Image DPI confusion - what is best advice for high res screen users?

[ship691]

Hi

I have been doing web design for 10 years, but I have only just discovered that images can have an actual DPI burnt into them. Is this true?

Until now I had simply worked in pixels and assumed that DPI (dots per inch) x inches was simply a rather clumsy way of calculating actual pixels. But today I have had serious trouble importing a particular image into msOutlook and it turns out that there is a DPI setting AS WELL as an actual number of pixels. And that on the image in question I had somehow managed to set it to a high value (300DPI) and every time I imported it into Outlook by any means you like, bl***y Outlook remove about half the pixels.

When I "Save For Web" from Photoshop there is no DPI settting offered, so I am assuming the web browsers ignore any DPI setting and simply take the image size from the height and width settings in the HTML. And if that is missing the browser will presumably just set (assuming the screen is running at native size, and assuming the browser is at 100% zoom) it at 1 pixel of source image to 1 pixel on screen.

However for those of us running windows on high resolution screens when need to increase the DPI setting away from 100% (technically I understand that this is called "96 DPI" although how many actual inches presumably depends on the physical size of your monitor!).

e.g. On my computer the screen is 1920x1200 on a 24inch screen and the text in windows keeps being rather too small to read. So I have changed the screen DPI in windows (using: Right-click on Desktop ==> Personalise ==> Display ==> Medium) from "Smaller 100% (default)" to become "Medium - 125%". I think my setting is in fact called "120DPI".

So now I am assuming that all images should be set to 96DPI which appears to be standard. BUT if my setup is running at 125% DPI it now appears that images from applications like FSCapture are creating images at 120DPI unless I change the default setting. But if I change it to 96DPI then BL***DY outlook increases the size of the image when I import it (on my computer which is at 120DPI remember).

What is the conclusion ?
Given that I *must* run my computer at 125% DPI (in order to read text)
- which are my best options for DPI setting?
Should I set everything to 120DPI? Or will that have weird effects when I come to display on other people's computers? Or what??

J

 

[logicearth]

Those "DPI" settings for images are only for printers. Has nothing to do with an image when it is displayed upon a pixel based monitor. When images are only going to be used upon a computer monitor, design in pixels, nothing more.

When you change the text size (mistakenly labeled with DPI) with in Windows, it does not change the pixel resolution. It just makes certain elements bigger, and certain applications zoom into their content. Setting text size to 120% within Windows has IE zooming in by default to 120%.

 

[ship691]

Those "DPI" settings for images are only for printers. Has nothing to do with an image when it is displayed upon a pixel based monitor. When images are only going to be used upon a computer monitor, design in pixels, nothing more.

Well that's what I *USED* to think, until today that is.

It turns out that bl***y MS Outlook does pay attention to DPI settings that are burn into images. To be honest I had no idea that images even contained DPI settings. But they do: rightclick on image ==> properties ==> details ==>
Horizontal resolution:
Vertical resolution:

It may be that on JPEG images have this setting, as I cant see anything similar for GIF images... I'm not sure.

But the important point my experiments seem to show that Outlook DOES pay attention to these values - in fact it re-sizes the image when it's being imported using them (how irritating is that?).

 

[mitchell65]

I am a bit confused here. How do you import an image using the email program "MS Outlook"? Do you mean when someone sends you an image as an attachment? If so then just save he image, scan it with your A/V program and open it in the image editing program of your choice. The only time an email program will resize an image is if you use the "E mail this image" function in an image editor but then if you have 10 years experience of web site building you don't need me to advise you NOT to use that system. It just reduces the image so that it will reduce the file size to a set minimum to enable fast loading and downloading. This feature is less used nowadays as upload and download speeds get better and better. Where image quality is important then if a file is too big to send as an email attachment then you can always use the free "Dropbox" or similar!

 

[Ranger4]

This Wikipedia website may help explain the DPI & pixel situation & explain some of the confusion on the issue.

Dots per inch - Wikipedia, the free encyclopedia