How big can you print a photo? What is the maximum size to print a photo from your camera? What is the biggest photo I can print? Everyone asks these questions, even professional photographers. Pros just know how to answer the questions. The truth is, regardless of how much you hear megapixels touted, there is more to that answer than just megapixels even though megapixels are part of the equation. First, how much data did the camera record (the megapixels)? Second, how far away will people be from the photo? Third, what are you printing the photo on to?
Megapixels are just a way of measuring how much data your camera is recording. Back in the days when film reigned supreme, the only question was how sharp was your focus when deciding how big you could print a photo. Now, we have to consider how much data is stored because no digital camera comes close to the amount of detail captured on film. It is a different way of recording photographs. Now, just because you have a 12 megapixel camera does not mean your image is a 12 megapixel photo. To get the full quality your camera is capable of recording you must set the quality to its highest setting. Anything less is throwing away data (and money).
The standard printing resolution for photographs is 300dpi (dots per inch) so you can calculate the approximate megapixels needed for each image size based on that resolution. Multiply the photo height and width each by 300 to get a basic guideline for pixels needed for a good print of that size. For example, an 8×10 multiplies out to 2400×3000 pixels. Next multiply those pixel dimensions together. Continuing our example, the 2400×3000 becomes 7.2 million. So 7.2 megapixels is needed to capture a photo you can print at 8×10.
Standard Print Sizes and Megapixels Needed
|Print Size||Pixel Dimensions at 300dpi||Megapixels Needed|
|Wallet||750x900 Pixels||.7 Megapixels|
|4x6 Print||1200x1800 Pixels||2 Megapixels|
|5x7 Print||1500x2100 Pixels||3.1 Megapixels|
|8x10 Print||2400x3000 Pixels||7.2 Megapixels|
Remember how your mom always told you not to sit too close to the TV? As kids we always ignored that advice but as adults we’ve probably noticed that sitting too close to the TV just results in the picture quality going down. That happens because TV displays are designed for specific viewing distances. When you sit at a distance in line with the design, the image is clearest. The same thing happens with print photos. Obsessed pixel peepers and their magnifying glasses excepted, large prints are meant to be viewed from a few feet away. No one plans for a 16×20 to be viewed by someone holding the image in his hand and staring at it. The plan is for it to be hung on a wall and viewed from several feet away. That means that a lower resolution photo (a photo with less data recorded) can still be printed at a large size with satisfactory results. The 8×10 is the smallest standard print size and should be viewed from at least 2 feet away. Taking that into account changes the number of megapixels needed. While 7.2 megapixels of information is needed to record a 300dpi 8×10, the intended viewing distance reduces the amount of information needed for a print that looks good visually. While not a perfect rule, you can get a rough idea of visually acceptable images by dividing the pixels needed by the viewing distance (in feet). This will give you a good idea of how little starting data (megapixels) you can get away with for each print size. For an 8×10 divide the ideally needed 7.2 megapixels by 2 feet. This lets you see you can print a 3.6 megapixel image at an 8×10 size for reasonable results. The bigger the image, the farther away people will stand when viewing the image and the better results this method will return.
Visually Acceptable Print Results
|Print Size||Idea Megapixels||Divided by Viewing Distance||Megapixels for Visually Acceptable Print|
|8x10||7.2 Megapixels||2 Feet||3.6 Megapixels|
|11x14||13.8 Megapixels||3 Feet||4.6 Megapixels|
|16x20||28.8 Megapixels||5 Feet||5.7 Megapixels|
|20x30||54 Megapixels||8 Feet||6.7 Megapixels|
Now we’re really getting into the nitty gritty of print quality. The surface that you chose for your print will have a huge impact on the resulting image and how much data you need for a print. The rougher the texture, the less data you need. This is because the texture of the surface limits the print resolution possible. The smoother or glossier the surface, the more data you need for a good print because those surfaces show every little detail. There are no good formulas for calculating this difference because surfaces vary so widely. However, most reputable canvas printers today create excellent prints with 150dpi instead of 300dpi so you can divide ideal Megapixel requirements in half for canvas prints. If you use a high quality consumer lab (Mpix or Circle Graphics Canvas for example) they can provide you with excellent guidance on data requirements for their specific products and printing equipment.
Remember that the above information assumes you begin with a technically good photograph that has nice exposure, clear focus, and is not noisy.