Photo Technical

To make the most of a camera, understand DPI, RAW and JPG – A23

I have some questions about processing digital pictures. Setting the DPI, what is the best software and the importance of matching it to the printer? How to best maintain quality in the process with a higher DPI initially? For example, how does the Canon Raw image versus a JPG influence the final product?  Is one better to shoot in RAW and save the images as RAW then process into JPG? –Chuck Macmahon

The last couple of articles were difficult to write.  Creating a workflow for the photographs you take is not a creative process, but a methodical one.  The writing of these articles as I’m sure the reading can be a bit tedious.  Nevertheless it’s an important aspect of the process of digital photography.  There is one more resource for downloading and storing your taken images that I should mention … later.

Right now I would like to respond to a question, rather questions posed to me by reader Chuck Macmahon, who wrote “Certainly appreciate your articles in Triton. I have some questions about processing digital pictures. Setting the DPI, what is best in the software and the importance of matching it to the printer? How to best maintain quality in the process with a higher DPI initially? For example how does a Canon RAW image VS a JPG influence the final product? Is one better to shoot in RAW and save the images as RAW then process into JPG?

When we talk about DPI we are talking about a printing term or printer resolution, that is “dots per inch.”.  Printers commonly print in round dots using very few colors.  Most printers on the market are dye or pigment inkjet printers, especially popular for photo printing.  Other quality printers, such as dye sublimation and laser printers, are available.

Dye inkjet printers were originally better in providing great saturated colors, while pigment provided greater longevity.  Today, technology has greatly improved the pigment color gamut, so for photography it is the ink of choice.

The few colors used by inkjet printers are magenta, cyan, yellow and black, or the secondary colors (primary colors are red, blue, and green).  These colors are mixed through the printing process to create a complete visual spectrum of colors.  Some printers use six or seven.  My Canon iPF 8000 has twelve colors, which is about the max.  The added  colors are based on variations of the secondary colors, that is light magenta, light cyan, light yellow, and glossy and matte black (for better black and white prints), etc.

Technology applies the ink to its substrate (printing papers, transparencies, etc.) most commonly by piezo or thermal technology, in droplets measuring commonly between 2 or more picoliters (1 trillionth of a liter).  Both technical approaches work well, and a smaller picoliter value (2, 3, or 4) is supposed to provide higher resolution results compared to larger droplet sizes.  I say “supposed” as other factors can affect output.

I have written this overview of printers and the primary technical aspects to provide a good basis for those readers who would like to get more informed before deciding on a printer to buy.

For those of you less interested in technical particulars I can tell you Canon, Epson, and HP are the top inkjet manufacturers.  They all make great photo quality printers.  Price can be an indicator of quality output, but it may also indicate print size, print speed and other features not necessarily having to do with quality.

One final specification that I would look for in a printer is the overall resolution of the printer.  The maximum resolution listed, such as 600X600, 1200X1200, 2400X1200 dpi, is based on ink dots.  These dots can be grouped tightly for darker output or loosely grouped to lighter output.  The higher the number denotes a higher capability for smooth transitions.

Digital cameras all list their range of resolutions in their specifications, and are based on square pixels arranged one next to the other vertically and horizontally.  My Canon S60 maximum resolution is 2592 X 1944.  Multiply this out, and yes this is rated as a 5 megapixel camera.  The actual range used depends on whether your taking small jpg’s, medium jpg’s, large jpg’s TIFF’s or RAW files.

Many cameras are not RAW capable, my compact S60 is.  If I can and if the shot is important to me (or for a client) I will always shoot RAW (or TIFF’s if this is an otherwise available choice).  Occasionally I take large jpg’s.  Any of these three would use the cameras’ maximum resolution.  So what is the difference? There are many, so let me give you a good overview.

jpg,s are a universal format, ready to be printed.  Although they begin or are taken in the RAW, internal camera hardware immediately processes it to 8 bits and deletes a lot of the information it determines isn’t needed.  This results in smaller files, thus allowing the storing of many more images on a given memory card in your camera, and that’s the positive benefit.

The negative result is these converted jpg files have eliminated a great deal of information that would be very helpful to have should they need or more important should you desire to make adjustments.  In future articles, using software, we will make adjustments in exposure, color, contrast and add other effects, and this can be far more effectively done with RAW (or lossless TIFF) files.

RAW files are simply not processed automatically, and remain to contain every detail as they were taken.  Chips in digital camera can produce 8, 12, even 14 bits of color depth/information.  Whatever the camera potential is, it is maintained in the RAW files.

The bottom line, if you can shoot RAW (also = best camera resolution) and convert to jpg.  To fully answer Chuck’s question there is still more to go.  A description of how the maximum camera and printer resolutions together in making the best prints still needs clarification, but at this time I ask for permission to come ashore.