Photographic FAQs
1. What is the best file type to use when I am saving digital images?
There are many different file types around for photographic images. Two of the most common are TIFF and JPEG. TIFF is the preferred file type as it does not compress or alter the information in an image file. As a result there is no loss of quality when the image is saved. A JPEG file is one which employs a compression technique to allow a large image file to be saved using less disk space. Some image editing software allows you to control the amount of compression used when saving as a JPEG and for photographic reproductions a higher quality setting (least amount of compression) is the best. As a general rule, assuming that disk space is not an issue, TIFF is best for images that you want to print, and JPEG is best for those that you want to send as email, or place in a web page.
2. What resolution should I use?
This depends greatly on the intended use of your image. For email or web pages a resolution of 100 pixels per inch (ppi) is quite sufficient, while 400 to 600 ppi is best for images that are to be printed. Of course, this also depends on how big you intend to print. A common misconception is that a larger print requires a larger ppi resolution when in fact the opposite is true. In other words, a 400 ppi image printed at 8”x10” (20cm x 25 cm) may only need to be 240 ppi when printed at 12”x16” (A3) but may need to be 2000 ppi when printed at the size of a passport photo.
3. What is the difference between ppi and dpi?
While some use ppi and dpi to describe the same thing, the two are different. Ppi stands for Pixels Per Inch and should only be used to describe the resolution of a digital image. Dpi is short for Dots Per Inch and only indicates the resolution used for printing. So an image that has a resolution 400 ppi can be printed at 150 dpi or 2880 dpi, the two being independent of each other.
4. Is digital better than traditional photography?
This often depends on the intended use of the image. Digital photography and image manipulation has contributed greatly to photography. In some cases it allows a faster turnaround of work, and enables photographers to do restoration work on old photographs without having to alter the original image. It is of course, a necessity for online images. However, for true archival images, traditional black and white photographs and negatives still offer the best medium. Black and white photography has been practiced for over 100 years, and so we know with certainty that these images will last indefinitely under the right conditions. Digital prints (those printed on ink jet printers) may only last a year or two for a basic printer, or for only a few years on professional models. There is also the issue of technology constantly changing, so what might be a standard today, maybe obsolete in a short period of time.
Info guides:
- Digital images [new window
170kb] - Photographic collections [new window 611kb] - Practical hints for the care of photographs
More information:
Telephone: +61 7 3840 7778
Fax: +61 7 3842 9060
Mail: Collection Preservation PO Box 3488 South Brisbane 4101
Email: imageproductionunit@slq.qld.gov.au
Last updated: 23rd March 2011
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