Portraits of Wildflowers

Perspectives on Nature Photography

Not exactly the repeat picture that it appears to be

with 21 comments

Click for greater clarity.

Click for greater clarity.

In a comment on this morning’s picture, Cindy Taylor wrote that she kept looking for something hidden in the thicket of dried-out giant ragweed stalks. Her comment made me think that such a dense picture would indeed be a good place to hide a message, and that’s what I’ve done with this follow-up photograph that at first glance (and second, and third, and fourth…) looks the same as the one from the previous post.

There’s nothing else new in this post, so if cryptography doesn’t appeal to you, you need read no further. On the other hand, if you’d like to decode the hidden message, here are the steps to follow. (You can also skip to the end of step 14 if you want to see the result of all those steps.)

I’ll give the instructions for Photoshop, but I assume Photoshop Elements and other photo editing programs that allow layers will work in a similar way.

1) Go back to this morning’s post and click on the image to bring it up in isolation in your browser window.

2) Copy this morning’s picture to your computer. On a Macintosh, which is what I have, all you have to do is drag the image to your desktop, where it will show up as an icon with the name giant-ragweed-colony-remains-7531.jpg. For Windows, I’m guessing that if you right-click on the image, one of the choices that comes up will be to save the picture to your computer. (On a Macintosh, control-clicking on the image offers that choice.) If one of you who uses Windows would like to confirm that or, if it’s wrong, let us know the right way to download a picture from a WordPress post, please do so.

3) Return to this follow-up post, click the picture to bring it up in isolation in your browser window, then copy it to your computer, where it should appear with the name hidden-message-7531.jpg.

4) In Photoshop, open the first picture you downloaded, the one called giant-ragweed-colony-remains-7531.jpg.

5) In Photoshop, open the second picture you downloaded, the one called hidden-message-7531.jpg.

6) From the Select Menu, choose All to select the entire image called hidden-message-7531.jpg. (You can also use the keyboard shortcut Command-A on a Macintosh or Control-A in Windows.) You should see “marching ants” around the edges of the image to confirm that all of it has been selected.

7) From the Edit menu, choose Copy. (You can also use the keyboard shortcut Command-C on a Macintosh or Control-C in Windows.)

8) Close the window containing hidden-message-7531.jpg. If asked whether you want to save changes, don’t save them.

9) Go back to the Photoshop window containing the first picture, the one called giant-ragweed-colony-remains-7531.jpg.

10) From the Edit menu, choose Paste (or type Command-V on a Macintosh or Control-V in Windows).

11) If the Layers panel isn’t already open, bring it up by going to the Window menu in Photoshop and choosing Layers.

12)  In the Layers panel you should see that you now have a Background layer and a layer above it called Layer 1.

13) In the Layers panel, Layer 1 should already be selected, but if not, click to select it.

14) In the Blending Mode pop-down menu near the top left of the Layers panel, change the blending mode from Normal to Divide (you can also change to Difference mode, but the result won’t be as legible). You’ll now be able to read the hidden message.

If you don’t have appropriate photo editing software or don’t want to go through all those steps but would still like to see the result, click on the tiny icon below.

After Divide Blending Mode 7531

And for those of you who would like to know how to put a hidden message into a picture, here are the steps.

a) In Photoshop, open (or create) an image that’s filled with lots of tiny details in which you can hide a message.

b) From the Tools palette, choose the Type tool (or press T on your keyboard).

c) Click at an appropriate place in the image and type your message, then press the Enter key. (I used 24-point type for my message.)

d) In the Layers panel, you should now see that you have a Type layer above your Background layer.

e) With the Type layer selected in the Layers panel, go to the Opacity pop-down menu near the top of the Layers panel and change the opacity from 100% to something small. I think I used 16%.

f) From the Layer menu, choose Flatten Image to merge the text layer with the image layer.

g) Save this image that now has your message hidden in it.

Note that someone who wants to read the hidden message must have a copy of the original image as well, so of course you’d make the original available only to people who are authorized to read the message.

It’s the discrepancy between the two versions of the image that allows the message to be made visible. I used to do a lot of 3-D photography involving side-by-side pairs of images; the difference between the view from the left eye and the view from the right eye is what the brain uses to create the illusion of depth. Clever brain.

© 2013 Steven Schwartzman

Written by Steve Schwartzman

February 22, 2013 at 1:00 PM

21 Responses

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  1. 🙂

    Vladimir Brezina

    February 22, 2013 at 1:02 PM

  2. This is a great way to hide an authorship notice in an image, in case you need to prove that an image someone else is using is actually yours. I’ve been doing this with many of my images, but I never knew of an easy way to recover the hidden notice. Now I know. Thank you!

    Spider Joe (@arachnojoe)

    February 22, 2013 at 1:21 PM

    • BTW, I think it would be helpful to have a summary explanation for those of us who know how to use Photoshop. It seems that to hide a message simply superpose the message with high transparency. To recover the message merge the original image with the coded image using “divide” blending.

      Spider Joe (@arachnojoe)

      February 22, 2013 at 1:25 PM

      • Hmm. It would be better if there were a way for third party to independently confirm the hidden notice without having to give the party the original image. It would be nice to have a technique for recovering the message that didn’t require the original.

        Spider Joe (@arachnojoe)

        February 22, 2013 at 1:33 PM

        • I seem to remember that there is software to do that, but I believe you have to pay a periodic fee to stay enrolled in the system.

          Steve Schwartzman

          February 22, 2013 at 1:39 PM

      • That’s a good summary. Thanks.

        Steve Schwartzman

        February 22, 2013 at 1:52 PM

    • I see one possible complication. If the person who pirates your image crops it to a different size and especially a different height/width ratio, you’ll have a hard time making the pirated image coincide with the original one to bring out the hidden message. There may be a way around that, but it would complicate the process.

      Steve Schwartzman

      February 22, 2013 at 1:36 PM

      • Also, I’m thinking that because it does require that a third party do the verification, we need a way for that party to determine which of the two images actually has the watermark. Otherwise the so-called “original” provided could actually be the one with the watermark — a false watermark.

        Spider Joe (@arachnojoe)

        February 22, 2013 at 1:39 PM

        • Good point. In case of a dispute, the file’s metadata includes the camera’s model and serial number. The original photographer most likely either still has the camera or has proof of having owned it.

          Steve Schwartzman

          February 22, 2013 at 1:48 PM

      • It’s easy to strip the metadata by re-exporting the image or by pulling it into software that allows you to change the metadata.

        Spider Joe (@arachnojoe)

        February 22, 2013 at 1:48 PM

        • Photoshop lets me change lots of the metadata fields, but not the camera data fields. Of course a hacker may know how to get around that.

          Steve Schwartzman

          February 22, 2013 at 1:55 PM

      • It takes effort to preserve metadata when a program creates a new jpeg from a previous one. The programmer simply need not go through this extra effort. There are umpteen scripts out there that manipulate images, and many are probably lazy scripts that don’t preserve metadata. From Photoshop, you could export to a format that doesn’t support metadata, such as a GIF, and then re-export that GIF as a jpeg. All metadata gone. Probably half of the graphics programs out there aren’t good about keeping metadata just re-saving a jpeg. Most probably do not copy metadata when exporting to PNG. So it’s easy for pretty much anyone to eliminate the metadata if they want to.

        Spider Joe (@arachnojoe)

        February 22, 2013 at 2:16 PM

        • After step 10 in my instructions, for example, all metadata has been removed from the pasted-in picture. What I don’t know, though, is whether/how how a pirate could go about inserting his own camera’s model and serial number into the Camera Data fields.

          Steve Schwartzman

          February 22, 2013 at 2:22 PM

      • Besides, should any image be uploaded to a web site that converts the image to a standard representation for the site or that caches the image in various sizes, the code for that web site very likely does not make much of an effort to preserve metadata. Most people probably unwittingly eliminate metadata just by uploading an image to a web site.

        Spider Joe (@arachnojoe)

        February 22, 2013 at 2:19 PM

  3. WOW!!! I am impressed!!!. I followed all the steps and it worked like a charm. and I didn’t cheat.


    February 22, 2013 at 3:52 PM

    • As a teacher, I can tell you from experience that it’s hard to get a long set of instructions completely right. When I went through the steps myself before posting, I realized that I’d left out step 7, which I naturally added. Thanks for letting me know that none of the steps in the current version were misleading and that the directions as a whole worked for you. And I’m impressed that you’re impressed.

      Steve Schwartzman

      February 22, 2013 at 4:17 PM

  4. Mercy that is too involved to attempt. Not for my pea sized brain but quite interesting.


    February 23, 2013 at 12:39 AM

    • I made it a follow-up rather than a morning post, so people would see it as optional. You can still click the little icon to see the result.

      Steve Schwartzman

      February 23, 2013 at 8:23 AM

  5. Need more time than I have this morning to give this a try, but I will. And I’m purposely not reading the comments just in case there’s a spoiler in there!


    February 23, 2013 at 8:09 AM

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