actual print size-want to be sure there is no pixelazation

Are you working with PDFs and using Acrobat? I ask because this is the Acrobat Printing & Prepress forum only. This may I think be a question for the Photoshop forum.

Hi Alinas,

Please find hereafter a crash courses in printing and resolution relationship.

First to know:

There are 2 different image types:

1. Vector: Vector images as created by tools like Illustrator can scale up and down to any reasonable size without quality problems.
2. Pixel: Pixel images like photographs or art work created by tools like Photoshop do not scale up without quality problems. They can, however, scale down quite good.

It is also interesting to note that an Illustrator file may contain also pixel graphics and that a Photoshop file may also contain vector art.

Now to the question of a correct resolution:

A correct print resolution is normally stated to be 300dpi at the reproduction size. This my vary for very high quality art books to 400dpi or lower dpi for lower quality newspaper prints. 300dpi is the standard, so that is a good point to keep in mind.

There is also a relation between the viewing distance and the required resolution. Big posters (A0) do not need a that high resolution as smaller prints (A4 or letter size). So for big posters I use a resolution of 100dpi. For standard brochure prints, I make sure that my pictures are at 300 dpi. My printer service provider for brochures sends me a warning, if the resolution is below 240dpi.

If you have the chance to start a design from scratch, look at the biggest size you need, considering above rules. For sizes of up to A3 I would use a resolution of around 300dpi. If you scale that design up to A2, the resolution will be only 150dpi. If you scale further to A1, your design will be at 75 dpi, starting to get limit. I suppose you understand the concept. The image will always have, in this case, the same size in pixels, only the pixel density will go down. Basically you will have no change to the picture.

If you need to scale up a pixel image, ie add more pixels to the picture, please note that a current version of Photoshop does a quite good job in recalculating the image, so that not too much of the sharpness gets lost. But there are limits. If you can avoid, avoid scaling up, if you can't, try to limit the scaling to the absolute minimum. I have learned, however, that I prefer scaling up in Photoshop and controlling the quality than letting the printers rip doing the scaling.