During this Design Cuts Live session, we were taught by the Photoshop master herself, Leslie Nicole from French Kiss Collections. There's no better person to learn from when it comes to the fundamentals of graphic design!
This week, she gave us a crash course on image resolution and colour modes. She discussed the differences between DPI and PPI, as well as what each file type means and what you can do with them. So get your notepads ready and prepare to soak up Leslie's knowledge!
To help you follow along, you can use the written tutorial below.
Here we have awesome tutorial by Leslie Nicole and something different than usual. Today, she dives into easy technicalities of Resolution and Color Modes.
Difference between DPI and PPI
DPI refers to Dots Per Inch, a term used for printers. It defines how many dots are going down per inch on a printer.
PPI refers to Pixels Per Inch, a term used in digital images and displays, such as monitors, iPhones, iPads etc.
Image resolution for printing needs to be higher than the resolution for web. 300 PPI is recommended for printing and 72 PPI is recommended for web and devices.
Before we get started, here’s a quiz question: which image is higher resolution?
Is it image A on the left, which is 3456 x 5184 pixels at 72 PPI, OR is it image B on the right, which is 800 x 1200 pixels at 300 PPI?
Answer: that was a bit of a trick question. Technically, Image B is set to a higher resolution output, but Image A is much larger in pixel dimensions. This means that image B can only print out at 4 inches tall whereas image A can print out at 17.25 inches! So don't be fooled by looking at 300 PPI for image quality; the pixel dimensions are important too!
What Do you Really Mean by “High Resolution”?
High Resolution: an image that is large in pixel dimensions or that has sufficient pixel dimensions for the intended output.
The PPI is only an output setting. 300 PPI does not automatically mean High Resolution! 300 PPI must be used in conjunction with an image size to be meaningful. In the case of an image that is 8x10 inches at 300 PPI, PPI is not a size, just a setting.
Another quiz question: which is a high quality image?
Image A, which is 3000 x 3000 pixels at 72 PPI OR image B, which is 3000 x 3000 pixels at 100 PPI, OR option C Both?
Answer: The answer is C; the two images are identical in quality. The pixel dimensions are the same, only the output resolution is different. If you changed the output resolution of image A to 300 PPI (without checking 'Resampling'), they would print out exactly the same.
So pay attention to your pixel dimensions more than your output setting. The final print dimensions and pixel dimensions are all that count. If you were to try and resize larger beyond that, that's where quality loss would occur.
Why 300 PPI?
This comes back to printing on an offset printer with half-tones. For large volume printing for newspapers, magazines, color documents, etc. we're looking at LPI (Lines Per Inch). With newspapers, you print out at 80 to 100 LPI, color documents, consumer magazines and catalogs at 133 LPI to 150 LPI. Fine art books and magazines at 175 LPI to 250 LPI.
So the actual rule of thumb is not 300 PPI but rather 1.5 to 2 times the LPI.
At 1.5 for 150 LPI, you would need 225 PPI image.
At 1.5 for 175 LPI, you would need 263 PPI image.
300 PPI gives you plenty of wiggle room for most instances in offset printing.
Printing with Inkjet
With inkjets, you don't really need 300 PPI. 240 PPI seems sufficient. There's no blanket rule, though running below 180 is the danger zone.
On the left, we have a graphic here with the color spectrum, visible to the eyes.
Prophoto RGB is the big Purple triangle that shows you the spectrum that Prophoto RGB will cover. You can create a document in Photoshop with Prophoto RGB and can shoot RAW images with it. This spectrum shows the coverage of the gamuts (with gamuts "describing a range of color within the spectrum of colors that are identifiable by the human eye (visible color spectrum)").
Adobe RGB is the orange triangle. It consists of a larger gamut than sRGB. It's actually closer to the ISO coated color space which is the offset printing. So those who are professionals in print will often work in RGB and it's a really stable environment for faithful print output. But there are catches to that: you need an Adobe RGB monitor (most are sRGB) and it's not always recommended for the web. If you save an adobe RGB file and put it on the web, it could look funky.
sRGB is the smaller dark blue triangle. It's the universal color space for web and devices. For example, your iPhone and iPad should be sRGB. Most labs and print on demand require this.
CMYK stands for cyan, magenta, yellow and (k) black. It is used in offset printing and is not recommended for the web.
Pantones are called spot colors, which are special premixed inks. A metallic or a fluorescent color would be a spot color because you could only obtain it by adding a fifth ink.
If you need to change your color space for output, you go up to 'Edit' and use 'Convert to Profile' (not 'Assign Profile'). That way the colors stay as faithful as possible to the original. Let's try changing it to Adobe RGB. On the surface it looks the same, but if you try to 'Save for web' again without converting it to sRGB, you’ll notice how it loses all its vibrancy and tones down.
Be mindful that sometimes if you place a texture that's sRGB on a Profoto image you're working on, you might notice the color fade away or go wonky. To fix this, you can go back to the texture, click 'Convert to Profile' on the profile you're working on, and then drag it in.
Let's go on sRGB now. Interestingly, what you can see here is capturable by the eye but not digitally. Every single color we're seeing on the whole spectrum fits within the sRGB triangle, but it's just representative.
An Exercise To Try
- Open a photograph or graphic. Save a copy and size it to 1000 pixels x 1000 pixels at 300 PPI, sRGB. Don’t enlarge it (crop to square if you need to - it’s just for the test).
- Then, save a copy at 72 PPI - Do NOT check Resample!
- Create a document that is 2100 x 1075 PPI, 300 PPI, sRGB.
- Now, drag (or copy and paste) both the 300 PPI and the 72 PPI documents into the 2100 x 1075 PPI.
What did you discover? You should see that they are both the exact same size in the new document! It’s the pixel dimensions that matter.
These instructions are for Photoshop/Elements but we imagine it would be the same in other programs.
Final Notes & Main Takeaways
- Start thinking of an image’s size in pixel dimensions.
- Notice how the pixel dimensions stay the same if you change the output resolution if you DO NOT check “Resample”.
- Resampling is a fancy way of saying “Resizing”. Never apply Resampling to your original file. If you need to change the size of an image, Save a Copy.
- 300 PPI is a good rule of thumb for printing but there is some wiggle room especially when printing to inkjet printers. (With that said, do follow the request from labs / printers if they request 300 PPI files.)
- Pay attention to Color Profiles, especially when 'Saving To Web'. Be sure your images for the web are in sRGB.
- There are many opinions on the best color mode to use for different workflows. Decide what you do mostly (photography, illustration, etc.) and how you will be outputting your work and then look for various articles and posts on color management and workflow.
Interesting articles on Color Workflow
Adobe RGB Versus sRGB Color Space – Which Should You Choose? Click Here
What is the Difference Between Adobe RGB and sRGB? Click Here
Everything You Need to Know about sRGB vs Adobe RGB. Click Here
sRGB vs Adobe RGB: How to Choose? Click Here
sRGB vs. ProPhoto color spaces on the Internet. Click Here