Adjusting Digitial Camera Resolution

Transcription

1 Adjusting Digitial Camera Resolution How to adjust your 72 ppi images for output at 300 ppi Eureka Printing Company, Inc. 106 T Street Eureka, California (707) (707) Fax ekaprint@pacbell.net (DSL line)

2 Adjusting Digital Camera Resolution People often ask Since all my images from my digital camera come into Photoshop at 72 ppi, how can I get them up to 300 ppi for output for a printing press? The process is actually very simple, you just have to uncheck a simple checkbox, but understanding why, and what it will do to your image, is more important. Here are the step-by-step guides: Step 1: Open the image taken with your digital camera in Photoshop. To increase the resolution, you really only have one choice (that will maintain the detail and sharpness of your image) and that is to lower the physical dimensions of the image (which raises the resolution). This is why three to six-megapixel (and above) digital cameras are all the rage. Why so large? So you can lower their physical dimensions (thereby raising the resolution) and still have a decent size image for outputting to your printer, or a printing press. The larger the original image, the larger your final high resolution image will end up being. Threemegapixel cameras produce larger images than two-megapixel cameras, and therefore enable you to create a larger high resolution image. How big? Read on

3 Step 2: You adjust the resolution by going under the Image menu and choosing Image Size (shown below). Unfortunately, you can t just type 300 in the resolution dialog box and click OK, or you d wind up with a very large, very fuzzy, very blurry image. Instead, before you do anything else in this dialog box, turn off the Resample Image check box. This enables you to change either the width and height of the image, or the resolution, without damaging the image in any way. It s the see-saw effect increase the resolution, and the Width and Height decrease proportionally, and vice versa. If you look at the Image Size dialog box shown below, the image we imported from the digital camera was x at 72-ppi resolution

4 Step 3: Before we adjust the resolution, we need to determine how we are going to output this image. If we are going to print this on a printing press, we have to ask the print shop what line screen they re printing the job. This figure will determine how much resolution we need. If the print shop told us it would be printing at 150 line screen, we could double that figure (to 300 ppi) for how much resolution we would really need to print that image. With Resample Image turned off, type 300 in the Resolution field, then look at the Width and Height fields. In the Image Size dialoge box below, you can see that by increasing the resolution to 300 ppi, it decreased the size of the image to x Uncheck - 4 -

5 Step 4: When you click OK, you won t see any change on the screen, but if you are one of those people who need to see a change to know it worked, just make sure Photoshop s Rulers are visible first (Mac: Command-R PC: Control-R) then you will at least see the measurements change, even if the image doesn t appear to have changed. As you can see, the key to increasing resolution is shrinking the physical dimensions and to turn off Resample Image before adjusting the resolution. RGB stands for Red, Green and Blue. It is how your monitor makes up all of the colors you see on the screen & how digital cameras capture information. Think light. CMYK stands for Cyan, Magenta, Yellow and Black. It is an image format printers use to make four color separations for the purpose of creating plates that are used on the printing presses to produce the printed material you have ordered. Think ink. This tutorial only addresses resolution and not the conversion of RBG images to CMYK. We ask that you convert your images before you send them for output. If you choose not to, we will do the best we can. Even though monitors always use RGB to display colors, the colors you see on your monitor will more closely match the final printed piece if you are viewing them in the CMYK color space. Be aware that computer monitors display colors in RGB that will not make the conversion to CMYK. These colors are said to be out of the CMYK color gamut. What happens is the RGB to CMYK translator just gets as close as possible to the appearance of the original using the CMYK makeup and that s as good as it can be. Some RGB colors won t make the translation very well. Here s a common example: many programs translate the 100% Blue in RGB into a somewhat purple-looking color in CMYK. We recommend a CMYK value of 100 C-65 M-0 Y-0 K to get a nice clean blue. Working in the CMYK color space allows you to select the CMYK recipe, or screen build, that gives you the results you want. Another helpful tool is Pantone s Four Color Process Swatch Book that will give you the screen build of CMYK ink formulas. ( So it s best to select any colors you use for your design elements using CMYK definitions instead of RGB. This way, you will have a better idea of how they will appear in your printed piece. If you have questions about the conversions, please give us a call

6 Step 5: Save your file in TIF format, not JPG. Why? Read on. JPG is the right format for photo images which must be very small files for web sites or for . The JPG file is very small, often compressed by 90%, or to only 1/10 of the original data size, which is very good when modems are involved. However, this fantastic compression comes with a high price. JPG uses lossy compression (lossy meaning with losses ). Lossy means that some image quality is lost when the JPG data is compressed and saved, and this quality can never be recovered. Most other file compression methods are lossless, like TIF, which means fully recoverable. Lossless compression always returns the original data, bit-for-bit identical without any question about differences (losses). We are used to saving data to a file, and getting it all back when we open that file. Our Word and Excel documents, our Quicken data, any data at all, we cannot imagine NOT getting back exactly the original data. TIF, PNG, GIF, BMP and most other image file formats are lossless too. This integrity requirement does limit efficiency, limiting compression of photo image data to only 10% to 40% reduction. But most compression methods have full lossless recoverability as the first requirement. JPG files don t work that way. JPG is an exception. JPG compression is not lossless. JPG compression is lossy. Lossy means with losses to image quality. JPG compression has very high efficiency (relatively tiny files) because it is intentionally designed to be lossy, designed to give very small files without the requirement for full recoverability. JPG modifies the image pixel data (color values) to be more convenient for its compression method. Detail that doesn t compress well can be ignored (removed instead of retained). This allows amazing size reductions, but when we open the file and expand the remaining data to access it again, it is no longer the same data as before. This lost data is like lost purity or integrity. It can vary in degree, but it is always unrecoverable corruption of the data. This makes JPG quite different from all the other file format choices, and is not recommended for high quality print reproduction. There are times and places this compromise is an advantage. Web pages and files need to be very small and some uses may not need maximum quality. In some cases, we are willing to compromise quality for size, and this is the purpose of JPG. Even worse, more quality is lost every time the JPG file is opened, compressed and saved again. So even editing a JPG image is a questionable decision. You should instead just discard the JPG file and start over from your archived lossless TIF master, and send us that file