DPI, sRGB, RAW, Sharpness, WHAT? | Newborn Mentoring Photographer
Posted on Jan 1, 2015
DPI May not Matter the way that you think it Matters
DPI stands for dots per inch (or pixels per inch as you think of the image files on your computer) and is considered an important term in the photography world.
However, it is common for us photographers to give it much more power than it really has!
You see, If we were to simply adjust the DPI as we prepare an image for its final destination, what we have done is exactly nothing. When re-sizing an image with pixels or percentages, only one piece of information is needed. To re-size an image with DPI exactly two pieces of information are always needed… The inches AND the DPI. Without both, changing the DPI will not impact the size of the image.
DPI and inches can be a convenient way to think of the size of an image, but there is absolutely no relevancy to think of an image in terms of Pixels and DPI. DPI always needs to be associated with inches for it to have any meaning and Pixels always stand alone. In the same way stating the inches of a particular image has no meaning unless you know the DPI.
We have a lot of different specifications for various companies or clients that we send digital files for. We can use the tools in our photo editing software to re-size images with the least effort depending on what specifications are provided. Here are some examples:
Ordering a 4×6 print from a photo lab:
The photo lab may tell you that the image should be 6″ x 4″ at 300 dpi. This is a perfect opportunity to re-size an image by specifying inches and DPI as you re-size. You could also re-size with pixels, but doing so would require you to multiply 300 dpi by 6 inches and by 4 inches to determine that they would like the file to be 1800 x 1200 pixels.
Ordering a canvas from a photo lab:
The photo lab may tell you that for a 20×30 canvas they recommend that the image be 4500 x 3000 pixels. This is the perfect chance to re-size the image with pixels only. There is no reason to know or adjust the DPI because when working with pixels, the DPI has no meaning. If you wanted to resize the image based on inches and DPI instead of pixels, you would just divide the pixels by the inches in the canvas to determine the DPI of 150 in this case.
What is sRGB and AdobeRGB Color Profile?
The sRGB profile is an index of colors that is widely prevalent and assumed. Other color profiles such as AdobeRGB allow storing more variations of color than sRGB allows. It is useful to have the additional information of color during the editing phase of a photograph but for almost every case it is necessary to convert the end product to sRGB color profile before passing the image to the consumer or another vendor. Most web-browsers and consumer photo viewing software that your clients have will be assuming the sRGB profile. Most print labs require an image to be in the sRGB color profile. If your image is indexed with AdobeRGB (or any other color profile other than sRGB) and sent to someone that is expecting sRGB, the results will be catastrophic. The image will look nothing like it is intended to.
If you set your camera to photograph in RAW mode, it is especially important to take note. Your color profile setting for your camera is only useful for JPG images. RAW images will be recording the full information in a more advance color profile such as AdobeRGB.
In summary, if you are using RAW mode on your camera, the color profile setting on your camera is ignored. However, it is necessary to make sure that when you are done editing and ready to export images that you use the correct color profile. sRGB will almost always be the correct choice. sRGB is best for Small Share-able files, Traditional Photo Prints, and High Resolution files sent to your client. AdobeRGB can be helpful for some personal inkjet printers that support it and some commercially produced inkjet products such as Canvases or Posters but only when supported by the photo lab.
If your camera is saving to JPG files, the color profile option of your camera can be used. Having AdobeRGB files is beneficial but only if you never forget to export your finished product into sRGB color mode when it is required. If you are inclined to make a mistake there, then the safest option would be to set your camera to record sRGB JPG files.
Why a lot of the picture style modes in your camera (Sharpness, Contrast, Color Profile) may not matter for you.
If you record your photos in RAW mode but have been plagued by wondering what sharpness and contrast (and other picture style settings) you should use in your camera, I would like to release you from that worry. These settings only matter for the JPG files that the camera records. Changing them will not impact RAW files, so you can completely ignore them.