How do I go from 72 to 300 ppi?

Hi everyone, I am a beginner at PS and need to save some images at 300 ppi.

They were shot as fine JPGs on a Canon 350D. When I open them in PS Elements 5

it says they are 72 ppi images. HOwever they need to be 300 ppi for printing

purposes. HOw do I do this? Many thanks!

Image > Size > enter new dpi which is 300, make sure the resample box is unchecked.

All are slightly different, but image resize. Go to the bottom of the box and change resolution to 300 from 72.

 

The picture will reduce by 3/4 size. You may need to up rez to get to necessary print size.

 

Now you know why you shot max file size always without compression.

Great! I've done it. Thank you both. I am still overwhelmed by PS despite we've been covering it for a few months in my photography evening classes. HOw long does it usually take before you can retouch photographs to make them look good? I'm not talking about PS wizardry - just cleaning up backgrounds, cutting and dropping stuff in and out, that kind of thing....

Do NOT change your PPI - it's utterly irrelevant. Only pixel values are important.

PPI values ARE important for printing. It's the ONLY place that they are important.

How long it takes depend how good your memory is, how good your instruction is, and how much you practice. I learned more in 4 months retirement than 2 years working.

 

How long does it take to learn to play a piano? Same thing.

 

If you have CS2, I recommend Photoshop CS2 for Dummies to start.

 

Do the basics first and learn where all the controls and tools are. Then do brighness contrast adjustments, color balancing, levels, curvers, layers, masking tools and masking, layer masking. Do one step at a time and move on. Then go back and review.

 

Never work on the original file. Lesson # one. Open the camera file and first thing is "save as" and rename it such as img 235psd.psd. Psd is the file extension and I also use it as the end of the name so I can identify it easily from the otiginal. You can save in PSD format with layers and adjustment layers intact and open and close as much as you wish without loss unlike JPEG which has a loss each time. You can also reopen and click on on a layer and rework it.

<i>How long does it take to learn to play a piano? Same thing</i><p>to play a piano you have to have the "gift from God"

same to be a photographer, but to manage the Photoshop, a little less :)

Size, resolution and the number of pixels are related as follows:

 

Pixels = Length (inches) x Resolution (ppi)

 

If you set any two variables, the third is fixed.

 

A digital image best described by the number of pixels on a side - 2000 x 3000 pixels for example, for a 6MP image. The same image can be represented by a low resolution (e.g., 72 ppi) and large size (as you observe in Elements) or high resolution (300 ppi) and a smaller size - about 7x10 inches. You can change the size or resolution without any loss if you use Photoshop/Image/Image Size and uncheck the "Resample" box.

 

You don't have to do anything if you "print to fit" - the printer will handle these calculations for you and maximize the print area. If you need a specific size, you need to set that size in Photoshop/Elements. If the resolution is then less than 300 ppi at that size, you need to check the "Resample" box and change the resolution at that size to 300 ppi. It usually doesn't hurt if the resolution is larger than 300 ppi, except for publication and some printing services.

when decreasing the dimensions of an image (without resampling), the pixel density increases.

 

when it gets to the point where you have something like 450 ppi or even more - how does the printer handle the extra pixels?

Hi Federica,

 

Just to restate all of the above in slightly different words, ppi (or dpi) is not a property of digital image files per se. It's how you tell Photoshop (or some other software/hardward system) how many of the image-file's existing pixels you want printed per inch of paper. This is why, if you change the dpi number from 72 to 300 with "Resample" unchecked in Photoshop, the resulting "image size" goes way down. The file itself hasn't changed, but the output size at which it would print at 300 dpi does.

 

In Photoshop, you then have to check "Resample" and enter your desired image size, to enlarge the file enough to print at that size at 300 dpi. And this enlargement does alter the image file...by adding pixels to it.

 

Sincerely,

 

Dave

Dave, now I'm getting confused. I have always thought that you do not check the resample box when you want to change the resolution of the image, especially from the low to high (72-->300)

The new pixels should not be created when you want to enlarge an image that is not big enough . So many times, someone takes an image that is low resolution (72 dpi) and just changes it to 300 dpi with the Resample Image box checked. This means Photoshop is creating new pixels where once there were none. When Photoshop resizes images, as an example, it takes one pixel and makes it into 4. It decides what color the other three pixels will be by looking at the pixels around it. Then it makes an educated guess as to what colors the new pixels need to be. It does a good job, but as it is spreading the original information thin by making other pixels like it, the image comes out fuzzy or blurry and there is a loss of detail. PHOTOSHOP CAN NOT CREATE NEW DETAIL.

Jerry, as pointed out above, digital files do not have "ppi." You do not change the size of a digital file by increasing PPI. PPI is a header instruction to the printer, and that's it. If you grow a photo beyond its native pixels, you do it by increasing the number of pixels. PPI is simply a calculation relative to print size. It's best to completely ignore it until the point of printing.

the question wasnt about changing the size of the image beyond its native pixels, it was about changing the resolution

in other words I dont understant why you whould need to check resample box when changing resolution from 72 to 300 dpi.

<i>it was about changing the resolution</i><p>

 

You change the resolution by changing the pixel dimensions. DPI is a header instruction, not a property of the file.

I too used to worry about 72ppi and all that, now I work with the maximum quality the camera can output (normally RAW and then convert to tiff or if forced to to jpg max quality). When printing from PhotoShop I always use the 'Print with Preview' option and adjust the size and location (central or edge) to suit the paper.

It is confusing, Jerry!

 

You said: "The new pixels should not be created when you want to enlarge an image that is not big enough."

 

Actually, if an image is "not big enough" (if it doesn't have enough pixels to print at your desired size and at the recommended printer resolution), then you MUST select "Resample," input the desired image size, and let Photoshop add pixels! That does affect image quality somewhat, but in reasonable enlargements, you won't see major problems.

 

All of photography entails compromizes. If an image isn't big enough (doesn't contain enough pixels), then you must somehow add pixels to it. This adding can be done either in Photoshop, or by upping a scanner's resolution (if the image file was created by scanning), or (if possible) by increasing a digital camera's resolution setting, to grab more pixels.

 

But if Photoshop tells you that an image "is 3x5 inches" at 72 dpi you must somehow add pixels to it (though not necessarily information), to get it to print at 3x5 inches at 300 dpi.

 

You also said: "So many times, someone takes an image that is low resolution (72 dpi) and just changes it to 300 dpi with the Resample Image box checked."

 

Yes, exactly! Image files contain a fixed number of pixels, which is independent of the resolution shown in Photoshop's Image Size window. The Image Size window simply reveals how large a file would print, if it were "put to paper" at 72 dpi (or, if Resample is not selected, at 240 dpi or 300 dpi).

 

A digital image file has no inherent size (in inches) until you select Resample, enter the resolution at which it wil be layed to paper, and then indicate the final print size. In some cases, pixels must be added before printing, and in others, taken away.

 

And yes, you can let your printer handle resizing, but its algorithms for doing so may not be as advanced as Photoshop's (especially when enlarging). (I ran afoul of this when I once let my Epson printer output an image at 8x10 inches, when Photoshop said that it would normally be a 4x5 at the output resolution. The result had a different look (which I rather liked)... sort of like an old-time newspaper illustration... but not one that I wanted in most of my prints! Maybe newer printers are better at resizing (especially upscaling), but I haven't upgraded yet!

 

Sincerely,

 

Dave

<i>You change the resolution by changing the pixel dimensions</i><p>Jeff, no offense, but I have never heard of this technique. So basically what you're saying you change the number of pixels across the width and height in order to change the resolution? It is possible though if you only constraint the physical size of the image.

The resolution of a file is the number of x pixels by the number of y pixels. DPI is, one more time, completely meaningless except as an instruction to the printer. A file has no inherent "DPI" (or "PPI"), it only has pixel dimensions. Its resolution is its size.

 

It is unfortunate that the terminology has become used in the way it has, because it is for the most part meaningless. What most people call dpi should be called "print resolution." That's all it is.

Dave, I see the debates are heating up a bit, understand me correctly. I just looked into the Scott Kelby ( PS2 for Dig Photographers) book regarding the subject in question. He talks here about "never-just-type-in-a-higher-number-with-the-Resample-Image-checkbox-turned-on" rule .He suggest to turn the resampling off to avoid soft-looking or pixelated prints. The physical size of the image ( cm/in) goes down when you type in the higher resolution and there absolutely no loss in quality. (p.103-104). <p>This rule does not apply to poster-size prints, where he recommends to turn the resampling on and to use Bicubic Sharper sampling algorithm (p.108-109)<p> According to the original question, the person wanted just to increase the resolution of the image from the digital camera for printing purpose, and there is no mention how big he/she wanted the print to be. <p> You almost convinced me that I was wrong, but after reading the book and "googling" this on the internet I see that all recommend to turn the resampling off. What do you think?

I have a feeling that we all are correct here, we just talk about the same thing called resolution but approach it differently.

Hi Again Jerry,

 

I don't have that book, but I'm wondering if it's warning against doing a large upscaling in only one step? With one exception, if this is done, many images will indeed show more artifacts and greater softness than they need to. This is why many photographers upscale in "10% steps" with Bicubic resampling.

 

The one exception that I know of is when using Photoshop CS's "Bicubic Sharper" resampling...for it, Adobe has recommended doing the entire resample in a single step. That makes sense, because a series of "sharpenings" will probably add its own unwanted artifacts to the final print.

 

In any event, returning to Frederica's original question, the Canon 350D's images aren't 72-dpi files just because Photoshop says they are! They don't have a native "resolution"...only a fixed matrix of pixels. And changing the 72 to 300 without Resample selected does not accomplish her desire to change them to "300 ppi for printing purposes." It only tells her how big the images will print on a 300-dpi printer. If that size is fine, then she's good. But if that size is too small (or large) she'll need to resample up (or down).

 

Sincerely,

 

Dave

"...I have a feeling that we all are correct here..."

 

I don't think so. If you don't know what exactly why you need to chnage the PPi - leave it the way it is. 72, 300 - it makes no difference whatsoever in 99.9% of cases. E.g, if you take your images to a typical minilab in a shopping centre - leave the PPI seetings alone - you will never have to worry about whether it's 72 or 300 - the prints will be identical as the minilab machine will do its PPi calculations automatically to output at its highest quality.

 

Only the pixel values are of any importance - again, in 99.99999% of cases.

yeah, you are always correct Ronaldo. I didnt say nothing but what I read in the Kelby's book and on the internet, if you want to question this, you should contact and question those guys