View Full Version : Pixels to dpi format?

12-06-2007, 10:24 PM
I am working on a cover for a coloring book. The size of the front cover is 10 7/8 x 8 3/8 and the print company needs it in pdf format at 600 dpi. Isn't there a Lightwave for print plugin or something that changes/convert pixels count into dpi format? Please I need help ASAP I have to get it to the printers by monday Dec 10.

12-06-2007, 10:51 PM
There's probably no need. As I understand it, if you're going to print, every dot would need a pixel. If you have to send 600 dots per inch, you have to send 600 pixels per inch, so no conversion would be necessary. If the cover is 10 and 7/8 inches, that would be 10.875 inches. If we have 600 pixels per inch and 10.875 inches, that would mean that we need 10.875*600=6525 pixels. On the other side we need 8.375*600=5025 pixels.

So we'd need 6525x5025 pixels. (I think)
BTW, you can enter "10.875*600" in the field. You don't need to multiply it yourself.

12-06-2007, 11:25 PM
The above is correct. But you are going to run into problems rendering at that resolution - most likely. If you do, save yourself much time and trouble and use Photoshop to upres the highest resolution you can render to the 600 ppi for the dpi the printer will need. Just make sure the proportions of the render are correct. What I then do is use the default image size settings in PS which is bicubic. Just set check resample/constrain proportions and set the size you need by the resolution. You will find very little if any noticeable artifacting with anything from 2 to 3 times the size. I do a lot of printing of oversize photo-quality prints of my artwork using this method with no problems and beautiful results.

12-06-2007, 11:42 PM
Yes, as Surrealist said, if you have problems rendering out at that size, use Photoshop, or better still the Photoshop plug-in "General Fractals" to up the Res.

12-07-2007, 03:17 AM
we use PhotoZoom for the resizing to bigger formats and it is great...it's not the same as rendering at the final format but the results are really good.

12-07-2007, 06:38 AM
Check with the publisher before scaling up in Photoshop, because even the best plug-ins can cause degradation of the image. Memory is cheap these days, anyway.

12-07-2007, 06:42 AM
... 600 dpi ... is this medical imaging for chemical film?
That's a bit steep. Most offsets work with 280 dpi max, most stipulate 300 dpi for some freedom, but 600dpi? Are you sure it wasn't the file clerk at the front desk that just checked his digital printer capacity that told you this? 600dpi printers are not comparable to 600 dpi images, although it sounds like they should. A 1200dpi printer works fine with a 300 dpi image. Rule of thumb is 4 dots per inch (CMYK) per pixel per inch.

Confusion arises because PPI and DPI are mixed in use in programs and daily life. PPI = pixels per inch is what your computer file is and DPI is what your printer is. It takes 4 dots to make 1 pixel, for one of each of the colors Cyan, Magenta, Yellow and Black.

12-07-2007, 06:51 AM
Confusion arises because PPI and DPI are mixed in use in programs and daily life.
..or even worse, when LPI come into play... ;)


12-07-2007, 06:53 AM
Just use this: