What are High Resolution Files?
According to legend, when a reporter asked Abraham Lincoln how long a man’s legs should be, Abraham Lincoln said, “Long enough to reach the ground.” When asking “How big of a file do I need?” the same can be said of image files. The purpose of the file determines the resolution level. In order to understand this, let’s start at the beginning.
At the dawn of digital cameras (and still true today), consumers and brides alike did not fully understand the term resolution. When new cameras arrived in the store, the advertising executives had to find a way to convince consumers to spend more money on newer more expensive cameras. Hence they latched onto one number which could be easily understood by most people. That was the number of mega pixels the camera could deliver. More was better and therefore worth paying more. But that is not necessarily true. It is also the quality of the camera sensor that determines the price. If you pay attention to today’s advertising, it is no longer about the file size. Today’s buzz word is “face recognition.” Tomorrow’s buzz word will be something else. But let’s get back to resolution.
When a wedding photographer with a digital camera captures an image, the digital image is actually being recorded by a sensor. All digital cameras have a light sensor. In turn, that light sensor is comprised of individual point sensors or pixels. After the camera captures the image, the data is stored internally in a manufacturer propriety format. The photographer can either save this file or convert it immediately into .jpg files, a digital image file standard. Furthermore many professional digital cameras allow the photographer to specify how many pixels to save in the file. That becomes the files’ dimensions or megapixels.
Next, you may have heard of pixels per inch (ppi) or dots per inch (dpi) in relation to resolution. This is just a handy conversion factor which allows you to determine how big the image will be on various output devices. Typically a monitor requires only 72 ppi, a fax machine 150 dpi and most consumer desktop printers 150 ppi. But is a pixel for display the same as a dot for printing? The answer to that depends on the actual printer itself. But for a professional photo printer the answer is no. In fact Mpix.com states the minimum acceptable resolution for their printers is 100 ppi! Here the resolution classification is determined by the actual output device being used.
So where did the common myth that 300 ppi is required for printing? Without getting too technical, brides need to understand a little bit about commercial (magazine) printing. Inks are not diluted. In order to create pink, the red dots are spread out to allow the white page behind to show through. This is called halftoning. If the pixels were to fall in between the lines of ink clusters, no image would be seen. Therefore, the general rule of thumb is the pixel resolution needs to be twice the lines per inch. As the typical line screen is 150-175 lines per inch, you’ll hear commercial printers saying, “You need a 300 ppi image.” But consumer printers and photo printers do not have the same requirements as a commercial web press.
If that was not confusing enough, as you can imagine, resolution classification is also dependent upon the size of the image which the user desires to create from the file. For instance a 1200x1800 pixel file would most certainly be high resolution when creating a 2”x3” wallet print as there would be 600 ppi available. But take that exact same file to create a 20”x30” poster print and it would only be 60 pixels per inch or low resolution on a consumer printer. Yet professional wedding photographers are able to make some very nice 12”x18” prints using professional printers from this file. In each case, the number of pixels did not change just how they were distributed across the surface of an output device to create the image you see.
So what is high resolution? And what do I need to know about it as a bride? As you have seen, it depends not only on the output device that is used to display the image but also the size of the image upon that display. In order to avoid the confusing resolution issue entirely, some wedding photographers are now calling the files, “digital negatives” or “image files” in their wedding contracts. Another approach taken by some photographers is to specify the client will receive files “suitable for producing prints as large as 8x10” or actually specifying the pixel dimensions or file size of the file which will be delivered. If your photographer is planning to deliver image files to you, it is best if you understand beforehand what you will receive and what size images you can print with those files.
A Chicago Illinois professional wedding photographer and owner of Magical Moments Photography, Howard's honors and achievements include becoming one of the first local Certified Professional Wedding Photographers. His work has been published in "Chicago Style Weddings," "Wedding Guide Chicago," "The Perfect Wedding Guide," and the "Daily Herald."
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