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TheDman

Dpi

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Hello,

 

I found this website while doing a Google search for "internet 72 dpi", trying to help a friend get a better understanding of dpi and it's affect (or lack thereof) on images. I was directed to the following page:

 

http://www.scrapgirls.com/graphic_resolution_size.htm

 

There is some information in this tutorial that isn't quite right, and I thought I would help straighten out the issue.

 

The first and most important point is, DPI has no affect on digital images. The internet is not 72 DPI; it is in fact no DPI at all. There are no inches on the internet. Saving a file at 72 DPI for displaying on the web is a meaningless exercise. You could save the same files at 1 DPI or 9,000 DPI and it would look exactly the same. The only thing that matters with digital files is pixels. The DPI setting on a digital file is just a bit of metadata that says "If I were to print this image on paper, please print the pixels at the following density". Also, the file size of web images is not affected by DPI. Try it yourself; change the DPI setting to 1 and 300 and save it both times. The file sizes will be the same.

 

The tutorial says "Because 72-dpi graphics have fewer dots...". This isn't true. The number of dots in your photo has nothing to do with it's DPI setting. The DPI is simply there to tell the printer how many of the images' dots to print in a given square inch of paper, should you send the file to the printer. Therefore changing DPI will change the size of the photo when it is printed. It will not change anything else, and is completely ignored by web browsers. Also, 72 DPI images do not have "larger dots" than 300 DPI images. A pixel is a pixel; it's size never changes. Dots do not get larger or smaller; only the density of them changes (how many dots are squeezed onto an inch of paper).

 

Hope this helps clear some of that up. One other somewhat useful fact: while 300 DPI has been the industry standard for printing digital files and is a fine setting, if you're trying to print big enlargements you can usually get away with much smaller DPI numbers. I can't tell the difference between a 300 DPI print and a 240 DPI print, and I've even printed photos at 140 DPI with acceptable results. Not recommended, but you can often get away with it if you must.

 

Derek

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Maybe I'm not clear myself on my understanding of dpi and ppi, but I think if you replace every instance of "dpi" with "ppi" (pixels per inch), then all the original info in the tutorial holds true. Often, we interchange the term "dpi" (a printer term, as you pointed out) with "ppi" (a Photoshop resolution term). Does that make more sense if you substitute ppi for dpi?

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Replacing those two terms wouldn't matter since both end in "per inch", and inches don't apply to the internet. Both are ignored. Plus, PPI would matter even less, since there is no setting for PPI in the properties of an image. As far as digital files are concerned a pixel is a dot.

 

Here are some good links on the topic:

http://www.apptools.com/examples/dpi.php

http://www.dpiphoto.eu/dpi.htm

http://www.nicholsonprints.com/Articles/dpi.htm

 

From what I understand the whole 72 DPI concept came about back when the Mac was invented, and Steve Jobs' group wanted a page of text to look the same size when printed as it looked on the screen, and they figured 72 DPI (again, only applicable when printing) was about the right setting to use for that. This was erroneously translated to mean 'computers are 72 DPI', which led to massive DPI confusion that still exists today.

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Oh, and I'm not trying to pick on this website or anything. I just Googled "internet 72 DPI" and your tutorial page was the very first link to come up!

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We don't really focus on web graphics here, we create projects for printing, so the pixels per inch kind of do matter. ;)

We request that those who post in our forum save a copy of their layouts at 600 pixels wide to keep the file sizes smaller for our gallery.

It helps if you look at the article in the context of what this site is all about: Digital Scrapbooking.

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I understand that, however I was referring to this particular turorial here: http://www.scrapgirls.com/graphic_resolution_size.htm

 

That tutorial contains such inaccurate statements as "72-dpi (dots per inch) means that there aren't very many dots", "300-dpi means that there are many, smaller dots", "72-dpi graphics... file sizes are small", and several others that are just wrong. And since this tutorial has such great Google ranking, it's just perpetuating the myths about DPI.

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Derek, I know I see a difference in the total size of my file for posting in the gallery here between when I save as 100 dpi and 72 dpi, the 72 dpi being a smaller file of course. So, it makes sense to me to post a smaller file to leave room for others.

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You seem to be missing Dman's point. He is correct in all he says. The tutorial is worded poorly and confuses those who do not understand the basics.

 

It doesn't matter whether one is in the digital scrapbooking world or merely fixing a few photos for print or web sharing - the information in that link is confusing. I am sure Roxanne knows the difference, but you cannot tell it from that tutorial. It needs to be rewritten.

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The tutorial was written way... way...way...back in 2004 and used the terminology and information as was understood that was used at that time. A lot of things have changed since then. Progress!

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