Olight SR91 ,super bright form lightake.com

Aug. 30, 2010 - PRLog -- The SR91 is similar to the SR90  reviewed earlier, both in terms of build and features. The only notable difference is that it has a smaller head. A toughened AR-coated glass lens sits in front of the huge head, protecting the optical components in within it. The smooth aluminum reflector used is very well polished though with some subtle but noticeable circular radiating lines running down the reflector cup, probably due to the machining process. The LED sitting at the bottom of the reflector is itself housed in it's own module and is well-centered with the reflector. On its exterior the head is almost totally covered in cooling fins with a brass ring sitting just behind the bezel where the shoulder strap attaches to. Towards the rear end of the head is the push button switch. It's a toggle switch which works much like a reverse clicky, so momentary operation is not possible. Mechanical travel is very minimal, and tactile feedback is also rather subtle. Looking in from the rear, there're the electrical contact points to the battery pack.

The entire light if finished in black Type 3 anodizing. The second part of the SR90 is the battery pack which houses six 18650 cells. Surprisingly, it actually weighs lighter than the head assembly. The battery pack comes with a screw-on protective cap, handy when the battery pack is kept in storage. Threads between the battery pack and head mate nicely with no cross-threading or grinding. The exterior of the battery pack is covered in a a series of rectangular-shaped ridges. Towards the rear end of the battery pack is another brass ring which the shoulder strap attaches to. The tail end has is crenellated and allows the light to tail stand without problems. The charging jack at the tail end is covered by a rubber flap for water resistance. Charging can be done with the battery packed either attached or removed from the head. Above the charging jack are four green LED's which serve as a battery level indicator. Pressing the battery level button will show the current capacity of the battery pack.

The Good - Well built, clean fit and finish. Easy charging solution. Handy battery indicator.

The Bad - Hefty size and weight.

The Relative - Beam tint close to sunlight white. Toggle switch button doesn't allow for momentary activation. Is able to tail stand. Includes useful carrying case and accessories.

The user interface is very simple, exactly the same as the SR91. Holding the switch down cycles between the high and low levels (alternates in one second intervals). Activating/deactivating strobe mode is done by simply double-clicking the switch on either output level. High/low output levels are memorized even after it's switched off. The beam profile output by the SR90 is a tight spot designed for optimum throw. The spot is well focused with some subtle darker areas within it, though due to the sheer intensity, it's practically unnoticeably in practical use. The corona just outside the hotspot has a four-point oval shape which is due to light reflecting off the LED's base and is not a defect in any way. Beam tint is very close to sunlight white, perhaps just slightly cool around the spill beam but warm around the corona. Relative to its output, runtime provided is average. This is to be expected since efficiency decreases as LED's are pushed harder. One thing to take note is that the light with instantly switch off when the battery is depleted with no noticeable prior dimming. This behavior is common with light running on multiple li-ion cells meant as a protection mechanism.

While the SR91 is advertised to put out less output from the emitter at 1500 emitter lumens (as compared to 2200 lumens of the SR90) in exchange for longer runtime, review tests didn't seems to suggest so. With the same battery pack as the SR90, the SR91 didn't seem to run any longer even though measured output is noticeably lower at 835 lumens. In fact it's shorter than the SR90.

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