Halv­ing and dou­bling

One clic k here, on e clic k th ere

NPhoto - - Nikopedia -

■ The stan­dard scales for both aper­ture (stops) and shut­ter speed (sec­onds or frac­tions of a sec­ond) are or­gan­ised the way they are so that each step or click in ei­ther case re­duces or in­creases the amount of light by the same amount. So, in­creas­ing the shut­ter speed by a sin­gle click will let in less light, so you have to open the aper­ture by a sin­gle click to let in enough light to com­pen­sate for this. This ap­proach makes it easy to keep the same ex­po­sure while chang­ing the mo­tion-freez­ing ca­pa­bil­ity of the cam­era and the depth of field (be­low). I wanted some wa­ter streak­ing for soft­ness in this shot, but was not cer­tain ex­actly how much, and how much depth of field around the vase was nec­es­sary. In man­ual mode, and with the cam­era on a tri­pod, I tried it at three dif­fer­ent shut­ter speeds,

each time halv­ing the ex­po­sure time, which also meant I had to dou­ble the aper­ture to com­pen­sate.

2 secs at f/32, iso100

1 sec at f/22, iso100

0.5 sec at f/16, iso100

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