How do I turn a large image with low dpi into smaller, higher quality
June 13, 2014 8:59 AM   Subscribe

I have a 20x20" jpg that is 72dpi. I don't have the original file, or any other versions of it. Using photoshop, how can I turn it into a smaller picture that is a higher dpi?

I've spent the last 30 minutes googling this without any success, getting stuck in internet cul-de-sacs about the "definition" of image size and what DPI actually means.

I'm trying to print an old image as a gift for someone who is very picky about pixellated images. He'd rather have a 3x3" image that looks very high quality than a 10x10 that looks pixellated.

I know this has to be easy as pie, but could someone tell me how to do this? I've got photoshop. The image size is currently 20" by 20" at 72dpi, I'd like to send it to the printer at ~200ish.

Thank you
posted by stewiethegreat to Technology (12 answers total) 3 users marked this as a favorite
Have you tried asking the printer themself? I imagine this is something they'd deal with on a regular basis.
posted by Maecenas at 9:01 AM on June 13, 2014

From the Image menu, pick Image Size. Make sure "Constrain Proportion" is checked and "Resample Image" is unchecked. Put 200 in for the resolution and click OK.
posted by Nonsteroidal Anti-Inflammatory Drug at 9:02 AM on June 13, 2014 [3 favorites]

Just ask the printer to print the image at 3"x3". You shouldn't need to do anything to it in Photoshop. DPI is largely a red herring here.
posted by pipeski at 9:03 AM on June 13, 2014 [3 favorites]

dpi is irrelevant, send the original picture and specify the size for it to be printed at.
posted by TheAdamist at 9:07 AM on June 13, 2014

I have Photoshop Elements, but the steps are likely similar:

Go to the Image menu > Resize > Image Size... (Alt+Ctrl+I)

Like NAID said, check ON Constrain Proportions, check OFF Resample Image.

You can choose to put 3 into the Width/Height box so that you get a 3"x3" image at 480dpi or you can do what NAID said and put 200 in to Resolution to get a 7.2"x7.2" image. The number of dpi for both versions of your image are the same mathematically.

If you really desire a 3"x3" image at 200 dpi, then check ON Resample Image and you can input 3 into Width/Height and 200 into Resolution. If you're just sending this to your own LAN printer, I'd just leave it at 3"x3" @ 480dpi described above.
posted by Seboshin at 9:08 AM on June 13, 2014

I think the OP might be trying to print the image on his own color printer, not sending it to a print shop.
posted by Johnny Wallflower at 9:09 AM on June 13, 2014

A JPEG file is just pixels. It does not know how large it is when printed out. That is something you choose when you print, or import into Photoshop.
posted by miyabo at 9:09 AM on June 13, 2014 [2 favorites]

-Open up the jpg in photoshop.

-Select All, copy

-File -> new, and when the box pops up you'll see below the space for the document's name the "Preset:" dropdown. It probably says "Clipboard", if it doesn't, pick that. The clipboard is where your computer is temporarily storing the information about the jpg you just copied.

-In that same box you'll see image dimensions (Width & Height) and below that "Resolution:", which will say 72. Type 200 (personally I prefer to print at 300 ppi, but 200 should be okay. You can also switch this from ppi to dpi - the logic is the same, really.) You'll see that the pixel dimensions stay the same, but if you switch the dropdown boxes next to width and height to inches, that dimension will change as you change the resolution.

-Click OK, a blank image should show up.

-Edit -> Paste, your jpg should paste right into your new image.

-Save in whatever file format you like, then print.
posted by Mizu at 9:27 AM on June 13, 2014

Open your file. Go to the Image pull down menu to IMAGE SIZE. In the dialogue box set document size to width 3, height 3, resolution 300. hit OK. That's it.
posted by a humble nudibranch at 10:32 AM on June 13, 2014

Several of the above instructions will work, but the very first step when resizing, editing, or doing anything at all to change a JPG file is to first save it as a lossless format like PSD, and then work from that file. That way your further saving and exporting will degrade the file appearance as little as possible.
posted by Mo Nickels at 11:55 AM on June 13, 2014

I don't actually want a 3" by 3" image, just to forestall further instructions of that nature. My goal is the largest print that will be high quality. Thanks Mizu, Mo and a few others that provided practical instructions.
posted by stewiethegreat at 1:08 PM on June 13, 2014

The size of the original image in pixels will give you an idea of the maximum print size. A 600px x 600px image at 200 DPI will give you (600 / 200) = 3 inches x 3 inches.

Photoshop will give you the option of specifying the image size when you print. If you work out the maximum size of your image based on the DPI you feel is acceptable, you should be able to specify the width and height under 'scaled print size' in the print dialog. As a check for your sums, the dialog will tell you what the PPI (same as DPI) is when you enter the values.
posted by pipeski at 2:50 PM on June 13, 2014

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