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The importance of image resolution

From: Illustrator CS4 One-on-One: Advanced

Video: The importance of image resolution

In this exercise, I'm going to introduce you to the somewhat confusing notion of image resolution. I'll show you how Illustrator makes it even more confusing. I'll show you how Photoshop handles image resolution beautifully. So the moral of the story is get the resolution right inside of Photoshop before you import the image into Illustrator. All right, so at the end of the last exercise, I went ahead and saved over the original Sepia image.psd file inside the 20 images folder. So I did the exact same work I did before and then I saved over the original image, which is important because that image had already been linked to the Final advertisement.ai file that we have seen a few times over the course of this chapter.

The importance of image resolution

In this exercise, I'm going to introduce you to the somewhat confusing notion of image resolution. I'll show you how Illustrator makes it even more confusing. I'll show you how Photoshop handles image resolution beautifully. So the moral of the story is get the resolution right inside of Photoshop before you import the image into Illustrator. All right, so at the end of the last exercise, I went ahead and saved over the original Sepia image.psd file inside the 20 images folder. So I did the exact same work I did before and then I saved over the original image, which is important because that image had already been linked to the Final advertisement.ai file that we have seen a few times over the course of this chapter.

And so since I have made a modification, Illustrator is going to be savvy to that modification. But I went ahead and saved this image at a different resolution. I'm just telling you that upfront. How do you know what the resolution of this image is? Well, you go up to the Image menu, and you choose the Image Size command. Now this is such a useful command here inside Photoshop, that's where I am, that you can press Ctrl+Alt+I or Command+Option+I in order to bring up the Image Size dialog box. And notice that the Resolution is set to 220 pixels/inch. Now what in the world does that mean? That means that there are 220 pixels packed in every linear inch of this image.

So 220 pixels per the width of an inch, and 220 pixels per the height of the inch. So that means in a square inch you have 220 times 220 pixels, which is 48,400 pixels which you would really think would be enough pixels to get the job done. But it actually falls short of the commercial print standard, which is 267-300 pixels per inch, and we'll come back to that in just a moment. But anyway, 220 is what it's set to. Go ahead and cancel out for now. And what that does is that determines the physical print size of the image. It also determines how big the image is when it imports into a print application like Illustrator or InDesign or what have you, all of which are resolution savvy.

All right, so I'm going to go ahead and switch over to Illustrator. I have open right now the Final advertisement.ai file and so notice when I switch over to Illustrator by press Alt+Tab or Command+ Tab on the Mac, it recognizes that the file has been changed. It says hey something has happened to one of the linked files. Do you want me to update it or not? And you would say yeah, absolutely update it. So we have the most recent version of that image. All right, it doesn't look any different than it looked before. And if you have been following along with me, as long as you did all the steps right, it should look the same as well. But something has happened because I was telling you there is a different resolution value at work right now. So go ahead and press Shift+Tab to bring up the Layers palette or at least I'll because my Layers palette is currently hidden. And I going to twirl open the image layer.

I'll find Sepia image.psd. That was the image we were just playing with a moment ago. Meatball it to select it. Sure enough, that's the image right there. If I go up to my Control palette, I can see that it is a linked file and I could click on that little link there to bring up the Links palette if I wanted to. I can also see, hey, there it is. Sepia image.psd. And I could hover over that option to see the exact path for the image on disk. And then I go over here Transparent CMYK. So far so good because I did convert it to a CMYK image and it does have transparency and it is not 267 pixels per inch. What in the world is that about? So PPI, pixels per inch, 267. No, it's 220. I just saw it a moment ago.

Well, let's confirm things. You can bring up the Links palette either by going to the Window menu and choosing the Links command or just by going to this link right there. So let's click on that guy and then click on the fly-out menu icon and I want you to choose Link File Info, and that will give you the real goods on this image inside this gigantic multi -panel xmp dialog box. And you will see right there that we have got the name of the author, and the file number, and his URL at istockphoto.com, and so on.

You want to go ahead and scroll over if necessary and then click on Advanced. And then this is so unfriendly but this is the way it works. Here inside the Property Tree, we go down to Schema http://ns.adobe.com/tiff/1.0/. So obvious right? Go ahead and twirl that open and then down below, there are the tiff:XResolution and YResolution values right there and they are the same value because we are working with square pixels. But they are measured in 10,000ths of a point. So we have 2.2 million over 10,000 essentially. If you divide 2.2 million by 10,000, you get 220. So it is acknowledging right here that the resolution of the image is 220 pixels per inch.

Now it's not acknowledging that in English or any language any of us would understand but that's what it means. So I'm going to click OK to get out of there. So it is most assuredly 220. Why is it showing it to us up here in the Control palette that it's a 267 pixel per inch image? And by the way, if we were to re-import this image, or we were to place it right now, it would appear bigger. And you know why don't I show that to you? Because you need to see what the results of resolution are. I'm going to go to the File menu and choose the Place command. This is the command that you use to place images into Illustrator.

And then inside of your 20_images folder, you will find Sepia image.psd. Make sure the Link checkbox is on. Click Place and it just comes in like so. Move it over and you will notice that this new image is bigger. See how her eyebrows are a little higher than they are over on the right, and her chin is cut-off down here on the left, and it's not on the right? So she is much bigger. That's because she has a lower resolution. So lower resolution means fewer pixels packed in a square inch and that means bigger image. When you pack more pixels into an inch that is higher resolution, you get a smaller image.

So there is an inverse relationship between resolution and size where digital imagery is concerned. And this one is acknowledging that it's PPI of 220 but they are the exact same image. If I bring up the Links palette once again, same image Sepia image.psd, Sepia image.psd. They are exactly the same size, they were modified on the same date, blah, blah, blah. They are the same file. All right, so let's just delete that guy. What's the deal? Why is this one saying it's 267? Because it's effective resolution is 267 because it scaled down.

So it's reduced in size and Illustrator just did that automatically, just automatically transformed it to maintain the original size. And you can change that if you want to, but in my opinion it's so convoluted as to not really be worth bothering going into. It's better just to do the work in Photoshop in the first place, so let me show you how. We'll go ahead and Alt+Tab or Command+Tab back to Photoshop. I'll go up to the Image menu. I'll choose the Image Size command. Ctrl+Alt+I, Command+Option+I on the Mac brings up this dialog box. Make sure Resample Image is turned off. If you turn it on and you change the Resolution value, notice that you are going to add pixels to the image. Now Photoshop is no magician where adding pixels is concerned. It just averages neighboring pixels using something that's called Bicubic interpolation and it makes the transitions between pixels softer, which after all this sharpening work is not something that we want. And it basically rewrites every single pixel in your image.

Talk about a lossy transformation. It's rarely a good idea to upsample images to add pixels inside of Photoshop. Better to turn Resample Image off and that's definitely what I want you to do here. And notice now the difference between 220 pixels per inch, in which case we have an image that is 7.3 approximately inches wide and tall because it's a square. And if I raise this Resolution value up to 267, the size of the image drops down to 6x6 inch square. Now here is something interesting to note. You would think that increasing the Resolution from 220 to 267 is no big deal. You are just adding 47 pixels per inch in each direction. But 267x267, which is the number of pixels inside of a square inch, delivers you 71,289 pixels.

So 71 up from 48, so you added more than 20,000 pixels per square inch. That's a big significant difference in the resolution of this image. And what it means is you are going to get smoother, sharper output when you send this illustration to a commercial printer. Click OK. Because you had Resample Image turned off you won't see any change inside the image window. That's because not a single pixel was been harmed. Then you would go up to the File menu and all that's happened is the Resolution value got changed, just a little bit of metadata, just a single number got changed. So go ahead and choose Save. There is no reason to choose Save As. You didn't do anything destructive. Just choose the Save command to update the file on disk.

Now Alt+Tab or Command+Tab back to Illustrator. Aha! It knows something happened. Click on Yes in order to update the image and it looks exactly the same because once again it fit it into that same image area. If you go ahead and meatball that image here inside the Layers palette, you will see that it says PPI 267. But it said that before, right? That's because it had been transformed to fit this space. What's the real resolution? Go to Link File, go to the fly-out menu, then choose Link File Info. Brings up the big old xmp dialog box again, twirl open that tiff option right there, this guy right there. Aha! Look down there.

XResolution and YResolution now say 267 blah, blah, blah. So all you really care about is those first three numbers and they are right, yes. Click OK. So all is right in the world. Thanks to the fact that you set the resolution of the image in Photoshop before you import the image into Illustrator.

Show transcript

This video is part of

Image for Illustrator CS4 One-on-One: Advanced
Illustrator CS4 One-on-One: Advanced

149 video lessons · 21492 viewers

Deke McClelland
Author

 
Expand all | Collapse all
  1. 28m 41s
    1. Welcome
      1m 7s
    2. Installing the dekeKeys keyboard shortcuts
      8m 59s
    3. Resetting the Function keys on a Mac
      4m 47s
    4. Installing the CS4 color settings
      4m 20s
    5. Loading the CS4 color settings in Illustrator
      6m 3s
    6. Loading the CS4 color settings in Bridge CS4
      3m 25s
  2. 1h 53m
    1. From the simple emerges the complex
      42s
    2. Introducing Pathfinder operations
      4m 17s
    3. Editing a compound shape
      4m 39s
    4. Adding to a compound shape
      3m 11s
    5. Inserting a subpath into a compound shape
      3m 56s
    6. Expanding a compound shape
      4m 53s
    7. Assembling primitives
      4m 42s
    8. Preparing a template in Photoshop
      7m 0s
    9. Uniting paths permanently
      5m 40s
    10. Minus Front vs. Minus Back
      1m 55s
    11. Working with compound paths
      6m 49s
    12. When in doubt, divide
      3m 54s
    13. Divide and Unite
      3m 2s
    14. Open path pitfalls
      5m 35s
    15. Strokes bad, fills good
      4m 38s
    16. Advanced Divide and Unite
      8m 59s
    17. Using the Crop operation
      8m 30s
    18. Expert Divide and Unite
      8m 45s
    19. "Ghosting" shapes with Fill Opacity
      6m 45s
    20. Anticipating and troubleshooting
      8m 16s
    21. Exclude and Intersect
      7m 24s
  3. 44m 59s
    1. Familiar one moment, different the next
      1m 3s
    2. Snapping to anchor points
      5m 41s
    3. Aligning a group to the artboard
      3m 34s
    4. Distributing objects on the artboard
      4m 16s
    5. Setting the key object
      4m 54s
    6. Distributing objects by space
      3m 6s
    7. Distributing objects by selections
      3m 19s
    8. Aligning point text
      6m 7s
    9. Aligning live text vs. using outlines
      4m 58s
    10. Aligning key letters
      3m 35s
    11. Aligning to key objects
      4m 26s
  4. 1h 4m
    1. CS4’s gradient renaissance
      1m 7s
    2. Applying a gradient
      6m 0s
    3. Dragging and dropping color swatches
      2m 55s
    4. Using the Gradient palette
      6m 27s
    5. Designing a shaded gradient
      5m 9s
    6. Saving a gradient swatch and adding a texture
      4m 2s
    7. Introducing the new Gradient tool
      4m 39s
    8. Editing color stops inside a shape
      3m 26s
    9. Setting multiple gradients to the same angle
      5m 0s
    10. Adding and adjusting radial gradients
      7m 20s
    11. Making a transparent gradient
      7m 6s
    12. Adding drop shadows (a kind of gradient)
      6m 28s
    13. Blends vs. blend modes
      4m 38s
  5. 1h 17m
    1. Creating freeform color flows
      1m 0s
    2. The power of CS4's transparent gradients
      10m 25s
    3. Creating a gradient mesh
      4m 30s
    4. Expanding a gradient to a gradient mesh
      7m 40s
    5. Adding and deleting rows and columns
      6m 13s
    6. Selecting and coloring points
      6m 5s
    7. Assigning colors with the Eyedropper tool
      7m 42s
    8. Cool mesh editing techniques
      3m 56s
    9. Warping and puckering a mesh
      7m 24s
    10. Applying precise finishing touches
      5m 48s
    11. Gradient strokes
      9m 45s
    12. Gradient text
      6m 50s
  6. 55m 35s
    1. The first of the dynamic functions
      1m 4s
    2. Making a blend automatically
      5m 48s
    3. Fixing problem blends
      3m 56s
    4. Making a blend with the Blend tool
      3m 6s
    5. Cloning and coloring a blended path
      4m 37s
    6. Creating a mask
      3m 53s
    7. Blending between translucent shapes
      5m 30s
    8. Blending along a curve
      4m 34s
    9. Adjusting the speed of a blend
      2m 58s
    10. Filling and stroking a mask
      4m 36s
    11. Creating a compound clipping mask
      6m 3s
    12. Nesting one clipping mask inside another
      6m 7s
    13. Ghosting nested masks and blends
      3m 23s
  7. 1h 13m
    1. Patterns that repeat forever and ever
      51s
    2. Introducing tile patterns
      6m 36s
    3. Beginning a core design
      5m 6s
    4. Building an interlocking element
      6m 25s
    5. Achieving precise radial symmetry
      4m 46s
    6. Rotating duplicates around a common center
      3m 10s
    7. Determining how a pattern repeats
      9m 54s
    8. Coloring the core objects
      5m 0s
    9. Identifying the rectangular tile
      7m 14s
    10. Saving tile patterns
      7m 19s
    11. Applying tile patterns to a shape
      3m 25s
    12. Protecting patterns from transformations
      7m 36s
    13. Moving patterns without paths
      5m 51s
  8. 1h 19m
    1. Illustrator gets natural
      1m 15s
    2. Introducing the vector painting tools
      3m 16s
    3. Calligraphic brush options
      4m 3s
    4. Pressure sensitivity
      5m 17s
    5. Editing a calligraphic brush
      5m 53s
    6. Repainting and smoothing paths
      5m 30s
    7. Making the paintbrush behave
      6m 16s
    8. Erasing stroked paths
      3m 17s
    9. Painting with the new Blob brush
      6m 24s
    10. Refining filled paths with the Eraser
      4m 14s
    11. Painting independent paths
      3m 53s
    12. The Selection Limits Merge options
      3m 20s
    13. Applying and scaling an art brush
      6m 23s
    14. Snipping a brushed path
      4m 55s
    15. Colorizing an art brush
      4m 9s
    16. Heaping a stroke on an art brush effect
      4m 32s
    17. Creating a custom art brush
      6m 51s
  9. 1h 44m
    1. The computer art world’s dynamic duo
      1m 7s
    2. Copying and pasting pixels from Photoshop
      7m 21s
    3. Linking is efficient, embedding is not
      2m 47s
    4. Editing an image in Illustrator
      7m 30s
    5. Filtering an image in Photoshop
      6m 34s
    6. Adding a filter mask in Photoshop
      6m 25s
    7. Masking a woman from the background
      3m 49s
    8. Creating a sepia effect
      6m 37s
    9. Adding a second gradient map layer
      2m 13s
    10. Achieving a graphic effect with Levels
      8m 10s
    11. Preparing an image for use in Illustrator
      5m 46s
    12. The importance of image resolution
      9m 40s
    13. Placing and linking images
      4m 43s
    14. Managing linked images
      6m 18s
    15. Integrating an image into a design
      5m 12s
    16. A better way to wrap text
      7m 28s
    17. Previewing the trim size
      4m 25s
    18. Layer comps and editable text
      8m 42s
  10. 2h 11m
    1. Transparency is safe and fun
      1m 27s
    2. Introducing the translucent composition
      4m 39s
    3. Assigning opacity to an Appearance attribute
      3m 41s
    4. Creating a knockout group
      5m 7s
    5. Defining an opacity mask
      7m 15s
    6. Using the Clip checkbox
      2m 41s
    7. Opacity mask tips and tricks
      3m 20s
    8. The Multiply blend mode
      6m 8s
    9. Adding to an existing opacity mask
      7m 53s
    10. Blending between parallel groups
      7m 27s
    11. Creating a gradient opacity mask
      4m 54s
    12. Employing an opposing gradient mask
      7m 57s
    13. Combining Multiply and Screen
      3m 49s
    14. Blend mode roundup
      5m 24s
    15. Mixing blend modes inside a single path
      3m 48s
    16. Blend mode and transparent gradient
      3m 49s
    17. Masking an entire layer
      7m 0s
    18. Combining Screen with 100K Black
      7m 43s
    19. Knocking out a drop shadow
      5m 18s
    20. But will it print?
      3m 8s
    21. Working with the Flattener preview
      8m 44s
    22. Rasterizing an illustration in Photoshop
      9m 16s
    23. Super-rich blacks and raster effects
      3m 35s
    24. Exporting TIFF artwork from Illustrator
      7m 48s
  11. 58s
    1. Until next time
      58s

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