Easy-to-follow video tutorials help you learn software, creative, and business skills.Become a member

Comparing seemingly identical images

From: Photoshop Masking and Compositing: Advanced Blending

Video: Comparing seemingly identical images

One of the great uses for the Difference mode is that it allows you to compare seemingly identical images and discover their differences. And here's how that works. We are looking at a photo from Fotolia image library, I absolutely love it because it's a great demonstration of Blend Modes, we have got this photograph in the background, then this falling type in the foreground set to the Screen mode I would imagine, in order to create this bright interaction. The name of the file is Access codes. tiff so I save the image to the tiff file format, I use LZW compression, which is entirely lossless.

Comparing seemingly identical images

One of the great uses for the Difference mode is that it allows you to compare seemingly identical images and discover their differences. And here's how that works. We are looking at a photo from Fotolia image library, I absolutely love it because it's a great demonstration of Blend Modes, we have got this photograph in the background, then this falling type in the foreground set to the Screen mode I would imagine, in order to create this bright interaction. The name of the file is Access codes. tiff so I save the image to the tiff file format, I use LZW compression, which is entirely lossless.

So it doesn't change a single pixel inside the image. Meanwhile, next-door, it looks like the same image; we will see that it's not in a moment. It's called Heavily compressed.jpg, and what I did was, I save that same file to the JPEG format, and I applied the lowest quality setting possible, which is 0. And as a result, if you go and zoom in on this image, you can see that we have all kinds of compression artifacts, they show up as these 8x8 pixel squares, and basically all of the pixels are rewritten, based on the color of the top left pixel and that's how JPEG works.

Now let's say we want to get a sense of what exactly has change between these two images. Well, I am going to right click inside this image and choose Duplicate Layer and then send it over to Access codes.tiff and change its name to let's say JPEG version and click OK. And now we'll switch back to the image at hand. To compare the two, I will go ahead and change the Blend Mode from Normal to Difference. Now first it's going to look like the image is gone completely black, so there must not be any differences between the pixels, because identical pixels set to the Difference mode cancel each other out.

However, that's not actually the case. So what I am going to do is press the Escape key to deactivate the Blend mode there. And I'm going to create a Merged version of these two layers by pressing Ctrl+Shift+Alt+E or Command+ Shift+Option+E on the Mac. We will go ahead and create a merged composite on a new layer. I will go ahead and call this new layer Merged as well. Now what you need to do is go up to the Image menu, choose the Adjustments command and choose Levels or you can press Ctrl+L, Command+L on the Mac and look at that histogram, there is some action going on in the very dark regions of this layer.

To make it evident, go ahead and grab that white slider triangle and move it very far over to the left hand side. And I am going to ultimately settle on a white point value of 20. So that we have a fair amount of distinction going on here and then I will click OK. Any pixel at this point that does not appear black has been rewritten, which means that applying a lot of JPEG compression in our case, has rewritten just about every single pixel in the image.

So any time you want to be able to compare two seemingly identical images and figure out if they are truly the same thing, then you can do this exact same tests we did here, using the Difference Blend Mode, going ahead in merging the two layers and then using the Levels command to exaggerate the differences.

Show transcript

This video is part of

Image for Photoshop Masking and Compositing: Advanced Blending
 
Expand all | Collapse all
  1. 1m 43s
    1. Welcome
      1m 43s
  2. 33m 15s
    1. When in doubt, blend
      2m 20s
    2. Where to find blending options
      4m 10s
    3. 27 blend modes, 6 groups
      4m 23s
    4. Opacity vs. Fill Opacity
      4m 41s
    5. The "Fill Opacity Eight"
      4m 59s
    6. Blending adjustment layers
      4m 43s
    7. Blend mode shortcuts
      7m 59s
  3. 27m 3s
    1. The power of standardized arithmetic
      6m 58s
    2. Photoshop's blending formulas
      5m 27s
    3. Darken formulas vs. lighten formulas
      4m 15s
    4. Contrast mode formulas
      7m 28s
    5. Inversion, cancelation, and HSL
      2m 55s
  4. 17m 50s
    1. Normal mode vs. Dissolve mode
      2m 11s
    2. Making a dynamic Dissolve effect
      2m 21s
    3. Creating a Dissolve text effect
      4m 48s
    4. The Behind and Clear modes
      3m 2s
    5. Filling a stroke with Behind and Clear
      5m 28s
  5. 43m 24s
    1. Darken vs. Darken Color
      4m 25s
    2. Creating filter effects with Darken
      5m 0s
    3. The Multiply and Burn modes
      6m 27s
    4. Cleaning up scanned line art
      7m 30s
    5. Comping line art against a photo
      5m 12s
    6. Colorizing comped line art
      5m 14s
    7. Masking with a darken mode
      3m 59s
    8. Refining a mask with Multiply
      5m 37s
  6. 33m 36s
    1. Lighten vs. Lighter Color
      2m 29s
    2. Creating filter effects with Lighten
      2m 47s
    3. The Screen and Dodge modes
      4m 35s
    4. Blending white type, darkening shadows
      3m 2s
    5. Creating a classic double-exposure effect
      3m 49s
    6. Making dark line art bright
      5m 11s
    7. Masking with a lighten mode
      5m 4s
    8. Refine, filter, and blend
      6m 39s
  7. 35m 18s
    1. Overlay, Soft Light, and Hard Light
      5m 2s
    2. Vivid, Linear, and Pin Light
      4m 2s
    3. The amazing Hard Mix mode
      3m 51s
    4. Two variations on a single mode
      5m 37s
    5. Adding clarity with a contrast mode
      4m 9s
    6. Creating a glowing, soft-focus effect
      3m 38s
    7. Blending an image with a paper texture
      4m 11s
    8. Turning flesh into stone
      4m 48s
  8. 18m 10s
    1. Difference, Exclusion, Subtract, and Divide
      7m 7s
    2. Comparing seemingly identical images
      3m 25s
    3. Creating type that inverts any background
      3m 30s
    4. Making inversion type black and white
      4m 8s
  9. 16m 57s
    1. Luminosity, Color, Hue, and Saturation
      3m 29s
    2. Colorizing artwork with layers
      7m 24s
    3. Correcting skin tones with Hue
      6m 4s
  10. 14m 57s
    1. Using the This Layer slider option
      6m 44s
    2. Using the Underlying Layer slider option
      3m 16s
    3. Achieving greater control with Blend If
      4m 57s
  11. 48s
    1. Next steps
      48s

Start learning today

Get unlimited access to all courses for just $25/month.

Become a member
Sometimes @lynda teaches me how to use a program and sometimes Lynda.com changes my life forever. @JosefShutter
@lynda lynda.com is an absolute life saver when it comes to learning todays software. Definitely recommend it! #higherlearning @Michael_Caraway
@lynda The best thing online! Your database of courses is great! To the mark and very helpful. Thanks! @ru22more
Got to create something yesterday I never thought I could do. #thanks @lynda @Ngventurella
I really do love @lynda as a learning platform. Never stop learning and developing, it’s probably our greatest gift as a species! @soundslikedavid
@lynda just subscribed to lynda.com all I can say its brilliant join now trust me @ButchSamurai
@lynda is an awesome resource. The membership is priceless if you take advantage of it. @diabetic_techie
One of the best decision I made this year. Buy a 1yr subscription to @lynda @cybercaptive
guys lynda.com (@lynda) is the best. So far I’ve learned Java, principles of OO programming, and now learning about MS project @lucasmitchell
Signed back up to @lynda dot com. I’ve missed it!! Proper geeking out right now! #timetolearn #geek @JayGodbold
Share a link to this course

What are exercise files?

Exercise files are the same files the author uses in the course. Save time by downloading the author's files instead of setting up your own files, and learn by following along with the instructor.

Can I take this course without the exercise files?

Yes! If you decide you would like the exercise files later, you can upgrade to a premium account any time.

Become a member Download sample files See plans and pricing

Please wait... please wait ...
Upgrade to get access to exercise files.

Exercise files video

How to use exercise files.

Learn by watching, listening, and doing, Exercise files are the same files the author uses in the course, so you can download them and follow along Premium memberships include access to all exercise files in the library.


Exercise files

Exercise files video

How to use exercise files.

For additional information on downloading and using exercise files, watch our instructional video or read the instructions in the FAQ .

This course includes free exercise files, so you can practice while you watch the course. To access all the exercise files in our library, become a Premium Member.

Join now Already a member? Log in

Are you sure you want to mark all the videos in this course as unwatched?

This will not affect your course history, your reports, or your certificates of completion for this course.


Mark all as unwatched Cancel

Congratulations

You have completed Photoshop Masking and Compositing: Advanced Blending.

Return to your organization's learning portal to continue training, or close this page.


OK
Become a member to add this course to a playlist

Join today and get unlimited access to the entire library of video courses—and create as many playlists as you like.

Get started

Already a member ?

Become a member to like this course.

Join today and get unlimited access to the entire library of video courses.

Get started

Already a member?

Exercise files

Learn by watching, listening, and doing! Exercise files are the same files the author uses in the course, so you can download them and follow along. Exercise files are available with all Premium memberships. Learn more

Get started

Already a Premium member?

Exercise files video

How to use exercise files.

Ask a question

Thanks for contacting us.
You’ll hear from our Customer Service team within 24 hours.

Please enter the text shown below:

The classic layout automatically defaults to the latest Flash Player.

To choose a different player, hold the cursor over your name at the top right of any lynda.com page and choose Site preferences from the dropdown menu.

Continue to classic layout Stay on new layout
Exercise files

Access exercise files from a button right under the course name.

Mark videos as unwatched

Remove icons showing you already watched videos if you want to start over.

Control your viewing experience

Make the video wide, narrow, full-screen, or pop the player out of the page into its own window.

Interactive transcripts

Click on text in the transcript to jump to that spot in the video. As the video plays, the relevant spot in the transcript will be highlighted.

Learn more, save more. Upgrade today!

Get our Annual Premium Membership at our best savings yet.

Upgrade to our Annual Premium Membership today and get even more value from your lynda.com subscription:

“In a way, I feel like you are rooting for me. Like you are really invested in my experience, and want me to get as much out of these courses as possible this is the best place to start on your journey to learning new material.”— Nadine H.

Thanks for signing up.

We’ll send you a confirmation email shortly.


Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

Keep up with news, tips, and latest courses with emails from lynda.com.

Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

   
submit Lightbox submit clicked
Terms and conditions of use

We've updated our terms and conditions (now called terms of service).Go
Review and accept our updated terms of service.