For our series “Ask the Printer” today we meet Renato Galbiati A pro user of the Adobe Suite, Renato owns Graffidea, a graphic design and printing agency specialising in advanced print solutions on special supports in Bergamo, Italy. Renato is also a well-known professional among the innovative Roland community of the so called “High-tech Artisans”. Over to you Renato:
‘In our work every day we realize creative layouts with images, intended for different purposes: from web campaigns to brochures to billboards. Our task is to prepare the right file for every need.
In this short article I will address some issues related to resolution of the images intended for the web and for digital printing.
To measure the image resolution we refer to PPI (pixel per inch), while DPI (dot per inch) refers to the print resolution of digital printers (plotters, ink-jets etc).
It’s essential that the image resolution is adequate for the intended use.
As the average monitor resolution is 72PPI, the right resolution for web campaigns is 72PPI. New monitors may have a higher resolution, but this is not yet the standard.
NOTE: from this window (above) you can also see a preview of how it will display on the browser.
If we start from a 300ppi image, the advice is to bring the resolution to 72ppi. This process will allow to have lighter images to be loaded quickly by all browsers and mobile devices.
Hence, if our image is in 300PPI we need to reduce it before online publishing. How to do that?
Open the file in Photoshop, version CC2015, and click on “Export” from the File menu, then on “Save for Web”. A new save dialog box opens up where we may select some settings: choose the right format depending on your needs (jpg, gif, png); the quality and the size modification in pixels.
Brochures, leaflets, cards, presentations
Different story when we need to prepare for print a layout containing images. First of all we need to check the image quality and make sure it’s adequate to support a perfect visualization by close distance. A good resolution should be at least at 200ppi, based on a minimum resolution of 6MP (mega pixel).
My colleague Sergio in the previous post gave some good tips about color profile in file-to-print conversion (RGB or CMYK). I will add that ideally the files should be delivered ready to print, and that we should not rely on the printer for all changes required.
A large format print gives us more room to maneuver and does not require all those tricks that are necessary when we deal with fine art.
The third case we consider here is the large format print: panels for tradeshows, stadium banners, billboards… Usually a work intended for large/wide format will be seen from distances greater than 3 meters; for this therefore it is not necessary for our images to be at a very high resolution. In fact, it’s not true that the larger the print, the greater must be the resolution. Rather, the opposite.
From an image with 300ppi resolution, in Photoshop we open the “image size” dialog (image/image size). From this window we can change the resolution of our image and therefore its size.
For example, let’s say we want to realize an extra-large poster with a base of 400cm. In Photoshop we will set the desired width and height proportionally, as in the image above. Make sure you have selected “Resample” and “softer Bicubic method for enlargements.”
As we said, for this intended use, we don’t need a huge resolution. We may set it to a value that can vary from 100ppi and in some cases even down to 50ppi, depending on the image quality and also on the type of work you are dealing with.
At this stage to enhance the final result, we may consider to add some contrast, by applying unsharp masking, or alternatively, with the classic “S” curve.’
Thank you Renato for sharing your tips with all of us!