Printing means to transfer images and sound (or the image of the soundtrack, to be precise) from one film to another. It is not so relevant, at this stage, if the original is a negative image or a positive image. Therefore, the printing equipment must produce a transfer that can be as close to the original as possible, from photographical and mechanical point of view.
Photographically, the image produced on the raw stock must have similar characteristics in terms of resolution, while the characteristics of density and contrast must correspond to the ones chosen by the grader or the person responsible for the duplication route.
In addition, the printer must perform exposure corrections (light changes) at the exact position and of the exact amount as per the instructions it received by the grader. Mechanically, the printing equipment must not add any unsteadiness to the images of the original. All of this is obviously ideal perfection, which does not exist.
We should also be aware that in the analogical domain, a perfect transfer is never possible; so a relative loss of information always occurs, as well as modification of the contrast due to the different types of printers used (e.g. contact or optical), and a certain degree of unsteadiness can happen. It is our responsibility to keep those "losses of quality" well confined within limits that we accept according to the purpose of our printing. Therefore, in case of serial printing of positive release print, the standards of quality required are usually lower than the ones required for duplication or the production of a preservation master. This does obviously mean that printing procedures as well as type of printing equipment to be used must be carefully chosen according to the production process we are undertaking.