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  • Post last modified:September 19, 2023

In this guide let's check out enclosed red dot VS open emitter, and quickly go over the pros and cons to help buyers make an optic loadout decision.

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Open VS Closed Emitter Red Dot 

The main difference between an open emitter red dot sight and a closed emitter sight that set them apart is weatherproofing capability.

Here are two optics: Holosun 507C and Holosun 509T

holosun 509t vs 507c side view

Closed Emitter

iwi x95 with aimpoint micro h1
Holosun 509t iso view

The closed emitter design fully protects the LED emitter diode and the internal to keep dirt, and debris out of the optic.

aiming with one eye open

This design is more common for long guns setups.

This means it works in rainy conditions, and the user can quickly wipe the lens clean even if it gets dropped in mud, wet sand, snow, and other nasty weather conditions.

Most red dot sights on the market feature the closed emitter design.

Weather Proof

holosun 509t covered with melting snow

Melting snow and dirt don't enter the optic at all. Just wipe it off and you're good to go.

holosun 509t reticle after cleaning snow off

No obstruction of the emitter LED

Field Of View

aimpoint micro 2 moa

Bigger window gives wider field of view.


  • Protects internal againts mud and rain droplets
  • Rugged and durable
  • Fully weatherproof include fog and icing
  • No sight removal required for battery swap (Almost all of them)


  • Too big for a pistol optic unless using

Open Emitter

holosun 510c on cz evo s3 sbr
holosun 510c reticle emitter

The open emitter design exposes the emitter without a rear lens, and the internal is NOT fully protected.

Sights like the Trijicon RMR and Holosun 507K are in the open emitter category, and are very popular for conceal-carry users and used as offset aiming sights.

The downside of an open emitter design means water droplets, mud, sand, snow, or other debris can get inside the pocket, and potentially obscure the reticle mirror projection, and the user has the dig everything out.

Weather Proof

holosun 507k dealing with melting snow

Melting snow is easier to deal with, and try to dig with a hook shaped object.

trijicon sro dealign with snow

Play with the slider below to see why a closed emitter is better at fighting against water droplets and debris.

open emitter led blocked by melting snow trijicon sro open emitter led

Melting snow is easier to deal with, and try to dig with a hook shaped object.

Trijicon SRO impacted by melting snow

If the water droplet or dirt don't come off completely, it will refract the LED reticle projection on the glass, and gives the user a blurry reticle.

trijicon sro clean 5 moa dot

After cleaning out the melting snow. It will be much hard when dealing with wet dirt or sticky debris.

Field Of View

holosun 507c x2 show reel

No noticeable difference between open emitter or closed emitter. Bigger window gives bigger field of view regardless the type.

Dot Clarity

Dot clarity is the same for open emitter or closed emitter optics. However, it can be challenging for shooters with astigmatism or other aging related eye problems.

astigmatism eyes looking at night

Vision problems that exist in your everyday life will affect how the reticle looks through an optic.