The questions is ? . . .

After a while the image looks like it has a metallic sheen in dark areas

‘Bronzing’ occurs when dye-to-dye interactions compete with the dye to substrate interactions. The dyes in the ink aggregate or crystallise on the paper surface, which leads to a loss in optical density. It can be limited by reducing the amount of black in the image.

Different colours seem to have merged

Colour to colour bleed is a common problem when the wrong stock is chosen. The ink doesn’t dry fast enough and its dyes are not immobilised quickly enough, with the result that they blend together. Bleed does not always happen immediately, but may happen some time after printing, particularly in the case of exposure to heat or humidity or by oil based/solvent based inks over time.

Inks do not dry

fast enough and

blend together

Edges look jagged

If the resolution of the file is too low or the enlargement too great then this can lead to ‘jaggies’, these are where the individual pixels of the image become visible and are especially obvious in the curved parts of the text that have been over-enlarged.

Low resolution output

 

High resolution output -

 

 

2400-3200dpi

 

 

 

 

 

 

 

 

 

The eye is very sensitive to ‘breaking’ of smooth curves. The figure on the right is double the resolution of the figure on the left, it’s easy to see that if the resolution is higher a smoother curve can be produced.

The image looks very grainy and pixelated, curves have a stepped appearance

Many images from the web or free CD’s can be of low resolution. In general a full-page bitmap file will be several megabytes in size, although the stored version may be smaller if it is compressed (e.g. jpeg).

An important factor in achieving quality prints is resolution. This related to how much pictorial information a file holds. The DPI (dots per inch), tells us the resolution of an image; the higher the dpi, the higher the resolution and hence the finer the detail of the printed image. High resolution is generally considered to be 1500-5000 dpi.

The ink seems to leak through to the other side of the paper

This is known as ‘strike through’ and occurs when the paper has insufficient absorption capacity for the density of ink. – Use a higher grade or heavier coated paper.

Paper is too

adsorbent and

ink can be seen

on back of sheet

The image is not the right colour

This can have many origins: the colour of the print may well not match that of the screen or the original unless great care has been taken to calibrate each element of the system. The colour of an image can be corrected either in the imaging application or in the printer driver. If you have several images from the same source, e.g. camera, scanner or CD, then they are likely to all have the same characteristics. Images that come from varying sources may need to be calibrated before use.

The image is too light or dark

This could be because the original image is very dark, or light, either change this in the application or use the controls of the driver to try to lighten the image. When scanning an image, try to use the white and black point controls to set the range of light and dark for the image. If it doesn’t print like the screen image this may be because your screen is not calibrated. Several tools exist to help set up the monitor, these are often shipped either with the image application or with the graphics card.

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