Multi-day time lapse of a solar installation - The camera

This a continuation of my last blog post illustrating my set up and process for a multi-day time lapse of a solar installation. In my first post, I went over the math to calculate how many shots were needed and what the interval duration of those shots needed to be. Today, I'll describe the camera set up that was used and why used what I used.

The Camera
My first thought when choosing a camera was a GoPro camera. It is small, lightweight, waterproof and wide angle. After researching it, I discovered that the Go Pro cameras only allow for a maximum interval duration of 1 second. This project needed between 30 seconds - 2 minutes depending on the full duration of the project. Unfortunately, the Go Pro was out.

Another consideration was power supply for the camera. If it needed to be on for multiple days battery life could be an issue. I didn't want the battery to die and not know it, thus stop capturing images. My Canon 1Ds MKII has an AC adapter that allows it to be plugged in. I'm sure AC adapters are available for a lot of cameras, but I already had one available for my 1Ds so that was a big decider for camera choice. With the AC adapter, the camera could be plugged in and run perpetually for as long it had capacity to record images.

The array was to be about 150'x50', so a wide angle was needed. Originally, I chose a 24mm but changed it to 20mm at the last minute. I didn't know exactly how big the array would be and where the exact positioning of the panels would be, so I played it safe with a wider lens. The resolution of the camera totally allowed for some cropping if the image is too wide.

I'm using a knock off Chinese made intervalometer to control the time lapse. It cost me $20 on E-bay and still works pretty good. Sorry Canon, this is one where I just couldn't justify the $150 price tag for your product.

The weather is predicted to be bright and sunny. Now it's time to go back in time and remember those cool little exposure guides on the inside of Kodak film boxes. It told you that in order to expose the 100 ISO film properly on a bright and sunny day, the exposure needed to be set at 1/125 sec at f/16. Based on my intervalmeter's limitations, the fastest shutter speed I can use is 1 second. 1 second is 7 stops brighter than 1/125 sec. For a 1 second shutter speed, that would require an aperture of f/180. Most lenses have a minimum aperture of f/22 or f/32 so it is necessary to cut down the amount of light entering the lens.

This requires a neutral density filter. which is a neutral grey filter that simply cuts down the amount of light entering the camera. For this project, I used an ND 8 which cuts the light by approx 3 stops. I also stacked a polarizing filter on top of the ND to further reduce the light by 1 1/2 stops. The polarizing filter also enhanced the saturation of the colors and reduced the glare on the reflective solar panels.

The the final exposure will be f/22 at 1/2 sec. Even this will be a little over exposed but the RAW files can be pulled down in Lightroom to achieve a good exposure.

My next post will describe the housing that protects the camera from the elements while it sits on the roof for a few days.