I just got my hands on a XSight 5 5-25 LRF and this morning was testing it alongside a HIK Alpex 4k (non LRF) and an Arken Zulus 520R
So, in daylight looking at my 100 yard airbrick target which I use to see how good the resolution is, my initial impressions are:
1. Between x5 and x10 magnification the Arken has a very, very slightly sharper image than the XSight.
2. Between x10 and x20 magnification the XSight image is very, very slightly smoother than the Arken image
The Alpex 4k struggled a bit because it's base magnification is lower so more digital zoom had to be used to get the same magnification as the other scopes and at those magnifications the image was not as sharp
It's OK to put a 4k sensor in a scope, but if the display is not also 4k then there is no advantage when using the scope normally (i.e looking through it)
There might be when playing back video recorded on the scope - if it's actually 4k
Going back to the display issue
The resolution of a digital scope (think about it as the smallest thing it can "see") is simply the size of a sensor pixel divided by the focal length of the objective lens.
The answer to that little calculation is an angle in mrad, but it's easier to think of it as the size of a square at some specified distance (usually 100m)
The smaller the size of the square, the more detailed the image
For the Zulus, the pixel size is 2.9 microns and the focal length of the objective lens is 65mm, making a single sensor pixel see a square with sides 4.4mm long at a distance of 100m
For the Alpex 4k, the pixel size is 2 microns and the focal length of the lens is 50mm, making a single sensor pixel see a square with sides 4mm long at 100m
For the XSight the pixel size is 1.55 microns and the focal length of the lens is around 68mm, making a single pixel see a square with sides 2.3mm long at 100m
From those numbers it's obvious that the X Sight should produce the most detailed image
However, the displays used in each scope make a big difference to the amount of detail we actually see when looking through the scope
The Zulus uses a 1920x1080 sensor and a 1920x1080 display so each sensor pixel maps directly to a single display pixel, so the user sees the image in the same level of detail as is captured by the sensor - a resolution of 4.4mm at 100m
The Alpex 4k uses a 3840x2160 sensor and a 1920x1080 display so this time, 4 sensor pixels are displayed on a single display pixel so, instead of the resolution at 100mm being 4mm, it's actually 8mm - which is worse than the Zulus
The XSight uses a 4056x3040 sensor and a 1280x960 display, so this time more than 9 sensor pixels are displayed on a single display pixel, so instead of the resolution at 100m being 2.3mm, it's actually 6.9mm - which is worse than the Zulus
In reality, anyone looking through these scopes is unlikely to be able to discern these levels of detail at 100m, but it does show that using a 4k sensor with a much lower resolution display doesn't give the user what they might be expecting
Cheers
Bruce