Photos from your cell phone and low resolution photos may look great on your monitor at “screen resolution”(72 ppi or pixels per inch), put printing these images is likely to pose an issue.
The small file sizemake forfast downloads and is easy to share online and you can get a lot of images on a memory card, but photos taken on a camera’s ‘basic’ or ‘low’ quality settings don’t cut it when you want professional quality images for print publication.
A resolution of 300 ppi is considered the minimum quality standard for printing photos.
If you are shooting for print output, capture your images at the highest quality setting your camera offers: High, Best, Fine.
This captures the shot using the lowest compression ratio or no compression at all.
Compression is how much of the potential information in an image file is discarded to keep file size down.
You can always re-sample down (from more resolution to less) but if you interpolate up, you lose information and lose image quality.
Saving a photo in .jpg format allows you to choose a compression level, depending on whether better quality image or smaller file size is more important for your purposes.
Shooting at high resolution may also give you the option of cropping and enlarging a portion of your image later, retaining enough data for a quality print, even after tossing some pixels to the cutting room floor.
You won’t get as many images on your camera’s memory card shooting at high-res but you can keep your creative options open by archiving your ‘keepers’ on CD or a back-up drive.
The industry standard resolution for quality photo output is 300 ppi. However, you may be able to get away with a ppi as low as 200 if the image is not too finely detailed, if it will be printed on low quality paper such as newsprint, or if it will be viewed from a distance.
The following formula can help you calculate:
1 How large a print you can make from a digital image with a given set of pixel dimensions and a given resolution (ppi)
2 What resolution a digital print will have printed at given output dimensions from a file with given pixel dimensions
3 What dimensions–in pixels–your digital image will have captured at given dimensions in inches and at a given resolution
Divide each dimension of your digital image (in pixels) by the print resolution desired (in pixels per inch). This will give you the largest print size (in inches) you can generate at that resolution.
Example: (1500 pixels / 300 ppi) x (2100 pixels / 300 ppi) = 5″ x 7″.
To capture an image of this physical size at this resolution, you would need a 3 megapixel (MP) camera:
1500 pixels x 2100 pixels = 3,150,000 pixels or approximately 3 megapixels
A 1 megapixel camera will yield a 3 x 5″ print at 300 pixels per inch (ppi)
(3″ x 300 pixels) x (5″ x 300 pixels) = 900 x 1500 pixels = 1,350,000 pixels or approximately 1 megapixels
A 2 MP camera will give you a ‘print quality’ 4 x 6″, a 3 MP camera, a 5 x 7″… and it would take a 7 MP camera to shoot an 8 x 10″ print quality image.