Difference between designs of Red Dot sights
Basically there are 4 different design configurations
Reflex
Tube
Holographic
Enclosed Reflex
REFLEX
Red Dot is produced by a Led Emitter reflected back to the shooters eye by front lens.
Small in size and lightweight
Normal viewing window is square
Dot sizes typically from 2 MOA up to 10 MOA
Long Battery Life up to 50,000 + hours
Not as durable as Tube designs
Open design allows snow/water debris to interfere with operation
Very suitable for Pistol and Shotguns
Can be inexpensive
If used with magnifier the dot will be enlarged as well as target
Parallax Free for practical purposes
HOLOGRAPHIC
Red Dot / Reticle is produced by a laser diode projecting a hologram back to the eye
Will still function if front lens damaged or partly obscured
Much more expensive than Reflex or Tube design due to its complex design
When used in conjunction with magnifier only target gets larger and dot/reticle remains same size for precision
Due to their cost typically they are more durable and optically superior
Bulkier and heavier than Reflex sights
Typically less battery life than Reflex around 500 - 1000 hours
Better for longer ranges with clearer brighter reticles
Work better if you have astigmatism, but will not necessarily completely cure problem
Reticle is projected out in front of sight mean it is potentially quicker to use
TUBE
Red Dot again is created by a LED Emitter
The tube design is better suited to used in harsh conditions as lenses can be easily cleaned
Easy to mount to dovetail rails or picatinny systems as tube design allows use of a wide range of mounts
Dot increases in size with magnifier
ENCLOSED REFLEX
Same specifications as open Reflex sights but does not have an issue with debris obscuring emitter so better for use in harsh weather conditions