Saturday, 29 September 2018

perspective - What is the image size of the Sun / Moon in the frame with a given focal length?


I'm interested in taking a picture of the Sun / Moon using a telephoto lens. For example like this.


It would be very helpful for me to know what the approximate image size of the sun / moon would look like at xxx mm in FF / Crop sensor.



Is there a formula or a similar image that can give me an idea of it?



Answer



The size of the sun or moon in mm in the sensor plane will be approximately


f / 110

where f is your focal length. A typical APS-C sensor is 16mm tall (or 15mm for Canon), hence a 1760mm lens would be required to fill the frame (vertically). 800mm would get you about half the frame, 400mm one quarter etc.


A "full frame" sensor is 24mm tall, so you'd need 2640mm to fill the frame, better get stacking those TCs!


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