How to Resize Your Stock Photos for Submission to Alamy or Acclaim Images
This is a copy of a post to the "Selling Stock Photography" forum on Yahoo.
--- In email@example.com, Jared Isham - eyeShum STUDIO wrote:
> I know this has been covered before but i can't seem to find the
> thread. I am finally getting my act together and start submitting to
> some stock sites. My first one being Alamy.
> I was wondering if anyone had some input on the best way to prep files
> for submission. I shot the photos with the Canon Rebel XSi in RAW
> format. The original RAW file is only 13.3 MB and they are requesting
> it to be a 48MB JPG. It is in RGB color mode at 8 bit. I can easily
> get it to 36 MB by converting it to a 32bit TIFF but any attempt to make
> a JPG ranges from 4 - 6 MB. They have the Canon XSi listed as
> recommended cameras so not sure what I'm doing wrong.
There are various ways to measure the "size" of an image but what it comes down to for
Alamy and most other stock photography sellers is PIXELS WIDE x PIXELS HIGH x 3
(RGB Channnels) = IMAGE SIZE IN MEGABYTES
So forget looking at the actual file size of the image saved to disk, at bit depth or file format.
Bit depth should be 8 bits per channel, file format is almost universally JPEG these days
(I recommend a quality setting of 11 when saving from Photoshop) and the actual size of the
file saved to disk does not matter at all since it can vary from under 1mb to tens of megabytes
based on final image size, compression and image content.
The megapixel rating of your camera is a place to start but 'megapixels' are based on a single
plane and not 3 planes (RGB) so if you multiply megapixels by 3 you get megabytes. a number
you can use. A 6 mp camera produces an 18mb image (6 x 3 = 18). A 10mp camera produces
30mb images (10 x 3 = 30). A 17mp camera produces 51mb images (17 x 3 = 51).
So you can see that only a 17mp or higher camera produes an image large enough for Alamy.
But Alamy allows interpolation. Interpolation is where you create addition pixels by sizing the
image up in Photoshop or another professional quality software program. The general rule is that
you can resize an image up 50% (150% of the original size) without seriously degrading image
Images from a 6 megapixel camera give us this:
Out-of-camera: 3000 x 2000 = 6mp -> 6 x 3 = 18mb
Resized 150%: 4500 x 3000 = 13.5mp -> 13.5 x 3 = 40.5mb
40.5mb is too small for Alamy so unless you always shoot off a tripod and have top quality lenses
you likely will not be able to size the images up more and produce acceptable quality.
Images from an 8 megapixel camera give us this:
Out-of-camera: 3600 x 2400 = 8.6mp -> 8.6 x 3 = 25.8mb
Resized 150%: 5400 x 3600 = 19.4mp -> 19.4 x 3 = 58.2mb
So with an 8 megapixel camera you can produce images large enough for Alamy, assuming their
minimum size requirement is 50mb. You just need to start with a very sharp, noise-free image and
then size the image up 150% of its original size. Unless you really know what you are doing you
should always use 'bicubic' when sizing up an image.
If you want to go right to the horses mouth you can read all about this subject on the Alamy forum at
My simplified rule for Acclaim Images is that an image must have at last 5,000 pixels in a least one
direction to be acceptable. There are exceptions to this rule - panoramic images, for instance - but
for the most part it works and is compatible with Alamy's requirements.
Group Moderator - Selling Stock Photography
Owner - Acclaim Images
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