Premium Member Damien Bhatti Posted June 20, 2007 Premium Member Share Posted June 20, 2007 Hi, I was just wondering whether someone could enlighten me as to the shutter angle of the bolex ebm, how it relates to light reading ? ie - what calculations need to be done when taking a light reading? Also I have heard that a percentage of light is lost due to the layout of the prism in other rx's - is it true with the ebm? if so how much should you compensate by? Thanks! Link to comment Share on other sites More sharing options...
Kip Kubin Posted June 20, 2007 Share Posted June 20, 2007 Hi, I was just wondering whether someone could enlighten me as to the shutter angle of the bolex ebm, how it relates to light reading ? ie - what calculations need to be done when taking a light reading? Also I have heard that a percentage of light is lost due to the layout of the prism in other rx's - is it true with the ebm? if so how much should you compensate by? Thanks! Download a manual for the Cam... they give a rundown of shooting speed to exposure ratings. %25 of the loght goes to the viewfinder If it's the same as an EL Film Speed Exposure Real Photometric 10fps 1/21 1/28 12fps 1/25 1/33 18fps 1/37 1/50 20fps 1/42 1/56 24fps 1/50 1/67 25fps 1/53 1/70 32fps 1/67 1/93 40fps 1/83 1/110 50fps 1/106 1/1/40 Link to comment Share on other sites More sharing options...
AdamBray Posted June 20, 2007 Share Posted June 20, 2007 This is for REAL, then ADAPTED. 12fps 1/33 1/40 16fps 1/45 1/55 18fps 1/50 1/60 24fps 1/65 1/80 32fps 1/90 1/110 48fps 1/130 1/160 64fps 1/180 1/220 It's my understanding that you open up by 2/3 of a stop to compensate for the prisim light loss. Link to comment Share on other sites More sharing options...
Bryan Darling Posted June 20, 2007 Share Posted June 20, 2007 This is for REAL, then ADAPTED. 12fps 1/33 1/40 16fps 1/45 1/55 18fps 1/50 1/60 24fps 1/65 1/80 32fps 1/90 1/110 48fps 1/130 1/160 64fps 1/180 1/220 It's my understanding that you open up by 2/3 of a stop to compensate for the prisim light loss. 2/3 seems a little high to me. 25% is what I've always done, which would be 1/4 stop which I often round to a 1/3 to make it easy. The simplest way to calculate exposures for something like a Bolex is to take your exposure compensation for the light loss of the vf and the difference in the shutter angle from the standard and translate that into an adjusted ASA. That way you can set your meter for a specific ASA and never have to worry about doing any math in your head when your out and about. As a side note, I use the L-508 cine and it has a wonderful function allowing you to dial in your shutter angle. It makes shooting a Bolex and Super 8 cameras a breeze. Link to comment Share on other sites More sharing options...
Nick Mulder Posted June 21, 2007 Share Posted June 21, 2007 The EBM shutter angle I think is the same as the EL at 170deg - ie. open %47 of the time - close enough to call 180deg ... The prism takes %17 of the light - this is from actual measurement ... For a run down of the arguments/confusion re. filter factors/stops and Log10 vs. Log2 that will no doubt arise in this thread - check out this one I prepared earlier: http://www.cinematography.com/forum2004/in...mp;#entry174916 Link to comment Share on other sites More sharing options...
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