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Camera FOV vs Focal Length

Camera FOV vs Focal Length

2005-05-09       - By Marc Bourbonnais

 Back
Reply:     1     2     3     4     5  

Well, it would depend on the final scan & crop of the images you're working
with. Usually you can see it with the aspect ratio. 1.33, 1.31, 1.37, 1.85...
Some of the default values in the drop-down camera list from XSI are a bit
misleading and slightly off in my opinion.

Usually in film, the largest full gate you can get is from a 0.98" x 0.745"
filmback window. Even this is usually cropped to 0.98" x 0.735" to get the
ancient 1.33 ratio. That's the Full Aperture in 35mm film. The other typical
formats are all crops inside that window.

Other classic values you might be working with are Academy aperture (0.864" x 0
.630", 1.37 ratio) or 1.85 framing (0.825" x 0.446", 1.85 ratio)

To be uber-picky, these last two framings should have a horizontal optical
shift, because of the sound stripe on the side of the film. Most of the time I
don't really bother with it.

Fun stuff, huh?

--
Marc Bourbonnais
3D TD
Hybride
(450)227-4245
 -- -- Original Message -- --
 From: Andre DeAngelis
 To: XSI@(protected)
 Sent: Monday, May 09, 2005 12:50 PM
 Subject: RE: Camera FOV vs Focal Length


 Thanks a lot for that Marc,

 

 So for 35 mm camera the 3 values are properly set up then?

 

 Andre

 


-- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- -----

 From: owner-xsi@(protected) [mailto:owner-xsi@(protected)] On Behalf Of
Marc Bourbonnais
 Sent: Monday, May 09, 2005 11:51 AM
 To: XSI@(protected)
 Subject: Re: Camera FOV vs Focal Length

 

 The relation between FoV, lens and aperture is correct in XSI. It's the same
trig relation between the 3 values.

 

 The problem is the incorrect default aperture sizes for the HD cams, so I can
assume you are working with these types of plates.

 

 The correct aperure size for high-end HD cams is 9.6mm x 5.4mm, roughly 0
.37795" x 0.2126". Not the default XSI values.

 

 The magic trig relation is :

 

 f = (0.5*Ap) / tan(0.5*FoV)

 

 where

 

 f = lens

 Ap = aperture

 FoV = Field of view angle

 

 of course keep track of mm vs. inches, and horizontal vs. vertical.

 

 --
 Marc Bourbonnais
 3D TD
 Hybride
 (450)227-4245

   -- -- Original Message -- --

   From: Andre DeAngelis

   To: XSI@(protected)

   Sent: Monday, May 09, 2005 10:58 AM

   Subject: Camera FOV vs Focal Length

   

   Hello All,

   

   Can anyone point me in the direction of a reference that explains the
formula for the relation between FOV, Focal Length and Film Aperture used by
XSI's camera?

   

   The presets in XSI's camera don't seem to correlate to what the table the
director has given us and I want to put a script/plug-in to reproduce the table
he has provided.

   

   AD

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<DIV><FONT face=Arial size=2>Well, it would depend on the final scan &amp; crop
of the images you're working with. Usually you can see it with the aspect ratio
.
</FONT><FONT face=Arial size=2>1.33, 1.31, 1.37, 1.85... Some of the default
values in the drop-down camera list from XSI are a bit misleading and slightly
off&nbsp;in my opinion.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV>
<DIV><FONT face=Arial size=2>Usually in film, the largest full&nbsp;gate you
can
get is from a 0.98" x 0.745"&nbsp;filmback window. Even&nbsp;this is usually
cropped to 0.98" x 0.735" to get the ancient 1.33 ratio. That's the Full
Aperture in 35mm film. </FONT><FONT face=Arial size=2>The other typical formats
are all crops inside that window.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV>
<DIV><FONT face=Arial size=2>Other classic values you might be working with are
Academy aperture (0.864" x 0.630", 1.37 ratio) or 1.85 framing (0.825" x 0.446"
,
1.85 ratio)</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV>
<DIV><FONT face=Arial size=2>To be uber-picky, these last two
framings&nbsp;should have&nbsp;a horizontal optical shift, because of the sound
stripe on the side of the film. Most of the time I don't really bother with
it.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV>
<DIV><FONT face=Arial size=2>Fun stuff, huh?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV>
<DIV>--<BR>Marc Bourbonnais<BR>3D TD<BR>Hybride<BR>(450)227-4245</DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT:
#000000 2px solid; MARGIN-RIGHT: 0px">
 <DIV style="FONT: 10pt arial">-- -- Original Message -- -- </DIV>
 <DIV
 style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
 <A title=andre.deangelis@(protected)
 href="mailto:andre.deangelis@(protected)">Andre DeAngelis</A> </DIV>
 <DIV style="FONT: 10pt arial"><B>To:</B> <A title=XSI@(protected)
 href="mailto:XSI@(protected)">XSI@(protected)</A> </DIV>
 <DIV style="FONT: 10pt arial"><B>Sent:</B> Monday, May 09, 2005 12:50 PM</DIV>
 <DIV style="FONT: 10pt arial"><B>Subject:</B> RE: Camera FOV vs Focal
 Length</DIV>
 <DIV><BR></DIV>
 <DIV class=Section1>
 <P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN lang=EN-US
 style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Thanks a lot for
that
 Marc,<o:p></o:p></SPAN></FONT></P>
 <P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN lang=EN-US
 style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p>&nbsp;</o:p><
/SPAN></FONT></P>
 <P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN lang=EN-US
 style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">So for 35 mm camera
 the 3 values are properly set up then?<o:p></o:p></SPAN></FONT></P>
 <P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN lang=EN-US
 style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p>&nbsp;</o:p><
/SPAN></FONT></P>
 <P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN lang=EN-US
 style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Andre<o:p></o:p><
/SPAN></FONT></P>
 <P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN lang=EN-US
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 </SPAN></FONT></DIV>
 <P class=MsoNormal><B><FONT face=Tahoma size=2><SPAN lang=EN-US
 style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Tahoma">From:</SPAN><
/FONT></B><FONT
 face=Tahoma size=2><SPAN lang=EN-US
 style="FONT-SIZE: 10pt; FONT-FAMILY: Tahoma"> <A
 href="mailto:owner-xsi@(protected)">owner-xsi@(protected)</A>
 [mailto:owner-xsi@(protected)] <B><SPAN style="FONT-WEIGHT: bold">On Behalf
 Of </SPAN></B>Marc Bourbonnais<BR><B><SPAN
 style="FONT-WEIGHT: bold">Sent:</SPAN></B> Monday, May 09, 2005 11:51
 AM<BR><B><SPAN style="FONT-WEIGHT: bold">To:</SPAN></B> <st1:PersonName
 w:st="on"><A
 href="mailto:XSI@(protected)">XSI@(protected)</A></st1:PersonName><BR><B>
<SPAN
 style="FONT-WEIGHT: bold">Subject:</SPAN></B> Re: Camera FOV vs Focal
 Length</SPAN></FONT><SPAN lang=EN-US><o:p></o:p></SPAN></P></DIV>
 <P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
 style="FONT-SIZE: 12pt"><o:p>&nbsp;</o:p></SPAN></FONT></P>
 <DIV>
 <P class=MsoNormal><FONT face=Arial size=2><SPAN
 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">The relation between FoV, lens
and
 aperture is correct in XSI. It's the same trig relation between the 3
 values.</SPAN></FONT><o:p></o:p></P></DIV>
 <DIV>
 <P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
 style="FONT-SIZE: 12pt">&nbsp;<o:p></o:p></SPAN></FONT></P></DIV>
 <DIV>
 <P class=MsoNormal><FONT face=Arial size=2><SPAN
 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">The problem is the incorrect
 default aperture sizes for the HD cams, so I can assume you are working with
 these types of plates.</SPAN></FONT><o:p></o:p></P></DIV>
 <DIV>
 <P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
 style="FONT-SIZE: 12pt">&nbsp;<o:p></o:p></SPAN></FONT></P></DIV>
 <DIV>
 <P class=MsoNormal><FONT face=Arial size=2><SPAN
 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">The correct aperure size for
 high-end HD cams is 9.6mm x 5.4mm, roughly 0.37795" x 0.2126". Not the
default
 XSI values.</SPAN></FONT><o:p></o:p></P></DIV>
 <DIV>
 <P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
 style="FONT-SIZE: 12pt">&nbsp;<o:p></o:p></SPAN></FONT></P></DIV>
 <DIV>
 <P class=MsoNormal><FONT face=Arial size=2><SPAN
 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">The magic trig relation is
 :</SPAN></FONT><o:p></o:p></P></DIV>
 <DIV>
 <P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
 style="FONT-SIZE: 12pt">&nbsp;<o:p></o:p></SPAN></FONT></P></DIV>
 <DIV>
 <P class=MsoNormal><FONT face=Arial size=2><SPAN
 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">f = (0.5*Ap) /
 tan(0.5*FoV)</SPAN></FONT><o:p></o:p></P></DIV>
 <DIV>
 <P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
 style="FONT-SIZE: 12pt">&nbsp;<o:p></o:p></SPAN></FONT></P></DIV>
 <DIV>
 <P class=MsoNormal><FONT face=Arial size=2><SPAN
 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">where
 </SPAN></FONT><o:p></o:p></P></DIV>
 <DIV>
 <P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
 style="FONT-SIZE: 12pt">&nbsp;<o:p></o:p></SPAN></FONT></P></DIV>
 <DIV>
 <P class=MsoNormal><FONT face=Arial size=2><SPAN
 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">f =
 lens</SPAN></FONT><o:p></o:p></P></DIV>
 <DIV>
 <P class=MsoNormal><FONT face=Arial size=2><SPAN
 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Ap =
 aperture</SPAN></FONT><o:p></o:p></P></DIV>
 <DIV>
 <P class=MsoNormal><FONT face=Arial size=2><SPAN
 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">FoV = Field of view
 angle</SPAN></FONT><o:p></o:p></P></DIV>
 <DIV>
 <P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
 style="FONT-SIZE: 12pt">&nbsp;<o:p></o:p></SPAN></FONT></P></DIV>
 <DIV>
 <P class=MsoNormal><FONT face=Arial size=2><SPAN
 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">of course keep track of mm vs.
 inches, and horizontal vs. vertical.</SPAN></FONT><o:p></o:p></P></DIV>
 <DIV>
 <P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
 style="FONT-SIZE: 12pt">&nbsp;<o:p></o:p></SPAN></FONT></P></DIV>
 <DIV>
 <P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
 style="FONT-SIZE: 12pt">--<BR>Marc Bourbonnais<BR>3D
 TD<BR>Hybride<BR>(450)227-4245<o:p></o:p></SPAN></FONT></P></DIV>
 <BLOCKQUOTE
 style="BORDER-RIGHT: medium none; PADDING-RIGHT: 0cm; BORDER-TOP: medium none
; PADDING-LEFT: 4pt; PADDING-BOTTOM: 0cm; MARGIN: 5pt 0cm 5pt 3.75pt; BORDER
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   <DIV>
   <P class=MsoNormal><FONT face=Arial size=2><SPAN
   style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">-- -- Original Message -- --
   <o:p></o:p></SPAN></FONT></P></DIV>
   <DIV style="font-color: black">
   <P class=MsoNormal style="BACKGROUND: #e4e4e4"><B><FONT face=Arial
   size=2><SPAN
   style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Arial">From:</SPAN>
</FONT></B><FONT
   face=Arial size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"> <A
   title=andre.deangelis@(protected)
   href="mailto:andre.deangelis@(protected)">Andre DeAngelis</A>
   <o:p></o:p></SPAN></FONT></P></DIV>
   <DIV>
   <P class=MsoNormal><B><FONT face=Arial size=2><SPAN
   style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Arial">To:</SPAN><
/FONT></B><FONT
   face=Arial size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"> <A
   title=XSI@(protected)
   href="mailto:XSI@(protected)">XSI@(protected)</A>
   <o:p></o:p></SPAN></FONT></P></DIV>
   <DIV>
   <P class=MsoNormal><B><FONT face=Arial size=2><SPAN
   style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Arial">Sent:</SPAN>
</FONT></B><FONT
   face=Arial size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"> Monday
,
   May 09, 2005 10:58 AM<o:p></o:p></SPAN></FONT></P></DIV>
   <DIV>
   <P class=MsoNormal><B><FONT face=Arial size=2><SPAN
   style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Arial">Subject:<
/SPAN></FONT></B><FONT
   face=Arial size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"> Camera
   FOV vs Focal Length<o:p></o:p></SPAN></FONT></P></DIV>
   <DIV>
   <P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
   style="FONT-SIZE: 12pt"><o:p>&nbsp;</o:p></SPAN></FONT></P></DIV>
   <P class=MsoNormal><FONT face=Arial size=2><SPAN lang=EN-CA
   style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Hello
   All,<o:p></o:p></SPAN></FONT></P>
   <P class=MsoNormal><FONT face=Arial size=2><SPAN lang=EN-CA
   style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><o:p>&nbsp;</o:p></SPAN></FONT>
</P>
   <P class=MsoNormal><FONT face=Arial size=2><SPAN lang=EN-CA
   style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Can anyone point me in the
   direction of a reference that explains the formula for the relation between
   FOV, Focal Length and Film Aperture used by XSI’s
   camera?<o:p></o:p></SPAN></FONT></P>
   <P class=MsoNormal><FONT face=Arial size=2><SPAN lang=EN-CA
   style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><o:p>&nbsp;</o:p></SPAN></FONT>
</P>
   <P class=MsoNormal><FONT face=Arial size=2><SPAN lang=EN-CA
   style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">The presets in XSI’s camera
   don’t seem to correlate to what the table the director has given us and I
   want to put a script/plug-in to reproduce the table he has
   provided.<o:p></o:p></SPAN></FONT></P>
   <P class=MsoNormal><FONT face=Arial size=2><SPAN lang=EN-CA
   style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><o:p>&nbsp;</o:p></SPAN></FONT>
</P>
   <P class=MsoNormal><FONT face=Arial size=2><SPAN lang=EN-CA
   style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">AD<o:p></o:p></SPAN></FONT></P>
</BLOCKQUOTE></DIV></BLOCKQUOTE></BODY></HTML>