300ppp = 118.11 pixels per cm = 13,950.03 pixels per cm2 200ppp = 78.74 pixels per cm = 6,200.01 pixels per cm2 150ppp = 59.06 pixels per cm = 3,487.51 pixels per cm2 120ppp = 47.24 pixels per cm = 2. 232.00 pixels per cm2 Considerations (traditional good quality photographic prints are usually between 200ppp and 300ppp): EXCELLENT (300ppp or more) GOOD (200ppp to 300ppp) ACCEPTABLE (150ppp to 200ppp) MEDIOCRE (120ppp to 150ppp) BAD quality (less than 120ppp) is equivalent to “not recommended”.
Photo size 4×6
I would like to scan slides and present them with a slide show on TV. 40-inch TV screen; Resolution: 1,920 x 1,080 pixels. How large should the scanning resolution be?
The dimensions of a slide are 36 x 24 mm, so the aspect ratio does not match that of the TV (TV = 16: 9 slide = 3: 2). We only calculate the pixel density of the image height, as this is the limiting measurement.
The maximum resolution of the scanner is 4000 dpi, a slide has the dimensions of 36 x 24 mm. Once you have calculated the number of pixels, you can use the dimensions of the poster to calculate the pixel density.
Dots per inch (dpi) simply indicates the number of pixels of a digital image that can be placed on one inch of printed image. In other words, dpi indicates the resolution or dot density of a printed photograph.
To get an idea, a billboard can be printed at 72 dpi, since it will be viewed from a relative distance. However, the optimum printout of a photograph should have a resolution between 240dpi and 300dpi. The improvement above this value, 300dpi, is negligible.
That said, I hope that everything is much clearer. Does it make sense to talk about dpi in digital photographs that we see on our computer monitor? no. If we are looking at it on a screen, it does not. If we are looking at it on a screen, a 500px image at 300dpi is absolutely identical to the same 500px image at 72dpi. Why? Because dpi is just the conversion factor that allows us to transform pixels into centimeters when printing (if we print that image, the 72dpi copy will be larger and lower resolution). As long as we don’t print it, it doesn’t matter.
Paper photo formats are usually defined in inches: the 10×15 cm format, for example, corresponds to 4×6 inches (1 inch=2.54 cm). For simplicity, formats are nowadays expressed in centimeters without decimals.
The traditional formats were developed to adapt to silver photography. The ratio is the relationship between the height and width of a photo. A 3/2 ratio (the width of the negative equals two thirds of its length) is the characteristic of a traditional format.