What is photo resolution
Among other criteria, the resolution of your photos greatly influences the quality of the prints. Here is some information to determine, according to the size of the desired print, the most adequate resolution for your photos.
Some definitions to clarify the subject
t’s the number of dots on your picture.
The number of dots determines the sharpness of your photo. The more dots you have on the same surface, the closer they are together, the less you distinguish them, and the sharper your image is. On the other hand, if you enlarge your photo by keeping the same number of pixels, they will be further apart and therefore more visible, the image becomes pixelated.
Dots per inch .
This is the ratio between the number of pixels and the area: 200 dpi means 200 dots on one inch, or 2.54 cm. A 300 dpi image will therefore be of better quality than a 200 dpi image because the dots will be closer together.
The DPI is the reference unit for photo resolution. The maximum resolution perceptible to the human eye is 300 dpi, so there is no need to go beyond this. Beyond this, the quality will not be improved since it is not perceptible.
Méga pixels .
This is the total number of pixels appearing in the same photo (number of dots in width X number of dots in height). The maximum number of pixels is related to the power and sensor size of your camera. The more powerful its sensor will be, the more pixels on the photo will be numerous and close together. The more powerful the sensor is, the better the quality will be.
The resolution of a photo is expressed in dpi. It is the ratio between the number of pixels per inch and the size of the print.
Resolution of the photo according to the format
The following table shows the number of pixels required depending on the desired print quality. Above 300 dpi the difference in print quality of a photo print is no longer perceptible to the human eye.
Small and medium print sizes
Every image consists of horizontally and vertically aligned pixels that correspond to the dimensions of the desired print in cm. “1062×1499” means that a 9×13 silver format print with a resolution of 300 dpi will have 1062 pixels over its height and a width of 1499 pixels.
The proposed resolutions for the posters take into account the distance at which the image will be viewed. The quality criteria for small and medium formats are not the same as those for photo posters. The maximum perceptible resolution changes according to the distance between the eye and the image. A poster in 200 dpi for viewing from a distance and a framed photo in 300 dpi will be of the same quality. The maximum resolution perceptible by a human eye at a distance of 40 cm is 200 dpi and 150 dpi at 50 cm.