72 dpi myth

[moscato_images]

Stu, I downloaded both of your images and they are both in 72dpi at different print sizes. I'm not sure what setting you are changing to make your DPI different, but they are both 72dpi.

-joshua

[moscato_images]

PhotographerC has some good input a few replies back. I havn't read anything that I havn't agreed with. I wrote the post just to get wheels turning for people who have not thought about the subject that they may dive into it a bit and get things straight. All of the key words DPI,PPI,SCREEN RES, PRINTER DPI, RESOLUTION etc... can be thrown around and are easy to get confused by one who knows little about it. I read all of the replies and everyone knows what they are talking about, just saying it different ways.

Someone suggested that I was saying DPI is completley irrelevant. Did I say that? Because if I did I'm sorry because it is not. DPI is only a number that is made from other numbers. It's not like you can improve DPI. Like PhotographerC said "you can't adjust DPI on your printer or camera."

Also, it does matter in certain cases what the DPI box says. Let's say you print on a wide format printer at 1200 printer resolution but your DPI box says 126.83DPI....most likely you will have banding. It all really depends on the output device. (WEB, INKJET, PRESS, etc...)

Of course there is no right answer for all of the output devices other than "learn what it all means and prep your files properly for the given device you are going to be printing/viewing on."

-joshua

-joshua

[StuHaluski]

Originally Posted by moscato_images

Stu, I downloaded both of your images and they are both in 72dpi at different print sizes. I'm not sure what setting you are changing to make your DPI different, but they are both 72dpi.

-joshua

thats why my second post.

I have learned something here but BUT at least I do know you gotta pay attn to dpi in print.

[moscato_images]

Originally Posted by StuHaluski

thats why my second post.

I have learned something here but BUT at least I do know you gotta pay attn to dpi in print.

Of course. More DPI the better quality. DPI=Quality. Thank you for posting and chatting about the subject Stu.

-joshua

[Blueprints]

So what DPI or resolution do you set your pictures to when you are posting them to your website to make them load faster.........

[rolandogomez]

Not sure where everyone was when this originally posted, but I just happen to notice it and there is too much misinformation throughout the threads--now let's hope I won't screw it up....

First, I'm not going to get in to the whole 72 "dpi" myth thing--don't have time, headed to Chicago shortly...

But let's clarify some things from what I've seen so far---

Macs were based on the 72PPI (not DPI) and Windows was based on 96 PPI originally--BTW, all desktop computers are "PC's" or "personal computers."

The reason we have 72 PPI/DPI is because of Picas and Points. In fact, if you open Photoshop and go to Preferences>>>Units & Rulers you will see Points/Pica sizes then under there "Postscript (72 Points/inch) Macs were adopted by graphic and creative professionals early on because you could practically measure the screen and compare it to your printed output--it was all about fonts back then more than images.

Now if there was ever a push about "72" it was because Photoshop started out as a "Mac/Apple only Program" until they bought out Aldus PhotoStyler and of course technology changes every Monday when the Board of Directors meet so 72 was adopted as the standard because it works with graphic, layouts, design, typesetters, photographers, art directors, copy editors, etc., but more important it worked with FONTS, postscript, etc. Even today newspapers, magazines, books, etc., are based on picas/points and "column inches" when it comes to design and printing--oh, and they use "line-screens" to print (Newspapers 65 or 85 and magazines 133, 150 or 175) Rule of thumb for photographers shooting for publication, "two times the line screen, plus/minus 20-percent" and shoot full-frame because an image is used in proportion (percentages) and column inches, not 5 x7's or 8 x10's.

Editors will kill you if you leave room for cropping in 35mm, digital or film for that matter. A sure sign of an "amatuer" publication shooter is one that leaves room in the frame of capture so they can print 8 x 10's to fit a frame.

DPI is irrelevant when it comes to monitors, cameras, scanners, etc., unless you have a target DPI you are shooting for in a printable outcome. You will still capture in PPI but it's only relavent if you have to output a certain file size.

The statement "DPI=Quality" is wrong unless you're a printer, and even then it doesn't mean anything if you have to interpolate to get to the higher DPI. Remember, Photoshop doesn't work in DPI, it's native is PPI.

Here's an example, two images, and you can download them and open in Photoshop to verify. The images look identical, if you download them and print them, you'll find out that one is much smaller in size when it comes to printing. In fact the first image is saved at 72PPI and the second at 300PPI. The amount of pixels in each image is the same!




So does an image have to be saved on 72 PPI for the web, the short answer is no. However, it's done that way because of postscript, fonts, picas, points, etc., from the old Mac days of 72PPI monitors. Creatives that worked on Windows back then had a monitor of 96PPI and had to calculate with the "133-percentage" rule. If you liked math then Windows (actually DOS back then) was for you.

Now back to some of the mis-statements. The two images below, from way back when screen captures, shows how if you check "resample" in Photoshop you will get not only a larger image on screen and on paper, but also a larger file size--look at the numbers, they are all relative to another in this type of example. If you do not check "resample" then you can change the PPI all day long and save it for the web and the image "screen" size will remain the same and it's only relative to the user's monitor settings (resolution).





The reason we see "pixelization" on a print with an image saved at 72 PPI is because there are 72 pixels in that one-inch and the human eye can see 72 little bricks in one inch--it's very difficult to see 300 little bricks fit into one inch. Monitors don't care what the print size is, they only care about the total pixels in length by the total in width, that's what it will display.

Now let's get the terminology straight. STOP talking DPI unless you're talking about a printer's output. BTW, the 300 DPI "myth" comes from the older laser printers. Why not print at 305 DPI? I don't want to get into that, but just be aware that 300 came from somewhere and it originated from laser printer technology.

Cameras capture in PPI, pixels per inch, not dots! Same with monitors.

Scanners scan LPI, lines per inch.

Now that's my two centavos worth...wishing everyone the best, rg sends!

[cclesue]

In all this (I might have missed it) I see no discussion of the raster function. Rasterization is what the computer and/or presentation device (monitor, printer) does to the input file to prepare such for presentation. Raster engines are resampling programs that take the information given them and spreads in out over the specified area. If there is enough information it might drop some of it or if not it will fill in the gaps by averaging from pixel to pixel. These raster engines are built into graphics cards and printers and to some extent monitors and they don't give a damn about DPI, PPI, LPI. etc of the input file. All they care about is how much info is given them and how thick or thin do they have to spread it. The only control the human element has in this is how big an input file and what are the final dimensions of the output. In other words assume you want an 8x10 print from your Printer (be it your personal Epson or the Noritsu at Costco's). You have a 6 meg file (2000x3000). You input this file and the raster engine takes the information and "fits" it to the desired output. In this case the engine will spread the 3000 pixels (the long side) over the entire long side of the paper. Ah ha you say that works out to 300 dpi or ppi. . . but to doesn't because the Epson was set to 720 dpi or 1440 dpi or the Noritsu is 320 or perhaps 280 dpi or the monitor is something else. In other words the raster engine DOESN'T CARE about all the work you did to prepare the file for output. All it cares about is how big do you want it and how much information does it have to work with. Obviously if it has more information to work with it will produce a better product, too little and the output will be lacking.
Having said all this there is one point that needs to be considered. Just how good is the raster engine of the output device and can anything you do improve things. The resampling engine in photoshop is pretty darn good but frankly speaking every time you fiddle with the information something is lost in the translation so the best thing you can do is don’t do it until the very last and only then if you either don’t trust the rasterizer in the output device or you are concerned about file size. For the most part the Raster Engine in the big pro printers is superior to the PS engine, but the one in the cheap HP and Epsons might be lacking. When cropping (in PS) set the size but leave the resolution field blank this will prevent the PS resampling engine from kicking in. We send our files to a Noritsu without resampling and the output is great. Finally if you MUST resample pick a dpi that is a derivitive of the output device. If your printer is set to 720 or 1440 then resample to 360 dpi or 240 dpi. I doubt the naked eye can tell the difference.

[Lynn_in_VA]

Originally Posted by cclesue

In all this (I might have missed it) I see no discussion of the raster function. Rasterization is...

for me, this post turned on the lights -- thanks!

Lynn