Pulsar magnification question

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andy66
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Pulsar magnification question

Post by andy66 » 13 Feb 2018, 21:42

Little confused on pulsar magnification specs, as we all know optical magnification over rules digital magnification in picture clarity. Now what I don't understand is why my helion xq38f has optical mag of x3.1 but the trail xq50 only has x2.7 where as the helion xq50 has x4.1. So why does the trail xq50 have less mag?

I hope that makes sense.

Andy

phoenix
BRUCE ALMIGHTY
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Re: Pulsar magnification question

Post by phoenix » 13 Feb 2018, 22:03

The optical magnification of a digital device like the Helion, Trail, Drone Pro etc, all of which have a sensor and a near eye display, depends on four things.
These are
Focal length of the objective lens
Diagonal size of the sensor
Diagonal size of the display
Focal length of the display optics
There's an equation that relates all these 4 factors and it can be found here http://www.pulsar-nv.com/support/nv_technologies/
The optical magnifications for the various Pulsar thermal spotters and scopes are:
Helion XQ 38F x3.1
Helion XQ50F x4.1
Helion XP38 x1.9
Helion XP50 x2.5
Trail XQ38 x2.1
Trail XQ50 x 2.7
Trail XP38 x1.2
Trail XP50 x 1.6

So, we have two lens sizes (38 and 50mm) and two sensor sizes (XQ and XP)
If we use the same sensor, the 50mm lens will give a higher magnification than a 38mm lens
If we use the same lens, the XQ will give a higher magnification than the XP (because the XP sensor is physically larger)
Going from 38mm to 50mm has a smaller effect on magnification than changing the size of the sensor from XQ to XP
Since they use the same objective lenses, sensors and OLED display, you would expect the Trail scopes to be the same magnifications as the Helion spotters.
They don't, and the difference is due to the optics they use for the OLED display.
The focal length of the display optics on the Trail scopes has been changed to improve eye relief so that the user doesn't get whacked with the recoil of the rifle. Unfortunately, the change in the display optics to improve eye relief also causes the overall magnification to be somewhat reduced.

Cheers

Bruce
Last edited by phoenix on 14 Feb 2018, 10:07, edited 1 time in total.
LAND ROVER - THE WORLD'S WORST 4X4 BY FAR

andy66
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Location: warrington

Re: Pulsar magnification question

Post by andy66 » 14 Feb 2018, 09:26

Fantastic Bruce, thanks for taking the time to write that its much appreciated.

Andy

blueroll
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Re: Pulsar magnification question

Post by blueroll » 14 Feb 2018, 16:32

Bruce.
More interesting info thanks. I am sure others would also appreciate the info you gave me about calibration, unless you already have and I missed it ?

phoenix
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Re: Pulsar magnification question

Post by phoenix » 14 Feb 2018, 17:18

I'm not trying to derail the thread, but, by special request from blueroll, here's the answer I gave him to to a pm'd question about thermal scopes:

Comparing the image on a Pulsar thermal with one of Clive's thermals needs to be done with some understanding of how these devices handle what's called "Non Uniformity Correction" (NUC)
The basic problem is that the individual pixels in the thermal sensor are not all perfectly matched, meaning that for the same amount of heat hitting each pixel, the electrical signal produced by each pixel is not the same - i.e for a uniform heat input, the signal output is non uniform, and this has to be corrected by the sensors electronics.
There are basically 2 ways of doing this, Pulsar uses one method and Clive's thermals use the other method.
In the Pulsar method (called "calibration") a matt black metal shutter is moved in front of the sensor (that's the clicking noise) so that each pixel receives the same heat input. The electronics looks at the output signal of each pixel and adjusts the signal level until it's the same for all the pixels. That process takes a couple of seconds and there's no signal available to view during that period, so the video freezes. Immediately after calibration, the image on the display is at it's best and it slowly degrades as the sensor non uniformity builds up again. If calibration is set to auto, the instrument will re-calibrate at fixed time intervals or if the sensor sees a big change in temperature.
Clive's thermals use "shutterless" NUC. This method uses an algorithm to continually adjust the signals from the pixels. This method means no freezing of the image at awkward moments, and was one of my main reasons for going for this type of thermal scope. The downside is that the image is never going to be as good as the Pulsar when it has just calibrated, but will be as good or better than the Pulsar for most of the time between Pulsar calibrations.
Hope that helps


Cheers

Bruce
LAND ROVER - THE WORLD'S WORST 4X4 BY FAR

B&W FOX
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Re: Pulsar magnification question

Post by B&W FOX » 14 Feb 2018, 22:05

Bruce

Thank you for the clear cut explanation on thermal and digital, my grey mater was able to take that in.

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Mini Magnum
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Re: Pulsar magnification question

Post by Mini Magnum » 15 Feb 2018, 12:09

Yes all down to magnification on the eye display as Bruce mentioned , from testing equivalent Helion models side by side against a Trail, I personally think the Trails give a better image, field of view and performance in poor atmospheric conditions also.

andy66
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Location: warrington

Re: Pulsar magnification question

Post by andy66 » 15 Feb 2018, 20:01

Some more great info, cheers guys.

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