Archived posting to the Leica Users Group, 1999/11/30
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]This is a multi-part message in MIME format. - ------=_NextPart_000_0013_01BF3B55.CD5F5860 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sorry, Elisardo, Jim is right! Depth of field is constant with a given magnification and aperture. = Only to the extent that changing focal length changes magnification does = DOF change. Likewise, changing distance only changes DOF to the estent = that magnification changes. Intuitively, with a longer focal length, = you are that much further away for the same magnification, so DOF = remains the same. Just to confuse you one step further, this is why MF = or LF are said to have less DOF than 35mm -- they have a larger image = size on the negative, so magnification is higher. Thus, if you are using a 60mm, 100mm or 200mm macro set to 1:2, all will = have the same DOF -- only the back ground changes due to the angle of = view -- you are much closer with the shorter focal lengths, but DOF = remains the same. If the same 2" tall subject takes up 1" on a 35mm = frame and 1" on a 6x6 frame, both will have the same DOF -- = magnification is the same; however, if the 2" subject occupies 2" image = height on the 6x6 filing the frame, there is less DOF because now = magnification has increase to 1:1. I believe this is in AA's The Camera -- I will look up the reference = when I get home. Tom Schofield ----- Original Message -----=20 From: elisardo louzan=20 To: leica-users-digest@mejac.palo-alto.ca.us=20 Sent: Wednesday, December 01, 1999 3:07 AM Subject: [Leica] RE: 75mm f1.4 DOF Jim, =20 Sorry, you are wrong! DOF is affected by the focal length of the lens = you use. =20 "Everything you know is wrong" by CTEIN PhotoPro September/October 1994 pp50-51 - ------=_NextPart_000_0013_01BF3B55.CD5F5860 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META content=3Dtext/html;charset=3Diso-8859-1 = http-equiv=3DContent-Type> <META content=3D"MSHTML 5.00.2722.1300" name=3DGENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=3D#b8b8b8> <DIV><FONT face=3DArial size=3D2>Sorry, Elisardo, Jim is = right!</FONT></DIV> <DIV> </DIV> <DIV><FONT face=3DArial size=3D2>Depth of field is constant with a given = magnification and aperture. Only to the extent that changing focal = length=20 changes magnification does DOF change. Likewise, changing distance = only=20 changes DOF to the estent that magnification changes. Intuitively, = with a=20 longer focal length, you are that much further away for the same = magnification,=20 so DOF remains the same. Just to confuse you one step further, = this is why=20 MF or LF are said to have less DOF than 35mm -- they have a larger image = size on=20 the negative, so magnification is higher.</FONT></DIV> <DIV><FONT face=3DArial size=3D2></FONT> </DIV> <DIV><FONT face=3DArial size=3D2>Thus, if you are using a 60mm, 100mm or = 200mm macro=20 set to 1:2, all will have the same DOF -- only the back ground changes = due to=20 the angle of view -- you are much closer with the shorter focal lengths, = but DOF=20 remains the same. If the same 2" tall subject takes up 1" on a = 35mm frame=20 and 1" on a 6x6 frame, both will have the same DOF -- magnification is = the same;=20 however, if the 2" subject occupies 2" image height on the 6x6 filing = the frame,=20 there is less DOF because now magnification has increase to = 1:1.</FONT></DIV> <DIV> </DIV> <DIV><FONT face=3DArial size=3D2> I believe this is in = AA's The=20 Camera -- I will look up the reference when I get home.</FONT></DIV> <DIV> </DIV> <DIV><FONT face=3DArial size=3D2>Tom Schofield</FONT></DIV> <BLOCKQUOTE=20 style=3D"BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: = 0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px"> <DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV> <DIV=20 style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: = black"><B>From:</B>=20 <A href=3D"mailto:louzan@worldnet.att.net"=20 title=3Dlouzan@worldnet.att.net>elisardo louzan</A> </DIV> <DIV style=3D"FONT: 10pt arial"><B>To:</B> <A=20 href=3D"mailto:leica-users-digest@mejac.palo-alto.ca.us"=20 = title=3Dleica-users-digest@mejac.palo-alto.ca.us>leica-users-digest@mejac= .palo-alto.ca.us</A>=20 </DIV> <DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Wednesday, December 01, = 1999 3:07=20 AM</DIV> <DIV style=3D"FONT: 10pt arial"><B>Subject:</B> [Leica] RE: 75mm f1.4 = DOF</DIV> <DIV><BR></DIV> <DIV><FONT color=3D#000000 size=3D2>Jim,</FONT></DIV> <DIV><FONT color=3D#000000 size=3D2></FONT> </DIV> <DIV><FONT color=3D#000000 size=3D2>Sorry, you are wrong! DOF is = affected by=20 the focal length of the lens you use.</FONT></DIV> <DIV><FONT color=3D#000000 size=3D2></FONT> </DIV> <DIV><FONT color=3D#000000 size=3D2>"Everything you know is wrong" by=20 CTEIN</FONT></DIV> <DIV><FONT color=3D#000000 size=3D2>PhotoPro September/October 1994=20 pp50-51</FONT></DIV></BLOCKQUOTE></BODY></HTML> - ------=_NextPart_000_0013_01BF3B55.CD5F5860--