Brandon Rubesh Posted March 26, 2008 Share Posted March 26, 2008 Just a quick question that I'm sure some of you know right off the top of your heads. I'm going to be shooting a 4k HMI through the windows of a cafe. Going next week to scout the cafe and was thinking about the distance I need outside the cafe to place the light. I'd like a stop of around a 5.6 to an 8 inside the cafe. I know there's probably some sort of formula for this, but I'm not sure of what it is. Thanks for any advice. - Brandon Link to comment Share on other sites More sharing options...
Mike Lary Posted March 26, 2008 Share Posted March 26, 2008 Have you checked to see if there are photometric charts available for the light? I don't know what light you're using, but a quick search came up with this: http://extranet.mole.com/store/images/backpage/6641-L.gif You'd just need to convert the foot candles to f-stop with a chart from the ASC manual or elsewhere. Link to comment Share on other sites More sharing options...
Brandon Rubesh Posted March 26, 2008 Author Share Posted March 26, 2008 I don't know exactly what light I will rent yet, but I was thinking a 4k HMI with some optional lenses. For the inside I would just have on hand kinos and smaller tungsten units for fill, eye lights, focus areas, etc. but I want the main source to be from the HMI placed outside. But thanks for the link, I'll check it out. - Brandon Link to comment Share on other sites More sharing options...
Brandon Rubesh Posted March 26, 2008 Author Share Posted March 26, 2008 Ok got it! for 50 ASA at an F8 I need around 400 footcandles, unless I'm mistaken. So with the different lens options that allows me a margin of between 25 and 150 ft outside the cafe. Thanks! - Brandon Link to comment Share on other sites More sharing options...
Premium Member Kevin Zanit Posted March 26, 2008 Premium Member Share Posted March 26, 2008 The 4K with lenses is a PAR, though many of the 4k PARs rent with a fresnel lens as well. Though your photometric numbers may give you the stop you are looking for, don't forget that you need spread as well. You may have plenty of foot candles, but its in a very small spot. Plan on needing to diffuse the light if you need it to spread and light a large space. (those are 18k fresnels through opal) Kevin Zanit Link to comment Share on other sites More sharing options...
Mike Simpson Posted March 27, 2008 Share Posted March 27, 2008 (edited) Maybe this should be a seperate subject but its somewhat related so Ill just ask. I was having a similar conversation dealing with a 4k thru a window yesterday, and we were trying to get the hardest light possible with a 4k fresnel. The window was about 5ftx5ft, the actor about 10 ft away from the window, the wall another 10 feet from the actor. So I asked for the light to be backed up and spotted in so it was hitting all of the window but not much more. My question: The gaffer told me I should flood the light out to get the as hard as possible. This seemed counter intuitive to me, and Im having a hard time wrapping my head around it. To me, it seems like I should spot the light in and back it up as much as I can while keeping the exposure good to get the hardest shadows. He claimed it should be as far away while full flood and maintaining good exposure. Anyone else run into this before? Edited March 27, 2008 by Mike Simpson Link to comment Share on other sites More sharing options...
Hans Engstrom Posted March 27, 2008 Share Posted March 27, 2008 Maybe this should be a seperate subject but its somewhat related so Ill just ask. I was having a similar conversation dealing with a 4k thru a window yesterday, and we were trying to get the hardest light possible with a 4k fresnel. The window was about 5ftx5ft, the actor about 10 ft away from the window, the wall another 10 feet from the actor. So I asked for the light to be backed up and spotted in so it was hitting all of the window but not much more. My question: The gaffer told me I should flood the light out to get the as hard as possible. This seemed counter intuitive to me, and Im having a hard time wrapping my head around it. To me, it seems like I should spot the light in and back it up as much as I can while keeping the exposure good to get the hardest shadows. He claimed it should be as far away while full flood and maintaining good exposure. Anyone else run into this before? With a Fresnel you get harder shadows when its flooded. It´s because when it´s flooded all rays travel parallel and when it´s spotted they don´t and may cross each other creating fuzzy shadows. Link to comment Share on other sites More sharing options...
Serge Teulon Posted March 27, 2008 Share Posted March 27, 2008 Ok got it! for 50 ASA at an F8 I need around 400 footcandles, unless I'm mistaken. So with the different lens options that allows me a margin of between 25 and 150 ft outside the cafe. Thanks! - Brandon Kodak tables show that 400fc = F4 on ASA 50 not F8 S Link to comment Share on other sites More sharing options...
Mike Simpson Posted March 27, 2008 Share Posted March 27, 2008 With a Fresnel you get harder shadows when its flooded. It´s because when it´s flooded all rays travel parallel and when it´s spotted they don´t and may cross each other creating fuzzy shadows. And that really makes a bigger difference than the extra distance you get from maintaining the same intensity by spotting and moving back? Link to comment Share on other sites More sharing options...
Hans Engstrom Posted March 27, 2008 Share Posted March 27, 2008 And that really makes a bigger difference than the extra distance you get from maintaining the same intensity by spotting and moving back? Yes it will. The extra distance will however be good to minimize the falloff but for sharp shadows I would go with flooding the fresnel. Link to comment Share on other sites More sharing options...
Nor Domingo Posted March 28, 2008 Share Posted March 28, 2008 Yes it will. The extra distance will however be good to minimize the falloff but for sharp shadows I would go with flooding the fresnel. Is that the same for a par, say a 4k arrisun, when flooded or is that only for fresnel lamps? Creating harder shadows, i mean. Link to comment Share on other sites More sharing options...
Tebbe Schoeningh Posted March 31, 2008 Share Posted March 31, 2008 check out the photometric calculator on arri.com Link to comment Share on other sites More sharing options...
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