Poor Image quality upon PDF export

PeterBreis0807 wrote:

thanks Peter

You have not said what "full size" means nor what resolution the final image is at. Nor what you are viewing it in.

full size meaning 1200 pixels across the screen (actual size - however i should call it).. on a 1920px wide monitor, the full size image is a little less than 2/3 it's width..

(the images, as i have them now, are 72 px/inch.. it's my understanding that the resolution shouldn't matter as i'm simply aiming for one pixel from the tiff to equal one pixel on the monitor.. (and actually, in the pdf, the images will be a little smaller than 1200px wide) maybe this is where i'm going wrong in my thinking and misunderstanding the PDF format but if it's jpg,tiff,etc then resolution doesn't matter for screen viewing)

No it isn't if you just spend a little time working things out.

i've spent more than a little time so far.. sorry if i sound as if i have a bad attitude about this but at this point, i guess i do..

Pixels are sharp when there is at least one for every screen pixel _at final view._ Every time you blow up the image on screen you effectively lower the resolution of the document images. There are obviously only so many pixels to go around.

right, i understand this much
jeff

Message was edited by: flat5
added some stuff in parenthesis up there about the resolution

no acrobat and no messing with the image (straight output from a render app)

i sent an email though.. my internet connection is all sorts of weird right now so hopefully you get it in one piece.

thanks
jeff

Message was edited by: flat5

--well,actually, the jpg was converted from a tiff but i get similar results with the tiff.. also, i sent a different smaller image (650x1000).. just trying to keep the email size down.. super windy in nyc tonight and i think it's somehow affecting the interweb 🙂 --

PeterBreis0807 wrote:
Not sure what you are expecting.

well, i'm certainly expecting better quality than what i'm getting..

The jpg is contrasty and it is lower resolution than you need, but you did say that above. Which means I am not looking at what you are looking at.

The color space is srgb and the conversion from the tiff would have reduced the quality a little or a lot depending on your settings.

it doesn't matter if i use the original tiff or the jpg.. for all intents and purposes, let's forget i even have the tiff.. the jpg should look the same in the pdf (imo)

Did you print to pdf or Export? If you exported, did you use "Best" as your setting.

i've done all sort of methods.. but yeah, always at highest quality if said method allows such settings..

It has lost some contrast and is a little blurry. It looks to my eye like the degradation you get from setting the jpeg quality a little low.

well, no.. it has gone from something that is in focus to something that is out of focus.. if i open the jpg in photoshop and do a 'save as' jpg with the quality set to 3 (with 12 being best), i will get similar results as putting the jpg in a pdf.. (albeit, a different type of quality loss but just as bad)

you've seen the comparison but just in case someone else wants to look, check here:
http://homepage.mac.com/jeffhammond/Sites/imgs/origVSpdf.jpg

that's a screenshot showing the jpg on the right and the pdf output on the left (both viewed in preview)..

it's unacceptable.. but like i said earlier, i think this is an inherent aspect of pdfs and i'd settle for a decent explanation as to why it happens..

OSX has some very smart frameworks built in, which do make bitmaps displayed on screen in Cocoa apps look better than they should. Not exactly helpful if you simply want to see it unenhanced.

but still, if that's the case, why isn't osx doing the same thing to the pdf.. (and also, i highly doubt the actual quality of the image is being shown in the pdf but when i view the jpg, i'm being shown an enhanced view to the point of making an out-of-focus image being an in focus image.
jeff

flat5 wrote:

*(self quote)* it's unacceptable.. but like i said earlier, i think this is an inherent aspect of pdfs and i'd settle for a decent explanation as to why it happens..

well, except for the fact that i can get much better pdfs via photoshop > photoshopPDF

PeterBreis0807 wrote:
I'd check the size of the images in all versions, it really comes down to the setting that the jpeg is set to. I don't think the problem is the .pdf, unless something in one of the settings is recompressing the jpeg, which will inherently soften a jpeg.

i simply fail to see the logic here.
the jpg looks just fine and i want the pdf to look the same.. it's that simple.

if i had a poor quality jpg to start with and put it in the pdf, it should look equally poor.. not even more worse.

further, i've put a 4000px wide jpg into pages and scaled it to where the final output when view on screen will be around 1000 px wide (similar sizing to what i'm trying) and the quality still suffers.. especially when compared to resizing the 4000img in ps to 1000px wide...

i don't see why it's such a big deal to recognize and/or admit that pdf exports via pages are screwing up the quality of the original images.

jpegs are compressed by rendering clusters of 16 pixels with detail being discarded and edges reinforced to simulate detail. Not too bad if you do this once, but twice and the effect introduces artifacts.

I am pretty well out of the loop because you didn't send me what you are looking at, you sent me smaller files.

does it really matter? the files i sent you are fine to get the point across.. (the actual project is 25MB and contains sensitive material).. it doesn't matter what files are being used.. stick a 20mp image in there and you'll see the same drop in quality when compared to the original.

If you have Acrobat you can extract the various images from the .pdfs and examine them for size (indicates more or less compression) and a close side by side view in Photoshop to see the jpeg artifacts which will give you a clue of how much/many compression/s has/have been applied.

i don't have acrobat

pdfs can have compression set to zero, so the image should be identical in or out of the .pdf.

apparently, if that's true, you can't set pdf compression to zero in pages.. that's for sure.
jeff

haha.. wow.. i don't know what to say at this point.
(as i guess what i say isn't being considered anyway)

Message was edited by: flat5
but hey, going off the printing thing..

the loss in quality is pretty much exactly what i'd expect if i were trying to print an image that appears around 10" wide on a computer at 72dpi.. but, i'm not printing and if i tried, the quality would drop even worse..

and hey, how about we switch it up a bit..

instead of me showing you that something is wrong and you not believing me even though i'm offering proof.. how about you show me that something isn't wrong..

put an image in a pages doc and export it as a pdf in whichever slick way you know how and show me that there's no image degradation going on..

Message was edited by: flat5

you can use this site to get a HQ resolution chart:
http://www.gpsinformation.org/jack/printer-tests.html

PeterBreis0807 wrote:
Pages would be using the presets in ColorSync.

To see what they are go to the ColorSync Utility inside your Utilities folder inside the Application folder.

Editing these can be a pain though and mostly undocumented.

i've made my own custom ones at various settings already to no avail..
i'm telling you all, i've tried so many things and nothing changes.

However I have now opened all 3 versions of the image from the pdfs you sent me and the "Original" jpeg in Photoshop.

They are identical. And when I say identical I mean identical.

I suspect you are simply not viewing them under identical conditions. I note that in the "side by side" version the 2 halves do not match, so there would have to be some interpolation on screen.

right, the pdf version of the image is actually downsized.. if anything, the quality (or perceived quality) should actually go up..

..and seriously, i'm not a noob at this stuff.. (well, i don't often use pdfs for images which is where my questions are coming from).. i fully understand resolution, color space, and all that other fun crap that goes along with computer based images

PeterBreis0807 wrote:

PS Do I detect an agressive undertone? Because I am not responsible for this, just trying to help, which I do not have to do. I'm not doing anything you couldn't do for yourself.

probably.. big deal.. nothing personal.

i do think helping would be more along the lines of listening to what i'm saying instead of ignoring it and reverting to 'no, this works' because seriously, it doesn't work..