Photograph Printing

The infos Photos section offers these pages for amateurs who want to demystify the terms used in the wonderful world of photography and learn more about printing photographs. PhotoLabo is sharing their Web searches on the subject, and the original sources are Wikipedia and some very informative blogs. If you have questions or want to add content to this page, please contact us by email at  info@photolabo.ca

1 - The Definition

This expresses the number of pixels in the image. This is a technical characteristic of the image, and it is very important. The definition is expressed either as the total number of pixels (8 megapixels, for example), or the number of pixels expressed as width x height (3200 pixels x 2500 pixels = 8 million pixels, for example).

2 - The Resolution 

This is a metadata, which means some additional data to the image included in the image file. The resolution is not a technical characteristic of the image, but a data that will be used for printing. The resolution is displayed in Dots Per Inch (DPI).

3 - The Megapixel

Digital cameras capture images as pixel elements, known as pixels. Simply put, a megapixel is equal to one million pixels.

Digital images are made up of thousands of these tiny, tile-like picture elements. The more pixels you have, the higher the image resolution (DPI).

Picture Quality

The number of megapixels is only one aspect relating to the quality of a camera, or the actual quality of a photo it is capable of producing. Factors such as camera sensor and the optical quality of a lens play equally important roles.

Besides the sensor and lens, other elements determine the quality of photos and prints. They include:

Good lighting of a subject

Proper focus

Image clarity (lack of blurring due to camera shake or incorrect shutter speed)

Shooting at the highest resolution and quality camera setting

In Summary

• The resolution is a simple numerical data used to adjust the definition of the image to be printed.

• Resolution is the minimum number of pixels per inch where the human eye cannot distinguish the pixels on the printed photo at the desired distance (see Table A). 

Printing Digital Photographs

The digital image becomes a photograph when it takes the form of an image on a sheet of permanently printed paper. The transition of the image file from the digital camera or scanner (possibly manipulated on a computer) to the final photo is done via a printer.

Currently, the best result is printing the digital image on photo paper.

A digital image can be characterized by:

These three values are interrelated: it suffices to know the value of two of them to determine the value of the third one:

Knowing the actual print size accessible with your digital camera.

Take a 4x6 photo in your hands and look at your image; notice how far away your eyes are from the photo, quite possibly about 30 centimetres (12 inches). Now look at a painting on the wall and note how far away you are; probably more than a meter (see Table A). We have made printing tests at 100 DPI for formats meant to be exposed on a wall, and even our professionals were surprised by the excellent results, even after sticking their noses on the 24x36 printed poster.

Procedures:

1 - Determine the definition of an image from your camera (directly in your camera or in the properties of the image).

2 – Divide your image definition (pixels size) by the desired print resolution (DPI) (Table A) and you’ll get the maximum size for most suitable results.

Scenario with an image the definition of which is 3200 pixels x 2500 pixels.

A professional photographer or the amateur expert prints at 300 DPI only by concerns that some details cannot be seen easily by Mr. and Mrs. "everybody"; he may then print a 10” x 8” photo with his image (3200/300 by 2500/300).

The amateur photographer will be pleased to learn that his image will be more than acceptable printed at 100 DPI on a poster 30 inches by 24 inches (3200/100 by 2500/100).

You can also calculate by the reverse way; that is, if you want to print an 11” x 14” photo at 200 DPI, you'll need an image that has 2200 pixels by 2800 pixels (11x200 by 14x200).

Table A