I don’t know if it makes a difference, by I am using a iMac running OS X.2.6. Paul
Paul,
You’re confusing the image size ( if printed ) with the size displayed on your monitor. The image size displayed on your monitor should be sized in pixels, not inches, since any image is displayed on a monitor based on the image pixel dimensions and the monitor’s current pixel per inch settings.
For example, a 72ppi image that is 800 x 600 pixels, will fill the screen of a display ( if the display is set at 800 x 600 mode ) . If you were to change the display ( in the Windows display settings ) to 1024 x 768 , the image would be smaller on the screen.
I think that’s what happening to you. Here’s a Jay Arraich article to help clear it up, <
http://www.arraich.com/ref/resolution.htm> .
🙂
Brent
Brent,
Thanks. The solution (it seems) is to type 72 (pixels/inch) in the resolution box. Then the number (for inches) used above it will correspond to the inches on the screen, and on other people’s screen when they look at my (Bob Dylan) photos on my Web site. I am going based on my memory and your use of the #72 to assume that if the image is going to be on the Web it should have a resolution of 72. Is that true for sending e-mail photos too? Is that done automatically when you choose ‘send by e-mail’ in the various programs?
–Paul
Paul,
For screen, it is better to only think in terms of pixels. Working on a copy…in Image>Resize>Image Size (with ‘constrain’ and ‘resample’ checked) make sure the units are saying pixels and type in about 600 for one dimension, letting the other dimension fill in. It is immaterial what the resolution says. This will give you an image which will fit nicely on a screen. Come back if you have trouble with this.
Nancy, I think that’s the best advice of all – ditch the inches/centimeters and work in pixels. I changed the default on my rulers to pixels and don’t go near the inch measurements until I’m ready to print. And I avoid any resampling unless it’s absolutely necessary for printing. Once I got that mindset, everything started to make sense!
Well…..almost everything….
🙂
Chuck
Chuck,
It’s just speaking screen language in its own tongue (pixels)
In article
wrote:
Thanks. The solution (it seems) is to type 72 (pixels/inch) in the resolution box. Then the number (for inches) used above it will correspond to the inches on the screen, and on other people’s screen when they look at my (Bob Dylan) photos on my Web site. I am going based on my memory and your use of the #72 to assume that if the image is going to be on the Web it should have a resolution of 72. Is that true for sending e-mail photos too? Is that done automatically when you choose ‘send by e-mail’ in the various programs?
Ignore the inches, centimetres and other distance measurements altogether for web images. Think purely in terms of pixels. That’s what determines the size of the image on a browser screen. It doesn’t matter what you type in the pixels/inch box so far as web images are concerned. Some of the images on my site are 90dpi while others are 72dpi depending on which machine I produced them on. All display the same size on both my machines.
For email the same thing /probably/ applies but it depends on where the images are displayed at the recipient’s end. All operating systems have a nominal pixels per inch setting. With Mac’s it’s usually 72dpi with other platforms it’s often 90 or 96. If the viewing application takes this into account and may scale the image to fit it. Browsers don’t and most email applications don’t which is why it doesn’t matter. PE2 takes this into account when you select to view at print size. The Preview application on your Mac also scales to take the dpi setting of the image into account. Try changing the dpi setting of an image without changing the number of pixels. Look at it before and after in Preview.
There is nothing whatsoever magical about 72dpi. Dots per inch are only important for printing. For screen display they are generally irrelevant.
To the several people that replied,, thank you for the advice. Are you saying (implicitly) that what I learned about images needing to turned into 72 pixels resolution in order to be posted on the Web was wrong? (I am assuming you know what I am talking about; if not I will look it up in my old how-to-make-web-sites manuals). I am resisting what you are saying only to the extent that I would prefer to reconcile it with what I thought I knew to be true. Thanks. Paul
My recent reply was sent before I read Peter Gaunt’s comments. I am still getting the hang of things here, and did not realize I needed to do something to see more messages. Here is my revised question: Were the manuals that told me that I need to adjust the resolution to 72 dpi for images on Web sites wrong, or have things changed since they were published? If 72 dpi is only relevant for Macs, did using 72 dpi mean that it was assumed we (who made our Web sites using Macs) were supposed to be only planning to be viewed by Macs? Thanks for any help.
By the way, if this stuff is all written down somewhere, I should probably just be reading that–instead of bothering people. I stopped reading the original suggestion once I concluded that 72 _was_ the magic number (it certainly solved my immediate problem). –Paul
I have a follow up question. Now that I have mistakenly turned all the images I was planning to add to my site into 72 dpi, should I redo them–or is it just a matter of there not being any requirement to use 72 dpi, rather than it is being positively disadvantageous. Once I typed in 72 dpi for resolution, I was able to control the image size. In other words, although I did not actually use a ruler and take measurements, it seemed that if I wanted to have my picture be three inches high, all I had to do is type in 3. But am I losing quality by doing this? Thanks. — Paul
Paul, try forgetting inches when you’re working with a digital image, unless you are going to print the image. What you want to create for web use is an image that’s perhaps 800 pixels by 600 pixels; if your original image is from a 3-megapixel digital camera, it will start out at about 2000 pixels by 1500 pixels, so you have to get rid of a bunch of pixels. One of the easiest ways is to use the Save for Web dialog (File>Save for Web). Just open that dialog and put the desired dimensions (or just one of them – the other will be calculated) in the area at the lower right of the dialog box and hit Apply. It will show you how large your new 800×600 Save for Web image will be in kilobytes, so you can gauge how long it will take someone on a dialup connection to download it. When you have the desired size (by adjusting the quality slider in the upper right), hit OK and you have the right-sized image for web use. And you never get into inches or pixels per inch or dpi (which is a misnomer carried over from printers). It takes a while to get used to the concept, but your computer could care less about inches and resolutions…
Chuck
Paul,
I really think this excellent website of Wayne Fulton’s will answer all of your questions. Start with this page
<
http://www.scantips.com/no72dpi.html>
This is a very comprehensive site with good information.
Paul,
Oh by the way, I don’t think that it was your inability to use this forum correctly which prompted your statement about just now reading Peter’s comments. For some strange reason his post, which he wrote an hour and a half AFTER mine, was posted above mine.
I have only scanned the scantips piece, but I find it reassuring that there are people who are motivated to make such cases so thoroughly. I came very close to spending the rest of my life typing in 72s. I will read more and report back if I have any remaining questions. If I may provide my own esoteric knowledge lead: <
http://www.wired.com/wired/archive/11.09/ppt2.html>. I have never used powerpoint, but I took a seminar with Tufte and would give his opinions weight. You can get the complete version at <
http://www.edwardtufte.com>. –Paul
Paul,
That link and many of the links it contained offered extremely fascinating reading. The ‘official’ report on the spaceshuttle tragedy was just released on Aug 26 and I learned a lot in the past couple of hours, thanks for the OT link.
Although no one answered it specifically, I am assuming that although there was no need to specify a resolution of 72 pixels per inch, having already done it, there is no benefit to my redoing my images. Please let me know if my assumption is wrong. Thank you.
I am glad that the link I provided was of some interest.
Paul
PPI has no meaning except for print output.
You can change it at any time without compromising your pixel data, assuming you are not working in JPEG and not resampling.
Mac
Paul,
You are correct in your assumption,as Mac says, no harm done. It’s the resampling that you have to watch out for lest you irretrievably throw pixels out the window.
Paul, maybe this will help. A monitor screen is a grid, like a checkerboard. There are so many pixels across and so many down.
In the old days, when macs were the machines for graphics, the decision was made that the resolution would be 72 pixels per inch for screen display, because in the print industry there are 72 points to the inch, and that way what you were looking at onscreen would be pretty close in size to the printed version. Then windows came along with 96 pixels per inch and that reasoning went out the window, so to speak.
Today the physical size at which a pixel displays varies from monitor to monitor. Generally it’s best to consider that many people with small monitors are running at a resolution of 600 pixels by 800 and try to keep images for onscreen display a bit smaller than that unless you don’t care if they can’t see everything at once.
But in many cases, the difference between say, a laptop with a 14" screen and one with a 12" one isn’t the pixel dimensions–they may both have 1024 pixels across–but rather the size at which each pixel displays onscreen. In other words, the 12′ monitor shows exactly the same amount of stuff, only smaller.
So all you really care about is how many pixels a side your image is.
Barbara,
<clapping> very nice!
