Introduction to Digital Photography
By Robert Carpenter Turner
Helpful guide to a few technical terms when having photographs professionally taken
There are a great many of my customers who are new to digital photography and find it hard to comprehend all the terms and expressions that are used. This short article is set out to help those of you who just wish to understand a few of the terms and some of the possibilities that digital photography has to offer. This is my personal way of working and will differ with other photographers, but I hope will set you on the right track.
I use a digital camera to take your pictures and then transfer these images to my computer. The photographs are always taken in colour but can be converted to Black & White if needed. No film is used and the images are kept as electronic files. After I have taken your pictures I then download these pictures to my computer, remove any blanks, shots with your eyes shut, etc., and renumber the pictures using your name so that they read john 001, john 002 etc. I can print you a contact sheet(s) with all the photos and numbering on or better still place them on the internet in a special package that only you can see by using the personal code I give you. I call this Web-View . Now the important point to remember here is that these images on the internet have to be downgraded to what is a low resolution of 72 dpi or in layman's terms 72 dots per inch. Of course I keep your originals safe and sound on my computer at 350 dpi or high resolution. In practice this means that the images you view on the net are nothing like the quality you get from the finished prints I make or the image files I put on CD for you. The Web-View images are only to give you, your agent or family or even all your wedding guests an idea of what are the best pictures from your photo-shoot . It is rather like looking at an electronic contact sheet. The great thing is they can be viewed anywhere in the world with an internet connection.
Why do you need to worry about resolution ? Low resolution will be properly be a jpeg file of 72 dpi and viewing size 5x7 ins and be about 250k file size. If you print from this or blow the picture up to a larger size it will be fuzzy. It will look fine on the net, and be fast to e-mail, but not what you need for quality brochure. A quality jpeg of 350 dpi and a viewing size of 10x8 at 350 dpi will have a file size of about 4 megabytes and take ages to download on the net but be just the thing to send to the printer or publisher.
Most performers think that they need prints when in reality they are more likely to need high quality image files to give to printers for programmes and brochures. If I give you a print and you send it on to a printer it is most than likely to be scanned into a computer loosing some of the original data, but if you send a high quality computer image file the printer has only to put this onto their computer with no loss of data. This avoids a stage where the image quality can be lowered and a process is avoided. Printers prefer quality computer images rather than hard copy photos. I do however know of one repro* company that prefers prints to make copy negatives by the old photo process. Ask me for details if you are unsure.
*What is a Repro company ? A company that makes lots of copies from the same photo - mainly for actors.
So when you have had your photos taken how do you want them put on CD ? Below are the types of computer files most commonly used. (There are others - ask me if you want something special.) Just to help you most people are happy with high resolution JPEG files but these can be a bit large for e-mailing quickly so you need to ask me to make you 2 copies of the same file, one low and one high resolution. I also can make these as Black&White computer files if that is needed.
The most commonly used digital image format is JPEG (Joint Photographic Experts Group). Universally compatible with browsers, viewers, and image editing software, it allows photographic images to be compressed by a factor 10 to 20 compared to the uncompressed original with very little visible loss in image quality.
The second most popular file is the TIFF (Tagged Image File Format) which is a universal image format that is compatible with most image editing and viewing programs. It can be compressed in a loss less way, internally with LZW or Zip compression, or externally with programs like WinZip. For those a bit more technical a JPEG only supports 8 bits/channel single layer RGB images, TIFF also supports 16 bits/channel multilayer CMYK images in PC and Macintosh format. TIFF is therefore widely used as a final format in the printing and publishing industry.
Unlike JPEG and TIFF, RAW is not an abbreviation but literally means "raw" as in "unprocessed". A RAW file contains the original image information as it comes off the sensor before in-camera processing so you can do that processing afterwards on your PC with special software.