Frequently Asked Questions

Frequently Asked Questions

I have put together some of the most commonly asked questions we get asked when talking about thermal imaging. 


Why does my thermal click and freeze?

All thermal imaging units have to recalibrate periodically and when they do the image freezes and you hear the shutter inside the unit click. This refreshes the sensor to keep the image sharp. In the settings you will have the option of having Auto calibration or Manual. If you put it into manual mode you will end up with double “ghost” images as cannot refresh unless you tell it to (by tapping the on button usually) and it has too much information to process. Auto mode will deal with this for you and force it to freeze, click, and refresh keeping the image clear. The freezing of the image can be a bit confusing to new users but you get used to it.


How do I set up my thermal imager?

Any digital viewing device needs a little setting up to enable you to see the clearest image it can produce. The eye piece that you hold up to you face is adjustable to allow you to focus clearly on the screen inside. With some units the whole dioptre piece spins but others have a small dial on the side. It is important to focus this to your eye/s first – and refocus is you lend to anyone else! (On binocular style focus each eye separately)

Once you can see the screen clearly you turn your attention to the rear focus wheel. This focuses the imager at different distances. Some cheaper units have a fixed focus but these aren’t really suitable for wildlife viewing. You simple adjust this until whatever you are looking at is clear. 


What do the different settings do?

There are several digital adjustments that can be changed to suit each user.

You can adjust contrast and screen brightness – everyone has different preferences so try them all. You may also want to change these if you are out at night – making the screen dimmer is more comfortable on the eye when you are in darkness.

There will also be some preset environmental settings that will help you get the best image for the weather conditions you are in. No thermal can see through water and in heavy rain or thick fog you will start losing the clear image you would get on a dry day.

These settings amplify the thermal sensitivity shown on screen – effectively making some parts look clearer. This does mean that other parts of the image lose clarity. It would increase the brightness of say the woodcock, but you would lose the detail of the long grass he is sitting in. The settings go up in increments and you should always use on the lowest one you can see with. If you leave in a high setting and go out when it is dry you image won’t be as good as expected.

Pulsar now uses Normal, High or Ultra High but previously used Rocks, Forest, ID and User

Zeiss uses Universal, Detection, Fog and Identify.

There are also options like image boost, or smoothing filters which also digitally manipulate the image or smooth any blurriness. The DTI 6 series has ZSIP Pro which use a very responsive algorithms that works effectively at keeping the image as clear as possible.

All these systems and settings take a bit of playing with and it’s worth spending time inside working through them to find out how each one works. If we have issues with image clarity on a device most of the time it’s because they are on the incorrect settings for the environment.


Do I want a monocular or binocular thermal?


This is the most popular and commonly seen style of thermal device. A single viewing screen which is held one handed to either eye. As they are smaller they are cheaper than the binocular style with the same sensor spec. They can be more practical when out in the field as they fit into a pocket easier – something that night time ringers find handy when they are also carrying a dazzling lamp, net and ringing gear.

The size within monocular models does vary in itself- the Pulsar Axion series being the smallest we recommend. These tiny units have smaller sensors and lenses however, so depending on usage may not be suitable for professionals. The Zeiss DTI family and Pulsar Helion’s and Telos are much bigger monoculars – with bigger capabilities – and are often worn round the neck.


The binocular versions are exactly as they sound! They have one screen inside but both eyes look at it, and you generally hold with both hands.

They are a natural shape to any birder and one that is certainly growing in popularity. They are carried round the neck, or sometimes in a binocular pouch. They are heavier and bulkier though so you would have to have a big pocket if that’s how you wished to carry them. I personally find them more comfortable than monocular when viewing for long periods of time.



Here are some great videos from Thomas Jacks on how to get the most from Pulsar units (the same principles will apply across other brands too)

 Pulsar Masterclass: Brightness, Contrast & Sensor Amplification (One Minute Guide) - YouTube

 Pulsar one minute guide: Why does my thermal image freeze? - YouTube

 Pulsar One Minute Guide: How to Fix a Fuzzy Image - YouTube

 As ever, if you have any questions at all please get in touch! 



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