Zeiss thermal imager

The heat is on

Zeiss thermal monocular a hunter’s buddy, says Con Kapralos

The outdoor sports optics market is awash with thermal gadgetry – some brilliant and some merely passengers in a rapidly transitioning sector – and whether it be thermal imaging riflescopes, spotting scopes or dual-purpose units many almost need a university degree to operate, exacerbated by poor technical manuals and instructions not to mention being designed with the user as an after-thought. Some thermal optics remind me of those old hand-held camcorders of yesteryear – bulky and unwieldy.

Thankfully the folks at Zeiss Sport Optics know what outdoor sportsmen and women expect and duly deliver in their superb products be they riflescopes, binoculars or night vision instrumentation. Their newly-released DTI 3/35 (and DTI 3/25) digital thermal imaging devices have been created by design engineers to meet the demands of hunters who want a compact thermal spotting monocular that’s easy to use with minimal fuss and smooth operation. Zeiss don’t hide the fact their DTI thermal monoculars are made in China but to stringent specifications as the fit, form and function live up to the brand name and heritage.

First impressions

The Zeiss DTI 3/35 is a compact thermal monocular measuring 193 x 60 x 65mm, the main tube slightly tapered in contour with a hard-wearing rubber coating around the inner metal frame. This tapered design takes into account the differences in hand shape and size which should suit most users and, being truly ambidextrous in design and layout, means southpaws are not disadvantaged by inconveniently located buttons.

Viewing the DTI 3/35 from the front, a 35mm objective lens is set within a recessed rubber collar which also serves to focus the image by simply rotating the collar as required. Focus adjustment is easily tweaked for a sharp image and also benefits from the fact that when set it stays sharp thanks to its frictionless positioning design. A rubber lens cap is supplied but this one’s captive to the body so can’t be misplaced or lost – it simply hangs clear of the objective ocular housing.

The operational buttons sit atop the body and are laid out in a way which benefits the unit’s ambidextrous design. From the front the on/off power switch is first while a quick press of the same button turns off the internal LCD screen to prolong battery life. Next button is the camera function which has a raised central dot for enhanced detection, a short press engaging the video function and a longer press switching between camera and video modes and it’s easy to move between these two for users who wish to record their observations day or night.

Magnification controls sit immediately behind the camera control button and are designed for ease of operation. The DTI 3/35 gives a standard view of 2.5x optical magnification but using either of the side buttons, digital zoom can be incrementally increased in four steps up to four times which is ultimately a 10x overall magnification (being digital in nature rather than optical) resulting in increased pixelation. At every stage you know the magnification setting which is displayed upper right on the internal LCD screen.

The rearmost button is ‘mode’ which serves two functions, a short press giving the choice of changing colour palettes between white, black, red-hot and rainbow and a longer press opening the main menu where you can tailor a myriad of settings such as LCD display (brightness, contrast, ‘Picture-on-Picture’) and other important functions such as auto-calibration. Crucially, first-time users must familiarise themselves with the layout of the operational buttons and what functions they perform by either reading the manual or viewing online instruction videos.

The rear of the unit has a soft rubber eyecup adjustable for both left and right-hand users which when held to the eye blocks unwanted light and makes viewing the internal LCD screen much easier. To the left of the main body near the eyepiece is a diopter focus dial, used to bring together the internal LCD screen, easy to adjust for differing eyesight and once set up to suit it gives excellent viewing with minimal eye strain and fuss-free observation. The DTI 3/35 comes with a neck strap which attaches to the body and allows the unit to sit centrally on the chest for ease of access.

In the field

Setting up the DTI 3/35 before heading out is vital for successful thermal imaging, as messing about trying to change settings is counter-productive. Zeiss claim a detection range of just over 1200m from their ≤50mk sensor and field of view of 19m at 100m gives excellent performance with great thermal scanning and imaging. In the field I found it excellent for both day and night-time use, especially daylight stalking through scrub and timber thickets where deer seem to bed-up during the day. The DTI 3/35 easily detected thermal footprints of deer standing motionless in the scrub which the naked eye would miss.

Additionally the unit came into its own when looking for downed deer in the scrub as the animal emits a thermal heat source even when shot and many deer managers in the UK use thermal devices exclusively during daylight for that very reason. For night-time hunting the DTI 3/35 is an excellent way of uncovering game and pest species without having to resort to a traditional spotlight until needed and while I only use thermal monoculars such as this for quarry detection and retrieval, I don’t tend to bother with the video or picture features as such, but that’s personal preference.

Many will find these two features to their liking with the ability to download image and videos to a PC through an integrated USB port which also charges the on-board lithium-ion battery (it gives a touted seven hours’ run time which I can vouch for). Internal memory storage in 15Gb will give several hours of video storage and quite a few pictures to boot. The DTI 3/35 can also be mounted on a tripod if needed but for general stalking use this wouldn’t be used.

In summary

The Zeiss DTI 3/35 thermal monocular (along with its sibling DTI 3/25) offer hunters and outdoors enthusiasts a compact and easy-to-use thermal imaging device. Weighing 450g it’s comfortably carried in a pocket or backpack and is a bonus for modern stalking hunters seeking an ‘edge’ when it comes to locating huntable species, even in daylight.

Game such as deer are becoming smarter with increased hunting pressure but using thermal imaging technology offers an additional advantage as, for the night-time hunter, using a thermal monocular such as the DTI 3/35 facilitates scanning areas for intended quarry without the need of powerful spotlights until taking a shot. Thermal imaging optics have changed the game when it comes to hunting and when used responsibly make for a great tool in the hunter’s kitbag. The Zeiss DTI 3/35 retails for $4499 and is available through all Outdoor Sporting Agencies dealers Australia-wide. More at www.osaaustralia.com.au


Focal length: 35mm
Sensor resolution: 384×288
Thermal sensitivity (NETD): ≤ 50mk
Display resolution: 1280×960
Display frame rate: 50Hz
Range: 1235m
Field of view (at100m): 19m
Optical magnification: 2.5
Maximum digital zoom: 4x
Zoom steps (in 0.5x): 1x-4x
Battery: lithium-ion – internal
Run time: Seven hours
Internal storage: 15Gb
Dimensions: 193x60x65mm
Weight: 450g
RRP: $4499
Distributor: Outdoor Sporting Agencies

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