OK, THERMAL OR IMAGE INTENSIFYING ?

Understanding the various systems and what they can or can't do can be complex for the beginner.

Hopefully after this boring ramble, the situation may be better understood ??

                                                        NOTE !

We should mention the often asked for devices, "Day / Night" scopes.

The so called day / night scopes at best, are a compromise in both situations and never really suitable for either. 

While thermal can be used day and night, is far more effective as a "night vision" device. 

When considering purchasing any N.V. especially a rifle scope, some thought should be given to the following. 

What do you want to shoot or observe? This may seem like an unnecessary question for a shooter, but it obviously governs the calibre of the firearm to be used and this in turn can influence your choice of scope. 

Image Intensifying night vision scopes have basically been developed from military applications, where most were for use with the 5.6 mm military round (.223), and as such no significant recoil is produced. 

Make sure your choice is one that will withstand higher recoil if you intend to use "high recoil" cartridges, or be prepared to use a recoil reduction system of some kind.

When considering "Night Vision" eg. Image intensifying devices, while they do require light to operate, you MUST be aware that they are NOT for use in daylight. Those that have inbuilt "Auto gating" prevents damage should a bright light come into view, while at the same time the resolution (lp/mm) decreases until that light is removed. Some have a bright light shutdown feature but not for daylight use.

There are so many specifications to understand with these devices, it is better to talk to us rather than try to explain it all in here.

Apart from the resistance to shock on the internal electronics  & lens etc, eye relief is critical when you intend to use even say a .243 W, but certainly .308 W, or .270 W etc. and upwards, as some N.V. scopes can have as little as 25 mm eye relief ! 

With some of the upper level thermal scopes (when using 75 mm - 100 mm focal length lenses at f 1.0) some of these devices strongly recommend that you use some form of recoil reduction system especially due to the size of those lenses when using high recoil firearms. 

Some manufacturers do state the resistance to shock but not all. 

GSCI image intensifying N.V. and Ti - Gear Thermal scopes are able to withstand .50 cal and it is stated as such. They are also rated for "machine gun" operation.   

It is absolutely essential that you can see what is in the background behind your target, meaning you must have the ability to see and identify any potential hazard that may exist far beyond your intended range, whatever that range may be.  

With regard to "seeing", and due to the fact it is more difficult shooting at night with any night vision, magnification should be considered.  

Generally speaking, most shooting carried out in daylight, a scope magnification of 6 X optical usually higher is used, it would therefore be logical to use as high a magnification as possible at night ?? DO NOT confuse this with digital magnification (zoom) though. 

Higher magnification is reasonably obtainable in image intensifying NV rifle scopes, but 6 X would still be considered as being "fairly high" while still keeping the lens size under control. 

When you are looking at night vision of any type, you need to be aware that as the optical magnification rises the system sensitivity decreases unless a faster lens (f number) is also used .

Lens size (f number) applies to all optical equipment with respect to overall sensitivity.

For thermal imaging, magnification is "fairly high" at 4 X, and this is where 17 micron pixel 640 X 480 FPA (Sensor) comes in to its own, as the image is still reasonably sharp when digital zoom up to 2 X is used and acceptable at 4 X zoom. 

DON'T be fooled by seeing high magnification specs such as "16 X" or even higher, read the specification sheet carefully as there are thermal scopes advertised as 2 X - 16 X magnification, but if you look carefully you will see it has a 50 mm focal length, (2 X optical nominal) and everything over 2 X refers to digital zoom only. 

6 X optical magnification becomes available with the use of a small FPA. (Physical size, regardless of pixel numbers) eg 384 x 288 as against 640 x 480 pixels with a 100 mm focal length lens. 

It is my preference to go no higher than 4 X optical using the 100 mm lens and the 640 x 480, 17 micron FPA. (See more on the "facts about thermal page).

Maybe, with the use of 12 micron sensors it is worth considering to gain some optical magnification. More on this below.

This needs some clarification, a smaller FPA, regardless why it is smaller, will produce a higher optical magnification for any given focal length lens due to its narrower field of view. BUT when this image is then interpolated to the AMOLED for viewing, it must be digitally "stretched" to fill the viewing screen and therefore some image quality is lost. 

The effect is the same as using the "zoom" on the device. 

For example, if you go from an FPA of 640 X 480 using the same pixel size and the same lens length to one of 384 X 288, you are effectively using a 1.5 X zoom.

This is just the same "loss of quality" as when you reproduce an image onto, say a computer screen for viewing. While this process does increase the overall size of the image, the magnification has not been altered as the ratio between the "target" and the "overall" image is still the same.

Do not confuse this with "zooming" from the device.

Hopefully the above can be understood to some degree, as all of this is very hard to explain in text !!

The following comments here will cause grief to those who believe a "12 micron image" will be superior to that of a 17 micron device due to the smaller pixel size.  

Let's look at a 12 micron sensor (FPA). 

Due to the fact that even with the same number of pixels, the FPA is smaller overall, yes, you do obtain a higher optical magnification, although when the image is interpolated to the AMOLED, the image quality viewed, is the same as that from a 17 micron device. 

Therefore, apart from the "benefit" of being able to use a shorter, and therefore cheaper, focal length lens for any given magnification, you have no image quality advantage over the industry standard 17 micron FPA, but you do not lose image quality.

CAUTION, while there are some devices available with LARGE 12 micron sensors, you will gain some amount of "better" image quality, BUT for an equivalent focal length lens your magnification will be lower, (See above explanation). 

Apart from the considerable extra expense, should you go to a longer focal length lens to regain magnification, you have even more expense and a bulkier device as well. 

All this needs very careful thought, the actual benefit is  an increase in optical magnification not a fantastic image quality improvement. 

So, yes it can be worth the choice for the benefit provided.  

You will note I have not mentioned digital devices at any point. They can have some exceptional looking figures, BUT digital requires high levels of additional Infrared to be operational at more than a few meters unless you have a full moon. 

Regardless of what a lot of internet experts claim, Infrared CAN be seen by nocturnal animals! (See below)

Why, just why I ask, should I be COMPELLED to provide "illumination" to make a NIGHT VISION device actually usable in the dark??

A WORD OF WARNING!  When choosing a N.V. scope of ANY kind, don't be misled by advertising "pictures" claiming the images shown indicate what can be attained with "their" equipment, especially where the "target" object almost fills the complete picture. 

This  means that the target is VERY close and not at the distance a user would normally expect to operate. 

The result is very misleading, but unfortunately, happens quite often.              

An example of this can be seen from a prominent thermal manufacturer.

​It is fully accepted that it is extremely difficult to reproduce an image that really represents the product in question. 

With respect to thermal imaging (As above), when a picture or video from a device is printed or displayed on a computer for viewing, the image has been GREATLY enlarged from the actual screen size within the unit. 

For  example, a thermal image reproduced onto your computer screen even as small as say, 150 mm x 120 mm will have enlarged the actual image about 250 times! The devices internal screen is absolutely MINUTE compared to the average size of any "reproduced" image. 

Remember the FPA "image" is somewhat less than one megapixel, although this image when viewed on the units own internal screen, it will appear completely "normal" to the user. 

Be aware that if you decide on any device image intensifying or digital, especially digital, that it will require additional IR to provide a workable range of operation. Nocturnal animals can see IR, as well as the very visible red light emitted from the illuminating devices around the commonly used 810 Nano-meter wave length up to about 850 Nano-meters, regardless of the fact it is widely claimed to be otherwise by online experts. 

It does occur in a variety of animals. There are documented cases of a few humans actually seeing covert IR. (920-940 Nano-meter wave length). 

After a time, those animals that can see the IR, will avoid IR light just as they did with a spot light.

As a final word, with a night vision rifle scope, you obviously intend to shoot in the dark, always choose a suitable calibre for your expected target and only shoot at a conservative range. 

It is not like shooting in daylight or even using a spotlight at night.