Image Interpolation & Resizing for Stock Photography Sellers
Posted July 25, 2008 by Fred Voetsch
Image Interpolation: Why & Where
The reason for image interpolation (image resizing) when selling stock photography is to make the photo as usable as possible. Many photographers also like the fact that a larger image often sells for more but that is an argument that too easily leads to abuse and results in oversizing of photos and poor quality.
Reason states that an image that is going to be resized to a larger size (interpolated) should be resized as the very first step in image processing for the following reasons:
- Image artifacts from JPEG processing have the least chance of being present and therefore enlarged, providing the best possible quality.
- Interpolation or resizing will only have to be performed one time and not by each stock photography site or agency.
These are the two overwhelming reasons for interpolating photos at the source. Many more arguments may be presented for or against this stand but in my years dealing with digital stock photography and digital images I have never heard a convincing reason to make me even consider another strategy for image interpolation.
Image Interpolation for Stock Photography: How and How Much
How to resize an image is usually simple: resize the image in Adobe Photoshop as you open your RAW image file. You do shoot RAW, don't you?
How much is also pretty simple: I suggest interpolating the photo to 150% of the original size, or 50% larger than the original image. Pixel size is the only thing to consider when resizing an image for stock photography: a 3000 x 2000 photo will be sized up to 4500 x 3000 pixels; a 4288 x 2848 image will be sized up to 6432 x 4272 pixels.
Why not more? It certainly is possible to generate a high quality stock photo in a larger size, provided your original photo is razor sharp and was shot in RAW or TIFF format. The problem is that too many photos are not as sharp as they should be and any more size is probably overkill. If you're shooting an 8-20 megapixel DSLR a 50% increase in size should put you right where most stock photography agencies want you to be.
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