Here you will find all of the information (appropriate links (including Dropbox folder links for homework), notes, reminders, etc.) for Photoshop 101 (Photoshop Basics for Artists) Week Two.
NOTE: Please respect the work, rights, and privacy of participating artists. You may view the uploaded homework efforts from the class within the Dropbox folder, but you may not download or manipulate their work in any way. Anya and I will be downloading uploaded homework or classwork images when needed/appropriate, but we will never share anyone’s images outside of the class without express permission from the author. All files in the Drobox folders will be deleted at the end of the course. In addition, please know that classes will not be recorded to respect each participant’s learning experience.
If there are files required for the week’s homework, then they will be available in a folder called “WeekX_Resources” in the appropriate week’s folder. You will need to download to files in this folder to complete the week’s homework. However, please be sure not to remove or add anything to this folder.
Today we will review the homework and some info from the last class, cover a relatively new file format WebP, file naming, goals and controls (e.g., Save As/Export), the Helmholtz–Kohlrausch effect, Color Modes (RGB, CMYK, and Grayscale,) Image Resampling, and Color Bit Depth (8, 16, and 24 bit.)
Each color on top has approximately the same luminance level and yet they do not appear equally bright or dark. The yellow (second from the left) appears to be much darker than the magenta (right-most). However, when the top image is converted to grayscale, we have the image on the bottom–a single shade of gray.
As to file naming: Moving forward, images should have the following format (where fields are appropriate):
Name_Title_Size-in-inches (height first)_Medium (if applicable)_Price (if applicable)_SMALL/MED/LARGE-or-PPI
Some definitions we used:
- Image Size Resample
This is an option in the image sizing window that, when checked, allows the changing of the actual number of pixels in the image. - Color Mode
Color modes or image modes are the basis for the representation of a pixel’s color value. These modes determine how an image will be represented on screen or in print. For instance, use CMYK color mode for images in a full-color print brochure, and use RGB color mode for images in web or e-mail to reduce file size while maintaining color integrity.
Different color modes:
1. RGB mode ((Red-Green-Blue) This is a universal mode which your desktop and camera use. RGB stands for Red, Green, and Blue so it manages colors via configurations/combinations of red, green, and blue. This mode has the largest gamut of the modes we discussed.
2. CMYK mode ((Cyan-Magenta-Yellow-Black) The next most common mode. This mode manages color in a way that is conducive to common printing processes. This mode has a smaller gamut than RGB as print media may not be able to “hit” all the colors that your computer displays can.
Fun Fact: The K in CMYK is known as the Key, because it’s the key plate that prints all the detail in a printed image. In printing, Cyan, Magenta and Yellow plates are properly aligned with the Key plate.
3. Grayscale mode This is the most basic mode, consisting of a single channel that maps values to grays, from black to white.
WHEN CHANGING MODES:
You can change an image from its original mode (source mode) to a different mode (target mode) by going to IMAGE>MODE. Keep in mind that when you choose a different color mode for an image, you permanently change the color values in the image. For example, when you convert an RGB image to CMYK mode, RGB color values outside the CMYK gamut are adjusted to fall within gamut. As a result, some image data may be lost and can’t be recovered if you convert the image from CMYK back to RGB.
TIP: Before converting images, it’s best to do the following:
• Do as much editing as possible in the original image mode.
• Save a backup copy before converting. Be sure to save a copy of your image that includes all layers so that you can edit the original version of the image after the conversion.
• Flatten the file before converting it as the interaction of colors between layer blending modes changes when the mode changes. (We will get to this next week!)
- Color Bit Depth
Bit depth quantifies how many unique colors are available in an image’s color palette in terms of the number of 0’s and 1’s, or “bits,” which are used to specify each color. This does not mean that the image necessarily uses all of these colors, but that it can instead specify colors with that level of precision. For a grayscale image, the bit depth quantifies how many unique values are available. Images with higher bit depths can encode more shades or colors since there are more combinations of 0’s and 1’s available.
Every color pixel in a digital image is created through some combination of the three primary colors: red, green, and blue. Each primary color is often referred to as a “color channel” and can have any range of intensity values specified by its bit depth. The bit depth for each primary color is termed the “bits per channel.” The “bits per pixel” (bpp) refers to the sum of the bits in all three color channels and represents the total colors available at each pixel. Confusion arises frequently with color images because it may be unclear whether a posted number refers to the bits per pixel or bits per channel. Using “bpp” as a suffix helps distinguish these two terms.
Most color images from digital cameras have 8-bits per channel and so they can use a total of eight 0’s and 1’s. This allows for 28 or 256 different combinations—translating into 256 different intensity values for each primary color. When all three primary colors are combined at each pixel, this allows for as many as 28*3 or 16,777,216 different colors, or “true color.” This is referred to as 24 bits per pixel since each pixel is composed of three 8-bit color channels. The number of colors available for any X-bit image is just 2X if X refers to the bits per pixel and 23X if X refers to the bits per channel.
TIP: The available bit depth settings depend on the file type. Standard JPEG and TIFF files can only use 8-bits and 16-bits per channel, respectively.
HOMEWORK: Due in Dropbox by Wednesday Oct. 24th
Homework: Locate a “high-res” color version of a favorite masterwork online and save it to your desktop. Using that file, generate two grayscale versions—one should be an “unweighted” desaturation and the other, a curated, weighted version that you feel best compensates for the loss of hue and chroma (saturation) contributions. Upload both to the homework folder as “high quality” jpegs in the ballpark of 200ppi@5x7". This is worth 4 points!!!
Bonus Scenario: You have been invited to participate in an upcoming book that explores how artists might reinterpret the value structure of their own color paintings, drawings or photographs if they were limited to grayscale. The publishers request 2 images of a single work, one with a simple unweighted desaturation, and one with an artist-curated, weighted desaturation. Both files should be print-ready, high-res (300ppi@8x10") but small enough to be sent via email. Please upload the two files you would send, formatted and appropriately labeled to this week’s homework folder. This bonus is with 2 points!!!
DROPBOX LINK:
Additional from this week: Philippe asked “Does it really make any difference is you save something at 5x7 inches @72ppi or 1.68 x 1.207 300ppi as they would seem to be the same?”
In most cases these files could be considered synonymous (if the pixels are exactly the same) in that if you open the two images on screen you will see absolutely no difference between them. Turns out though there is a difference if you try to drag and drop them into a word processor.
For example, here’s two copies of my painting Paradise. One is saved at 5x7" @72ppi while the other is 1.68x1.207" @300ppi. Either way the pixel dimensions on both are 362x504. They are so alike that even this program discourse kept displaying the same image.
This is how they appear though when dragged into a word doc:
As you can see one becomes much smaller than the other. The issue is how some software treats the measurements. (Page-setting software like InDesign does the same thing.) This is because in both cases the target environment is one that measures things in real-world units (centimeters or inches), so it uses the dpi metadata to decide how to convert your image’s pixel dimensions to real-world dimensions. For example, a 600x600-pixel image at 300dpi will appear on the page at 2x2 inches.
By contrast, most screen-based environments (Photoshop, the web, etc.) measure things in pixels so no conversion is needed: each pixel in your image simply occupies one pixel of your screen.
So, if you’re preparing an image for print on paper or other physical media and you’re asked for a specific dpi (which will usually be 300), you should stick to it to ease the workflow at the print end. (Of course, a page designer can always convert your 72dpi image to 300dpi without losing anything, but why make things difficult?) Note that this only ever applies if your image is going to be placed on a page (for example, in a magazine or book), which is why it so rarely makes a difference. If you’re just printing photos full-page (either on your own printer or sending off for photographic prints) the dpi will make no difference.
Herb asked “Is RGB in Photoshop the same or equivalent to sRGB.?”
Honestly at first I thought it would likely be the same thing but it turns out that Adobe has their own RGB mode which is simply called Adobe RGB.
While both Adobe RGB and sRGB have advantages and drawbacks, it seems Adobe RGB provides more flexibility in switching the profiles thanks to a wider range of colors. The photograph taken in Adobe RGB mode can be converted to sRGB. By contrast, because they utilize a simpler color space, sRGB photographs cannot be converted to Adobe RGB.
You can learn more all about the differences here:
Some software mentions: