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Thanks to Imalent for providing the DDT40 for review.


Video Review

Below is a video review of the DDT40. Due to my old image hosting site closing down, I've got new restrictions on image uploads and have replaced the "Construction" section of my reviews with a more detailed video review.

[video=youtube;EHxfAyiIYi4]https://www.youtube.com/watch?v=EHxfAyiIYi4[/video]
This video is available in 1080p HD, but defaults to a lower quality. To select the playback quality click the settings button (looks like a gear) after you've started the video.




Manufacturer's Specifications

Price: 200 USD





Plus, here's a few shots with some good detail.







User Interface

See the video for a complete description of the user interface.


Action Shots

You can click on any of these shots to see them full size.

Light in Hand


MugShot


BeamSlice


White Wall
ISO 100, f/3.5, 1/20"


Indoor Shots
ISO 100, f/3.5, 1"


Outdoor Shots
ISO 100, f/3.5, 2.5"



Long-Range Shots
ISO 100, f/3.5, 15"



Performance

Submersion: I submersed the DDT40 under a foot of water for about an hour, clicking the switch several times. I found no evidence of water entering or damaging the light.

Heat: The DDT40 gets hot quickly on it's highest output. After the automatic stepdown, the temp drops down to just being warm.

Drop: I dropped the DDT40 from about a meter onto various surfaces (including grass, carpet, dirt, and hard wood), and found no cosmetic or functional damage.

Reverse Polarity Protection: All four batteries are in a single parallel circuit, so it's very important to put each battery in correctly.

Over-Discharge Protection: The DDT40 shuts itself off when the voltage reaches about 3.7V.


Spectral Analysis

coming soon...
All light that we see as white is actually made up of several different colors put together. The relative intensities of the different colors in the mix are what determine the tint of the white we see. For example, cool white LED's have a lot of blue, and warm white LED's have more red or yellow. This measurement was done on a home made spectrometer. The plot below the picture is corrected for the spectral sensitivity of the human eye. Note: the peak in the 900nm region doesn't really exist, it's a piece of the second-order spectrum that's showing up here because of the high intensity of the light source.

Output and Runtime

coming soon...
ANSI FL-1 runtime ratings are the time it takes for a light to fall to 10% of it's original output (counting from 30 seconds after turning the light on).

The vertical axis of the graphs below represents a relative brightness measurement using a home made light box. The horizontal axis is time in hours:minutes:seconds. Runtimes are stated in hours:minutes:seconds. These graphs may be truncated to show detail.

Mode Comparison

Max

coming soon...






Throwing Distance

ANSI FL-1 standard for stating a light's throwing distance is the distance at which the peak beam intensity (usually at the center of the beam) is 0.25 lux. I calculate throwing distance and candela (lux at 1 meter) by measuring peak beam intensity at five different distances and using the formula lux*distance^2=constant.


Note: A calibration factor of ~6.88% has been added into my throw measurements starting on 9.11.14. To compare the throw of a light I reviewed previous to that date, multiply the candela value by 1.0688 to get the corrected value.


Notes

The T25 is built for 2x26650 batteries, but has an adapter sleeve included for the use of 2x18650 batteries (same length, smaller diameter). However, standard 18650 lithium ion batteries can't supply the necessary current to get to the max output. Standard li-ion chemistry uses cobalt (ICR), which gives higher capacity but lower discharge rates. I'll be testing the T25 with manganese chemistry batteries (IMR) for higher discharge but lower capacity.