IP's Geek Corner
FAQ's
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If you have any questions regarding print or design please view the FAQ's section below, if your questions can't be answered here then please feel free to post it on our forum where somone from the IP studio's or the public will answer it for you!

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Colour is colour, right? Wrong! Depending on your application and use, there are two main colour referencing formats you will come across: RGB and CMYK. These two colour formats are for completely different uses, but the result of the two formats is the same to our eyes.
 

RGB: the primary colours of light

RGB is an acronym for Red, Green and Blue: the primary colours of light. When your computer monitor or television screen reproduces images, the three primary colours are mixed together in varying shades and strengths. The important distinction here is that light, rather than ink, is used to reproduce an image. Just because a picture looks one way on a monitor or television screen does not mean that it will be reproduced accurately on paper.
 

CMYK: the primary colours of ink

CMYK is an acronym for Cyan, Magenta, Yellow, and Black: the primary colours of ink. When your printer reproduces images, the four primary colours of ink are mixed together in varying shades and strengths.

You are probably noticing the pattern about now, in that RGB and CMYK do the same thing but in different ways. What you have to understand is that RGB references light and CMYK is ink.

 

What all of this means.

You cannot print in RGB and you cannot view pictures on a monitor in CMYK. So, to answer our first question of how to know when you are using which colour format, monitors display in RGB and printers display in CMYK.

A conversion process has to take place to go from viewing pictures on a monitor to viewing the same pictures in print. What's more, the conversion is not always perfect or accurate. As to how this affects colour printing: there may be differences between what you see on the monitor and what you get back from the print shop. You can compensate for this by calibrating your monitor and through printing proofs to make sure your work is translating properly.

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JPEG (Joint Photographic Experts Group)

JPEG is a standardised image compression mechanism. JPEG is designed for compressing either full-colour (24 bit) or grey-scale digital images of "natural" (real-world) scenes.

It works well on photographs, naturalistic artwork, and similar material, not so well on lettering, simple cartoons, or black-and-white line drawings (files come out very large). JPEGs handle only still images, but there is a related standard called MPEG for motion pictures.

JPEG is "lossy", meaning that the image you get out of decompression isn't quite identical to what you originally put in. The algorithm achieves much of its compression by exploiting known limitations of the human eye, notably the fact that small colour details aren't perceived as well as small details of light-and-dark. Thus, JPEGs are intended for compressing images.

A lot of people are scared off by the term "lossy compression". But when it comes to representing real-world scenes, no digital image format can retain all the information that is projected on your retina. By comparison with the real-world scene, a JPEG loses far less information than a GIF (see FAQs for definition.)


Quality v Compression

A useful property of JPEG is that the degree of lossiness can be varied by adjusting compression parameters. This means that the image-maker can trade off file size against output image quality.

For good-quality, full-color source images, the default quality setting (Q 75) is very often the best choice. Try Q 75 first; if you see defects, then go up.

Except for experimental purposes, never go above about Q 95; using Q 100 will produce a file two or three times as large as Q 95, but of hardly any better quality. If you see a file made with Q 100, it's a pretty sure sign that the maker didn't know what he/she was doing.

If you want a very small file (say for preview or indexing purposes) and are prepared to tolerate large defects, a Q setting in the range of 5 to 10 is about right. Q 2 or so may be amusing as "op art".
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The reason why you would need to convert outlines to text is because even though most printers have an extensive font library, there is no guarentee that they will have that specific font, or that your chosen font will look the same on the printer's computer.
That's why in the Adobe Creative Suite, old Freehand versions and Coral Draw you have an option to convert the text to outlines, which means they become a line drawing instead of a font, taking away any need to provide the actual font.
To find this option in the program, it will usually be under the "Object" or "Text" menu on the upper menu bar.

If you are using a program such as Quark, which doesn't have this option, look for an "Embed Font" option when saving the document.
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If you need to supply your own artwork to a printer and you want your artwork to go right to the edge of the finished printed product then you need to supply your artwork with "bleeds".
This is because when the printer cuts the artwork to the required size you have to have a certain amount of room for the cutting to be inside the coloured area.

 

At IP we ask for at least a 2mm bleed. This means (as you see in the diagram above) that when the artwork goes to the edge you need 2mm excess all around. So if your finished product is 85mm x 55mm the artwork needs to be supplied at 89mm x 59mm (2mm each side!) But it is very important that any text or important image is at least 4mm inside the cut marks, not the bleed marks.

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GIF (Graphics Interchange Format)

The Graphics Interchange Format was developed in 1987 at the request of Compuserve, who needed a platform independent image format that was suitable for transfer across slow connections. It is a compressed (lossless) format (it uses the LZW compression) and compresses at a ratio of between 3:1 and 5:1

It is an "8 bit format" which means the maximum number of colours supported by the format is 256.

There are two GIF standards, 87a and 89a (developed in 1987 and 1989 respectively). The 89a standard has additional features such as improved interlacing, the ability to define one colour to be transparent and the ability to store multiple images in one file to create a basic form of animation.
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It is very important to save your work in the right way, both for print and for web.

When saving a document for print, it is best to save it as a PDF format. Make sure all images and fonts are embedded or converted to outlines (see FAQs for how to do this) and it is at 300dpi. It is best to check with your printers if you want to give them the original aplication format. At IP we use all of the Adobe Creative Suite 1. To avoid font issues convert text to outlines. It is important to save the colour profile in CMYK .
WORD is not an acceptable format for print!

When saving artwork for a web application it is best to save the colour profile in RGB. JPEG, GIF, and PNG are the best formats for web (see the FAQs for more details).
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JPEG vs GIF

JPEG is not going to displace GIF entirely. For some types of images, GIF is superior in image quality, file size, or both. One of the first things to learn about JPEG is which kinds of images to apply it to.

Generally speaking, JPEG is superior to GIF for storing full-color or grey-scale images of "realistic" scenes; that means scanned photographs and similar material. Any continuous variation in colour, such as occurs in highlighted or shaded areas, will be represented more faithfully and in less space by JPEG than by GIF.

GIF does significantly better on images with only a few distinct colors, such as line drawings and simple cartoons. Not only is GIF lossless for such images, but it often compresses them more than JPEG can. For example, large areas of pixels that are all exactly the same color are compressed very efficiently indeed by GIF. JPEG can't squeeze such data as much as GIF does without introducing visible defects. (One implication of this is that large single-colour borders are quite cheap in GIF files, while they are best avoided in JPEG files.)

Computer-drawn images (ray-traced scenes, for instance) usually fall between photographs and cartoons in terms of complexity. The more complex and subtly rendered the image, the more likely that JPEG will do well on it. The same goes for semi-realistic artwork (fantasy drawings and such).

JPEG has a hard time with very sharp edges: a row of pure-black pixels adjacent to a row of pure-white pixels, for example. Sharp edges tend to come out blurred unless you use a very high quality setting. Edges this sharp are rare in scanned photographs, but are fairly common in GIF files: borders, overlaid text, etc. The blurriness is particularly objectionable with text that's only a few pixels high. If you have a GIF with a lot of small-size overlaid text, don't JPEG it.

Plain black-and-white (two level) images should never be converted to JPEG; they violate all of the conditions given above. You need at least 16 grey levels before JPEG is useful for grey-scale images. It should also be noted that GIF is lossless for grey-scale images of up to 256 levels, while JPEG is not.
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PNG (Portable Network Graphics format)

In January 1995 Unisys, the company Compuserve contracted to create the GIF format, announced that they would be enforcing the patent on the LZW compression technique the GIF format uses. This means that commercial developers that include the GIF encoding or decoding algorithms have to pay a license fee to Compuserve. (Users of GIFs or non-commercial developers are not affected.)

However, a number of people banded together and created a completely patent-free graphics format called PNG (pronounced "ping"), the Portable Network Graphics format. PNG is superior to GIF in that it has better compression and supports millions of colours. It is important to note that PNG images are far superior for clarity of image edges on a transparent background because a PNG file saves in millions of colours as opposed to a GIF image which can only save up to 256 colours.
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