When comparing F.lux vs Greenshot (for Windows), the Slant community recommends F.lux for most people. In the question“What are the best power user tools for Windows?” F.lux is ranked 5th while Greenshot (for Windows) is ranked 10th. The most important reason people chose F.lux is:
Helps provide better sleep for more energy during the day.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Can help sleep better
Helps provide better sleep for more energy during the day.
Pro Eases eye strain
Decreases color temperature at night, changing the normally fluorescent blue of an LCD monitor to a soft orange. Much easier on the eyes, especially in a low-light environment.
Pro Subtle transition
The transition from daytime to nighttime color modes takes an hour by default and will detect your current timezone, meaning that it will happen in the background at sunset, often without you noticing.
Pro Free and open source
Greenshot is licensed under GPL with source code available on BitBucket.
Pro Freezes screen when you capture
When you enter a capture mode, the screen content is preserved as it was when you started capturing.
Pro Allows annotating, highlighting and obfuscating screenshots
Pro Can capture an entire webpage
Instead of just capturing the visible portion of the page, this tool can capture all of the page in one image by scrolling through the page, taking images at set points and then stitching the images together.
Pro Can be quickly invoked with the print screen button
Pressing the print screen button will allow you to select the captured area.
Pro Selecting custom rectangle is the default
Easy to use selection tool with a magnifier to select only the part of the screen that you need.
Pro Classic UI design makes it easy to use.
Cons
Con Takes a while to get used to
After installing F.lux, the screen will look a lot more yellow. This takes about a week to fully get used to. You can ease into it by setting the color temps higher than the recommended defaults.
Con Scrolling window capture is only working in Internet Explorer
Con This version only works on Windows, not Linux nor Mac
However, the same author now has a separate version of Greenshot for iOS, which is available (for a small fee) in the Mac App Store at https://itunes.apple.com/us/app/greenshot/id1103915944