Enlarging Digital Images for Publication
© Darrell Young

Is it possible to take the output from a six-megapixel digital SLR camera and enlarge it until it meets the file-size and quality standards of publishers for digital image submission?

This question is being discussed all over the Internet. A large number of people are using cameras in the six-megapixel range, and would like to sell their images to stock agencies, or submit them to magazines for publication. Most stock agencies require a minimum file size of 50 megabytes to accept a submission. But, a six-megapixel digital camera produces a file that can be converted to an 8-bit TIFF image of only about 17.5 megabytes, well below the standard. To find out if it is possible to enlarge (interpolate) images from 17.5 to 50+ megabytes, and still maintain quality, I decided to use a couple of easily available software programs.

As a test image I chose a low-contrast picture of three cute children standing by a dam. This is a handheld shot taken with a Nikon® D100 digital camera in RAW mode, and later converted to an 8-bit TIFF at 17.5 megabytes. I am showing the test image as a 600 pixel wide JPEG with 10% compression, and mild sharpening.

The image I cut out from the non-interpolated test image has no manipulation of any sort. The cut out from the interpolated image, being 50% larger, had to be reduced to show an apples to apples conversion. The red rectangle shows the part of the image I cut out for viewing of the interpolation methods. Here is the test image:


First, I used LizardTech® Genuine Fractals to do the enlargement (interpolation). In Figure 1 below, you will see two 300x350 pixel images. The one on the left is a cut out at 100% from the 8-bit TIFF image. The one on the right is the image after I used Genuine Fractals to enlarge it to 52 megabytes (175% setting at 300dpi), and then converted it to an 8-bit TIFF. Can you see any differences!

Next, I used Adobe® Photoshop CS, and its excellent "Bicubic Smoother" to interpolate (enlarge) the image to 56 megabytes. In Figure 2 below, you will see a comparison of the original 17.5 megabyte 8-bit TIFF and the interpolated 56 megabyte 8-bit TIFF (13.5x20 inches at 300 dpi). Can you see any differences?
Now, let's see a direct comparison between the Photoshop CS and Genuine Fractals Conversions. In Figure 3 below we see the Photoshop on the left and Genuine Fractals on the right. Can you see a difference in these?

Since you are only seeing mildly compressed JPEG files, and cannot see the original TIFF images, let me give you my opinion of these conversions.

  • The Genuine Fractals® and Photoshop® conversions both exhibit slightly more contrast.
  • The apparent sharpness of the Genuine Fractals image is a little higher than the original TIFF.
  • The apparent sharpness of the Photoshop conversion is slighty less than the original TIFF.
  • Both interpolations maintained an accurate color representation.
  • Neither of the conversions caused much increase in noise (grain).
  • Since the 300x350 interpolated images were reduced by 50% to the size of the non-interpolated image, there could be some loss of quality from the reduction. But, amazingly, the interpolated images are still of similar quality to the original image. This shows how well the two software programs do at interpolating.
  • Both enlargements provide an image that may be used in a two-page magazine spread.

Is there a winner? Well, in my opinion the Genuine Fractals image was slightly sharper looking than the Photoshop image. So, personally, I choose Genuine Fractals as my normal conversion tool. Photoshop CS also provided an excellent image. If a bit of sharpening were done on either conversion, I think there would be little difference between them in final appearance. If you would like to examine the original TIFF files yourself, I have included links to the individual files at the end of this article.

Both Genuine Fractals and Photoshop CS were able to provide a professional level of digital image interpolation. I would not be afraid to submit a 50+ megabyte file from either of these fine software tools to a stock agency or magazine.

So, six-megapixel digital camera users can be happy that the output from their camera may be acceptable for publication without significant loss of quality from the interpolation process.

Keep on capturing time...

Source TIFF Image Download
Untitled Document
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