Archived posting to the Leica Users Group, 2003/08/21
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I think you,d have to focus on the father because of the flat field as you say.But i,m not sure. simon - ----- Original Message ----- From: "Christer Almqvist" <chris@almqvist.net> To: <leica-users@mejac.palo-alto.ca.us> Sent: Thursday, August 21, 2003 12:43 PM Subject: [Leica] focusing (was zone f.) > (resending this message) > > OK, I know the answer to this question could be: 'go and do some > test shots', and also that the question may be slightly on the > theoretical side, but anyway, here we go: > > Imagine for a second that you want to make a picture of three people > standing on the other side of the street. The street is 4 meters > wide. One of the people, let us call him 'the father' stands directly > opposite you on the curb, four meters away from you because you also > stand on the curb. Also on the curb on the other side of the street > from you, but three meters to the left of the father is his son, and > similarly, three meters to his right is his daughter. Obviously the > children are five meters away from you. > > In this situation most people using an M will focus on the father > because he is so conveniently located right there where the little > yellow window is, that we use for focusing. Others will focus on the > father because they have heard something about flat film plane and > they take that to mean that everything at a 'picture plane' paralell > to the film plane will be at the maximum sharpness if the distance > set equals the the minimum distance from the film plan to the picture > plane (i.e. measuring at 90° from camera to picture plane). > > Now imagine you want to take a picture of just the children, but > with the children remaining in their original position. In this > situation, most people would focus on one of the children (and thus > set the distance to 5 meters) and then reframe the picture to include > both of them. With the flat film theory as I understand it, the > children would not appear as sharp on the negative as they would had > you not refocused, i.e. they would have appeared sharper on the > negative had you not changed the distance setting from 4 to 5 meters. > > Please tell me what is right and wrong in the above. Please do not > tell me that it does not matter because it will be covered by depth > of field, because I know that is not true, at least not for large > lens openings. > > Rgds > > > -- > Christer Almqvist > D 20255 Hamburg and / or > F 50590 Regnéville sur Mer > > please look at my NEW b+w pictures at: http://www.almqvist.net/chris/dozen/ > > old pictures still at: http://www.almqvist.net/chris/new > -- > To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html