How to Make Red Filter for Flashlight: 4 Best Picks for Stargazing (2026)

Updated November 2026

Learning how to make red filter for flashlight use is a simple project, and it can save your night vision during stargazing. A red filter cuts the blue and white wavelengths that make your pupils contract, so your eyes stay adapted to the dark. Below you will find four ready-made filter options and the criteria we used to choose them: fit for common flashlight sizes, material suitability, ease of attachment, and how well owners tend to describe the color and durability.

At a glance

Our Top Picks

Quick Comparison

Product	Best for	Key feature
Nitecore Colour Filter 34mm Red	Nitecore-style lights	Threaded 34mm fit
Eagle Beam Endurance Filter Set	Multi-color needs	Red, green and blue set
MANKER E05 II Filters	Compact flashlights	Lightweight 7.9 g
Selens Color Filter Paper	Custom cutting	Large flexible sheet

Nitecore Colour Filter 34mm Red

Best for: Owners who want a threaded filter that fits their light cleanly.

This is a good fit for anyone with a 34mm-compatible Nitecore flashlight who wants a filter that screws on without improvising a mount.

Pros

• Threaded design sits securely on the light head
• Consistent deep red output

Cons

• Only useful if your light matches the 34mm thread

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Eagle Beam Endurance Filter Set

Best for: Users who want red as well as other color options in one set.

This set suits hunters, anglers and campers who switch between night-vision modes and want more than one filter color on hand.

Pros

• Includes red, green and blue filters
• Designed for the Endurance flashlight line

Cons

• Fit is specific to Endurance-type lights

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MANKER Filters for E05 II Flashlight

Best for: Small pocket lights where weight and bulk matter.

Owners of compact E05 II-style flashlights often want a filter that adds almost nothing to the light’s weight.

Pros

• Very light at 7.9 g in the red version
• Available in both white and red

Cons

• Thin material can scratch if handled roughly

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Selens Gels Color Filter Paper

Best for: Anyone who wants to cut a custom filter for an unusual light shape.

This large sheet works well for makers who are comfortable trimming gel to fit a bezel, tube or lens holder.

Pros

• Large 15.8 x 19.7 inch sheet covers many projects
• Flexible enough to wrap around cylinders

Cons

• Needs cutting and taping, so it is less convenient than a ready-made filter

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Buying Guide

Check your flashlight’s lens diameter

Measure the bezel or head before buying. Threaded filters need an exact match, while gel sheets can be trimmed to size.

Choose the right material

Gel and film are thin and inexpensive, but they fade and tear. Rigid filters last longer but usually fit fewer lights.

Consider how you will attach it

Threaded filters screw on, while gels need tape, a rubber band or a cut-out ring. Pick the method you will actually keep up with.

Confirm the color output

Deep red (around 620 nm and longer) preserves night vision best. Lighter red or amber tints let in more blue light, which can affect dark adaptation.

Good picks for this: Nitecore Colour Filter 34mm Red and Selens Gels Color Filter Paper

FAQ

Can I make a red filter from ordinary red plastic?

You can, but many colored plastics pass too much white light. Gel or film made for stage lighting gives a cleaner, more predictable red.

Does a red filter fully protect night vision?

It helps your eyes stay adapted to the dark, but it does not make you completely night-blind. Keep the light dim and use it only when you need it.

Will a red filter make my flashlight dimmer?

Yes, a filter reduces brightness because it blocks part of the light. Expect noticeably less output, which is the trade-off for preserving night vision.

Conclusion

For a threaded fit on a matching light, the Nitecore filter is the most straightforward choice. If you want several colors or need something for a compact light, the Eagle Beam set and MANKER filters cover those needs. For custom projects, the Selens gel sheet gives you the most flexibility.

Sources

• Background on how the human eye adapts to darkness and why red light is used in observing (nasa.gov)
• Night sky protection guidance and recommended low-intensity lighting practices (nps.gov)

Related reading

• Red Filter Flashlight App: How to Use One for Stargazing (2026)
• Why Use Red Film for Flashlight Beams? 5 Reasons and How to Do It
• Red Light Flashlight Online: How to Buy the Right One for Stargazing (2026)

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