Friday, September 7, 2018

Sora in low light

This past weekend I wanted to get in a full morning of birding and photography. So I timed my arrival at the Dairy Mart Ponds for sunrise: 6:15am. I was kind of hoping for the first lovely golden rays of dawn's light.

 As often happens in San Diego, though, a marine layer forms at night and overcast skies are frequent into late morning. So "sunrise" in the Tijuana River Valley this morning was a very gloomy dark gray.

Well, okay, I've also been watching YouTube videos extolling the virtues of the even light produced by overcast skies or fog. At least there shouldn't be any harsh shadows. And newer cameras can shoot at high ISO without too much graininess. If I take lots of shots , a couple of them might have acceptable sharpness, even at slower shutter speeds--especially with my image stabilized lens.

There was a cooperative Sora out in the open on a pond. Unfortunately, the little trail gave me only one view through the foliage. The bird was 20 feet away and below me about 10 feet. I had to stand up and shoot down at the bird below me. So these aren't artistic shots. They only show the exposure possible with my bird photography gear: Canon EOS 7D Mark II camera with Canon EF 100-400mm f/4.5-5.6L IS USM lens.

I attempted several photos early, 6:38 am. Only the one below turned out acceptably. I've been doing a lot of Manual Mode photography. But in this low light I didn't want try to guess the difficult exposure in Manual mode with the Evaluative exposure metering mode and dialing in a couple of stops of Exposure Compensation. Instead I chose Aperture Priority and Spot Metering and let the camera do all the hard exposure work as the bird moved from dark background to backlit.

6:38am, heavy overcast: 1/60 sec, f/5.6, 400mm, ISO 4000
I set ISO to 4000. The camera can go higher. But anything more than 2000 produces notable grain--especially in darker areas. The sweet spot on my zoom lens at 400mm is f/7.1. But I set it down 2/3 of a stop to f/5.6, which is wide open at 400mm. That does three things. It lets in more light (good), gives a very shallow depth of field (bad for focusing on a bird more than an inch or two in depth-front to back of focal plane [tail is too far away and out of focus]), and isn't the sharpest lens setting (bad). With me choosing ISO and aperture, I let the camera choose the shutter speed, to make the exposure correct.

At only 1/60 of a second, the above photo suffers a bit of blurriness from camera shake and bird movement. It's not very sharp, but it's the best that could be done with the available light. Handheld at 400mm I should be shooting at least 1/800 of a second or faster, but the image stabilization on the lens helps greatly. Still, I shouldn't shoot that long lens handheld at less than 1/250. I don't use a tripod so it is unlikely I can take those "blue light" bird photos before sunrise or after sunset unless I really change my birding/photography technique and habit.

It was an hour later when I went back and got additional photos with the bird still out in the open!

Heavy overcast, 7:42am: 1/320 sec, f/5.6, 400mm, ISO 2000.
So, the light came up enough I could set the ISO to 2000. I left the aperture at f/5.6. The shutter speed came up to 1/320 of a second. That is sufficient for stationary birds only.

Sora. Tijuana River Valley, San Ysidro, California. September 2, 2018.
Later in the morning I was able to photograph some other birds under bright overcast skies. I'll share those in future posts.

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