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5. Night Vision Modes
FrogEye
supports three night vision modes.
•
NVD (Night Vision Device) mode
is FrogEye’s primary night vision mode and uses the camera’s built-in ‘single
photon detector’ (SPD). The principal advantages are the highest target resolution (best target detail with a given
lens), best contrast and effective wet environment / underwater use because no external intensifier module is required
and the FL-400 lens and Canon lens hoods can be used. Target resolution is approximately 2x – 3x better than I2
mode, meaning the same target detail can be seen from 2-3 times greater distance than I2 mode or with ½ to 1/3 lens
focal length as compared to I2 mode.
•
I2 mode
(image intensifier mode) requires an Astroscope 9350 image intensifier module from Electrophysics to be
switched between the camera housing and the lens. For best resolution and contrast, the 9350 should be equipped
with a GEN3 OMNI4 central intensifier unit, model 9350CIU3-IV. The principal advantage is the wider field of view
compared to NVD mode due to the larger size of the FrogEye color sensor. The wider field of view makes it easier to
locate a target. Light sensitivity is about the same as NVD mode with dark frame subtraction and the cooler switched
on. Because cooler operation in NVD mode is limited to three minutes per shoot, I2 mode also has the advantage of
providing best sensitivity for continuous camera operation.
•
Dual-stage
operation is similar to I2 mode, except that the NVD sensor is selected instead of the color sensor. Thus,
the light is first amplified in the intensifier unit and the image is then further intensified by the NVD sensor. The
principal advantage is the ability to use very short exposure times (often 1/100 sec or less) even in dark environments.
The camera can be swept about quickly and moving targets are easily captured. However, the short exposure time
(few photons), the smaller size of the NVD sensor as compared to the color sensor and the lower resolution of the
image intensifier module as compared to the NVD sensor by itself result in a somewhat blurry image.
Night Vision Mode
Image Resolution Principal Advantage
Min. illum. @ F1.4
Min. illum. @ F4
Color Sensor (daytime
operations)
1004 x 1004 pixel
Best images are available with
this sensor during the day.
0.6 Lux (full moon – deep
twilight)
6 Lux (twilight)
NVD Mode
658 x 496 pixel
Best target resolution, contrast
and ease of use in wet
environments and underwater.
0.0001 Lux (moonless clear
night)
0.0001 Lux (quarter
moon)
I2 Mode (Requires
Astrophysics 9350
image intensifier
module)
1004 x 1004 pixel
Widest field of view eases
target locating. Best sensitivity
for continuous camera
operations beyond the 3
minute limit of the NVD cooler.
0.0001 Lux (moonless clear
night)
0.001 Lux (quarter
moon)
Dual-Stage Mode
658 x 496 pixel
Shortest exposure time for
working with moving targets
and quickly sweeping the
camera in dark conditions.
< 0.0001 Lux (moonless
overcast night)
0.0001 Lux
(moonless overcast
night)
Abandoned barracks at night:
NVD mode 1/3 sec exposure (left), I2 Mode 1 sec exposure (center), Dual Stage Mode 1/180 sec exposure (right)
