As well as printing a selection of digital images at the maximum size two standard tests are done, one using an Agfa test image to check for sharpness and colour accuracy and the other using an ePHOTOzine test sheet to compare paper handling, drying and stability.
The Agfa test has several colour patches, a grey scale, a text box and a line test ranging from 0.2 point to 1.2 point with black on white and white on black. There are also various registration boxes and a colour chart. From these graphics we can assess the following:
The red and black boxes feature text in Times Roman, in font sizes ranging from 2 to 10 points.
We check how the type appears across the different font sizes?
Edge definition of colours
The colour pattern consists of adjacent CMYK and RGB patches to help us judge and compare edge definition of each colour and we can see if colours blend into each other.
The grey step wedge spans relative densities of 0 to 100 allowing us to judge the way in which a progressive greyscale is built up and the neutrality of the greys?
The colour chart makes it easier to judge the approximate colour range of the inkjet printer and the way the inkjet material reproduces colours. We look to see how well defined the colours are and whether they blend into each other. We an also check to see if there's a clear distinction between different values of red, green, blue, purple and so on.
The series of six differently coloured patches allow us to check the registration accuracy achieved by the printer, and the inkjet medium the image is registered on. Look for ghost images and patterns in the black lines.
Inkjet printers should be able to reproduce fine line art within reasonable limits. This test reveals how fine a line the printer can reproduce and, most importantly, how well the inkjet paper can reproduce a certain line width. Printing black on white and white on black gives clear evidence of how a line appears on the grid with the black background? And how fine a line can be reproduced in black against the white of the paper?
As well as technical tests using the test card we can also test various paper characteristics visually. These include the following:
Horizontal lines that sometimes appear when printing graphics usually occurs when the print head carriage return is misaligned. Bleeding Merging of contiguous colours.
Bronzy gloss over dark colour areas that is most noticeable when the photo is angled in the light.
When inks exhibit coalescence they dont mingle well. One effect is that the printed colour doesnt look smooth.
An irregular and irreversible deformation of the paper following the delivery of a critical amount of ink onto the paper.
Undesired curling of the paper. When this happens the paper will lift at the edges when you lay it flat.
Reduction of inks in the direction of the paper's fibres.
A loss of gloss after drying that's most noticeable with black.
Where the print is spotted - caused by irregular drying.
Where image and colours become visible on the back because the ink penetrates too deeply into the base.
If spreading has occurred, a dot will look too big and asymmetric.
We do a number of tests as the paper is emitted from the printer. These include the following:
As soon as the first part of the print is revealed we touch to see if the paper is dry.
The same test is done one minute later and five minutes later.
Ideally the print should be dry immediately to avoid marks when you lift it away from the printer.
Place another piece of paper over a part of the photo as soon as it printed to see if it sticks.
A second test is done after 5 minute.
This shows whether you can take prints out and stack them without damage.
Once the paper is dry we use a finger to forcefully rub the paper to see if it will smudge.
We drop a small amount of water onto the surface, leave for 30 seconds and then try to blot it up rubbing to see if the water affects the printed image.
We drop a small amount of coffee onto the surface, leave for 30 seconds and then try to blot it up rubbing to see if the coffee stains the printed image or affects the inks.
A finger nail is used to try to scratch the surface of the printed image. This tests the paper's durability.
We angle the print to the light and look for tiny pin sized tracking holes that occur when some papers are used with an Epson printer.
Here the colours are seen to spread, due to inadequate drying.
Our thanks to Agfa for supplying advanced test information and the useful test file.
The paper's ability to prevent fading when exposed in daylight for any length Ultraviolet fastness is determined by the specific inks and media used to create an image. Epson and HP are constantly claiming new lightfast figures but perfect UV stability does not exist yet. All materials show a loss of density under ultraviolet light. We are placing a test print in window light and leaving it there for six months to see what the effect of daylight will have.