June 25, 2025
By Jack Hennessy
Over the past few years, during several hog hunts in Texas, I’ve become decently familiar with employing thermal optics to deliver dirt naps to invasive bacon. From the competition side, as well as personal defense, I’ve been a big fan Holosun’s rifle sights for years, as they’re reliable, crystal-clear, and never seem to want to die (very similar to Texas boars). Needless to say, I was very excited when Holosun announced they were marrying their tried-and-true dot technology with thermal imaging through the DRS-TH.
What Is A Thermal Optic, And How Does It Differ From Night Vision? A thermal optic uses a digital camera at the front of the optic to analyze heat signatures and translate that information into an image seen from the eyepiece. Night vision, whether analog or digital, relies on ambient or infrared light to increase visibility.
With digital technology, what the user is looking at is essentially a small TV screen. Even at a 1x setting, size is not exactly 1:1 as it would be if simply looking through glass. Because of this, it’s important to become very familiar with how contours and sizes can vary at every zoom level when seen through digital optics versus glass.
Said differently: You want to be sure that Texas "wild hog" is indeed a wild hog and not a steer for which you’ll pay over $2,000 should you pull the trigger.
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Even through thick humidity, fog, or smoke, thermal optics will detect objects emitting a heat signature, which is a touted advantage over night vision.
Holosun DRS-TH Features Red dot sight (RDS) integrated with thermal camera Up to 50FPS refresh rate Digital magnification: 1x,3x, 5x. Internal video recording and image capture system Three RDS reticle options: 2MOA dot, 65MOA circle, 65MOA circle with 2MOA dot. Three digital reticle options 1P67 Certified (meaning the optic is fully protected against dust and can withstand temporary submersion in water up to 1 meter for 30 minutes) Two rechargeable 18350 flat-top batteries Magnetic USB charging interface OLED display: 1024x768 pixels Sensor Resolution: 256x192 12.8 daylight and 4 night vision compatible RDS brightness settings Window size: 1.25×0.98 inches Internal storage capacity: 24GB of available memory Description of components for the Holosun DRS-TH. Initiial Impressions The optic is sturdy, like a mini-18-ounce brick. The fundamental controls, in regard to the red-dot sight, are very intuitive for anyone who has ever picked up a red dot. The digital sight options, like any thermal optic, require some light reading, or a decent degree of patience for hands-on self-study.
Turning on the thermal functionality can be touchy. The power button actuation is not exactly a quick press and not exactly a long press. A “firm, slightly extended press” is how I would best describe it. The thermal reticle takes approximately 5 seconds before it appears, as a Holosun loading screen precedes it while the thermal camera analyzes data in order to project an image (same as every other thermal optic).
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My favorite first impression: How easy it is to zero the red dot and then co-witness the thermal reticle in a lower-light setting.
Calibrating And Maintaining Zero Half-MOA turns for windage and elevation make sighting in the innate red dot very simple. From there, once the thermal-camera lens is removed and the thermal functionality powered on, an operator can work within the settings to co-witness the thermal reticle. It does help to do this in low lighting and adjusting the reticle can only be done at 1X zoom, so it does take some trial and error to get it the two just right.
Three options for the thermal reticle exist: One T reticle that displays MOA drop at various zooms, and then two others designed provide a reticle for a 5.56 zeroed at 50 yards and a reticle for a .308 zeroed at 100 yards. In theory, the notches with numbers are meant to represent a shooter’s holdover at designated yardages.
The reticle on the right details specifics on holdovers for a 308 WIN rifle zeroed at 100 yards. Example: In theory, via the 3X zoom, if the target stood at 300 yards, the operator would place the center vertical line and horizontal line labeled 3 on the target. But anyone who has ever filled out a DOPE card for various barrel lengths with various ammunition, both suppressed and unsuppressed, knows there isn’t exactly a standard reticle in terms of holdovers as it relates to distance. I opted to rely on the MOA reticle.
While the red dot itself will not zoom, the thermal picture and reticle will zoom to 3X and 5X. While daylight remains, it does appear strange to have a sight picture at 1X overlayed with a zoomed-in green depiction of the same environment. However, once the sun completely sets and only dark remains, the zoom functionality works well. It’s at this point that I turn off the red dot and rely solely on the thermal reticle.
Thermal Image Quality The resolution is low—one of the lowest I’ve experienced with a thermal optic. However, this thermal works as intended and, even with the bonus of a red dot, is approximately half the cost of only-slightly-higher-resolution thermal optics on the market.
At 1X, it was easy to spot deer moving across a field at 300 yards.
Whitetail moving across a south-central Kansas farmer’s field well after dark. Worth noting: the screenshot shared here appears in black and white, but the optic’s screen itself displays green, black and white; so, the gray seen in the image actually appears on as a shade of green. The reticle, as well, is not a plus sign but rather whatever reticle the shooter has chosen. Also noteworthy: the resolution seen here, as you see it, appears crisper on what is basically a 1-inch-by-1-inch optic window, versus the size of the screen on which you’re viewing the image now.
Recorded images and video are also done a VERY small file size. For comparison, the majority of photos taken with an iPhone clock in at 9 MB. A 25-second video recorded on the Holosun DRS-TH is 9.5 MB. This allows for an operator to take far more videos and photos, but at lower quality.
Translation: If Oscar-worthy cinema is the number-one criteria for picking a thermal optic, this one is not for you. If a simple video to remember a hunt or to confirm shot placement upon video review is your goal, the DRS-TH works dutifully.
Uploading videos and photos to a computer is incredibly simple and only requires the same charging cord to upload—not a mini memory card that slots into a bigger memory card, as is the case with many other thermal optics. The thermal image itself is available in four settings: WH (where warm objects appear white hot), BH (where warm objects appear dark), HL (where warm objects are highlighted, fairly similar to WH), and OL (where warm objects appear outlined in green). It seems the OL would work best when light is still present, when wanting to clearly survey a scene but still pinpoint objects emitting a thermal signature (for you gamers, the OL seems like some Call of Duty wallhack minus the walls).
It is important to note it’s not only living objects that will emit a thermal signature. When night hits, anything that has been cooking in the sun will also give off a heat signature—this includes rocks, steel targets, etc. For those new to thermal optics, this may take some getting used to, but is how the technology is meant to work.
Steel targets that have spent the day baking in the sun will emit a heat signature and remain visible to a thermal optic for hours after dusk. Accuracy After sighting in the red dot for subsonic 300 BLK rounds then co-witnessing the thermal reticle, I was able to verify zero during nighttime hours with zero issues.
The red dot maintains a zero, no questions asked; but an operator should understand the thermal reticle is based on the image and data the thermal camera has collected. This data, via the default flat-field correction setting, will refresh every minute. If the rifle is kept steady, via a tripod for example, there will be zero issue maintaining a thermal-reticle zero in relation to the sight picture; but should a shooter find his or her self swinging the rifle often or adjusting his or her point of aim frequently, it may be necessary to adjust the flat-field corrections setting to manual, to where a long press of the magnifying glass will refresh the image to ensure the reticle lines up 1:1 with the sight picture.
Relying on solely the thermal reticle while zoomed, shooting offhand, impacts matched up with trigger pulls from 30 yards. Fun fact: Via the BH setting (instead of WH), it is easier to see paper targets at night. Settings The base red dot is adjustable to 8 different brightness levels while thermal modes preset a wider array of menu options.
The optic itself defaults to the shake-awake setting, same as most Holosun red dots, but will enter sleep at 10 minutes. The sight will instantly wake up to the last setting with any motion of the sight. The sleep timer can be adjusted between 10 minutes, 1 hour, or 12 hours, or disabled entirely. Do note: The sleep setting only works for the red dot. The thermal will remain on until manually powered off.
In terms of settings, other fine-tuning is possible, noted well by the 41-page instruction manual.
Many adjustments are possible in regard to thermal image settings. I personally am a fan of the thermal-setting buttons facing me, versus sitting atop the optic like so many other thermal scopes. While it may not be possible to see the rear-facing button icons in low light, navigating a button pad that faces me—in my opinion—is easier than trying to fumble between those organized on top.
Battery Life The DRS-TH comes with two 18350 flat-top rechargeable batteries. It would appear it’s possible to purchase these same rechargeable batteries online, so it is possible to swap in a fresh pair afield should the original pair die. In my experience, a lot of thermal scopes offer an internal battery or something proprietary that prevents a user from changing to a fresh set of batteries on the fly. I think Holosun did very good on this one.
It took a handful of hours to fully charge the included batteries. At night, at medium brightness, battery life seemed to dimmish 10% every hour; meaning, from my experience, a fresh pair of charged batteries may last upwards of 10 hours at medium brightness for the thermal setting.
The DRS-TH Strengths and Weaknesses The DRS-TH builds upon Holosun’s proven red-dot technology. The resolution of the thermal imaging is indeed low but the manual claims it can detect heat signatures out to 500 meters. From my experience, this appears to be true, but understanding exactly what it is detecting at 500 meters may be a gamble.
Based on the resolution, I don’t know if I’d feel comfortable taking a shot at anything past 300 yards, but this is coming from a guy who was taught to pick a hair on a whitetail before pulling the trigger.
Some users have suggested the best application for the optic is personal or home defense, but I’d argue using this optic for such an application, at least in regard to the thermal functionality, would only make sense in very specific scenarios. For starters, it takes time to power on the thermal setting. But, if for example, the optic brightness was set up perfectly to run in outline (OL) mode alongside a weapon-mounted light (WML) while still relying on the red dot but using the thermal to detect outlines, that could make sense, I feel.
But for varmint hunting or dropping hogs under 200 yards during night hours, the DRS-TH works very well. For you turkey hunters who appreciate the damage raccoons do to poultry populations, this DRS-TH is a great solution for eradicating trash pandas.
Eliminating one’s silhouette and staying equally vigilant and patient goes a long ways when predator hunting . For me, who sometimes enjoys memorizing suppressed subsonic 300 blackout ballistic charts (e.g., approximately 4 inches of drop every 25 yards starting at 50 if zeroed at 25), I like my volume low and my targets close—whether through a spot and stalk (better shower up and know the wind), or the tried-and-true method of remaining patient at a field’s edge. In that regard, Holosun’s DRS-TH is a dream come true, but dreams aren’t always one-size-fits-all. For each shooter’s application, it’s best to assess all criteria.
Reach out to me on Instagram (@WildGameJack) with any questions or comments.
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