Finding the Best Resolution for All Your Photos and Images
A question that several attendees had during this year's FastTrack to Success Bootcamp had to do with the correct resolution for images. What they learned is that there is no one right answer. Here's the complete scoop:
Before submitting files to the printer or your client, make sure the photos and images you're using are in the correct resolution. The resolution depends on how you are going to use the images.
If image resolution is unnecessarily high, files will take a long time to display and print. If the resolution is too low, print quality will be poor.
Here are typical examples of various types of print pieces you may create, with guidelines for which resolutions to use. Image resolution is expressed as the number of pixels displayed per unit, usually as pixels per inch (ppi):
- Newspaper ads: 130-170 ppi
- Low-end brochures: 200-250 ppi
- DM packages (sales letters, magalogs): 300 ppi
- Fine art & coffee-table books on high-end glossy stock: 400-600 ppi
It is always best to speak to the professionals who will be printing your job to find out what they need. (And don't forget to save your images in CMYK. That is the color mode printing presses require.)
Sometimes, you may just want to print a few quick samples on your ink jet printer. You can usually obtain good results with images at around 150-200 ppi. You can keep the color mode in RGB.
Slide Show Considerations
If you want to save images for a slide show to show your portfolio to your client or to give a presentation, the resolution depends on your output device.
If you're displaying the slide show on a computer monitor, the optimum dimensions (not resolution) could be 1024 x 768 dpi, 1280 x 1024 dpi, or even 1600 x 1280 dpi, depending on the monitor.
However, if you'll be displaying the slides through a projector, most newer projectors have a native resolution of 1024 x 768 dpi. Some are even 1280 x 1024 dpi. You may want to create a template that matches the native dimensions of your monitor or projector and fit all your images within those dimensions.
When saving images for the Internet, any resolution above 72 dpi is overkill because that's the best monitors can display. (That will change with HD monitors in the future.) But don't focus solely on the resolution of the image. Focus instead on the total pixel count. You calculate total pixel count by multiplying horizontal pixel count by vertical pixel count.
You're going to want to limit the image to 740 total pixels, with most images at a much lower count of 200-400 total pixels.
You have to know your audience to know what size image to use. Are they a “captive” audience waiting to sign off on an image? Are they browsing your portfolio? Or do they want to see the full-size image? This will determine their attention span for download times.
It's often a good idea to use small thumbnails to capture a viewer's interest. Thumbnails link to larger images, which can be displayed on demand. The small thumbnails typically range from 50-75 pixels, and the large gallery images range from 300-600 (or larger if your viewer wants or needs to see larger images).
Of course, the tradeoff is between file size and image quality.
Another important factor here isn't just image dimensions, but compression settings. 99% of the images you post to the Web will be in JPEG format. A 740 x 740 pixel JPEG could be 80k or it could be 2 megabytes in size, depending on the amount of compression you specify. With JPEG, the more compression, the smaller the size but the lower the quality.
Once again, you're trading file size for image quality.
Keep the color mode in RGB when making images for the Internet or solely for viewing on monitors or with projectors.
Warning About Saving in JPEG Format
Every time you save an image in JPEG, you decrease the image quality. Rather than simply saving in JPEG, it's best to save the original at the highest resolution possible as a Photoshop, Illustrator, TIF, or PNG image (depending on the source of the image).
Then make a copy of that image for future manipulation (such as reducing its resolution, decreasing its total pixel count, or compressing it as a JPEG).
NOTE: PNG images are similar to JPEGs in the way they compress images, but you don't lose quality when they're compressed or when you do successive saves. However, you cannot be sure the person viewing the image on the Internet has a browser that can handle PNG images, so you should not use them for Web images.
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