darryl walthall Posted July 21, 2006 Share Posted July 21, 2006 I like to overexpose negative stock 2/3 stops sometimes. If I close my shutter angle to 90 degrees, how do I factor in the 2/3 stops over exposure? whats the equation ? Link to comment Share on other sites More sharing options...
Premium Member Stephen Williams Posted July 21, 2006 Premium Member Share Posted July 21, 2006 I like to overexpose negative stock 2/3 stops sometimes. If I close my shutter angle to 90 degrees, how do I factor in the 2/3 stops over exposure? whats the equation ? Hi, 180 degrees to 90 is one stop. 1 2/3 stops is what you are looking for. Stephen Link to comment Share on other sites More sharing options...
darryl walthall Posted July 21, 2006 Author Share Posted July 21, 2006 so does a 90 degree shutter cause flicker with HMI lighting? Link to comment Share on other sites More sharing options...
timHealy Posted July 21, 2006 Share Posted July 21, 2006 (edited) by itself not neccessarily. are you using magnetic or flicker free ballasts and what will be your frame rate? See the link to David comment about exposure vs flicker below. for magnetic ballasts http://www.panavision.com.au/Information/Flickerfree60Hz.htm http://www.panavision.com.au/Information/Flickerfree50Hz.htm flicker free ballasts are generally flicker free from 20 -30 frames per second in silent mode, but this shoulds be checked with different manufacturers. In the flicker free mode you can shoot at most frames rates and shutter angles. David Mullen had some helpful advice here: http://www.cinematography.com/forum2004/lo....php?t6927.html Also helpful http://www.cinematography.net/Pages%20DW/H..._Time_Lapse.htm an interesting side note: In the Harry Box book, he describes a method to shoot flicker free with magnetic ballasts by using more than one light. Say if you are using three phase power. If you put three lights into a bounce or through a frame, and plug each into a different phase, the three varying phases and cycles will balance out and you would be able to shoot at any frame rate with any shutter angle .... theoretically. I have not tried it but it sounds like it should work. Obviously test test test. Best Tim also may be helpful http://www.panavision.com.au/Information/ShutterOpenings.htm Edited July 21, 2006 by heel_e Link to comment Share on other sites More sharing options...
Daniel Stigler Posted July 22, 2006 Share Posted July 22, 2006 so does a 90 degree shutter cause flicker with HMI lighting? Tell your gaffer to check the HMIs with a flickermeter when getting the gear. I have set cameras to all kinds of combinations of shutter angles and running speeds (and ramps) and there never were any problems with flickerfree ballasts. Link to comment Share on other sites More sharing options...
timHealy Posted July 22, 2006 Share Posted July 22, 2006 Tell your gaffer to check the HMIs with a flickermeter when getting the gear. I have set cameras to all kinds of combinations of shutter angles and running speeds (and ramps) and there never were any problems with flickerfree ballasts. a flicker meter!? what the hell is that? I think you're pulling our legs. Unless you are talking about a meter that checks cycles which I have always understood that they don't work properly with flicker free ballasts. Best Tim Link to comment Share on other sites More sharing options...
Daniel Stigler Posted July 22, 2006 Share Posted July 22, 2006 a flicker meter!? what the hell is that? I think you're pulling our legs. Unless you are talking about a meter that checks cycles which I have always understood that they don't work properly with flicker free ballasts. Best Tim I'm deadserious. http://www.thedopshop.com/item.cfm?itemID=211 Link to comment Share on other sites More sharing options...
timHealy Posted July 22, 2006 Share Posted July 22, 2006 I'm deadserious.http://www.thedopshop.com/item.cfm?itemID=211 ok so how does this work and what does it mean?: "it will also read percentage of flicker - which other frequency meters do not." Best Tim Link to comment Share on other sites More sharing options...
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