Image File formats and sizes
Downloading images
FAQs about using digital images
About
Contact Us
Contributors
Factsheet
Image Usage
Site Map
We envision most images being in the public domain, unless otherwise stated. If an image is listed as "public domain" you are free to use as you wish. No need to ask for permission for those images in the public domain. We just ask that you please give credit to the photographer and the National Biological Information Infrastructure (example, Photo credit: John Doe/NBII.Gov).
If an image is listed as "Copyright held by Source", then the copyright is held by a designated third party. Please contact the person or organization listed under the "source field" to get permission to use their image(s) in which they hold copyright to. By clicking on the link provided as Source, you will be directed to their website or a web page for contact details or more information.
If an image is listed as "Copyright held by Creator", then the copyright is held by the photographer. Please contact the person or organization listed under the "source field" to get permission to use their image(s). You may be directed to the organization who the photographer worked with, so by clicking on the link provided as Source, you will be directed to their website or a web page for contact details or more information. The organization listed may provide information about usage, the photographer and/or how to contact the photographer.
The "Rights Qualifications" field may also give some information as to who or how an image may or may not be used, and when permissions are required.
Downloading images
For downloading the medium, web, or high resolution image, use their respective button in the green colored box, then follow one of these steps:
- Click-and-hold (Mac users) or right click (PC users) the resolution desired on the image's data record page. Then simply select 'Download image to disk' (Mac) or 'Save target As...' (PC) to save to your computer's desktop.
- If you happen to just click on the 'high resolution' or 'medium resolution' button, the image will pop up in a new browser window. From there you may also click-and-hold (Mac users) or right click (PC users) to download the image file to your desktop.
*Please note, not all formats are available for all images.
FAQs about using digital images
What color mode are the images?
All the images from the NBII Image Library are saved as RGB format. This is so they are as versatile as possible for the end user. RGB format gives the end user more control over image usage and special effects than other formats.
How large can I print the digital images?
As a general rule, our images can safely be enlarged to 125% of their original size without adversely affecting quality (i.e. a high resolution image at approx. 8.5x11" can enlarge to 10x15", a 1.25 to 1 ratio). Since it's critical to know what resolution you need for the output device or final end use of the image, we recommend you follow these guidelines:
- For print quality (i.e. brochures, factsheets, posters, exhibits) – use the high resolution file
- For presentation/power point quality – use the medium resolution file
- For screen/web and multimedia quality – use the thumbnail
When I enlarge an image, how do I keep it at it's best quality?
Our high resolution images have been optimized for a final print size of approximately 8.5"x11" using a screen frequency of 150 lpi (or 300ppi - often referred to as dpi). You may, however, print the images at a larger size and still maintain adequate quality. To maintain the best image quality, use this general guideline: The image resolution (ppi) should remain equal to twice the screen frequency (lpi). So for example in this case 150lpi x 2 = 300ppi. You have three options for enlarging an image:
- Use a lower screen frequency.
If you require only a 130 lpi screen frequency, you can enlarge the image to approx. 9"x14" at 260 ppi and still maintain the 2-to-1 ratio of ppi to lpi (i.e. 130lpi x 2 = 260ppi). Lower screen frequencies will allow you to enlarge the images even further. Screen frequencies are dependant on your final output requirements. For example, if you're using an image for a brochure that will be professionally printed, typically a 150lpi screen frequency is used.
- Resample the image to a higher resolution.
Resampling refers to changing the pixel dimensions (and therefore display size) of an image. When you down sample (or decrease the number of pixels), information is deleted from the image. When you resample up (or increase the number of pixels), new pixels are added based on color values of existing pixels. Many image-editing programs use an interpolation method to assign color values to any new pixels it creates, based on the color values of similar adjacent existing pixels in the image. So for example, if you take a high resolution image from our library and resample the resolution from 300ppi to 400ppi, it increases the pixel dimensions and the file size.
Resampling can, however, cause the image to appear somewhat out of focus or blurry. To compensate for this, you may want to apply a sharpening filter to the image to eliminate some of the blurring. Experiment with this technique to determine if the results will be satisfactory for your needs.
- Use a lower ppi-to-lpi ratio, such as 1.5 to 1.
Following the guidelines above for maintaining image resolution (ppi) equal to twice the screen frequency (lpi) is to ensure the highest image quality. You can go below this ratio with relatively little noticeable difference in quality. By using the ratio of 1.5 to 1, you can enlarge our high resolution images to 10.5"x16" at 225ppi (i.e. 150lpi x 1.5 = 225ppi). You should never go below a 1-to-1 ratio of ppi to lpi. Generally a 1.25 to 1 ratio is the lowest you can go. Experiment with various ratios to determine which will work best for your needs.
