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Predilux : iOS app for gaffers and DPs
Georges Harnack posted a topic in General DiscussionHi, 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
Measuring Light Output
Jacob Mitchell posted a topic in LightingHi 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
As always thank to anyone in advance who reads this and your generosity with sharing your opinions and experience. I am in the process of prepping for a particular shoot, one of which that I do not have any experience in the type of shooting, although I'm eager to learn. Basically, the job requires me to 1 shot of a small rodent being shipped in from abroad on a closed set in a studio. We are to film it inside a box with 30cm width and 100cm length; interior walls fully blacked out, and the box is filled with sand and a few elements of grass. In this box it will be able to move around freely and jump (the rodent can jump 12cm on each leap). I need to have a hole in the box for the lens. They need this to be captured in as high a frame rate as possible, however we are still concerned with subjecting the rodent to too much light which could potentially harm it. After speaking with the animal handler, he has told me the light the rodents are used to would be just a bit brighter than sunset, which is not great. This means 240 FPS is more than likely not an option but I would prefer not to go below 120 FPS (96 FPS is the minimum for sure). The shutter speed will have to be higher than the average for this also as the rodent I suspect moves and jumps quite fast. To add to this I will need a high F stop to capture the rodent in sharp focus to limit any soft shots (I am trying to get a focus puller on this job if budget will allow). So putting all these factors together it does seem I'm going to need to light this quite brightly , and if the animal care provider does not agree on the lux levels of the light I will have to sacrifice the F-Stop sharpness a but along with reducing the high frame rate. Now a few questions for anyone who may have some experience with filming animals in a studio in tight areas or in small mammal camera boxes: What lens/lenses would you suggest for capturing this creature? The client has requested they only need 1 shot, but I'm thinking if budget allows having a wider lens to capture the interior of the box and the rodent in a full shot, and then secondly a macro lens to hopefully capture an extreme close up as it jumps in mid air - poking the lens through the same hole just changing the lens (I'm thinking perhaps 2x Arri Master Primes as they are the sharpest lenses I have worked with before - suggestions are welcome on brand and especially suggestions on focal length? Its difficult to know this just going off a the 30cm width and 100cm length; I will only have access to the box the day before so will try to arrange a test even if its on my small Black Magic camera. Also any tips on if I should be thinking of using extenders or macroscopic lens adaptors for macro shots, or if I should indeed be looking mainly at macro lenses for this What cameras are recommendable? I personally am looking at the Red Helium as it has the option to record 2K in 240 FPS max and various other below frame rates, or the Arri Alexa Mini at 200FPS in 2K Pro Res. I originally actually thought of the Red Gemini as my research shows it performs best in low light situations, however this camera is not an option from my preferred rental house. Lighting: How can I light the rodent in the box? In my head there is 3 options - 1. Top of box is a netted material which will keep the rodent in and allow my light to shine through above it (any suggestions on material welcome) - 2. small LED's stuck to the interior top of the box - 3. A hole again through the box with a light shining though (although this means my lighting shape and direction can not change so quite limiting. ------ My first thought is to use an Arri M8 or M18 as the main light with a 45 degree back angle; Also putting in a small piece of white cloth on the interior of the box to get some light bounce back to fill in the front. (I'm lighting to make it look like a real sunlit setting). The M18 I will spot 50%. From my calculations 120 FPS at ISO 1200 with a shutter angle of 90 degrees at 50% spot would allow me to bring the F-Stop to 11 at a distance of roughly 5 metres. Now 5 metres for an M18 to the rodent may actually be to intense for the animal so an M8 may be more sufficient. Going by Arri's photometrics the majority of their lights are recommended to be kept at a safe distance of at least 5 metres but I assume that is not intended to mean for rodent size. Would be interested to hear if anyone has a solution for this in terms of using a different light or managing to put the light through the hole but at distance without leaving a gap in the box. I have to make sure the rodent is not affected by the heat or burned so I have been thinking going LED if I could get enough light in there for my frame rate. Any need for a Focus Puller? Normally I would of course want this crew member on board, but the budget is so tight right now and the nature of the shoot makes me wonder if their services would be void when regarding the speed and uncertainty if the animal. F11 should keep this sharp in my opinion, but again not doing this shoot kind of shoot would appreciate your opinions. I have attached 2 reference pictures of for the shoot. It is screenshots of the same type of shoot filming a gerbil in a confined space. Notice the hot slash of light across the sand, that is pretty much what I am going for. I am also trying to get the same focal length if anyone has suggestions on what this could be. I will have some pictures soon of what the box will look like so I will share that too. Any experience or suggestions is seriously welcomed so please let me know your thoughts or any questions you might have. Thanks so much.
Buying a first light meter
Will Davies posted a topic in Students and New FilmmakersHello everyone, I've been involved in video production for a while now and am now keen to learn more in depth about lighting and getting more experience in the field. Reading about meters, I understand how helpful they are in determining contrast ratios and light levels on interiors and locations, and are especially beneficial when shooting film (I'm getting into shooting 35mm stills lately). My max budget is around £200-400. So far my eyes are on the Sekonic L308X for its footcandle/lux readings, easy-to-find battery and size. However, the things holding me back are: Lack of head rotation (not a good look on set?) Flat disc accessory might be easy to lose Lack of spot meter reading Ideally, I'd love to have a 758 Cine, but I find they're hard to come by on ebay (plus can get a bit pricey if in a bidding war). I could go for any of the high end photographic meters, but I'm unsure about the lack of footcandle/lux settings in a majority of them. Is this a problem if I need to perform/communicate something quickly? Would I be better off getting a cheaper lux meter separately? Ultimately I hope to buy something that's reliable for starters, but will come in handy years down the line. Thanks. 🙂
Recreating Late Afternoon Light.
michael c barlas posted a topic in LightingHey 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
Light Meter Reading Preferences and Whys
Doyle LaCrua posted a topic in LightingGreetings 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.