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Found 6 results

  1. 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 predilux@wid.la Thanks for reading this post and we hope you thought it was interesting, Georges Harnack for the Predilux Team
  2. Hi group, Well I was always wondering: Why don't lenses provide the F stop which exactly corresponds to the light actually hitting the film emulsion or sensor (not accounting for lens flare and other random factors, just the glass inside the lens)? So in reality: if I get an F stop value from, say, a light meter, I most likely will get it in T stop. Otherwise the "exposure triangle" would make no sense (to me that is). Looks like some lenses are reducing as much as one stop while others perhaps a third of a stop. There is some information for some lenses regarding the actual T-stop, but many don't come with that information - and even with that information: what to do? Now add certain filters and you're into some serious math.... The only thing that remains the same (F stop/T stop) is of course the depth-of-field/focus. Fully automatic digital cameras with 100% matching lenses (or built-in ones) most likely take all that into account (to varying degrees of success IMHO). But what about using different lenses with no electronics and a 100% manual exposure? With film, once it's in the camera (and you don't have a variable shutter angle) your only way(s) to control exposure is/are lighting, filters and F stop. Please let me know how you go about the F stop vs. T stop issue and avoid under exposure. As always: any reply highly appreciated. Christian
  3. Hi, I'm Ben, a learning camera assistant who chose not to study film and is now catching up on production etiquette and techniques! I recently pulled focus on a short film for a great DoP (Tansy Simpson) here in London and at one point she asked me to push the iris to a 'two plus' Now i assumed this meant something like a t2.1, or did it mean 2.5? I'd love to get clarification on this as I was too worried she might think I was an amateur if i asked! Thanks in advance for any help offered, Benjamin
  4. Hi all :) When using a metabones speedboster, how do you really gauge the true aperture the lens is giving you? I mean from a practical point of view, you keep it mind that you get +1 stop of light hitting the sensor. But from a tech point of view, if your lens is set at let’s say 2.8 (and it’s the fastest the lens can get to), does the camera shows you the added stop? Or is it a passive speedboaster that doesn’t trasmit aperture values? In case it doesn’t trasmit that, you just keep in mind that if the lens is set at 11, you could set f/8 on your light meter? So in practice can you use a ND 0.3 paired to the speedbooster to get a slightly shallower depth of field without having to change your lens aperture? Thank you, Stefano
  5. Hi everybody, I was wondering how people control the aperture and pull focus during a steadycam shot for example. Is it possible through only one remote? Or I'd be necessary to do so with 2 different motors and and remotes? Thank you in advance for the help, Davide
  6. The fact that I'm creating a topic of this nature may come to a surprise to many of you, but I feel it's necessary because I'm getting at least three different answers based on my own research. 1) Wikipedia: http://en.wikipedia.org/wiki/16_mm_film#Super_16_mm WP states the camera aperture is 12.52 by 7.41 mm (0.493 by 0.292 in). This gives us an aspect ratio of 1.6884:1 (1.69:1). Unfortunately, nothing is cited clearly in that article (shocker!). For an interesting twist, the entry also lists regular 16 mm as having a height of 7.49 mm (0.295 in). I thought Super 16 just extended the horizontal dimensions of the format, not also shrink it's vertical dimensions. 2a) Arri: http://www.arri.com/camera/film_cameras/16_mm_film/arriflex_416416_plus.html (click on the "Technical Details" tab) 2b) Panavision: http://www.panavision.co.uk/pdf/downloads/equipment-info/other/formats-guide.pdf I lumped these two together because they both cite the same specifications: 12.35 by 7.49 mm (0.486 by 0.295 in). This gives us less horizontal resolution than what's listed in WP's entry, but now matches the height of regular 16 mm. We now have an aspect ratio of 1.6475:1 (1.65:1). 3) Kodak: http://motion.kodak.com/motion/uploadedFiles/Kodak/motion/Hub/eb/choices/Choices_INFOGRAPHIC.pdf You'd think these guys would offer evidence corroborating with the camera makers, but they say it's 12.42 by 7.44 mm. Their Super 16 "Sell Sheet" (http://motion.kodak.com/motion/Products/Format_Choices/index.htm ; click the Super 16 mm tab) at least confirms that regular 16 mm is still 7.49 mm in height. Their Super 16 film dimensions calculate to an aspect ratio of 1.6694:1 (1.67:1) which is the closest match to the often touted 1.66:1, in my opinion. So we're left with three different physical descriptions. Which one is correct? What does SMPTE, ANSI, and/or ISO state for the record? (I'm not a member of any so I'd appreciate it if those who were could chip in.)
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