I purchased the Arsenal AI 2 (Pro) some time ago and must admit I have not used it quite as often as I thought I would, part of that is because I don't always get to travel and also having a young family makes it hard to get as much time as I would like for photography.

For those who are not aware, Arsenal AI 2 is the second generation of smart camera trigger that interfaces with your camera and uses AI to set the camera settings (aperture, shutter speed, ISO) to get the best photo out of the environment that the smart trigger identifies (i.e., water has a slower shutter speed for get blurring compared to say an action shot).

The benefit of this trigger is that it understands the scene (based on machine learning) and tries to optimize the camera settings to let you focus on the composition of the photo rather than the technical aspects, the camera trigger can also use a machine learning algorithm to bring the best colors out of the scene.

With that in mind, lets discuss Long Exposures. I had to travel for work recently and knew I would be returning past a waterfall so thought this would be the perfect opportunity to make a quick stop and try out the long exposure stacking feature of the Arsenal AI 2.

Long exposures are when the shutter speed is left open for a (somewhat) lengthy period of time to capture the static elements of the scene, it is often used at night but can also be used with water photography. During the day a camera would usually meter and to get the right exposure the shutter speed would be fast (somewhere between 1/20 – 1/2000 second) however, this is clearly not long exposure. To get around this, and to have a longer exposure, photographers will usually put a neutral density (ND) filter on the front of their lens which reduces the amount of light coming to the sensor, as a result the camera will expose for longer and you will get a long exposure image.

Long exposure images are commonly used with water as it leads to the silky appearance of the water, a fast shutter speed leads to capturing all the detail of the image and ‘freezing' the motion of the water whereas longer shutter speeds mean the motion is not frozen and the water ends up silky.

There are a range of reasons you may not want to use a ND filter, the most simple is you don't have one on you (which was the case), but you may also not want to wait for a longer period of time to capture one image, or possibly your lens does not have a filter thread as well and you cant attach a ND filter to the lens.

In this case, Arsenal AI 2 presents a different approach. Rather than taking one image for say 1 minute, why not take lots of individual photos at a fast shutter speed, and use stacking to combine all of these images so that it in effect simulates the longer exposure, leading to a silky water flow, without needing to have a 1 minute exposure time.

Whilst I cant recall the settings exactly, I told arsenal to take an exposure that simulated about 1 minute, this was with an aperture of around f/11, the shutter speed was about 1/30 seconds, and from memory the ISO was fairly low, the image was taken with a Sony A7R 4 and a Tamron 28-75mm f/2.8 . The image below is the image that was produced, where the left hand side is the fast shutter speed image, and the right hand side is the image where the long exposure was simulated (effectively multiple stacked images). You can click on the middle of the line and drag left and right to see more of the fast shutter speed, or simulated slow shutter speed image.

Image 1: Comparison between Fast Shutter Speed (Left) and Simulated Slow Shutter Speed (Right).

As you can see it looks like it does a fairly good job of the longer exposure, I am sure if I extended the time it likely would have looked much better, as would post processing these images but I really wanted to show the effect more than my post processing skills specifically. If you are interested in the Arsenal AI 2 (I used the PRO Version), you can find out more here.
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