Changing PDF to bitmapped tiff without changing resolution or size.

[garys53312489]

  Background: We have lost our RIP server, we don't print a lot of long run envelopes anymore... but do.

Our imagesetter requires 2400 dpi one bit tiffs to burn a plate.

  After a lot of messing around I have finally figured out how to do the above, and make a 1 bit tif the platesetter will accept. However... I can't get the images to stop reducing slightly.

 Example. 

Original file is a PDF of a black only PDF. Page size is 13.33 x 18.86 in. (It MUST stay that size.)

And the PDF is 2400 dpi. (Must be 2400 or platesetter will reject)

  I open the PDF in photoshop, no matter what I do it changes the canvas size to 13.33 x 13.33. Even though in the PDF I changed every page box to 13.33 x 18.86. No matter what I do it make sit square.

Fine. So after opening, I change the canvas size to 13.33 x 18.86. 

  I then change the image mode to bit mapped. And save as tiff.

  The result is a 2400 dpi tiff, the size is correct as 13.33 x 18.86... however the image itself is approx. 30% or so reduced in size.

  I'm thinking this is happening when opening the PDF and it changes to 13.33 x 13.33.

  Kind of stressing. A person will lose their job if I can't figure this out. We are not going to spend the money on a new RIP, we will outsource the long runs...and a guy loses his job.

Thanks for any assistance.

[jane-e]

If you have Adobe Acrobat Pro, try one of these two methods:

• Single image
  Selection tool > right click > Save image as... > save as tiff or jpeg
  
  
• All images
  File > Export To > Image > jpeg, tiff, or png
  

"Even though in the PDF I changed every page box to 13.33 x 18.86. No matter what I do it make sit square."
How did you make this change in the PDF?

~ Jane

[garys53312489]

You can't export a 2400 dpi resolution PDF with that page size in Acrobat Pro.

One of the many things i have tried.

Thank you though.

[TheDigitalDog · Accepted solution]

Try ensuring the TIFF is is exactly the correct pixel dimensions. Exactly. For example, 13.33 x 2400 is 31,992 pixels (we're talking a big file here)! You need exactly 43,992 pixels on the other dimension. The resolution tag can and should be 2400 but the important attribute is the pixels. You may need a blank document exactly this size first, save as the TIFF you need, then attempt to 'rip' the PDF in Photoshop and place it into that document. 

[garys53312489]

Yeah they are pretty big until you export with LZ compression, which makes it about 300kb... but the raw file in Photoshop is 1.6 GB before compression... luckily I have a good Mac so it isn't too slow between steps. 

  You might have an idea here, and I see what you are saying. By creating the blank tif with the correct size, and then placing the art in afterwards, and then re-exporting again might work.

  Thanks!

[D Fosse]

Yeah they are pretty big until you export with LZ compression, which makes it about 300kb...

By @garys53312489

Something's completely off here. You don't seem to realize just how big 13.33 x 18.86 at 2400 ppi is! It's not big, it's a gigantic file, much bigger than most people will ever need, for any purpose.

There's no way you can export that and end up with 300 kB. That's compressing an airplane to fit in a matchbox! In that case it has to be massively downsampled and probably 99% of the original pixels discarded.

You need to get your dimensions straight first. This can't be right. Find out how many pixels you need. Size and ppi are indirect measures to Photoshop. It works only with pixels.

Pixels per inch (ppi) is not a standalone measure. It's an equation: total number of pixels/size in inches = ppi.

[garys53312489]

2400 dpi not ppi

[jane-e]

---

@garys53312489 wrote:

2400 dpi not ppi

---

DPI (Dots of ink per inch) is set by the physical printing device.

https://99designs.com/blog/tips/ppi-vs-dpi-whats-the-difference/

~ Jane

[garys53312489]

  It's confusing... if I change the resolution anything other than 2400 - the imagesetter will fail with an error stating - "file does not match resolution of the device". 

Works everytime with it set to 2400.

[TheDigitalDog]

Jane is correct but then I suspected the imagesetter might fail without having the actual document set (far too high) and apparenly it did. 

Take an Epson desktop printer as an example. Its output resoution is 1440 or 2880 DPI but you would NEVER create a document with that actual, physical pixels. You can send the print driver an image as low as 180PPI but ideally a bit more** and it does indeed produce 1440 (or 2880) dots per inch. 

But this imagesetter may be a very different beast. It may not need an actual document with 2400 pixels per inch yet, you describe that without this, it either doesn't print the size correctly or just takes a dump. 

So based on what you report, while Jane and the article are obviously correct, the issue is handing something to the imagesetting that will not pop an error. And after that, having it produce a print sized as you 'specified'. 

I'm not sure this will ever work. But again, a massvely large (and unnecessary document/TIFF) may work. Maybe. 

** https://www.digitalphotopro.com/technique/photography-workflow/the-right-resolution/

[garys53312489]

Yay!... this worked.

Step 1 - Create a blank file in Photoshop set at 2400 and 13.33x19.886 size.

Step 2 - Drop the PDF image, it will rasterize.

Step 3 - Change to grayscale

Step 4 - Change to bitmap (to get the 1 bit)

And whalaah - it is a 2400 resolution tiff, and it did not change the image size.

Files are about 300mb.

Only thing, which I may have to play with... photos are a bit muddy, the dot changes. But we almost never print photos on envelopes.

[Lumigraphics]

You may be seeing dot gain, depending on the press and medium you are printing on. High-quality coated paper handles ink differently than newsprint, for example. Old-school metal plates seem to work better as well, poly plates are ok for medium runs and paper for shorter. Are you outputting to film or directly to plate?

[garys53312489]

Metal plate, CTP.

You can see the dot change on the plate, almost as if there is dot gain... as in somewhere in the process of making the file a bitmap the screens darkened.