Immersive Optics Prismatic Scopes

Immersive Optics is a new name in riflescopes, but they also represent the latest iteration of a technology with a long pedigree, given that some of the earliest sniper rifles were equipped with scopes constructed on the prismatic principle embodied in Immersive’s debut range, as well as in the majority of compact binoculars.

Fellow reviewer, Mark Camoccio has been trying out a couple of Immersive’s models on sub-12 ft/lbs airguns, but I wanted to see what the range has to offer FAC-holders who run high-power air, rimfire and centrefire rifles. To this end, UK distributor Thomas Jacks featuring Immersive’s ‘Rapid’ (MDR) and ‘Extended’ (MDE) reticles, respectively. Before taking a detailed look at these, however, it’s worth considering what makes prismatic scopes different – and in several ways better - than their conventional counterparts.

Pros and cons

On the credit side, prismatic scopes give you a far wider field of view than conventional scopes, will focus closer targets, are more compact and generally lighter, plus typically present a significantly brighter image. Conversely, you get minimal to zero eye-relief, no zoom, a reduced adjustment range, a taller stance and limited or no alternative mounting solutions. A further difference is a super-tight depth-of-field, which is excellent for parallax rangefinding but less so for keeping a moving target in focus.

To put this in a practical context, let’s compare Immersive’s 10x40 model with a conventional 10x42 scope (in this case from SWFA). Some of the differences are huge, others modest. Thus, for the Immersive, the field-of-view at 100m is almost 300% greater (11.4 vs. 3.9m); overall length is 62% less (135 vs. 357mm); weight (inclusive of mounts) is 44% less (485 vs. 700-grams); and minimum focusing distance is 40% shorter (6 vs. 10m). Conversely, the eye-relief is cut by 83% (17 vs. 100mm) and the adjustment range by 17.5% (28 vs. 34 MRAD).

Variable optics

Given that almost no one uses a fixedpower scope these days (it was actually quite hard to find a plain-Jane 10X scope for the preceding comparison), it would be easy to write off prismatic scopes on that score alone. But let’s not rush things! First, we should ask why variables are so popular.

The answer is that variables optimise the key benefits of fine target detail and wide field-of-view at different ends of the zoom range. So what’s not to like? Only the optical cost this incurs in terms of reduced light transmission and changes in exit-pupil size and eye-relief as the magnification is dialled up and down, plus the practical and time-critical liability of discovering you’ve left your scope on the wrong magnification for the next target.

By contrast, a prismatic optic gives you the best of both worlds: great magnification and field-of-view at the same time, with no optical shifts, and no awkward surprises. Additionally, since you always have ample magnification, your reticle is always fully visible in all its detail, and always subtends the same distances. This is something that can’t be said of either second or first focal plane variables.

In optical terms, therefore, prismatic scopes have lots going for them, but there’s an elephant in the room, and its name is ‘eye-relief’! You have to have your eye up against, or very close to, the ocular lens. That’s fine for airguns and rimfires, but potentially bad news with harder-hitting cartridges.

There is a way to increase the eyerelief, however, and that’s to reduce the magnification, which is exactly what Immersive have done with their 5x24 and 5x30 models. The result is an extra 28mm of eye-relief, giving 45mm overall, which should be plenty for anything up to around .243 Win in a standard-weight rifle. Consequently, the 5x30 was a pleasure to use on my .223 AUG Z SP, especially as these more-compact models give up little or nothing by way of field-ofview to their higher-magnification, larger-lensed counterparts.

Get fitted

The 24mm models also have the virtue of setting their objective lens within a 30mm tube, which brings us to the question of how the unusual dimensions of a prismatic scope impact on the mounting options available. Sensibly, the 24mm models are available with or without a dedicated mount, since they are compatible with any 30mm ring mount, giving you multiple options for height and reach. With the other models, you get what you’re given. That means an increase in bore offset, compensated for by sturdiness of build, perfect dimensional matching, and +/- 80 MOA of adjustable pitch!

The pitch adjustment is a genius feature as, in addition to cancelling out both the small reduction in overall adjustment and slightly-increased boreoffset typical of prismatic scopes, it perfectly accommodates the looping longrange trajectories of the low-recoiling rifles to which such scopes are best suited due to their limited eye-relief. On my .223, I left the adjustment at zero, since I wasn’t shooting at long range, but on my FAC FX Impact and .22LR Anschutz, adding 60 and 25 MOA of negative pitch respectively, enabled me to plink at 200m targets while keeping the scope’s internals opticallycentred and maintaining a dead-on hold.

Adjusting the pitch was quick and easy, too. The ring engages with the base across a toothed arc, so you simply loosen the screws in the underside of the mount, use the scale on the side of the base to set the angle you want (based on ballistic predictions or observed fall-of-shot), and re-tighten the screws to re-engage the teeth. It’s a world away from the trial-and-error guesswork involved in setting up most adjustable airgun/rimfire mounts, and massively cheaper than the dedicated centrefire equivalents offered by EraTac and Dutch Long Arms.

Better still, Immersive Optic’s mounting system comes complete with standard, long and longer bases. I went straight for the longest, so as to obtain the rearward extension needed to compensate for the reduced eye-relief. To be honest, I don’t know why the extended bases have a full-length clamp, since the extra cross-bolts are inevitably redundant in reach-back mode, but at least the extra hardware didn’t get in the way.

The finer details

Now we’ve identified what prismatic scopes and Immersive’s mounts bring to the table, it’s time to consider the rest of the options and features. First, there’s a choice of MOA or MRAD formats, though this applies only to the turrets and reticles, not to the mounts, which are calibrated in MOAonly. Clicks are 1/4” @ 100 yards or 0.1 MRADs @ 100m, with a sensible 15 MOA or 5 MRADs per turn for 5 full turns. The dials are quite small and offer no turn indicators, but they are clearly marked, give positive clicks and come with protective screw-on caps. Also good are the tethered rubber lens covers that can be stowed neatly out of the way by pressing them onto the turrets.

Focusing is taken care of by a parallax adjustment dial on the left-hand side and a small dioptre ring inside the rubber eye-cup. The eye-cup can also be easily removed if you prefer - as I did - not to make physical contact with the scope. In the centre of the parallax turret is a rubberised button that controls the reticle illumination via a long press for ON/OFF and short presses to scroll through 6 brightness settings. Power comes from a CR2032 cell located in a compartment under the button. I prefer my reticles centre-lit only, but Immersive has chosen full-reticle illumination, which many like and which comes in cheaper. At full intensity, there is little backscatter, and the illumination is sufficiently intense to accentuate the reticle even in full daylight. As usual, I would prefer more brilliance at the top end and more subtlety at the bottom end, but the reticles were so easy to read as-is that I mostly left the illumination turned off!

As for parallax, the short depthof- field permits precise rangefinding, especially in the 14x50 model, and a stick-on ranging strip is provided so you can do your own calibration. Undoubtedly a great feature for airgun shooters, at firearms ranges it’s neither here nor there, except insofar as it requires a little more attention to maintain the focus than with conventional scope.

Conclusion

I really enjoyed my time with the Immersive Optics prismatic scopes and would happily run either on my FAC air, rimfire or small-bore centrefire rifles. Images are big and bright, plus the reticles are 100% visible and show true MRAD values at all times, doing away with the awkward first or second focal plane dilemma. The small size and low weight of these optics is an eye-opener, too, making me seriously ask why so many of my rifles bear such big, heavy optics. In fact, the 5x24 is so perfect on my AUG, I think it’s going to stay there!