How can I blow up a picture and keep its resolution?

Depends if this is a digital file already or a piece you want to scan.

1st if it is a digital file already you will need to purchase a blow up program like FRACTALS. Just do a search on it, it will allow you to blow the image up on screen and in print without loosing much detail.

2nd if it is an image you can scan than just make sure you scan at a resolution high enough to get the size you need.

The rule of thumb with scanning is scan at 150 dpi at final intended size. So if you want to double the image size, scan at 300 dpi. 150 x 2 = 300 dpi. Get it?

Hope that helps

If you are scanning a picture, you should raise the resolution as high as you can in the scanning program. Once it is done scanning, you want to take that image into photoshop. It is there where you enlarge the photo then lower the resolution to 300+ dpi. 300 dpi is the lowest amount of dpi for good quality.

Use Photoshop CS or better.

Chose IMAGE/IMAGE SIZE, then ensure Bicubic Smoother is checked. In the Document Size area change Inches to Percent, then in the dialog boxes to the left put in 10 percent and chose OK.

Do this as many times as necessary to get the image size you wish. Hint - make it into a MACRO

Increasing by 10 percent preserves resolution!!

Use Photoshop but you can only go to 150% of the size of the image unless you have a very high quality image to start off with.