PROBLEMS

41 Think you want to print out a photograph with a size of DIN A4: 210 × 297 mm

maintaining a printing quality of 200 dpi. Which resolution would the image need?

To calculate the resolution of the image needed for printing at 200 dpi (dots per inch) on a DIN A4 paper (210 × 297 mm), you can follow these steps:

Step 1: Convert the paper size from millimeters to inches.

Since there are 25.4 millimeters in an inch, you convert the dimensions as follows:

• Width: $210 \, \text{mm} \div 25.4 \, \text{mm/inch} \approx 8.27 \, \text{inches}$
• Height: $297 \, \text{mm} \div 25.4 \, \text{mm/inch} \approx 11.69 \, \text{inches}$

So, the dimensions of the DIN A4 paper in inches are approximately 8.27 × 11.69 inches.

Step 2: Calculate the image resolution.

The resolution required for printing is the product of the paper dimensions in inches and the desired printing quality in dpi.

• Width resolution: $8.27 \, \text{inches} \times 200 \, \text{dpi} = 1654 \, \text{pixels}$
• Height resolution: $11.69 \, \text{inches} \times 200 \, \text{dpi} = 2338 \, \text{pixels}$

Final Answer:

The resolution of the image needed to print a DIN A4 photograph at 200 dpi would be 1654 × 2338 pixels.

42.- Which resolution would the same picture need to have a 300 dpi picture?

To convert a picture to have a resolution of 300 DPI (dots per inch), we need to adjust the number of pixels in the image based on its physical dimensions (in inches).

1. Convert paper size to inches:

Width: 210 mm÷25.4=8.27 inches

Height: 297 mm÷25.4=11.69 inches

2. Calculate the required resolution at 300 DPI:

Width resolution: 8.27 inches×300 DPI=2481 pixels

Height resolution: 11.69 inches×300 DPI=3507 pixels

To print the same image at 300 dpi on DIN A4 paper, the required resolution would be 2481 x 3507 pixels.