rubbish quality of bitmap images when using "reduce file size"

peace flaps · March 19, 2008, 05:09:24 AM

for a lot of the jobs i have to do at work, i create 1200dpi bitmap images (usually tif files) and place them into quark or indesign - then export as pdf files.

obviously, some of these files can be quite sizeable and need to be reduced for emailing for approval.
up until recently, these reduced files showed no loss of quality (when previewed on screen or printed out) but now there seems to be a massive difference between the reduced file and the original.

checked in the prefs section of acrobat but the compression options don't seem to make much difference.

any pointers as to where i'm going wrong?

thanks in advance - joe

frailer · March 19, 2008, 05:27:16 AM

Hi and welcome, peace flaps. There's plenty of experience here, and there'll be some more input for you...in the meantime; have you tried Advanced>Print Production>Optimize?...as an alternate route? You can set/adjust in there too. Could be your Prefs have gone whacky, as well.

peace flaps · March 19, 2008, 05:37:37 AM

cheers.
just tried the optimise route to see if its any better and it gives the same crummy results - looks like i need to toy with the settings a bit more

also - just as an example, here is what is happening:
http://www.zshare.net/download/9172786706f886/

fingers crossed that its just a setting needs altering

almaink · March 19, 2008, 06:15:22 AM

Even 1200 DPI bitmaps are pretty small if they R converted to 1 bit bitmaps. CCITT Group 4 is what I use, I see your using Group 3. Remember 300 DPI will never look like 1200 DPI, I don't care WTF U do. I would stop the resample and just use CCITT Group 4 compression.

peace flaps · March 19, 2008, 09:05:30 AM

excellent work guys - it was due to the downsampling (the settings must have changed - maybe after an update?)

left the CCITT Group 4 on and its giving the nice results that i'm used to.

this site rox!

ninjaPB_43 · March 19, 2008, 10:03:52 AM

Quote from: peace flaps on March 19, 2008, 09:05:30 AMthis site rox!

indeed! Tell all your friends.

Sparky · March 20, 2008, 08:38:30 AM

Quote from: peace flaps on March 19, 2008, 09:05:30 AMexcellent work guys - it was due to the downsampling (the settings must have changed - maybe after an update?)

left the CCITT Group 4 on and its giving the nice results that i'm used to.

this site rox!

we're just a bunch of "rox m sox m robots" :cool:

Tracy · May 21, 2008, 02:05:21 PM

Quote from: almaink on March 19, 2008, 06:15:22 AMEven 1200 DPI bitmaps are pretty small if they R converted to 1 bit bitmaps. CCITT Group 4 is what I use, I see your using Group 3. Remember 300 DPI will never look like 1200 DPI, I don't care WTF U do. I would stop the resample and just use CCITT Group 4 compression.

Hey can someone explain how to use this CCITT? I always thought reducing file size always caused it to look low rez, I didnt know you could do it another way. Thanks

Tracy · May 21, 2008, 02:16:02 PM

Ok, so you have to do it while your making the pdf. I sometimes make a reduced pdf from a high rez one, for emailing.
Thanks

Tracy · May 21, 2008, 02:20:29 PM

Oh I see they have seperate options of CCITT3 and CCITT4 and 4 is the way to go!
I will play around with this, yay learned something new again.

Tracy · May 21, 2008, 03:35:24 PM

I played around with some pdfs and they do indeed make better reduced pdfs with the CCITT4!
I did find in acrobat under advanced_pdf optimizer also has the CCITT4, Thanks

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rubbish quality of bitmap images when using "reduce file size"