Pulsar Telos XL50 - Question for the Experts?


Well-Known Member
Surprised to see in today's Pulsar announcements that the XL50 Telos sensor only has a thermal rating of <40mK whereas the XP50 Telos is <18mK. It's this aspect of use in rain/clag/etc that I personally rate most in my Telos. Am I missing something here?

I know the XL50 uses a 1024x768 12 um pixel sensor whereas the XP50 is only a 640x480 17um sensor but, IMHO it's better to detect a heat source (albeit a little less distinct) than having a very clear picture of nothing.

Very interested to hear the views of our resident experts on this aspect please @mealiejimmy @Blackwood Outdoors etc. Not sure this will possibly prompt many upgrades...........................:-|
See this post and do not get duped into a lot of the marketed figures. 17 micron has much larger pixels than 12 micron models, so they are more sensitive. Pulsar could state there 20mk but most users wouldn't have a clue as there is no real standard apart from the Black Box method, so anyone can claim whatever netD they want and write it as specification figures.......

I personally own a Merger XL50 because they have the best thermal image out there and many other benefits against others. The dual view is immense, when I'm driving slow scanning I don't feel sick, theres no lag and when I turn it on, every function can be accessed instantly. At long range the sharpness of the image shows a lot more clarity than other thermals.. it's a pleasure to view through.... after using one, everything else just looks poor...
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All Pulsar products with 12 micron 640x480 sensors have NETDs of 40mK and all the XP and XQ models with the older 17 micron sensors (640x480 and 384x2880 are either 18mK or 25mK
The simple fact is that making the sensor pixels smaller makes it more difficult to get the NETD down to the values achieved for sensors with larger pixels
Despite what HIK and others claim for their 12micron sensors they are not<20mK
As Ian says, NETD has become a major marketing point and one where claims can be made that can only be tested numerically in a laboratory
Basically, all thermal sensor pixels are resistors that change their resistance with temperature.
A small electrical current is pushed through each pixel and the voltage developed across the pixel depends on it's resistance - and therefore on the amount of thermal radiation reaching the sensor pixel
Those signal voltages are amplified and processed to produce the image seen on the display
Each manufacturer has it's own signal processing algorithms and this is what leads to differences in the appearance of the final image
In good thermal conditions, lower NETDs don't result in a significantly improved image over sensors with higher NETDs since the temperature differences between the animals we are looking for and their typical backgrounds is large enough for even the poorest performing thermal to detect them
Where NETD becomes important is in recognising background features well enough to allow the safety of a potential shot to be assessed
In poor thermal conditions (high humidity) high NETD thermals will still detect animals but the background image detail can be reduced to the point where it is a uniform grey, so no assessment of the safety of a potential shot can be made


As an example lets looks at a Thermion 2 XG50 (40mk netD) against a Stellar 2.0 (20mk netD) both 12 microns but one has a stated double the sensitivity of the other.

If you take both of these scope models out you would think if we disregard weather performance that the sensor with a 20mk netD would show more image detail than a sensor claimed to be half as sensitive ? That doesn't happen, the Thermion 2 XG50 shows better target detail and sharpness, evident more at longer ranges, even throughout the full digital magnification range. This is a fact, others can test themselves if they have the products at hand..

So you have to take some of these figures with a pinch of salt and actually test the products out in the field to know what performs..

The only 12 micron Pulsar product that has extra software algorithms and gain to enhance the sensor that bit more without degrading quality is the Thermion 2 XL50 which sits at 35mk netD, they could push it to 25mk, but the image would lose so much in-target definition and the terrain would lose finer details , that it would degrade the product and result in a cartoon image affect..
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