Depending upon the atmospheric conditions I set the ISO high first thing in the morning. If the Sun is at the horizon, not quite up yet I set it at 1250, quite high for my liking. I set my camera on aperture priority mode, I choose the f-stop which I will set a bit high as well. I rarely begin above (higher number smaller aperture) f-8 the highest I can set the camera for minimal background noise.
The Green Heron was taken at noon when the Sun was directly overhead, ISO 640, f-6.3 with a shutter of 1/3200. Had I set the ISO lower to 320 I would have gotten more detail, I must admit I didn’t think of it at the time. The shutter speed would have been a bit slower perhaps, or it may have remained the same. The Sun was bright but it may have still caused the lower aperture to collect the same amount of light as if it were at 640 causing the shutter to stay open longer. That happens a lot during the early hours, when the ISO is at 800 when reduced to 500 many times the shutter speed remains the same. When It does I set the camera to the lower setting. That’s during the morning hours while the Sun is rising, at dusk when it is setting the ISO must be increased.
The Sparrow was taken late afternoon while the Sun was setting, it was during the Golden Hour. The camera settings had to be changed due to the dimming light, raising the ISO in the diminishing light is needed. In turn the shutter speed will slow down, the f stop remains at the lowest possible setting for the lens. In my case with the Tamron 100-400mm it is f-6.3.
I hope that all makes sense, but as usual it’s all about lighting.
Jacques Lebec Flutter Shutter