Saving a photoshop document as a .pdf results in blurry / pixelated images

Question

Hi All,

I am using Photoshop CS2 to design a leaflet which is intended for distribution by email as a .pdf. My document is 72 dpi, which i believe is a suitable default for non-printing use.

There is one image in the document, a logo, and this is always appearing pixelated in Acrobat reader when i save the doc as .pdf. It looks fine in Photoshop. I have tried just about every option and combination of "Save As" options, nothing makes any difference.

I have tried both tiff and jpg versions of the image, to no avail. I also notice that if i choose no compression when Saving As, the resulting file size is gigantic - 10+ megs, even though the image is only 10k! And the image STILL is pixelated.

Any suggestions?

Thanks Richard.

Answer 1

OK, I have fixed this - sort of.

The image looked pixelated when displayed in Acrobat Reader at a display zoom of 100%. I assumed that 100% would simply mean that if doc was say 1,000 pixels wide, it would render at 1,000 pixels on the screen. However this is not the case. I don't understand what 100% means exactly, however at 100% it is being rendered at a somewhat larger size, say 1,300 pixels. Hence the image is pixelated as it is being stretched. If I reduce zoom to ~70%, then it renders fine.

I'm guessing that Acrobat is attempting to render the doc in terms of "inches" and not pixels. My doc is A4 = 8.5 inches wide, I think Acrobat is rendering an 8.5 inch doc at my screen resolution, which per careful measurements with a ruler is 110 dpi.

Anyway, the solution is therefore a) de-zoom to 70%, or, as I imagine most people will assume 100% is the optimal zoom, b) to re-do the doc at 110 dpi, or a little higher, to accomodate whatever typical resolutions are these days.

Answer 2

A normal Windows display is considered by Windows to be 96 DPI, regardless of your actual monitor size or resolution. I don't know what it is for a Mac.

Answer 3

If it's a logo, you should embed a vector version of it instead so it scales properly regardless. This is simply not a Photoshop job, nor is creating a PDF leaflet a Photoshop job.

But as a rule of thumb, regardless of the intended media, use atleast twice the dpi needed for it - especially if you use non-scalable graphics elements. Also, the 72 dpi idea as you noticed simply isn't true - searching for 72 dpi myths or facts might give some useful result atleast trying to explain the wierdness of it...

Answer 4

Photoshop really isn't the best choice for publishing tasks such as design of leaflets and posters. Sticking within the Adobe family if you have deep enough pockets, you could look at InDesign for page layout and Illustrator for vector artwork for figures and logos.

On the free and open source side of the divide, consider Inkscape for line drawings and Scribus for page layout.

Scribus is in many ways a better producer of high-quality PDF documents than any of the Adobe tools. It is a large and complicated tool that is really intended for high end publishing, but it will get the job done.

Your problem with things looking pixilated is almost certainly the result of the settings used for image compression when Photoshop transformed your page image into the bitmap image layer of a PDF page. I have never been happy with that approach, myself, because of the kinds of problems you are having.

When producing a PDF for print, you need to have all of your graphic elements sized so that layed out on paper, at least as many pixels are available in the image as on that much paper. At 300 dpi, a 2x3 inch photo must be at least 600x900 pixels. Depending on lots of other factors, it may be important that the image be sized to an integer multiple of the actual print resolution for best results. Depending on your print provider, you might also need to make sure that your illustrations use only in-gamut colors for the intended print process...

When producing a PDF for screen use, it is conventional to assume that screens are 72 or 96 dpi. Neither is precisely correct, but both are close enough to true for the average user. Note, also, that documents for use on screen should almost certainly be prepared in the SRGB color space, which is based on the colors available on an average uncalibrated RGB monitor. Avoid the temptation to use niche color spaces such as AdobeRGB, because they will only look right to the vanishingly small percentage of users that know about color workflow and have calibrated monitors. Incidentally, you have calibrated your monitor, right?