Black Diamond Cosmo Review: Headlamps

Black Diamond is a brand geared toward the more committed outdoor enthusiast. So if you’re thinking of taking your camping relationship to the next level then our Black Diamond Cosmo review is here to help.

Written by: | Reviewed by: Kieran James Cunningham
Last Update:
Disclosure: The team at My Open Country highlights products we hope you might find interesting. If you buy them, we get a small share of the sale revenue from our partners at no additional cost to you. This never drives our decision as to whether or not a product is featured or recommended – you can read more about our editorial process here.

Black Diamond Cosmo Review

Our Rating: 3.5/5

The Black Diamond Cosmo headlamp is an affordable yet powerful choice for every outdoor application. The Cosmo excels in long battery life. It is durable and water resistant. Its lighting features range from a super bright primary lamp to a red LED night vision bulb.

This product is designed for a wide range of uses. From camping to backpacking, caving to rock climbing, hiking to home use, this headlamp will light the way in any night time or low light situation.

This product does have some limitations. The single button control is disliked by some users. Others have reported that the battery door latch is prone to break under rough treatment. The lamp itself is also dimmer than others in its class.

Key Features

  • Dimmable distance lamp and proximity floodlight
  • Red LED night lamp can be used to reduce eye strain
  • One size fits all adjustable elastic headband fits anyone from small children to the exterior of adult climbing helmets
  • Long battery life on high settings, super long life on low settings
  • Storm proof—Tested to withstand rain and sleet from any angle.

Category Scores

Trail Finding
Battery Life
Ease of Use
  • PROs

    • 3 light modes including emergency strobe light
    • Lightweight
    • Durable and water resistant construction
    • Up to 250 hours of continuous use
  • CONs

    • Comparative dimness compared to competitors
    • Single button control can be frustrating

Hands on Review

The Black Diamond Cosmo is lighter and less expensive than many headlamps in its class while maintaining many advanced features.

Trail Finding

The Cosmo’s adjustable features will maximize your safety as you navigate. The primary distance lamp at its full power of 160 lumens allows you to see far into the distance. If trip hazards are a concern, you can switch to the floodlight. Using this feature, you will be able to clearly see nearby obstacles and avoid them. Turn on both the distance lamp and the floodlight to benefit from both these features at once.

In the unfortunate event that you are lost or injured, switch to the strobe feature to get the attention of your traveling companions or other hikers.

The Cosmo is also rated as being water resistant to IPX 4, so you don’t have to worry about malfunctions in the rain or near falling water (REI). Just don’t go swimming with it, as it is not entirely waterproof.


The Black Diamond Cosmo is equipped with a dimmer function so that you can select the exact amount of light you need. This setting ranges from 4 lumens to 160 lumens.

By way of comparison, at the maximum 160-lumen setting, your floodlight will appear roughly equivalent to a 20-watt incandescent bulb. That might not seem like a lot, but 160 lumens is sufficient for most tasks in an area with no light pollution. The beam of the distance lamp has been tested to extend for approximately 30 meters, despite the manufacturer’s 50-meter claims.

Suppose you need to take a trip to the campground’s bathhouse or the nearest tree in the middle of the night. You know that turning on the lamp with brightness of 160 lumens is likely to elicit moans of protest from your friends. Lucky for you, the Cosmo headlamp is equipped with a red “night vision” LED for use around the campsite. This type of low-level light reduces eye strain and won’t disturb sleepers or blind anyone. Some users even report reading in bed using this feature – without disturbing their roommate!

Red lighting is also useful for specialized applications in which you don’t want your own eyes to adjust to brighter lighting, such as when star gazing. Use the red LED to consult your printed sky map, then find the star you are seeking to identify without waiting for your eyes to adjust, as you would if using a standard flashlight.

Battery Life

The Black Diamond Cosmo headlamp boasts an impressive 50 hours of battery life even when used on the highest setting. If you are seeking to conserve power, the Cosmo can produce a whopping 250 hours of light at its lowest setting. Still, this is an optimal average, so expect to get less actual life from your 3 “AAA” batteries, especially during cold weather. A locking feature prevents the light from being turned on accidentally, such as in your pocket or backpack.

Ease of Set Up

The Black Diamond Cosmo is considered easy to control. One button operates all headlamp functions. Press the button once to activate the primary bulb, twice to switch to the floodlight. If you hold the button down while the light is turned on, you access the dimmer control. When holding the button, the light will slowly dim to its lowest point of 4 lumens, then slowly brighten to 160 lumens once again. Simply release the button to select your preferred brightness. To switch between the regular light and the red night vision light, hold the button while the light is turned off.

However, some users find this one button control system difficult to use. The sequences can be difficult to remember, and therefore the user is left pushing the button without knowing which setting to expect.

The lamp is held on the wearer’s head by an elastic band with two adjustment points. Between the elastic and the adjustments, the headlamp is designed to fit a variety of wearers. The size of the band can be reduced to fit small children, or expanded to span the exterior of an adult’s climbing helmet. Some users, however, complain of skin irritation caused by contact with the adjustable clips.


Weighing only three ounces with batteries installed, the Black Diamond Cosmo is frequently reported as being lightweight and comfortable to wear. The minute weight of this product is due to the light polycarbonate material that comprises the compact 2.5 inch by 1.5-inch tiltable headlamp. This lightweight feature is especially useful on long hikes or other occasions in which you will wear the light for an extended period of time.

Technical Specifications

Best UseBackpacking
Bulb TypeLED
Bulb Detail1 TriplePower LED/1 DoublePower LED/1 DoublePower red LED
Red Light ModeYes
Beam TypeFlood / Spot
Max Light Output (Lumens)160 lumens
Light OutputHigh: 160; low: 4 lumens
Max Beam Distance (m)60 meters
Beam DistanceHigh: 60; low: 12 meters
Brightness LevelsMultiple/adjustable
Average Run TimeHigh: 50; low: 250 hours
Batteries3 AAA
Dimensions2.5 x 1.5 x 1.5 inches
Weight With Batteries3 ounces


In exchange for this extended battery life, the Cosmo sacrifices lamp brightness as compared to similar lamps. In the proximity floodlight setting, it tends to have a hot spot in the middle of the beam with little light reaching the peripherals creating a narrower “tunnel-vision” than alternatives on the market.

Best Applications

The Black Diamond Cosmo is recommended as a headlamp for backpackers and applications where long battery life is essential. It has by far the best battery life in its class, with similar headlamps clocking less than 4 hours of battery life.


This headlamp is caught in a tight spot in terms of value. For half the price, you can purchase headlamps that perform almost as well. For $10 to $15 more, you can increase your lamp’s brightness severalfold. This headlamp may still be the best value for you, however, if extended battery life is your primary concern.

Other Versions & Accessories

For those concerned with looks, this sleek headlamp comes in five colors: aluminum, black matte, grass, octane, and plum. The version currently available from most retailers is lighter in weight than previous versions. No accessories are currently available, but don’t forget to bring extra batteries.




COAST HL7 330 Lumen Focusing LED Headlamp with TWIST FOCUS™, Black

If you are willing to spend a little more than the cost of the Black Diamond Cosmo, you can upgrade to highly superior headlamp performance. The Coast HL7 has been tested to have more than 4 times the brightness of the Cosmo, with twice the span of the proximity beam.

The beam length is approximately four times the length of the Cosmo’s, resulting in better trail finding. The one drawback is the battery life. The Coast HL7 only clocks 3.4 hours of run time on its highest setting.



Petzl TIKKINA Headlamp - Simple, Lightweight, Compact 250 Lumen Headlamp for Hiking, Climbing, and Camping - Black

The Petzl Tikkina is about half the price of the Black Diamond Cosmo, yet it outperforms in some areas. It has double the Cosmo’s long lasting battery life, yet the lamp’s brightness and distance are slightly better. This lamp is probably the best value for anyone looking to spend $30 or less.

See here for a full review of the Petzl Tikkina.



Black Diamond Spot Headlamp Black

If you are hooked on Black Diamond products, the Black Diamond Spot might be for you. It maintains decent battery life as compared to its little brother, the Cosmo. However, for just $10 more in price, the Spot outperforms the Cosmo in brightness and proximity mode span.

Last update on 2023-05-29 / Affiliate links / Images from Amazon Product Advertising API


Brian has been an avid hiker and backpacker since he was a small kid, often being taken out into the wilderness on trips with his father. His dad knew everything about nature and the wilderness (or at least that's how it seemed to a ten year old Brian).

After high school, he went to university to read for both a BS and MS in Geology (primarily so he could spend his time outside rather than in a classroom). He's now hiked, camped, skied, backpacked or mapped on five continents (still need to bag Antarctica) & 30 of the US states.

Email - Portfolio

Leave a Comment