How does a red dot work?

[71T Targa]

I've been looking at red dot sights and I can't seem to get my head around how they work.

Does my eye/head need to be in the same place every time? It seemed like I the dot moved depending on how I looked through the sight.
With iron sights you have three points in a line, rear sight, front sight, and target. You eye must be on this line. With the dot you only have two points, and your eye can be off-line.

I just don't get it...

[legion]

In a traditional red dot sight, yes, your head has to be in the same position every time for it to work.

In a holographic sight, as long as you can see the target through the sight, it moves the red dot to be over the target.

[ODDJOB UNO]

if yer from INDIA..................a RED DOT means ..............STOP DO NOT PASS GO, YOU HAVE BEAN HIRED AS A COMPUTER TECHNICAL REP!

[m21sniper]

Parallax shift is theoretically not an issue for a reflex sight.

Wiki on Reflex sights:

Reflex sights use refractive or reflective optical collimators to generate a collimated image of a luminous or reflective reticle. This collimated image is reflected off a dichroic mirror or beam splitter to allow the viewer to see the field of view and a reflection of the projected reticle (e.g. a red dot) simultaneously. If no magnification is utilized, this gives the viewer a theoretically parallax-free image of the reticle, superimposed over the field of view at infinity"

A reflex sight with no magnification can be held at any distance from the eye (see eye relief), and at almost any angle, without distorting the image of the target or reticle, and without causing the reticle to "move" relative to the target. But parallax compensation is not perfect, and depending on the sight's design, the range to the target, and the magnitude of angle at which it is looked into, aiming error can be non-trivial due to parallax.[2]

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It depends on the sight. Some are better than others. But generally speaking at close (ie gunfightin') range, with the weapon mounted to your shoulder even close to properly, it will not be an issue of any concern.

Use your cheek to stock weld to ensure that you maintain a good firing line down your optics.

[ODDJOB UNO]

seriously with a red dot the "brightness" goes away alot when in extreme sunlight. lots of fun to use otherwise, but i sure as hell wont spend a wad of money on them. buy a leupold/nikon/swarvorski/zeiss etc. traditional sight and yer GOLDEN!

[Shawn 357]

Originally Posted by legion

In a traditional red dot sight, yes, your head has to be in the same position every time for it to work.

In a holographic sight, as long as you can see the target through the sight, it moves the red dot to be over the target.

Right on the money! I looked really stupid when I had just bought an eotech and kept trying to use it like a scope and line up the dot with the front sight on my barrel

After I got used to the holographic sight I started to really like them. You keep both eyes open and put the rifle wherever is comfortable (very fast to use!). If you like shooting at stuff over 50 yards there are better options though.

-Shawn

[Crowbob]

Hmm. Now i don't understand even better.

[71T Targa]

So the dot needs to be in the middle of the lens? If so, why isn't there a cross-hair or something?

[Porsche-O-Phile]

They suck. Use a laser or a scope. YMMV. I don't like 'em at all.

[legion]

You can actualy get "red dot" scopes that have different reticles than just a simple red dot, but the name has stuck of the style of aiming device.

[m21sniper]

Originally Posted by 71T Targa

So the dot needs to be in the middle of the lens? If so, why isn't there a cross-hair or something?

At the ranges you'll ever be using one "close enough" is plenty good enough. A proper hand hold for a pistol, or a proper cheek-stock meld will ensure that parallax is not an issue at any reasonable range.

[m21sniper]

Originally Posted by legion

You can actualy get "red dot" scopes that have different reticles than just a simple red dot, but the name has stuck of the style of aiming device.

Common feature. My Walther has that. Most new ones, even cheap ones, can also switch between a red and green reticle.


Walther PS-55 reticle

Green reticles and lasers are the future. Soon you won't see any red stuff left at all.