Deconstructing sensor dynamics, optical reach and flight tracking geometry on the Canon EOS R7 and Sigma 150-600mm f/5-6.3 Contemporary.
Follow the light from the front element to the sensor plane. Select a stop on the schematic to see what it changes.
The R7 sensor is smaller than full frame, so it records the centre of the projected image only. Multiply the focal length by 1.6 and 600mm frames like 960mm would on full frame, while 150mm behaves like 240mm. Pack 32.5 megapixels into that area and each pixel is about 3.2 microns wide, which is why high altitude traffic still crops well and why sloppy shutter speeds show up immediately.
Three settings, one budget of light. Aviation work spends it differently to almost every other kind of photography.
Working order on the spot: choose the shutter speed the aircraft type demands, set f/8 unless the light is gone, then let ISO make up the difference.
Where the aircraft is, how fast it crosses your view, and how much air you are shooting through decide the frame before the camera does.
What your arms have to match is angular speed, not ground speed. A jet at 250 knots crossing 400m away sweeps past far faster than the same jet at 3km, so the closer pass needs a faster pan and a faster shutter. Track the aircraft through the viewfinder before you press the shutter and keep panning after it, so the whole burst sits on the same arc.
Hot exhaust and sun baked tarmac bend light unevenly, and at 960mm equivalent you are magnifying that turbulence as much as the aircraft. Nothing in editing fixes it. Shoot early or late, shoot across grass rather than down a runway, and shoot high angles that keep the line of sight out of the hottest air.
Perceived size scales with focal length divided by distance. Slant range is altitude divided by the sine of the elevation angle, so an aircraft 900m up passing at 30 degrees is about 1.8km away along your line of sight. At 600mm on APS-C that fills roughly a fifth of the frame width, which is your cue to either wait for a lower pass or accept a crop.
Overhead departures are close and fast: high shutter, wide pan. Distant approaches are slow and hazy: hold f/8, keep ISO down and pick the cleanest column of air you can find.
Figures on this page are working guides from real sessions, not fixed rules. Light, altitude and air quality change everything.
