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Tuesday, July 23, 2013

Same image, different job. FAQs


During our working week we get many requests from clients as to format requirements for images.


"I've grabbed this picture from our web site is it OK to use for my print job?"

So... Here's a guide, hopefully simply explained, as to how to get your pixels purring.


When preparing graphics for a web or print job there are key requirements that must be considered. 
  • Is the image large enough in pixels - dots per inch (DPI)?
  • What's the colour spec for the image...  Spot PMS, RGB or CMYK?
  • What's the final production size of the image when used (pixels for screen, millimetres/inches for print)?
OK, deep breath, here we go....

COLOUR MODEL:
RGB. This is a colour gamut made up of three colours, Red, Green and Blue. Web or on-screen graphics are a combination of these three building blocks. This is because you are looking at the finished product through your monitor/tv which is displaying RGB pixels.
CMYK.  This is how litho print is reproduced by printing four colours, Cyan, Magenta, Yellow and blacK.  The arrangement of the litho printers screen 'dots' in these four colours give the impression of almost any specific colour combination.  Next time your at your local bus stop sporting a large display poster (the bus stop, not you!), take a closer look, you'll be able to see the small CMYK dots which make this up (just make sure the other bus travellers don't spot you!).  

Be aware though that certain colours lose integrity when reproduced in CMYK mode as opposed to RGB, blues and oranges are particularly prone to this.  See these examples below...




Sometimes to overcome this the best option is to print a 'fifth' colour - a spot PMS.
SPOT PMS. This is a second colour option that can be used with or without CMYK for print.  It's a prepriority colour system by Pantone (Pantone Matching System) for printing flat pre-defined mixed colours.  Great for specific branding colours and guaranteeing an exact colour match... but use with caution, this adds to your printing price if used with CMYK (4colour printing) adding an extra colour 'plate' for each PMS used.


IMAGE RESOLUTION:

Image resolution relates to the amount of detail in an image.

Image resolution for digital images is measured using pixels per inch (ppi) or dots per inch (dpi). The more pixels/dots there are in a given square inch, the more detail the image has... the higher its resolution.

If it's a print job you need images at the finished size it appears in the design at 300dpi, CMYK.

For Web/on-screen you don't need such a high resolution, monitors just don't need that amount of detail information, you'll need to dig out images at just 72dpi RGB at the viewers pixel size.

If it's going to be run out internally on the in-house office printer, you rarely need anything over 150dpi (most modern printers can handle CMYK or RGB)

So... What happens if you've only got RGB web graphics for your printed prospectus?
Well, no need to panic just yet, your designer has all the tools to convert the file to CMYK for print, RGB would not give a good colour reproduction when the printer prints out for a CMYK destination.  But you must be aware that it can only be used at the finished size it's required at 300dpi.
So if your image is 100mm at 72dpi when you increase that to 300dpi the actual reproduction size reduces to around 24mm

We always create our graphic elements at the highest resolution possible. Experience has told us that once a client has approved the lower resolution web version they invariably decide that they'd like to produce a leaflet or advertisement utilising the same graphic - it's then an easy job to go back to the high res original and re-save for the new project saving time and money.

The problem comes when you scale your web grabbed 72dpi graphic up to beyond the 300dpi interpolated conversion size for print.  The 'bit map' image will start to degrade and pixelate.  Not a pretty look.

Here' an example of a web-resolution image being scaled up beyond it's limit for print.  Note the 'blurryness' of the enlarged shot.




VECTOR GRAPHICS
The vector file format has none of these scalability issues because of it's mathematically calculated colour, rather than pixel based bit map, any size can be enlarged without any degradation in quality.  Great for illustrations, logos and flatter colour formats. Not so good for detailed photography.

We design a logo to work in it's simplest mono form first, vector format is ideal for this.  If it maintains visual impact in black & white it will generally work in any colour situation.


If your not sure...
The ideal scenario would be for the designer to originate your artwork requirements from scratch.  Supplying your logo and graphics in the correct colour and size options in a variety of formats for web, internal use (Word, PPT presentations etc) and print.  They would originate any photography or images to the correct size and resolution.

Final warning.
Printers proofs are always recommend before biting the bullet and going with the final print run.  Variables like paper stock absorbency, brightness and ink coverage could all make a difference to it's final look.

Hopefully all this helps and doesn't confuse too much, but don't worry your designers know what they're doing!




Mark Fletcher
Graphic Designer

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