 96ppi compared to 72ppi…there really isn’t much difference in terms of quality. So this is further reason not to worry too much about changing the defaults (if you eaven can).
ZIP
But Zip
In all honesty, 96ppi compared to 72ppi…there really isn’t much difference in terms of quality
There is no change in quality at all!! The pixels are the same.
There is no change in quality at all!! The pixels are the same.
Shsssssh! He might not know that. <kidding>
Thats more reason not to worry about the PPI.
In all honesty, 96ppi compared to 72ppi…there really isn’t much difference in terms of quality
I think thats a true statement contrary to the whole pixel resolution argument. Is there a big difference between 92ppi and 72ppi in terms of montior resolution? Of course not.
Is there a big difference between 92ppi and 72ppi in terms of printing resolution? Hardly.
The point: it doesn’t matter either way.
In regards to this forum topic, my statement seems to contradict the whole point. Sorry ’bout that…I either got my antenae crossed again or I simply didn’t have enough coffee this morning (you can never have enough).
Bottom line: monitor resolution and printing resolution are not the same thing.
David,
You typed all of that just to discount yourself with this quote…
"That is why I ask to change the default output setting of ImageReady to 96 ppi.
Because 72 ppi is not using my or your monitors full resolution potential."
The reason the default is 72 has nothing to do with the resolution of the monitor and everything to do with the default print resolution of web browsers. Windows Web browsers print @ 96 PPI (I tested IE and Netscape and I don’t know if Mac’s have a different default print resolution). In most cases the number is irrelevant anyway as most of us design pages for viewing, not printing. At any rate if your page is viewable at 800×600 it will print to standard 8.5"x11" paper just fine.
If you need something to print more precisely you should have downloadable PDF’s anyway.
David,
Stop worrying about it!
There is NO resolution data saved in a jpg when you Save for Web in Photoshop or when you Save Optimised from IR. In both cases all meta-data including sizing/image rez data is stripped from the file to give the smallest possible file size. Setting a different ppi would have ABSOLUTELY NO EFFECT.
Thats called a cartho ray tube. Actually it’s a cathode ray tube.
uggh! My antenae were crossed. Time to take ’em to the shop and get ’em fixed I think. Thanks Ruth for pointing out that typo.
Searched the web for magnum pi. Results 1 – 10 of about 60,600. Search took 0.85 seconds.
Ah. So sorry. You’re quite right Ruth. <scraping and bowing>
🙂
