document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=970283>Question 970283</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The exposure volume EV of a photograph can be calculated from the time, t, in seconds that the shutter was open and the value of the f-stop,f, the picture was taken at using by using the logarithmic equation:\r<BR>\n" );
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document.write( "EV=logbase2(f^2/t)\r<BR>\n" );
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document.write( "use the properties of logarithms to expand the formula for EV:<BR>\n" );
document.write( "For this part I did: 2 Logbase2 f - logbase2 t\r<BR>\n" );
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document.write( "b. Keith takes a picture of a waterfall with a shutter speed of 1/60 second at f/5.657. he likes the exposure of his picture, but want to leave the shutter open four times as long to better capture the motion of the water. What f-stop should he use on his next picture.\r<BR>\n" );
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document.write( "This is where I am having some trouble. I started by doing 4(1/60)=1/15 and that is my t. I know I am solving for f, but is 5.657 my EV?  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #592938 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=592938\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The exposure volume EV of a photograph can be calculated from the time, t, in seconds that the shutter was open and the value of the f-stop,f, the picture was taken at using by using the logarithmic equation: <BR>\n" );
document.write( "EV=logbase2(f^2/t) <BR>\n" );
document.write( "use the properties of logarithms to expand the formula for EV:<BR>\n" );
document.write( "The correct equation is 2*log2(f)-log2(t) <BR>\n" );
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document.write( "b. Keith takes a picture of a waterfall with a shutter speed of 1/60 second at f/5.657. he likes the exposure of his picture, but want to leave the shutter open four times as long to better capture the motion of the water. What f-stop should he use on his next picture. <BR>\n" );
document.write( "This is where I am having some trouble. I started by doing 4(1/60)=1/15 and that is my t. I know I am solving for f, but is 5.657 my EV?<BR>\n" );
document.write( "No, your EV is what it was on the original photo. <BR>\n" );
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document.write( "Find the EV on the original picture::<BR>\n" );
document.write( "EV = 2log2(5.657) - log2(1/60) = 5 - (-5.91) = 10.91<BR>\n" );
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document.write( "Solve for \"f\"::<BR>\n" );
document.write( "10.91 = 2*log(f) - log2(1/15)<BR>\n" );
document.write( "10.91 = 2*log(f) - 3.91<BR>\n" );
document.write( "log2(f) = (1/2)14.82<BR>\n" );
document.write( "log2(f) = 7.41<BR>\n" );
document.write( "f = 2^7.41 = 170.07<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
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