|
Size: 566
Comment:
|
Size: 2988
Comment:
|
| Deletions are marked like this. | Additions are marked like this. |
| Line 12: | Line 12: |
| Guideline values for image resolution: || Print Method || Paper Coating || Resolution ppi || Screen ruling lpi (lcm) || |
'''Guideline values for image resolution:''' || '''Print Method''' || '''Paper Coating''' || '''Resolution ppi''' || '''Screen ruling lpi (lcm)''' || || Sheetfed || Coated || 350 || 175 (70) || || Sheetfed || Uncoated || 300 || 150 (60) || Preparing the images with resolution 350 ppi, you ensure the resolution is sufficient for all printing. If you know which paper will be used, you can surely prepare the images to a lower resolution. As a benefit you’ll get a smaller file size, otherwise it has no importance. {{{#!wiki note '''NOTE!''' Enlarging the image in a layout reduces the effective resolution. E.g. after enlarging a 350 ppi image to 200%, the real resolution is no more than 175 ppi. }}} === Total Ink Coverage in CMYK images === The total sum, in percentage, of partial colours in the darker areas of an image are determined according to the paper and press used. In addition, this value is also affected by any UCR or GCR function that is used. Today, the ICC profiles include this information. By using a proper profile in colour separtaion a correct TIC (Total Ink Coverage) value is determined automatically into the images. The total ink values used for standard output profiles are described in the table below. The total ink values in the table – and the functionality of the profiles – are based on the printing according the values defined in standard. Guideline values for Total Ink Coverage (TIC): ||'''Print method''' ||'''Paper coating''' ||'''Ink coverage %''' || ||Sheetfed ||Coated ||300 || ||Sheetfed ||Uncoated ||290 || === Dot gain === Dot gain is determined in images according to the print method, paper and the colours used. Grafostil follows the dot gain values defined in ISO 12647-2 standard. The dot gain increases graually when going from hevy coated paper to uncoated paper. Also, dot gain values are included in an ICC profile. For this reason, it is important to know at the image production stage for which process and on what kind of paper the job will be printed, and then use a proper output profile for the CMYK conversion. === Enlargement of images in publications === If the image resolution is in accordance with the guideline values, you can safely scale the image in publications from 75% to 125% of original size. '''The greater the change in image enlargement, the poorer the quality of the printed image.''' If you intend to reduce the size of the image to less than 75% of original size, make the change in the image processing program. |
Use of images
Image resolution
Ensure that the image resolution is sufficient for printing. Ideally the image resolution is twice the screen line. The screen line ruling is determined according to the used paper and press.
Guideline values for image resolution:
Print Method |
Paper Coating |
Resolution ppi |
Screen ruling lpi (lcm) |
Sheetfed |
Coated |
350 |
175 (70) |
Sheetfed |
Uncoated |
300 |
150 (60) |
Preparing the images with resolution 350 ppi, you ensure the resolution is sufficient for all printing. If you know which paper will be used, you can surely prepare the images to a lower resolution. As a benefit you’ll get a smaller file size, otherwise it has no importance.
NOTE!
Enlarging the image in a layout reduces the effective resolution. E.g. after enlarging a 350 ppi image to 200%, the real resolution is no more than 175 ppi.
Total Ink Coverage in CMYK images
The total sum, in percentage, of partial colours in the darker areas of an image are determined according to the paper and press used. In addition, this value is also affected by any UCR or GCR function that is used. Today, the ICC profiles include this information. By using a proper profile in colour separtaion a correct TIC (Total Ink Coverage) value is determined automatically into the images.
The total ink values used for standard output profiles are described in the table below. The total ink values in the table – and the functionality of the profiles – are based on the printing according the values defined in standard.
Guideline values for Total Ink Coverage (TIC):
Print method |
Paper coating |
Ink coverage % |
Sheetfed |
Coated |
300 |
Sheetfed |
Uncoated |
290 |
Dot gain
Dot gain is determined in images according to the print method, paper and the colours used. Grafostil follows the dot gain values defined in ISO 12647-2 standard. The dot gain increases graually when going from hevy coated paper to uncoated paper. Also, dot gain values are included in an ICC profile. For this reason, it is important to know at the image production stage for which process and on what kind of paper the job will be printed, and then use a proper output profile for the CMYK conversion.
Enlargement of images in publications
If the image resolution is in accordance with the guideline values, you can safely scale the image in publications from 75% to 125% of original size. The greater the change in image enlargement, the poorer the quality of the printed image. If you intend to reduce the size of the image to less than 75% of original size, make the change in the image processing program.