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How to Size Your Image Files for Enlargements
by Barry Baker


Disclaimer: Please let me begin by saying that if you do not use a software program to alter your images before they are printed then you need not worry about resizing them at all. Simply allow your lab to size the images for you. For 4x6 images it’s usually not even necessary to adjust the file sizes. However, if you do use Photoshop or Elements and you are ordering enlargements, you must take care that your images are sized correctly or you will find that your lab of choice may be trying to print your 16” x 20” from the equivalent of a tiny postage stamp. We all know that spells trouble! So, if you are resizing your images to be printed to a specific size you will find the following information to be useful.

There are basically two tools available to re-size your image for enlargements: 1) Resize Image (Elements) or Image Size (Photoshop) and 2) Crop Tool.

In the image box, the image size consists of two parts (Example 2). 1) Image size can be expressed in both inches or millimeter/centimeters and 2) dpi (dots per inch) which is also referred to as ppi (pixels per inch). Most digital cameras will capture the image at 72dpi and size it as representative of anywhere from 20" x 30" to 40" x 60" screen viewing resolution.

example two

April Tips

The first method we will cover is the Image Size or Resize tool in Photoshop Elements. It is important to note that when down sizing the image size for printing the dpi should also be changed to 300dpi. (Example 3) This is where most of the mistakes are made on resizing images.

Let’s get started! In Photoshop or Photoshop Elements, select and open an image. After the file opens, follow these steps to re-size your image: In the Menu Bar of Photoshop, click on “Image” and then “Image Size”. In Elements, click on “Resize Image” and then “Image Size”. The image size box will then pop up (Example 2). This shows you “Pixel Dimensions” and below that the “Document Size”. Below there are several options which must be checked in the correct order. Leave “Scale Size” unchecked. Please check “Constrain Proportions”. Leave “Resample Image” unchecked. With “Resample Image” unchecked, we will work with the “Document Size” box. On the “Resolution Line” simply change the dpi from 72 to 300, (Example 3). You may notice that the documents Height and Width changed and that it appears smaller. This is now the actual size that the print can be printed for maximum sharpness. Depending on the camera, the image might be anywhere from 6" x 8" to 9" x 14". This is a big reduction from the 40" x 60" that some cameras may show. The reason you can't actually print your image that big is because the 72dpi is for screen resolution only while viewing on the computer. If you wish to change either the document size or resolution, but not both then check the resize box. This allows an independent size change.

example three

Please Beware!
If you leave “Resample Image” checked and simply change the “Height” and “Width”, the dpi will stay at 72 and the file could possibly shrink to no more than a thumbnail size. This is the most common mistake I see when images are sent in to the lab for printing. The image will be sized at 4"x 6" and 72dpi, but when printed this would be converted to an actual size of 0.96" by 1.44" at 300dpi - in other words, a thumbnail!
If you want your print to be larger than 9"x14" how do you do it? Fortunately we can usually print the file larger than it's theoretically optimum size would be. Most printers will hold the image together at 240dpi and larger prints are viewed from several feet away. At 240dpi the 9" x 14" becomes a 12" x 18" inch print (Example 4). But what about printing a 16" x 20" size? Well, almost all of the larger prints in the 16" x 20" or larger range do not require as high a dpi count as and 8" x 10" print would. This is directly tied to viewing distance for the print. Many large format printers in fact print as low as 150dpi. The image we have been working with would actually be 182dpi, so it should reach 16" x 20" without any noticeable loss of detail from where you would normally view such a print.

example four

The second method of re-sizing to use is the Crop Tool. The crop tool is very useful for resizing and recomposing your photograph and doing away with of any unwanted area.
First, click on “Crop Tool” (Example 5). Now the crop sizing information will appear along the top of the screen. Set the “Height” and “Width” that you want and set the dpi to 300. Next, place the cursor at what will be one of your desired corners. Then drag the tool diagonally across the image to where you want the crop to end (Example 6). Notice that the areas to be cropped out are now shaded dark. This helps you to decide if this is really the way you want the image cropped. If this cropping pleases you, press the “Enter” key and the crop will be implemented.

example five

example six

Tip: When you manipulate an image and save it, give it a letter after its original name. Example: “saxplayer” becomes “saxplayerA”. Then if you manipulate the image further, your next saved file name might become “saxplayerB”. This leaves the original file intact so that if you change your mind about any work you have done you will still have the original unaltered file.

File Types:
I recommend saving your files as tiff files as opposed to jpeg files. A jpeg image file is fine in its original state, but after performing any alterations on the image you should then select “Save As” and save it as a “Tiff” file. My reasoning is that a jpeg file will re-compress and become smaller each time you save it. A Tiff file will stay the same size, and not reduce in size every time you save it. When saving a file as a tiff for printing, it should be saved as an 8 bit file and not a 24 bit. Most mini lab machines simply cannot open 24 bit files. You should also be certain to not select any of the tiff compression options such as LZW since most machines cannot read these files either.

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