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Hi, We are two technicians working in the film industry in France (a grip guy and a gaffer) and we just discovered this very interesting forum. We particularly noticed that gaffers and cinematographers were asking questions about light output and what aperture is obtained at a certain distance. It happens that with the help of two IT engineers we developed an iOS app responding to this question about 2 years ago. First and for all, we’re not going to post messages everywhere on this forum to sell our app nor are we going to pollute your threads to gain in visibility. We just think some of you might be interested in what we created and since we’re a really small team working on off-time we can’t do any real advertising, so you probably wouldn’t know our app existed. Our app is called Predilux (for pre-diction and lux for light) and predicts the exposure as measured by a light meter, by choosing a light source and a distance. Or inversely predicts the distance to the light source by specifying the exposure. Predilux takes into account: Camera settings (FPS, ISO, Shutter angle) Source settings (Focalisation, Lenses, Grids, Dimmer, CCT, etc) Gels mounted on or close to the source (All ROSCO e-colour+ range) All results have been experimentally verified by us with a light meter in rental houses. For each source setting we made several measurements at different distances and this took a lot of time. So Predilux does not rely on constructor’s data, but on real data reflecting the state of the equipment as found in rental houses. Our data sometimes differs from the constructor’s data. Here is a quasi exhaustive list of the sources measured and included in the Predilux (12/2019) : Tungsten ARRI 150, 300 Plus, 1K Plus, 5K Fresnel, T10, T12, Rubylight (MFL lamps) Briese 77, 100, 140, 180 with lampes ranging from 650 W to 2K Mole Richardson Softlite 1K, MaxiBrut 16 (MFL lamps) Openfaces such as Redhead, Blonde, Desisti Renoir 5kW and LTM Cyclight 2K ETC Source 4, Dedolight, Zaplight, CMC 20K, etc. HMI ARRI AS 575, 1200, 4K, 6K, 12K, Arri M18, M40, M90, ArriMAX 12K & 18K K5600 JokerBug 200, 400, 800, Alpha 1600, 4K, 9K, 18K AFM 575, 1200, LTM Cinepar 2.5K Fluorescent KinoFlo 2ft, 4ft & 6ft LED ARRI S30, S60, S120, S360 KinoFlo Celeb 200, 250, 400, 450, 850 DMG SL1, SL1 mini, SL1 Switch, MaxiSwitch Mole Richardson Tweenie, Senior, Tener Aladdin Biflex 1x1, 1x2, Flexlite 1x4, 350 Dedolight bi90, Cineroid LMD400, Velvet V1 Balloon Airstar Gaffair 1200, Elipse 4000, PAD 9ft x 9ft, Tube 16K If any of the administrators of this forum wish to try out our app, we would be happy to give them one or several free life-time activation codes. For all the other users, our app is available on the Apple Store (). An Android release is planned. If you have questions or requests, don’t hesitate to contact us at this address email@example.com Thanks for reading this post and we hope you thought it was interesting, Georges Harnack for the Predilux Team
Hi All! As a student, each projects means a way to stretch myself further. If I'm not trying something new (or a little bit scared) on a project then I feel like I'm not taking steps forward. Lately I've been doing pretty in-depth floor plans and 2D pre-vis, and it has been working wonders for every project. However, I'm still working to get exactly what I want in my head to paper, so that on set my images are not a surprise. Is there a way I can tell how many foot-candles a certain light will output? I'm wanting to essentially know exactly how powerful a light I'll need to expose to a pre-determined f-stop. I'm familiarizing myself with inverse square law, so all I'd need is an output at any one distance and could work from there. Is this just a knowledge gained from experience? Or is there a practical way to determine output? Thanks, Jake Mitchell
Hey everybody, My name is Mike, I am an Electric and I will be gaffing for a short film. I have to recreate late afternoon light to shine through a window. My question is do I have a strong enough light source? My main light source is an Arri Tungsten 5k. The DP wants it about 20 or so feet away from the window. We are on the second story so the light will be on a stand about 16 feet high. The DP wants afternoon light (4300k) to shine through the bathroom window. So I will gel the 5k on a 4x4 frame with 1/2 CTB (4600K). He also wants some New Hampshire Frost on it. Using Arris Photometric Calculator I calculated the Arri T5 5k light source at: 21ft. Middle flood to give me a 3914 Lux. Aperture at F13.8 ASA 800 30fps Wikepedia says Lux for a sunset/sunrise to be 400,1000 for an over cast day, 10 000 for full daylight. My 3914 Lux does not take into account my 1/2 CTB gel and Hamphire Frost. So ultimately I am asking where my light is placed right now 20ft away though 1/2CTB and Hampshire Frost, do I have enough light or Lux to recreate late afternoon sun? Yes I can lower the aperture on the camera from the 13.8. Or should I rent a 10k. Keep in mind I only have one Grip to help me. Thanks a lot for any help in advance, it is much appreciated. Cheers, Mike
Greetings all, I'm excited to be a part of a community so generous with it's knowledge. I'm really trying to wrap my brain around the Sekonic L-758cine light meter and it's advance capabilities. This might well be a very tremendous question... Footcandles, Lux, Foot Lambert, and cd/m². I'm hoping to understand in what situations it'd be best to use these light measuring features. Are these just a preference? Where and why would you use them? Thank you sincerely for your time.