Geekoto GT-250 User manual

INSTRUCTION MANUAL
GT-250
Made in China
[e-mail]

Foreword
Warning
Part Name
Battery
Power management
Modeling lamp
Wireless mode selection
TTL Flash mode
M Manual
S1/S2 Flash mode
Multi-frequency flash mode
Group setting / channel setting
Wireless flash shooting
C.Fn: Set custom features
Specifications
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- 02 -
- 03 -
- 09 -
- 10 -
- 10 -
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- 11 -
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Contents

Before using this product
Please read this manual carefully to ensure that you can use it safely.
Please save this manual for future reference.
GT250 flash is a wireless TTL flash with built-in 2.4G wireless 陣 system, The
C series trigger can remotely control the function of TTL/M/Multi mode of
GT250 flash; at the same time, it can also be used in combination with the TTL
master-slave function flash, TTL outdoor flash light and the TTL studio light.
With the GT250 flash, you'll get a more simple shooting experience in complex
lighting changes. Accurate flash exposure is automatically obtained for ease
of shooting.
Product highlights ：
Wireless TTL system is fully compatible：With built-in GEEKOTO 2.4G
wireless 陣system. it can support Canon E-TTL, Nikon i-TTL and other TTL
automatic flash system; can be used as a slave unit of a wireless multi-lamp
flash system, Shooting is fast and simple.
Sturdy, compact and portable: The flash power is up to 250W, making it easy
to carry in comparison to other lights of this capacity.
Replaceable lamp holder, a variety of light-emitting methods: Multiple sets
of optical lenses, uniform light, LED modeling lights.
High-quality AV display: intuitive display and easy operation.
Built-in 2.4G wireless transmission: 50 meters ultra-long distance.
Studio light quality: power up to 250Ws.
Creative unlimited professional power supply: use well-known Korean brand
battery, large capacity power box (14.4V/2900mAh), 0.01-2.2s callback, full light
500 flashes or more.
Wireless control: Built-in GEEKOTO 2.4G wireless 陣 system, can realize TTL
control, external can use GEEKOTO C-1 (Commander) remote control, wireless
control flash power size and trigger flashing simultaneously; while leaving 2.5mm
sync jack, can realize a variety of synchronous triggering methods.
Dimming accuracy: The power adjustment range is broad (1/1-1/128), and the
22-level precision is fine-tuned.
The color temperature is constant: The color temperature is maintained in the
range of 5600 ± 200K.
Advanced features: Support 1/8000 second high-speed synchronization,
high-speed strobe, high-speed remote control synchronization trigger.
Foreword
- 01 - - 02 -
Warning
The GT250 is a portable flash solution consisting of a flash, wireless remote
trigger and various light effects accessories. The GT250 flash, compact and
portable, powerful, built-in battery capacity, support full speed, for outdoor
shooting and live shooting; provides good light quality. This portable and
efficient light quality is an ideal source for photo-enthusiasts and professional
photographers of all types.
Please keep it dry.
Do not disassemble the product. If the product fails, it must be inspected
and repaired by our company or authorized maintenance personnel.
Do not allow children to come into contact with this product
Do not disassemble, impact, crush or put into fire. If there is severe swelling,
do not continue to use it. Do not place in a high-temperature environment
exceeding 50℃.
Do not flash the flash head directly against the human eye (especially the
baby's eyes), as it may cause visual impairment in a short period of time.
Do not use the flash near chemicals, flammable gases, or other special
substances that may be sensitive to the flash of the flash speedlite. Under
special conditions this may cause fire or electromagnetic interference. In
these cases, please pay attention to the relevant warning signs.
This product is not waterproof. Please pay attention to avoid water
exposure in rainy and humid environments.
If any malfunction occurs, turn off the flash immediately.

Name of Parts
Body:
- 03 - - 04 -
2.5mm Sync Cord Socket
Name of Parts
Body:
Ventilation Area
Power Switch
Battery
Compartment
Light Sensor
Lithium Battery
Battery Release Slider
USB Port (for firmware upgrade)
LCD Control Panel

- 05 - - 06 -
AV Panel
S1/S2
M/Multi
TTL
C.Fn
+ Button
<SET> Button
(long press for
custom function)
- Button
<GR/CH> Group/
Channel Button
(long press for channel)
Reset (pressing
GR/CH button and
MODE button at
the same time)
MODE/Modeling
Lamp button
(Long Press for
modeling lamp)
Flash Ready Indicator/
Test Button
Name of Parts
Body:
Name of Parts
Mask
Battery Level
Flash Compensation Level
Group
2.4G Wireless
Channel
Modeling Lamp
HHS
Beeper
Standby
Timer
Overheat Protection
Frequency
Min
Sec
•The display will only show the settings currently applied.
•When button is pressed, the AV panel will illuminate automatically.
(1)TTL Auto-flash
Auto-flash Output
TTL: Auto-flash
(2)M Manual Flash
M: Manual Flash
Manual Flash Output

- 07 - - 08 -
(3)Multi Strobe Flash
Name of Parts Name of Parts
Flash Frequency
Number of Flashes
Multi: Strobe Flash
(4)S1 Slave Mode
S1: Slave Mode
(4) S2 Slave Mode
S2: Slave Mode
(5)Custom Mode
C.Fn Custom Mode

Lithium Battery Power Management
1.This flash unit uses Li-ion polymer battery, which has a long service life.
When the battery is fully charged, it will offer 500 times of charge and
discharge cycles.
2.Battery is safe and reliable. The inner circuit of the battery is designed
against over-charge, over-discharge, over-current and short circuit.
3.This battery takes only four hours to be fully charged.
Cautions
1.Do not short circuit.
2.Do not expose to moisture or submerge into water. This battery is not
waterproof.
3.Keep out of reach of children.
4.Do not charge the battery continuously over 24 hours.
5.Store in dry, cool, ventilated places.
6.Do not dispose in fire.
7.Scrapped batteries should be disposed of according to local regulations.
8.Please charge the battery to 60% for long-term storage.
9.If the battery has been stored for over 3 months, please recharge the
battery.
Battery Level Indication
Make sure the battery pack is securely loaded in the flash. Check the battery
level indication on the AV panel to see the remaining battery level.
Features
Battery Level
Indication on the
AV Panel
3 Bars
2 Bars
1 Bar
Blank
Blinking
Meaning
Full battery
Medium battery
Low battery
Lower battery, please recharge.
Battery exhausted, the flash will auto power off in 1
minute.
Note: when in this state, please recharge the battery
as soon as possible (within 10 days).
Then the battery can be used or be placed for long
periods.
ON/OFF Power Switch controls the on/off of the flash unit, please turn
off the power when not in use. This product is designed with automatic
standby feature, it will go to standby mode when not operated, (approx.
30/60 minutes).
Modeling Lamp
Wireless Flash Mode
GT-250 can only be set as a slave unit (receiver end). Long press the
wireless selection button for 2 seconds to switch the radio transmission
function.
Wireless Mode
OFF
Radio Transmission
Flash Mode
M / Multi
TTL / M / Multi
- 09 - - 10 -
Long press <MODE/ > button
until the display on the AV panel
for turning on the LED modeling
lamp.

This flash has three flash modes: TTL, Manual (M), and Multi (Strobe).
In TTL mode, the camera and the flash will work together to calculate the
correct exposure for the subject and the background.
Press < Mode/ > button to cycle through all three flash modes.
TTL Mode
Press <Mode/ > button to enter TTL mode. The AV panel is displayed < TTL >.
TTL Autoflash
Flash Compensation
With flash compensation function, this flash can adjust from -3 to +3 in
1/3rd stops. It is useful in situations where minor adjusting of the TTL
system is needed based on the environment.
Setting Flash Compensation:
• Press <+>, “+0.3” means 1/3 step, “+0.7” means 2/3 step.
• Press <->, “-0.3” means 1/3 step, “+0.7” means 2/3 step.
•To cancel flash compensation, set the amount to “+0”.
High-Speed Sync
High-Speed Sync (FP flash) enables the flash to synchronize with all camera
shutter speeds. This is convenient when you want to use aperture priority for
fill-flash portraits.
• With high-speed sync, the faster the shutter speed, the shorter the
effective flash range.
• Multi-strobe mode cannot be set in high-speed sync mode.
Manual Flash
In manual mode, you can cycle through all the power output 1/128 to 1/1
in 1/3-stop increments.
For a proper exposure, please use an external flash meter or the meter
within the camera.
1.Press <Mode/ > button, until the AV panel display <M>.
2.Press <+> <-> button to set desired flash output.
- 11 - - 12 -

Flash Output Range
The following table makes it easier to see how the f/stop changes when you
increase or decrease the flash output. For example, when you decrease the
flash output to 1/2, 1/2-0.3, or 1/2-0.7, and then increase the flash output to
more than 1/2, 1/2+0.3, 1/2+0.7, and 1/1 will be displayed.
Figures displayed when reducing the flash output level→
←Figures displayed when increasing the flash output level
1/41/21/1
1/1–0.3
1/2+0.7
1/1-0.7
1/2+0.3
1/2-0.3
1/4+0.7
1/2-0.7
1/4+0.3
······
······
S1/S2 Flash Mode
Optic S1 Secondary Unit Setting
Press <MODE/ > to choose S1
function so that this flash can function
as an optic Slave flash. With this
function, the flash will synchronize
with the main flash, the same effect
as that by the use of radio triggers.
This helps create a multiple lighting
effects.
Optic S2 Secondary Unit Setting
Press <MODE/ > to choose S2
function, so that this flash can
function as an optic slave flash in
M manual flash mode. This is useful
when cameras have pre- fla sh
function. With this function, the flash
will ignore a single “pre-flash” from
the main flash and will only fire in
response to the second, actual flash
from the main unit.
Multi Strobe Flash
- 13 - - 14 -
With strobe flash, a rapid series of flashes is fired. It can be used to capture
multiple images of a moving subject in a single photograph. You can set the
firing frequency (number of flashes per sec. expressed as Hz), the number
of flashes, and the flash output.
Press <MODE/ > button, until <MULTI> will display on the AV panel.
Setting the Number of Flashes and Flash Frequency
Press <SET> button to choose flash frequency and press <+> <-> to set the
number.
Press <SET> button to choose flashes, and press <+> <-> to set the number.
Calculating the Shutter Speed
During the strobe flash, the shutter remains open until the firing stops.
Use the formula below to calculate the shutter speed and set it with the
camera.
Number of Flashes / Flash Frequency = Shutter Speed
For example, if the number of flashes is 10 and the firing frequency is 5 Hz,
the shutter speed should be at least 2 seconds.
To avoid overheating and deteriorating the flash head, do not use stroboscopic
flash more than 10 times in succession. After 10 times, allow the camera flash to
rest for at least 15 minutes. If you try to use the stroboscopic flash more than 10
times in succession, the firing might stop automatically to protect the flash head.
If this happens, allow at least 15 minutes' rest for the camera flash.

• Stroboscopic flash is most effective with a highly reflective subject against a dark
background.
• Using a tripod and a remote control is recommended.
• A flash output of 1/1 and 1/2 cannot be set for stroboscopic flash.
• Stroboscopic flash can be used with”buLb”.
• If the number of flashes is displayed as “--”, the firing will continue until the
shutter closes or the battery is exhausted. The number of flashes will be limited
as shown by the following table.
Maximum Stroboscopic Flashes
1/4
1/8
1/16
1/32
1/64
1/128
1
7
14
30
60
90
90
2
6
14
30
60
90
90
3
5
12
30
60
90
90
4
4
10
20
50
80
90
5
4
8
20
50
80
90
6-7
3
6
20
40
70
90
8-9
3
5
10
30
60
80
Flash
output
Hz 10
2
4
8
20
50
70
11
2
4
8
20
40
70
12-14
2
4
8
20
40
60
15-19
2
4
8
18
35
50
20-50
2
4
8
16
30
40
60-99
2
4
8
12
20
40
Group Setting / Channel Setting
GT-250 adopts GEEKOTO 2.4G wireless system, which has good compatibility
with other products of our lineup.
As a slave unit, GT-250 is automatically compatible with Canon / Nikon /
Sony / Fujifilm TTL system according to the master unit.
By using GEEKOTO C1(Commander) trigger you can use one or more
GT-250-TTL flashes simultaneously.
1.Setting Communication Group
Short press <GR/CH> wireless button to switch group in A / B / C / D.
Long press <GR/CH> wireless button till “CH 1” flashes on the AV panel. Then
press <+> <-> to switch channel from 1 to 16.
- 15 - - 16 -
2.Setting Communication Channel

When using the GT-250 and GEEKOTO C1(Commender) series trigger
together，the C1 can control the flash function such as:
• Flash Mode: TTL/M/Multi
• Sync Mode: First-curtain sync, second-curtain sync, and High-speed sync
• Control the power level •Modeling Lamp ON/OFF •Beeper ON/OFF
- 17 - - 18 -
Wireless Flash Shooting
Positioning and operation Range (Example of wireless flash shooting)
•Auto-flash shooting with one slave unit
• Use the supplied stand to position the slave unit.
• Before shooting, perform a test flash and test shot.
• The transmission distance might be shorter depending on the conditions such as
the positioning of slave units, the surrounding environment and weather conditions.
• In the event of wireless signal interference, if there’s a miss flash please change
the wireless communication channel.
Transmission distance is
about 50 meters.
Wireless Multiple Shooting
You can divide the slave units into two or three groups and perform TTL
auto-flash while changing the flash ratio (factor). In addition, you can set
and shoot with a different flash mode for each firing group, for up to 4
groups.
• Auto Shooting with Two Slave Groups •Auto Shooting with Three Slave Groups
A
B
A
B
C
Wireless Flash Shooting

- 19 - - 20 -
The following table lists the available and unavailable custom functions of this flash.
1.Long press <SET> button for 2
seconds to enter the C.Fn menu.
2.Choose custom function signs.
Press <+> <-> to set custom function
signs.
3.Change the setting.
Press <SET> button to choose
between customize functions
4.Exit C.Fn menu.
Long press <SET> button to exit.
C.Fn :Setting Custom Functions
Setting & Descriptions
OFF
No Operation
Auto Standby
Setting Signs
OF
30 min
60 min
Functions
Standby Modes
Custom
Function Signs
F1
ON
OFF
OFF
ON: Trigger 2 times
for 1 cycles,
1st flash of the trigger.
ON
OFF
OF
01
Beeper
Mask
F2
F3
Can be triggered as the
second curtain
OF, 0.01~30s
Delay Flash
F4
Version Information
F9
ON: Trigger 2 times
for 1 cycles,
2nd flash of the trigger.
02
Technical Data
Model
Wireless Slave Unit Mode
Flash Mode TTL/ M/Multi
GT-250
Radio transmission mode (compatible with Canon & Nikon & Sony & Fujifilm)
Slave radio transmission
Guide No. (1/1 Output) 60(m ISO 100)( Special 7-inch reflector)
POWER
Power Output
Stroboscopic Flash
Flash Compensation
Sync mode
Delay Flash
Mask
Beeper
Modeling Lamp (LED)
Optic Slave Flash
Flash Duration Indication
·Wireless Flash (2.4G transmission)
Wireless Flash Function
Controllable Slave Groups
Transmission Range (Approx.)
Channel
250W
8 steps: 1/128~1/1
Provides (up to 40 times, 199Hz)
±3 stops in 1/3 stop increments
High-speed sync (up to 1/8000 seconds), first-curtain sync, and second-curtain sync
0.01~30s
√
√
√
S1/S2
√
Slave unit, OFF
4 groups: A, B, C, D
50m
1~16
·Power Supply
Power Supply
Full Power Flashes
Recycle Time
Battery Indicator
Power Indication
·Sync Triggering Mode
·Color Temperature
·Dimensions
Volume
Net Weight
Lithium battery pack (14.4V/2900mAh)
420
Approx. 0.01-2.2s
√
Power standby automatically after approx. 30 minutes without operation.
2.5mm syncline, a wireless control port
5600±200k