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The Image Size command

From: Photoshop CC One-on-One: Fundamentals

Video: The Image Size command

In this movie, I'll introduce you to the Image Size command, which allows you to change the image size and resolution of an entire image. To get to the command, you go up to the Image menu, and choose Image Size or you press the keyboard shortcut control Alt+I or Cmd+Option+I on a Mac. And that brings up this dialog box that now contains a preview, so you can anticipate the effects of your changes on the image. And you can either drag that preview to a different location, or you can center it at a specific point by moving your cursor out into the image window and clicking.

The Image Size command

In this movie, I'll introduce you to the Image Size command, which allows you to change the image size and resolution of an entire image. To get to the command, you go up to the Image menu, and choose Image Size or you press the keyboard shortcut control Alt+I or Cmd+Option+I on a Mac. And that brings up this dialog box that now contains a preview, so you can anticipate the effects of your changes on the image. And you can either drag that preview to a different location, or you can center it at a specific point by moving your cursor out into the image window and clicking.

And in this case, I've centered the tyrannosaur's head Inside that preview. Notice up here at the top, the word Dimensions, which shows the image size in pixels. So it's 918 pixels wide by 632 pixels tall. You can click this down pointing arrow head and switch to some other unit of measure. However, I don't recommend you do that, because pixels are always going to give you the best sense of what's happening inside your file. We also have the size of the image in RAM, that is in memory.

So anytime you open an image in Photoshop, the program loads the image completely uncompressed in RAM and an uncompressed RGB image takes up 3 bytes for every pixel. One byte for the red information, a second byte for the green, and a third for the blue. And, as a result, if you ever wanted to compute how big an image is in RAM, all you have to do is measure its width, 918 by its height 632 by 3. Next, notice these width and height values.

They represent how big the image is when you go to print it or when you place the image into a vector-based program, such as Illustrator or InDesign. They are not indicative of the size of the image on screen. Now, by default, these two values are linked to each other, so that you're going to scale the image proportionally. If you'd rather stretch the image non-proportionally, then just click on this little chain icon in order to break the link. But I want to go ahead and keep it on, because for this image, I would rather resize it proportionally.

Notice this Resample checkbox down here. This means that any modifications you make to these values will change the number of pixels inside the image. The word Resample merely means that Photoshop has to rewrite the pixels by averaging the existing ones. So let's say I want to increase the resolution value. Because Resample is turned on the resolution value is not linked to the width and height values. So I can change that value independently to 300 pixels per inch for example and that's going to increase the size of my dinosaur.

Now, whenever you're upsampling, it helps to be able to see a larger preview. And you can, by expanding the size of the dialog box. You can drag one of the edges like so or I'm going to go ahead and fill up the entire screen here by dragging the Image Size dialog box up to the top left corner and then you can drag down on the bottom right corner in order to make this dialogue box as big as you want it to be. Now, I'm going to go ahead and click and hold inside the image. And notice when I do, Photoshop shows me some jagged transitions. So in order word, it's just blowing up the pixels.

When I release, it shows me what the image is really going to look like. When it smooths out those transitions, that smoothing process, which is ultimately a function of averaging the pre-existing pixels, is known as interpolation. Now, I don't expect you to remember all these terms right now. So I am going to explore them in more detail in future movies. Now, because we increased the resolution, we're adding pixels to the image and that's known as upsampling. If we were reducing the number of pixels, that would be called downsampling. Notice also that my dimensions up here have changed. So the actual image size has grown now to 2754 pixels wide by 1896 pixels tall. And, the image has also grown in RAM, now to nearly 15 megabytes, so this is a whopping change.

We're increasing not only the width of the file by 300%, but the height of the file as well, and as a result, we're inventing 9 pixels for every 1 that we used to have. But let's say you don't want to modify the number of pixels inside the image, you just want to change the resolution value and let the image shrink in print. So right now it measures 9 inches wide by 6 inches tall on the printed page. If I turn off the Resample checkbox, notice all the values are now linked together.

And because I increase the resolution value, I'm squishing more pixels into a linear inch. That decreases the physical size of the image when I print it. We'll now print at about 3 inches wide and 2 inches tall. If I wanted it to print larger, then I would just go ahead and dial in a lower resolution value, such as say 72 pixels per inch. And now, the image will print at nearly 13 inches wide and nearly 9 inches tall. And of course, you can modify these values as much as you want. If you know for example that you want to print the image 12 inches tall, then the other values will change to accordingly.

And in my case, the resolution drops precipitously. And then finally, you have this Fit To pop-up menu that contains a bunch of predetermine sizes here, all of which are going to in one way or other resample the image, that is change the number of pixels that are at work inside this file. And that, folks, is your introduction to the Image Size command. In the next movie, we'll take a look at a practical application.

Show transcript

This video is part of

Image for Photoshop CC One-on-One: Fundamentals
Photoshop CC One-on-One: Fundamentals

102 video lessons · 20346 viewers

Deke McClelland
Author

 
Expand all | Collapse all
  1. 31m 49s
    1. Welcome to One-on-One
      1m 51s
    2. Opening from the Windows desktop
      5m 35s
    3. Opening from the Macintosh Finder
      7m 14s
    4. Opening from Photoshop or Bridge
      3m 52s
    5. Opening an image from Mini Bridge
      2m 39s
    6. Opening through Camera Raw
      5m 11s
    7. Closing one image and closing all
      5m 27s
  2. 49m 25s
    1. Navigating your image
      40s
    2. The dark vs. the light interface
      3m 12s
    3. Navigating tabs and windows
      4m 32s
    4. Panels and workspaces
      6m 20s
    5. Zooming incrementally
      6m 22s
    6. Zooming continuously
      2m 43s
    7. Entering a custom zoom value
      2m 25s
    8. Scrolling and panning images
      2m 31s
    9. Rotating and resetting the view
      2m 11s
    10. Cycling between screen modes
      3m 10s
    11. Using the Navigator panel
      3m 38s
    12. Using Retina and HiDPI displays
      4m 3s
    13. Adjusting a few screen preferences
      7m 38s
  3. 1h 2m
    1. Digital imaging fundamentals
      1m 45s
    2. Image size and resolution
      6m 34s
    3. The Image Size command
      6m 9s
    4. Common resolution standards
      4m 7s
    5. Upsampling vs. real pixels
      7m 59s
    6. Changing the print size
      8m 15s
    7. Downsampling for print
      5m 14s
    8. Downsampling for email
      6m 22s
    9. The interpolation settings
      6m 40s
    10. Downsampling advice
      5m 5s
    11. Upsampling advice
      4m 15s
  4. 53m 20s
    1. The layered composition
      1m 40s
    2. Introducing the Layers panel
      4m 12s
    3. Adding, scaling, and aligning layers
      5m 27s
    4. Dragging and dropping layers
      4m 36s
    5. Stack, reveal, and rename
      3m 1s
    6. Opacity, history, and blend mode
      6m 5s
    7. Duplicating a selected portion of a layer
      5m 32s
    8. Applying a clipping mask
      3m 58s
    9. Blending inside a clipping mask
      4m 10s
    10. Finishing off your artwork
      3m 13s
    11. Creating a new layer and background
      4m 24s
    12. Layering tips and tricks
      7m 2s
  5. 26m 13s
    1. The art of the save
      54s
    2. Four things to know about saving
      5m 59s
    3. Saving layers to PSD
      6m 34s
    4. Saving print images to TIFF
      4m 48s
    5. Saving an interactive image to PNG
      3m 40s
    6. Saving a flat photo to JPEG
      4m 18s
  6. 32m 16s
    1. Honing in on your image
      1m 43s
    2. The new and improved Crop tool
      4m 35s
    3. Editing your last crop
      6m 29s
    4. Cropping to a specific ratio or size
      5m 57s
    5. Straightening a crooked image
      4m 44s
    6. Filling in missing details
      6m 44s
    7. Using the Perspective Crop tool
      2m 4s
  7. 44m 51s
    1. First, there is brightness
      2m 12s
    2. How luminance works
      4m 18s
    3. The three Auto commands
      3m 27s
    4. Automatic brightness and contrast
      6m 5s
    5. The Brightness/Contrast command
      2m 47s
    6. The dynamic adjustment layer
      4m 4s
    7. Editing adjustment layers
      3m 52s
    8. Isolating an adjustment with a layer mask
      3m 31s
    9. Introducing the histogram
      4m 58s
    10. Measuring an adjustment
      3m 34s
    11. Using the Shadows/Highlights command
      6m 3s
  8. 44m 33s
    1. And second, there is color
      1m 31s
    2. Identifying a color cast
      3m 34s
    3. Correcting a color cast automatically
      3m 57s
    4. Changing the color balance
      6m 10s
    5. Compensating with Photo Filter
      3m 11s
    6. Adjusting color intensity with Vibrance
      3m 29s
    7. Correcting color casts in Camera Raw
      5m 46s
    8. The Hue/Saturation command
      5m 26s
    9. Summoning colors where none exist
      4m 8s
    10. Making more color with Vibrance
      4m 27s
    11. Making a quick-and-dirty sepia tone
      2m 54s
  9. 55m 46s
    1. Making selective modifications
      1m 10s
    2. The geometric Marquee tools
      6m 1s
    3. Aligning one image element to another
      4m 59s
    4. The freeform Lasso tools
      3m 59s
    5. The Polygonal Lasso tool and Quick Mask
      5m 19s
    6. Cropping one selection inside another
      6m 15s
    7. Creating rays of light
      4m 44s
    8. Quick Selection and Similar
      4m 11s
    9. Making it better with Refine Edge
      4m 56s
    10. Integrating image elements
      2m 39s
    11. Magic Wand and Grow
      5m 17s
    12. Refine, integrate, and complete
      6m 16s
  10. 53m 49s
    1. Your best face forward
      1m 0s
    2. Content-Aware Fill
      6m 11s
    3. Using the Spot Healing Brush
      5m 36s
    4. The more capable "standard" Healing Brush
      5m 55s
    5. Meet the Clone Source panel
      3m 53s
    6. Caps Lock and Fade
      4m 57s
    7. The Dodge and Burn tools
      5m 1s
    8. Adjusting color with the Brush tool
      6m 35s
    9. Smoothing skin textures
      5m 58s
    10. Brightening teeth
      4m 0s
    11. Intensifying eyes
      4m 43s
  11. 50s
    1. Until next time
      50s

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