The Triggertrap Mobile, including the associated dongle and cable, together form a remote control to operate your SLR camera using a smartphone ( iOS or Android). Triggertrap supports more than 300 camera models and the App has more features over other smartphone camera remote control. Normally, when you do long exposures without any remote, your camera is limited to 30 secs. Some other brands have a limit of 1 minute. For Long Exposure HDR, you often need more then 30 secs to capture all your brackets. For example: When your basic exposure is 20 secs, your +2 exposure will be 80 secs. To get this exposure, you can put your camera in bulb mode and keep track of the exposure with a stopwatch. Most people will use the stopwatch on their smartphone to do this.

Wait a minute…’re taking a picture and holding your smartphone to make sure you have the correct exposure time. Wouldn’t it be great to have the phone control the camera and stop the exposure at the correct time? This is exactly what Triggertrap does.


Below you can see a set of brackets taken with Triggertrap in LE HDR mode. The 3rd image is my middle exposure. The Triggertrap app asks for your middle exposure time to calculate the other exposure times, depending on the amount of brackets you want and with the exposure steps you have set in the app.


To get the right exposure you need to check your camera’s histogram. When using the histogram, you can check that you have captured all tonal values. Normally when you do night photography, the in build camera lightmeter doesn’t work well. It will calculate a faster shutter speed, resulting in a slightly under exposed photo.

Correct your shutter speed

When you use Triggertrap LE HDR, your camera should be in bulb mode and in manual focus, but before we set the camera in bulb, we need to find out the correct shutter speed (Exposure time). For this we keep the camera in M-mode and check the light meter on the LCD or in the ocular. Make sure you don’t use spot metering, but instead, set your camera to matrix metering. 

Turn your dial for the shutter speed so that the light meter reads “0”. We know already that this will give us a under exposed photo, so we keep turning the dial until we are 2/3 or 1 stop over exposed. This works great when the shutter speed is 15 secs or less. Let’s say we have a shutter speed of 20 secs and the light meter is in the middle. We need to over expose 1 stop to get all the tonal values inside the histogram. Turning the dial won’t help because it stops at 30 secs. Now we need to do a little math to find our base exposure.

For every stop we need to over expose, we need to double the exposure time. So, 20 secs will become 20 x 2 = 40 secs. To under expose 1 stop, we need to divide the exposure time by 2.

Next step is to set the camera in bulb mode, turn on the live view and start focusing. Remember that when you use Triggertrap, that the camera needs to be in manual focus. By using Live View focusing, we can get sharp images when the autofocus fails to focus due to low light conditions. Now that we are focused and the composition is set, we are ready to dial in the values in the Triggertrap app.

For this example the values are as follows:

  1. Dial in the middle exposure – (40 secs)
  2. Set your number of exposures – (5)
  3. Set your prefered EV step – (1)

This will result in 5 bracketed exposures:
10, 20, 40, 80 and 160 secs.

When your shutter speeds are getting to long, you can always increase your ISO. Keep in mind that the fastest shutter speed, when using Triggertrap in bulb mode, is 1/16 sec.

zaanse schans

The final edited photo

If you don’t have Triggertrap yet, you can find out if your camera is supported by using the cable selector here.

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