This is the question that we, at PhotoHand, get every day – why can’t you blow up my photo into a poster after you have retouched it. The answer is that the size of the photo is too small. To print a small poster – the size of a standard sheet of paper, your photo has to be at least 5 Megapixels in photo terms, which equals 5 Megabytes in computer terms.
A photo image is described by two parameters: “Image Size” and “Image Quality”. The image SIZE is defined by the total number of pixels – a collection of small dots. The number of pixels per square inch defines the QUALITY of the image.
If the number of pixels (the size) of the image can’t be changed after the image has been captured, the image quality is defined AFTER you have taken the photo. Image quality or resolution will be defined when you decide how many pixels (dots) should be per square inch of your photo.
More pixels/dots per square inch mean higher resolution and subsequently higher quality of print. 72 dpi (dots per inch) are perfect for the web but not for printing. Quality printing requires 300 dpi.
So, the more pixels you capture from the start, the bigger photo you will be able to print after these pixels have been squeezed into square inches by 300 in each.
Here is a sample of calculations:
Suppose you want a print sized 4 by 6 inches in photo quality.
(4in x 300dpi) x (6in x 300dpi) = 1,200 pixels x 1,800 pixels
This equals 2,160,000 pixels (roughly 2.2 Megapixels) in total which is approximately 2.2 Megabytes.
To make it easier, we put together this cheat sheet for you.
We hope we were able to help, but if you still have questions please contact us through our website www.PhotoHand.com.