My first question of the year!
When seeing through the viewfinder, it is always at the largest aperture setting permitted by the lens. So assuming I'm using 10-20 f4-5.6, I realise at 10mm F4, the view is equally bright as 20 F5.6. And the metering gives identical exposure settings.
So what does this mean?
I understand that the aperture circumference is focal length/f number. Am I right?
If I'm right, at 10 F4, aperture circumference is 2.5mm. While at 20 F5.6, aperture circumference is 3.5714mm. Given that it is bigger, why the viewfinder didn't go brighter, and the metering didnt give a faster shutter speed?
I heard, that it could be due to more light being lost within the lens barrel as I go from 10mm to 20mm, hence the viewfinder didnt appear brighter. Is this true?
Thanks in advance for clarifying my doubts!