Page Size, Aspect Ratio, Print Resolution

This is a technical blog on Page Size, Aspect Ratio, Print Resolution and is based on the standard print resolution of 300 dpi (dots per inch). If you’re not a technical person or are not interested in figures, you may stop reading at the end of this paragraph and rest assured that Stuart Brown Photographic know the mathematics behind this and can take all the headache out of producing stunning brochures by doing the graphic arrangement for you.

The rest of this article is for the benefit of anyone interested in print sizes and resolutions for brochure production. Most brochures are printed on an “A” format paper, typically A4, the first thing to note about these sizes is they all have a 5:7 aspect ratio:

Page Size Aspect Ratio Print Resolution

Aspect Ratio of A4 sized brochures, single and double page spreads

A5 149mm x 210mm, divide both sides by 30 = 5×7

A4 210mm x 297mm, divide both sides by 42 = 5×7

A3 297mm x 420mm, divide both sides by 60 = 5×7

A4 portrait brochures open up to a double page spread of 297mm x 420mm (exactly A3 size) retaining the 5:7 aspect ration albeit switching from portrait to landscape, however when used in landscape the double page spread takes on a panoramic format of 210mm x 596mm.

A4 double page spread landscape, 210mm x 594mm, divide both sides by 35 = 6×17

Well very nearly a 5:7 aspect ratio in all cases. A4 portrait (297h x 210w) opens up to A3 landscape (297h x 420w), hence if imagery is required to allow borderless printing in this size, it’s a simple matter of producing a mixture of portrait and landscape images in a 5:7 aspect ratio. Switching to A4 portrait, opens up to an internal page spread of 210mm (high) by 596mm (wide), divide both dimensions by 35 and you get very nearly a 6:17 aspect ratio. It’s perhaps interesting to note at this point that both 5″x7″ and 6cm x 17cm are standard film sizes in large and panoramic format cameras and are both still in use today. Digital cameras, however generally have either a 2:3 or 3:4 aspect ratio, so in order to produce images in these aspect ratios some cropping (loss of pixels) must be done.

Printing Bleed

One further technical complication in borderless printing is the need to have a “bleed”, printers generally ask for a 3mm bleed all round to print borderless. E.g. an image would be sized 216mm x 303mm to print A4 (210mm x 297mm), with 3mm off the top, bottom and both sides of the image not being printed. Printers will also generally require a resolution 300 dots (or pixels) per inch. I.e. Page Size, Aspect Ratio, Print Resolution for borderless printing:

A4 Image with 3mm bleed

3mm bleed on A4 landscape document

A5 149mm x 210mm > 155mm x 216mm (6.1″ x 8.5″) > 1831 pixels x 2551 pixels > 4.5 mega pixels

A4 210mm x 297mm > 216mm x 303mm (8.5″ x 11.9″) > 2551 pixels x 3579 pixels > 9.1 mega pixels

A3 (equivalent to A4 portrait double page spread) 297mm x420mm > 303mm x 426mm (11.9″ x 16.8″) > 3579 pixels x 5031 pixels > 18 mega pixels

A4 landscape double page spread 210mm x 594mm > 216mm x 600mm (8.5″ x 23.6″) > 2551 pixels x 7086 pixels > 18.1 mega pixels

Camera Sensors

The two most common types of camera used in professional photography are, small format digital single lens reflex (DSLR) and medium format digital. Full format DSRL cameras have a 24mm x 36mm (2:3 aspect ratio) sensor and medium format typically around 40.4mm x 53.9mm (3:4 aspect ratio). So in order to be able to produce images suitable for printing at these resolutions, even more pixels will be required in the original file prior to cropping.

DSLR Sensor Requirements – Single Image Shots

The impact of Page Size, Aspect Ratio, Print Resolution for printing from DSLR image files on required sensor resolution:

A5 borderless, 1831 x 2551 pixels, 1831 pixels high > 2747 pixels wide > 5 mega pixels

A4 borderless, 2551 x 3579 pixels, 2551 pixels high > 3827 pixels wide > 9.8 mega pixels

A3 borderless, 3579 pixels x 5031 pixels > 3579 pixels high > 5369 pixels wide > 19.2 mega pixels

A4 landscape double page borderless, 2551 pixels x 7122 pixels > 7086 pixels wide > 4724 pixels high > 33.5 mega pixels

With this progression in pixel requirement, we can see only the highest resolution DSLR cameras have sufficient pixels to produce A4 landscape double page borderless spreads from single image shots, image stitching would allow lower resolution cameras to generate the required number of pixels. At the time of writing most current DSLR cameras have in the range of 16 – 22 mega pixels with a few specialist models in the 36 – 50 mega pixel range.

Medium Format Sensor Requirements – Single Image Shots

The impact of Page Size, Aspect Ratio, Print Resolution for printing from medium format digital files on required sensor resolution:

A5 borderless, 1831 x 2551 pixels, 2551 pixels wide > 1913 pixels high > 4.9 mega pixels

A4 borderless, 2551 x 3579 pixels, 3579 pixels wide > 2684 pixels high > 9.6 mega pixels

A3 borderless, 3579 pixels x 5031 pixels > 5031 pixels wide > 3773 pixels high > 19 mega pixels

A4 landscape double page borderless, 2551 pixels x 7122 pixels > 7086 pixels wide > 5315 pixels high > 37.7 mega pixels

As most medium format digital cameras come with either: 50, 60, 80 or 100 mega pixel sensors, producing the required print resolution with this type of camera is not going to be an issue.

Conclusions

As large format cameras were mentioned earlier, scanning form 4″x5″ film, typically generates a maximum native resolution of up to around 70 mega pixels on virtual drum scanners and up to 320 mega pixels on wet mounted drum scanners depending on settings, providing adequate resolution to crop to almost any paper size.

One way to overcome the limitations placed on printing large images caused by the number of pixels on smaller or older digital cameras is to stitch multiple images together to form a large one, this is in fact quite a commonly used technique to produce panoramic images. Producing panoramic landscapes in this way generally works well. The technique though is not without limitation, if for example a long low rise building such as. a train shed were to be photographed with the camera positioned centrally and panned left and right the outcome would be “barrel distortion” where the building tapers to each end. In examples such as this when viewing with the human eye, the human visual system kicks in using the most powerful image processor in the world, the human brain, which produces an undistorted view in our minds that cameras find challenging to reproduce.

By engaging Stuart Brown Photographic, specialist architectural photographic equipment, skills and techniques are used to overcome the limitations of page size, aspect ratio, print resolution and distortion.