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They say you start to see the pixels in an image when it is printed around 200 dpi/ppi or less, right? I'm looking at some images here at 100% view in photoshop, and when I open the image size window, it tells me that the images are between 70-100 ppi each. However, I measured the images on my screen and they are both larger than the shown print size, AND I see no pixels or other signs of poor quality in the image being displayed on my monitor.

So my question is: Why would the image print in less quality/smaller size than it displays? Is it really necessary to print in 200+ ppi (or the more recommended 267-360 for HQ) to get a quality print, or am I missing something here?

Since many are unique designs that I've spent a fair amount of time on, I'd hate to have to discard, upsample, or restart from scratch. Any help you can provide would be much appreciated.

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Well I'm no print expert by any means, but I'm pretty sure it isn't a 1:1 comparison between what you virtually "see" on your monitor and what's physically printed. Paper is not equivalent to a monitor. But I'll let someone else give you an actual answer, because again, I'm not experienced. I just know 300 ppi is the way to go for quality prints. –  Johannes Jul 12 '13 at 21:03

4 Answers 4

However, I measured the images on my screen and they are both larger than the shown print size, AND I see no pixels or other signs of poor quality in the image being displayed on my monitor.

This is due to how images are rendered on a screen vs. how they are rendered in print. On a screen, 300 pixels gives you 300 individual points of resolution on the screen.

On paper, though, it'd different. 300 pixels of information need to be printed using a dot pattern (screen) so that the four CMYK colors can be visually blended. So it's not really an equal comparison.

Is it really necessary to print in 200+ ppi (or the more recommended 267-360 for HQ) to get a quality print, or am I missing something here?

It really depends on the printer and the image. Sometimes a photo with only 150ppi of data can look just fine on paper. But a detailed pen sketch my look horrible at 200ppi.

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Ok, well first off I'd like to debug the misconception you have about screen resolution. 100% view doesn't always necessarily equate to the same size in the real printable world. Depending on the monitor and the calibration this comparison can be extremely different and isn't an accurate measure of things.

Secondly, as good as monitors are these days, you'll never get a true representation of the quality of a print. For example, most images on websites are optimized at 72dpi and they look fine on the monitor, but I would never consider printing these images because they'll never produce a professional print even if they look fine on a website. Printing brings out all the blemishes of your digital images and that's why it's important to design on resolutions above 300ppi.

I hope that doesn't significantly affect all the work you did, but I wouldn't recommend printing anything under 225ppi (depending on the medium of course)

The best thing you can do is just focus on making sure your settings are ok in the future.

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Thanks for the help. Unfortunately, I'm now in the unavoidable position of either discarding or upsampling some of the images. Some may be reworkable, but others involved images that came to me at only 96 ppi. I hear that Photoshop CC has vastly improved upon the upsampling system in CS6 so maybe I'll take a look into that. Either way, I'll definitely be more careful with my res. in the future. –  Will Jul 13 '13 at 17:20
    
Hi Adam. 1) 72ppi is an historical unit and it is nothing to do with electronic media. Electronic media is ppi independent. 2) Design on resolutions above 300ppi, it has not much sense. In any case 300ppi flat, at 100% size, would be ok. 3) Printing anithing under 225ppi, again is a relative idea. A poster? a big banner? a blurry background? All thoose cases can be under 225ppi. –  Rafael Jun 23 at 18:59

There are several different and somewhat related issues being presented in this thread. I will address one of them, how to see accurate print size on screen when you use Photoshop. This is not done to assess the print quality but "print presence" or how a print may appear in the selected image size. This is, unfortunately, set incorrectly in Photoshop but fixing it is relatively straight forward. After that you will choose "View/Print Size" and what you see on the screen will be the actual print dimensions. Of course, large print sizes will not fully fit on all displays but the parts of the image will still display in accurate inches. Here is how to fix this problem:

  1. Create a blank document that has 300 dpi print resolution, 9″ x 9″ in dimensions. This will create a blank document 2700×2700 in pixel dimensions
  2. Fill it with white if it is not already filled
  3. From the menu choose “View/Print Size”
  4. With an accurate ruler and using great care not to damage your screen measure the displayed dimensions in inches. In all likelihood it will be a good deal smaller than 9 inches
  5. Divide 9 inches by the actual measurement you obtain from the screen which will provide the correction factor. I am not using an example since this number may vary from one screen to another.
  6. Now, go to “Edit/Preferences/Units & Rulers” and find the screen resolution. Most likely it is set at 72 pixels/inch
  7. Multiply the current ppi, 72, by the correction factor you calculated above and enter that in the screen resolution field. Click OK.

The resulting screen resolution may have a decimal fraction, that’s OK and it will not necessarily be 96 ppi either. My screen’s actual resolution turns out to be 94.299. Your number will likely be different from this

From now on, when you choose “View/Print Size” your screen will display the actual dimensions of the print.

You can read a slightly expanded version of this on:

http://www.keptlight.com/photoshop-view-print-size/

where some recent changes to Photoshop CS6 are also explained.

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As a simple way to visualize resolution, the higher the resolution is, the smaller the pixels will be once printed. That's why you see a different size on your screen depending on the resolution when looking at the image's dimension; if the resolution is 300ppi for example, the pixels will be smaller and more concentrated. If the image is 72ppi, the pixels will be bigger once printed. It's better to not use the ruler on your display to measure the size of an image for this reason, but it's possible.

It's easier to simply trust the measurements and dimension of the file when looking at the "image size" in Photoshop (eg. inch, centimeters, etc.) That measurement is also the one that will be used in your other publishing software if you import your image. An image imported in InDesign with 1000x1000 pixels at 300ppi will look smaller than the one imported at 1000x1000 pixels at 72ppi for the reasons explained above.

How dot-per-inch works with printing

Examples of different resolution vs dimension

In general, in printing, you can think of resolution as dots of ink; the smaller the dots, the closer they'll be and the less they'll be visible on paper. And the smaller these dots are, the clearer the image will be. That's why the requirements for printing are higher than for web use.

But it's not entirely true that 1 pixel once converted to be used for print will be shown as 1 dot. It depends on how the rip system will encode these pixels to fit the printer's quality. For example, if you use an image at 30ppi (30 pixels-per-inch) and print it, there will more than one dot to reproduce that one pixel as seen on the screen and the printed image will look blurry. If the printer is a high resolution one (eg. uses 300dpi), it will always fill with extra dots the missing "pixels" on its grid.

Dot-per-inch and low vs high resolution printing

As the unit for the resolution says, if you have 30 pixels-per-inch (30 ppi), they'll logically be "bigger" than a 300 pixel-per-inch (300ppi) image if printed. The printer will not create one bigger dot for each pixel, it will split that big pixel into many small dots instead (see image above) and fit as many it can according to how many line-per-inch it can print in that grid. In offset printing, the size of the dots will only change depending on the color density of each color separation (Cyan, magenta, yellow, black and spot colors) and the quality of the printer. In short, the quantity of dots represents the quality of printing and the real size represents the color density.

size of dots and color density on offset printing

Some precision: Pixels are used as a unit for screen display (eg. web projects), ideally not for print. Even if they have a square shape, their real "physical" length will change depending on the device you use and the aspect ratio (eg. web vs video.) That's why when referring to size/dimension for print projects, it's more precise to simply use the resolution and the measurements using imperial, typographic or metric units of length (eg. centimeters, points, picas, inches, etc.) It's closer to the final expected printed result than pixels. More details on pixels here.

Digital printing looks better at 200dpi and up and the offset printing should be at least 266dpi (preferably 300dpi and more for color, and 600dpi for black and white texts). If you print on a laser printer in your office, you can go as low as 150dpi.

By the way, ppi or dpi are both terms used for resolution but they represent the same value in software like Photoshop (see this post for more details: Why does Photoshop call ppi "resolution"?)


How to change resolution on a low resolution image in Adobe Photoshop

Regarding the question about your low resolution images... you can still salvage them within some limits or at least try.

As I explained above, the higher the resolution, the smaller the pixels. What you can do to salvage your low resolution files is to raise the resolution of your image proportionally with your image dimensions.

I don't know what's the dimension of your images, but maybe you'll be surprised at the size they can be printed even if right now they're at 72-100ppi. If your image is really big at low resolution, it can be printed about 1/4 of its size.

Now, what you can do is to open your file in Photoshop, and go on the top menu "image" and then select "image size."

As you see on the screenshot below, you should uncheck the box "resample" before changing the resolution or the size of your image. Otherwise it will create "fake" pixels and increase the resolution of your image artificially which will make it look very low quality.

How to change the resolution in Photoshop

After you uncheck that "resampling" box, you should see the "link" that ties together the height/width/resolution. Change your resolution to 266ppi and see how the size changes. The new dimension is the minimum print size you can use your image for. As I mentioned, you can use 200ppi, and at the limit even 166ppi for digital printing (ex. Xerox, color Laser.)

How to safely resize an image or picture in Adobe Photoshop

Also, you will notice that the number of pixels didn't change at all beside it's the size of the pixel that was changed, not the quantity.

Now you can have a look at all your images and see how big they can be printed. If you're fine with the size, you can simply save your image with this new resolution.


If you really need to increase the size of your picture, there is some tolerance of about 20%; that means you can increase the size of your image of about 20% before seeing significant pixel distortion. To do this, you'll open your "image size" again, but this time check the "resampling" box, and change the size of the image to 20% bigger. This is to be done with precaution and if the result doesn't look good when you look at your image at 100% of its size on the screen, that means it's going to look probably as bad once printed!

Source: Pixel image - pn-design.co.uk, Resolution vs size image - i.stack.imgur.com, DPI image - e-education.psu.edu, LPI image - ajslabels.com

Edit: I added some precisions due to the confusion about measurements and units.

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Let us continue this discussion in chat. –  DA01 Jun 24 at 4:09

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