I was on a nightshoot capturing the Milky Way at the weekend with a colleague. He was using a Nikon D750 and I a Canon 5D MkIV. We were using similar settings but getting significantly different results with my colleagues photos quite a bit brighter. Here are the settings and the exposure details. Nikon D750, Lens Sigma 24mm f/1.4 set to infinity focus. Full Matrix and Spot Focusing. ISO 1600 with a 15-20 second exposure. Auto White Balance Canon 5DMKIV, Canon 16-35mm f/2.8 set to infinity. Spot focus and single spot. Iso 1600 and 30 second exposure. Auto White Balance and also a dally with Tungsten with similarly brightness results. I was assuming the f/1.4 versus the f/2.8 would cancel out with the double exposure but maybe it is not a linear curve. Can anyone shed any light? Many thanks
To keep it simple, the math is wrong 2.8 to 1.4 is two stops brighter so a 15 second would be quadrupled 15 to 30 is one stop 30 to a min is another stop. (2.0 is the full stop in between) And second, regarding your question about linear, it is linear for digital, not for film. If you use film there is a heavy reciprocity failure on long exposures so a calculated 1 min exposure on film may take a few minutes depending on which film you would use. That being said digital can create a lot of ugly noise & hot pixels, .. wiith long exposures as the sensor gets quite hot.
Thanks Jonesy. I guessed that was the case. We went on a thunderstorm shoot last night using the same equipment but spent hours trying to establish the differences but concluded that the f/1.4 to f/2.8 was the main factor. As you could see from the equipment we were using digital not film so it is linear.
I will do another comparison as I have a 50mm f/1.4 lens so we are both shooting with the same aperture and see what results we get.