The 300dpi myth

All through my time as a newspaper and magazine journalist, the respective design departments sang the same pitiful mantra when asked what size images they required for print: “Any size, so long as it’s 300dpi”.

Like any good myth, this statement is rooted in partial authenticity – a veneer of truth to make it seem plausible. However, the “300dpi myth” is a half-truth. Okay, it’s a damn lie – and one that does nothing to explain image size, resolution or quality. It could also get in the way of selecting or using a quality image in your next print project or editorial piece.

With the digital age in full swing and almost every industry professional with access to at least one quality imaging device, one would have thought that the “300 dpi myth” would have gone the way of the plesiosaur. But the myth reared its scaly-assed head again for me this year when an editor friend sent me an image to confirm whether it was of sufficient quality for print.

You’ve probably guessed by now that my friend was worried that he could not use the image because it was “only” supplied at 72dpi. It’s easy to get wrapped-up in the 300dpi myth. I know this because back in the days of film, I refused to use a repro house because they always supplied scanned images at 72dpi and not what the design department said they wanted, which was obviously 300dpi.

My bad.

So, if you have been listening to an editor or designer who has been equally infected with the 300dpi disease, please print this article out, take it to them to read and banish their bad advice from your mind forever.

In short, the “300dpi myth” is a load of bollocks because almost any image can be converted to 300dpi in software such as Photoshop without interpolation. Even the online Google logo can be converted to 300dpi.

The 300dpi value, by itself, does not represent anything of any real value in terms of identifying image size or resolution. Yes, it’s important for print designers to supply final image files in CMYK and at 300dpi for the printing process, but many (most?) digital cameras have a default output set to RGB and 72dpi. This does not mean the respective photographer or your camera is turning out sub-standard images.

Pixels determine image size
The fundamental determining factor for image size is the actual pixel dimensions of the image file. This information is located above the “Document Size” in Photoshop. Multiplying the pixel width by its height reveals its “megapixel” size.

A 6mp DSLR would output pixels at around 3000pixels wide by 2000 pixels high. 3000×2000 = 6mp.

My 12mp DSLR outputs pixels at around 4256 wide by 2848 high. 4256×2848 = 12.1mp.

The Megapixel and DPI Relationship
There is a relationship between the number of pixels and the final print size which can easily be seen in an image editing program such as Photoshop.

Note the first Photoshop screen capture. At 300dpi, my 12mp (4256×2848 = 12.1mp) image will happily be able to print an image on a page 36cm wide and 24cm high. That’s way over a standard A4 page, which measures 21cm wide and 29.7cm high.

Note the second Photoshop screen capture. At 300dpi, my 6mp (3000×2008 = 6mp) image will happily be able to print an image on a page 25cm wide and 17cm high.

At 72dpi the same 6mp image can be printed at some monstrous size as indicated by the third screen capture above.

So, as you have probably now noted, the DPI as “dots per inch” or “pixels per inch” is an indicator of pixel density, not actual image size. The two are certainly related, but on it’s own, DPI does not offer any indication of image size or quality.

Tags: 300dpi, design, Photography, photoshop, print, printing