TFB Review: InfiRay Finder Series FH35R LRF Thermal Monocular


TFB Review: InfiRay Finder Series FH35R LRF Thermal Monocular

TFB Review: InfiRay Finder Series FH35R LRF Thermal Monocular

2022-02-10 00:00:00

This is a review of the InfiRay FH35R Thermal Monocular .Thermal imaging gives you the ability to detect heat both during day and night.

These devices are typically used by hunters for scouting before and after the shot, but there are many other uses like finding missing persons. I really like this InfiRay.  It has a good image quality, it's easy to use and it's relatively small and light. On top of that, there's a built in Laser Range Finder (LRF) and the device is reasonably priced. It's been my companion on several driven hunts, and I've used it to scout various areas to discover the performance and possible limitations.


Below: The driven hunt. During moments of “silence” it's pretty nice to have a thermal monocular to scout around and let time pass. A thermal is pretty good for safety as well, as you can see other non-targets like fellow hunters. A thermal monocular is a perfect companion for many reasons.



The heart of the InfiRay Finder FH35R is a 12μm@640×512 pixel pitch high-resolution thermal sensor with a NETD of≤35 mK. The lower the NETD, the better, and it affects how clearly you can see objects and makes it easier to get the right focus among many other things. The objective lens is F35/1.0 and a frame rate is 50 Hz. The detection range is said to be 1818 meters. I did follow a helicopter for a very long distance, definitely much longer than 2 kilometers and it was still clearly visible. All this is displayed on an OLED with 1024×768 resolution.

Below: InfiRay Tube TD50L Digital Night Vision Riflescope (back) and the FH35R monocular.


The battery life is reasonable. I guesstimate you can run it for about 3-5 hours. Luckily you can replace the battery and continue using it. My unit came with a charger and two Li-ion batteries. Note that I used it during winter time only, which most likely reduces the battery time compared to summertime.


Overall, the build quality seems acceptable and it has IP67 protection for water and dust. The outer body is made of hard plastic, the buttons are rubberized, and you can operate it with gloves.


InfiRay Tube TD50L Digital Night Vision Riflescope with 940 IR Lamp (left) and the FH35R monocular.

Thermals On Ice

The InfiRay FH35R is 160x90x50 mm and weighs about 400 grams. It fits the hand quite nicely and slips into the pocket without a problem.

Setting the ocular is easy, and it’s done with the switch on the left side (not the battery cover). There’s also an infrared sensor switch that controls and switches the display on and off automatically to save power, and it works great. If the device is hanging in the straps, it’s off, if it detects your head, it turns on. Wonderful!


Image Quality

If you haven't looked into a modern high-end thermal, you should. The sensor has 640×512 pixels and it delivers a good quality image.

A lof of people say you can't get a sense of depth in a thermal. I wonder if they've tried a modern one? Of course the picture is flatter than in a traditional optic, but to say that you don't get a sense of depth is wrong – because you do! If it's pitch black you can also use the focus wheel live to get an understanding which objects that are more distant than others.

Below: Walking couple at 35 meters. Chimney at almost 2000 meters. Note the smoke from the right chimney. There's a Picture-In-Picture function if you like.


Another example with a lot of depth in it. Sign at 7 meters, car at 40 meters, fence to the left and houses further away in the back.


Below you can compare white hot and red hot. There’s a person on the bridge, distance about 260 meters.


You can see the houses 1900 meters away, and the line in the center of the image where there is ice vs clear water.


450 meters to the concrete bridge in the center of the image. White hot. Note that during winter almost everything is the same temperature on a cloudy day like this, so the image quality may improve radically if there is heat from the sun warming up objects.


The FH35R come with 32GB of digital storage for videos and photos, plenty enough. You can  transfer videos and photos to a computer through cable or using WiFi to your mobile device. You can record audio if you like. There's an ARCA adapter to be able to mount it on a tripod attached here (my personal one).


On/Off, Menu, arrow up/down works for LRF and Camera/Video. To record a video, long press the camera icon and it starts recording with a short delay.



I enjoyed using the InfiRay FH35R and was impressed by the ergonomics, size and image quality. They also managed to include a Laser Range Finder in the package, which is quite impressive and an appreciated function. However, there are some minor things that InfiRay could improve until next time. When scrolling around the menu, it's not always clear which icon/function you're about to chose, and what it does. A few of the color pallettes are a bit crazy in my opinion, but white hot worked very well and red hot was good on animals close by. I didn't really have any issues with the unit at all. If you're looking for a thermal monocular in this segment, you should check it out.

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