Quick!! I need info on dpi!

[SabrinaO]

Swift responses are GREATLY appreciated!! I need to post some pics, but I don't know what to set the dpi as. I read that 240 is good but then I read that 300dpi is good. I'm just confused

 

[Erikah672]

Mine are usualy posted at 300dpi

 

[table1349]

DPI and PPI Explained – Andrew Dacey Photography
DPI, PPI, Pixels - Facts and Fallacies

 

[Bitter Jeweler]

72 for web posting.

 

[clanthar]

Hi,

I took this photo last week. Here it is posted for you at 3 different dpi values so you can see the difference. The first version is 72 dpi, the middle version is 300 dpi and the bottom version is 1000 dpi.

I did not post the same photo three times. Each is a separate image and the dpi values are as I noted; you can download them if needed to verify. Each photo is 400 pixels wide. A 400 pixel wide photo can be 72 dpi, 1000, dpi or 3000 dpi. Post it on a website and it'll be 400 pixels wide. The top photo at 72 dpi is 5.5 inches wide while the bottom photo at 1000 dpi is .4 inches wide. But on your computer screen they're both 400 pixels wide.

Take Care,
Joe

 

[Alter_Ego]

I use 150dpi to 300dpi to print and 72 for web.

 

[Boomn4x4]

dpi is 100% irrelevant to web posting. Set the DPI to 10.... it dosen't matter. The image will look exactly the same as if it were 72, 150, even 300.

DPI only matters to printing.

Any one that tells you that you should set your DPI to 72 for web is simply wrong and does not understand what they are talking about. 72 (and you sometimes hear about 96) are logical numbers in computer programming. These numbers are simply "made" up so that a computer's operating system can balance the difference between how text prints on paper and how text looks on screen... it has NOTHING to do with images.

Text is size is determined by "Point"... I'm sure you've heard the term, "I'm typing in 14 point font size". A "Point" is defined in computer logic as 1/72's of an inch printed on paper. If you are typing in 12 point font, when you print it, it will physically print as 12/72's of an inch tall. This is where the 72 dpi myth came into play, but as you can see the 72 really has nothing to do with dpi or even images, it only has to do with text.

The 96 is used to convert a text size to a screen resolution. Windows made up the number 96 to covert that 12 point font to get a number of pixels to display. (12/72 X 96) means that Windows will display the text on the screen as 16 pixels tall. Incidentally, Windows also has a setting called "Large Font" that you can access in yoru control panel. This changes that imaginany 96 number to 120. This is to be used for visually impared so that the font is printed on the screen larger. (12/72 X 120) will display that font on the screen as 20 pixels tall.

Incidentally, Macintosh uses the conversion factor to be 72... which pretty much takes a step out of the calculation... so its displayed on screen as 12/72 X 72.... which effectivly makes it display ast 12 pixels tall. The reason was simple because "back in the day" when the first Macintosh computers came out... they strived on the "What You See Is What You Get" (WYSIWYG) approach. Since all Macintosh computers came with their own monitors... all the monitors were exactly the same size and they could use the exact same dimentions. So by using 72 as a "resolution" it converted perfectly, a 12 point font would print on paper exactly the same size as it would print on the screen. Macintosh kept that logical number of 72 ever since.

 

[SabrinaO]

Thanks everyone! I wish i could thank you all individually, but that would take too long. ALL of you are awesome! Im more confused than ever though...LOL. Plus i just realized lightroom has PPI instead of DPI. :x lol. What do i do if im just posting online for PPI?

 

[Boomn4x4]

Thanks everyone! I wish i could thank you all individually, but that would take too long. ALL of you are awesome! Im more confused than ever though...LOL. Plus i just realized lightroom has PPI instead of DPI. :x lol. What do i do if im just posting online for PPI?

PPI is, again, irrelevant to displaying images on a screen.

Video monitors do not understand ANY concept of "inches".... they only understand pixels. The operating system does not know how many inches tall the monitor is or how many inches wide it is. The operating system only sends it X number of pixels tall by X number of pixes wide, and the monitor puts them on the screen. It dosen't care about inches at all. If you see a computer term and the term has "inches" in it... the monitor can't use it.

Honestly, there really isn't much of a difference between DPI and PPI. They are often used interchangably. The only real difference is that DPI only relates to how many dots of ink a printer puts on the paper per inch where as PPI is the number of pixels the computer sends to the printer. If you have a printer that is capable of printing 150 dots per inch, and the computer sends it a picture that is 300 pixels per inch, it'll only print 150 dots per inch. If you have a printer that is capable of printing 300 dots per inch, and you send it a picture that only has 150 pixels per in, it'll print at 150 dots per inch.

But either way, as you can see, the word "monitor" never comes into that explaination because both DPI and PPI have nothing to do with video display. If you want to understand how resolution, dpi, and ppi related to how an image looks when printed out.... then that is a completly different discussion.

When it comes to displaying images on a screen, the ONLY thing you need to worry about is how many pixels wide by how many pixels tall the image is... eg 640x480

 

[KmH]

Honestly, there really isn't much of a difference between DPI and PPI. They are often used interchangably.

There is a huge difference between dpi and ppi and they are not usable interchangeably.
First dots are round and pixels are square or rectangular.

The only real difference is that DPI only relates to how many dots of ink a printer puts on the paper per inch where as PPI is the number of pixels the computer sends to the printer.

The dpi also depends on the printer head technology and the number of nozzles the print head has. Some of the newer inkjet print heads have as many as 170 nozzles.

If you have a printer that is capable of printing 150 dots per inch, and the computer sends it a picture that is 300 pixels per inch, it'll only print 150 dots per inch. If you have a printer that is capable of printing 300 dots per inch, and you send it a picture that only has 150 pixels per in, it'll print at 150 dots per inch.

A single pixel is rendered by many dots of different colors, even a B&W. A 150 dpi printer would not be able to properly render a 300 ppi image.

A 1200 dpi printer uses 1200 dots of ink in every inch to render the colors of the pixels in that same inch. If you were printing a 300 ppi image, each pixel would be made up of 16 much smaller ink dots (1200 dpi x 1200 dpi / 300 ppi x 300 ppi). The dots don't all print right on top of each other, they form an array that approximates a square or rectangular pixel.

Note that dpi only applies to inkjet printing, not chromogenic printing, which uses a light senstive emulsion that has had the image projected onto it and is then developed in a variety of chemical solutions.

 

[Boomn4x4]

Honestly, there really isn't much of a difference between DPI and PPI. They are often used interchangably.

There is a huge difference between dpi and ppi and they are not usable interchangeably.
First dots are round and pixels are square or rectangular.

That is great if you are trying to confuse her more that she already is.

dpi and ppi are, from the simplistic approach, pretty much the same.

Unless you are printing to paper, don't worry about either.