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		What is trap? What happens if I don't trap? Can you describe conventional trapping? What about current electronic prepress systems? How should I trap type? What if the background is not clearly dark?
		THERE IS NO CHARGE FROM REPROS FOR TRAPPING.
	TO TOP	What is trap?
		Trapping is used to compensate for minor amounts of misregistration. The process attempts to maintain the precise shape of the graphic element in one or two of its process colours by distorting the shape in its other colours. It creates an overlap of colour areas that "traps" certain colours of one image in the area of the adjoining colour element.
	TO TOP	What happens if I don't trap?
		Any movement of even a few thousandths of an inch can cause visible gaps or blurs between an object or letter and it's coloured background. Therefore trap is necessary when two tints or shapes border each other and/or a linework element (including text) and a tint meet. Without trapping, misregistration during printing will produce an objectionable gap or an undesirable line of a different colour, appearing on the border between the two colours. Misregistration occurs when two or more overprinted images are aligned improperly. Reasons for misregistration include: • Misalignment of the printing plates • Shifting or stretching of the paper • Inconsistent amounts of ink used • Environmental variables such as very hot, wet, dry or    humid weather conditions during printing. • Inconsistent amounts of ink used • Film output on incompetent imagesetters.
	TO TOP	Can you describe conventional trapping?
		Conventional (non-digital) trapping is performed by separately treating each separation film of the four process colours. The overlap is created photomechanically by distorting the image on the positive or negative film, making the element either thicker or thinner without altering its basic shape or position. A linework image can be expanded in one of its colours by exposing the negative through a diffusion sheet onto another film, or making a "spread". Spreads are also referred to as "fatties" or "swells". The width of a linework element can be reduced by a similar technique using positive film. This is called choke. Other names for chokes are "skinnies", "shrinks" or "squeezes". With conventional trapping methods, images are trapped per separation; that is, they may be choked in one film separation and spread in another.
	TO TOP	What about current electronic prepress systems?
		Electronic prepress systems treat a colour image as one complete entity, not as four individual films. The potential problem of misregistartion is handled on the image-processing system by creating an additional image in the form of a "frame". This frame is either an expanded or reduced copy of one or more colours of the original image. On the Scitex electronic prepress system, a frame is created between two colours if any of the following conditions occur: • The colours are significantly different in darkness, • The colours are significantly different in hue, • Neither colour is dark. That is, they both contain a    low percentage value for the same separation. The frame is usually created on one side of the border between two tints. The direction of the frame is based on the following rules: Light tints usually spread into dark tints. That means that the lighter colours of an image should spread into the darker image or tint area. Type must be kept as sharp as possible (to avoid distortion). If the type is lighter than its background, the lighter colours of the type should be spread outwards towards the background. If the type is darker than the background, the lighter colours of the background should spread under the type.
	TO TOP	How should I trap type?
		There are four general kinds of type "settings". 1 Overprinting type of 100% black Black type normally prints only in the balck separation, although image processing systems handle the black in all colours. In this case, no trap is needed. The black type is altered to include cyan, magenta and yellow percentages as the background. If misregistartion occurs, no gap or line will be created since the underlying colours are uniform throughout the tinted area. 2 Overprinting type composed of black and other colours Frequently, the density of black linework is increased by adding a second colour to the black. In this case, the shape of the linework in the additional colour is slightly reduced to compensate for potential misregistration, enabling the black to hold the original shape. 3 Type knocking out underlying colours When 100% black type knocks out underlying colours, the area under the type is 0% (white paper) for each colour separation. In this case, misregistration of only one separation causes an unsightly line on one side of the element. Knockouts like this should be rarely used because of the high risk of misregistration. For this kind of type, as with mixed black type, a frame is created inside the type which consists of the 100% black and the cyan, magenta and yellow values of the background colour. Any shift during printing (less than the frame width) will be unnoticeable and the type will remain distinct. 4 Reverse type Reverse or white type is the most problematic for trapping since misregistration can cause not only objectionable line on one side of the letter, but can also partially fill the letter with the colour of the shifted separations. The general rule for trapping reverse type is to create a frame outside the letter. The frame colour/s should be the lower value colour/s of the background tint, so that the highest value colour (other than yellow) will hold the type outline. In theory, misregistration can still cause a gap, but it will be less objectionale than partial filling of the letter. As a rule, small serif letters should not be reversed. In the four type examples described above, the darkest colours will maintain the shape of the letter while the other colours are altered: if the text is darker than the background under the text, if the text is lighter than the background away from the text. In all four situations, subjective judgement may still be required.
	TO TOP	What if the background is not clearly dark?
		This common situation calls for a subjective decision on the part of the prepress system operator. The solution may be to create a frame by combining the values of the two predominant colours, or to select the colour which simply appears to be the darkest. In any case, the most viable solution here is to rely on Repros' practical experience.
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