Comparison of a 300 l/mm blazed at 500 nm and a 300 l/mm blazed at 300 nm:
How to read this plot ? The 300 nm blazed version is only superior to the 500 nm blazed version for wavelength inferior to 3500 A. The 500 nm version is two time superior to the 300 nm version at 6000 A (for example). The use of the 300 nm blazed grating is very limited (only of course for extreme UV).
Comparison of a 300 l/mm blazed at 1000 nm and a 300 l/mm blazed at 500 nm:
The two have the same efficiency at 6500 A. The 500 nm is 1/0.27=3.7 more efficient at 5500 A, and the 1000 nm version is 2.25 time more efficient at 9000 A.
Comparison of a 600 l/mm blazed at 750 nm and a 600 l/mm blazed at 500 nm:
The 500 nm blazed version is only superior to the 750 nm for wavelength inferior to 5650 A. For observe Halpha line, the 750 nm is preferred (an important consideration, the 600 l/mm grating is the base model for UVEX).
The same gratings but for the IR region:
Of course, the 750 nm blazed is the more efficient for the IR.
These plot are useful for selecting the better grating for a given application.
Christian Buil