First, I know similiar issues has been discussed here before. Ive read them, but I cant find what Im looking for.
Secondly, I have some experience with adobe and graphic design, so hopefully this isnt a basic error from my part
For some reason when I place an image in ID it looks kind of crappy. Jagged edges. I know it's just a preview and it can be set to 'high'. That isn't my problem. Problem is, when exporting ID-file, the PDF looks crappy too. I've tried with hi-res images (300dpi) and PDF:s (from my cad software, SolidWorks) but none of them looks good enough.
I got decent result when I scaled a huge image down considerly. But I could still see some jagged edges. Tomorrow Ill try with a Illustrator file and see if the problem somehow is related to Photoshop (Ive experienced some issues with PS before), but since my PDF:s dont look too good, I doubt I will see any diffrence.
When viewing on my iPhone or Ipad it looks much better, but still not good enough.
So, I have 2 questions. First why is ID behaving like this? And secondly, if this is how ID is supposed to work, how high quality must my images have?
I use ID 5.5
You get jagged edges when you have a slope. Whether the jaggies are visible depends on how small the steps are relative to the overall dimension. A 45 degree slope spread over 3 units will look like a set of stairs, but spread over 300 units it will probably look pretty smooth, especially if there is anti-aliasing.
So basicly there will always be a some loss of quality?
Say I would like to convert some of the images at our website (http://www.rutgerdesign.se) into A4-size PDF, what resolution would I have to use?
Both monitor screens and modern printing techniques use grids of some sort for output, so yes, technically, there will always be some loss of crispness for any output that has edges that are not aligned to that grid. The question becomes how small a step can you discern with the eye? and the answer is it depends on how sharp the edge contrast is and how far away you are viewing the output.
There is no single "correct" resolution, but there are some rules of thumb that will get you by. InDesign will show you two resolution values for your raster images, Actual and Effective. Actual is the saved resolution at the saved size in Photoshop, and is completely meaningless. Waht counts is the effective resolution, the resolution of that image at the size you have chosen to use it on your page. For digital printing, an effective resolution around 200 ppi is a good target for continuous tone, and for typical commercial printing (150 linescreen on press) 300 ppi effective resolution is a good working target, assuming the output will be viewed at arm's length. Soft images require less resolution, very fine detail may require more. Line art (monchrome) rasters should typically be placed with an effective ppi equal to the output resolution of the printing device (2400 to 2800 ppi for press, 600 to 1200 for most printers), but as a practical matter, 1200 is a "good enough" value most of the time. Vectors are without resolution until output, and always convert to the resolution of the output device for maximum available smoothness. It's possible your CAD drawings are not actually smooth curves, too, but really short straight line segments, and enlargin thaose tends to make that more obvious.
A good discussion of resolution can be found at Distance-Resolution Formula
I have all the files at work. but heres a link to another pdf. It should be at least 300ppi. Ive printed it as a quite big poster, with no jagged edges at all, but I didnt use ID at that time.
A preview on Google docs doesn't tell me much, but there's nothing in that file that should be raster but the shadow, so you could presumably get good quality output as a billboard.
If you are placing vectors in ID, you are going to get some loss of quality in the on-screen preview because ID is making a jpeg to show you. There should be no jaggies in your printed output beyond those imposed by the limitiations of the output device. A 300 dpi printer would probably show jaggies, 600 dpi less so, and 1200 dpi or press output should appear smooth fo art similar to that poster.
Im only concered with digital viewing, at the moment. The PDF (link in previous post) has jagged edges. I wonder why, and how I can make the image smoother. Its a PDF I made today.
To be clear. I want to make a PDF with good quality for digital viewing.
With vectors in PDF you're likely to see jaggies at some zoom levels and not others, and it matters what resolution setting is set in the Acrobat prefs, and to a large extent on things you can't control (including that resolution setting) like smoothing that are all user preferences. The bottom line is you have not control at all over what sort of equipment your viewers are using, or the software, so you can ony do the best possible job on your end and hope for somethig acceptable on their end.