2 questions

November 29, 2006

Hey all,

I have 2 questions and as much as I would like to separate them into 2 threads, since most probably I'll be asking even more questions after I receive the answers (lol), but I'm gonna keep them together instead.

Qn 1. Reliability of practical lights.

How do you tell if the practical bulb or tube at your shoot location is mercury, cheap fluorescent, etc etc and the issues that comes with it eg. constant colour temperature, exact wattage (if it's not labeled anywhere) and flickering issues (shooting on film at 25fps)? Are there any other things I should look out for to decide if a certain practical light is usable or not?

Qn 2. An exposure scenario

After lighting my scene with 4ft kino tubes, I'm getting a reading of f2.8 on my subject's face and on the walls closest to it. In other parts of the frame, I'm getting a reading of f2, f1.4 (shadows) and f1 (shadows).

f1.4 and f1 are in the most parts of the frame. My lens is only capable of opening to f2.8 and my frame is set as such. How dark are we talking about here and how much detail in the shadows can I get with a 500T filmstock?

I apologise if the 2 questions are very demanding, but I'm preparing for a shoot and these are the things that is bugging me. I would love to do a test shoot to see the results for myself, unfortunately there is no budget for it and I would like to hear from you guys who may have come across similar situations as I have right now.

Many thanks.

December 2, 2006

Anyone wanna help me out? If I had posted this thread in the wrong subforum, let me know.

Thanks

Jonathan Bowerbank · December 2, 2006

Hey Zulkifli,

#1: Regarding the color temperature of your practicals, I'm assuming you don't have a color temp. meter. Rosco has a great little handbook that has a list of various fluorescents, mercury vapor, etc., organized by manufacturer and model. The list tells you how to either correct the practicals or to correct your tungsten lights for the shoot. For example, for a Cool White fluorescent practical, you'd place a full CTB & full Plus-Green to correct your tungsten lights for that color temperature...or you'd place a CTO with Minus-Green to correct the practical itself.

#2: What brand of film are you shooting on? Kodak Vision2 5218 500T stock really has a lot of latitude. With your key at 2.8, and your fill at 1.4 you're getting a good 4:1 ratio which is still giving us a lot of detail in the shady areas. The f/1 shadows are creating an 8:1 key to fill ratio, which means the shadows are getting pretty dark and your shots getting some really good contrast. It all depends on what sort of mood you're hoping to get in your scene. But again, Kodak stock is really great, and if you feel you need to push it a stop to get some more detail in your shadows, then I suggest you try it out and see if you're happy with the look you get.

good luck!

Jon

Jonathan Bowerbank · December 2, 2006

Oh, by the way, if you're not able to get your hands on a Rosco filter facts booklet, I can scan a couple pages of the one I have and send'em to ya if you like. Just message me your email.

Hal Smith · December 2, 2006

Oh, by the way, if you're not able to get your hands on a Rosco filter facts booklet.

There's a link for "Filter Facts" on Rosco's TechNotes webpage.

http://www.rosco.com/us/technotes/filters/index.asp

Jonathan Bowerbank · December 2, 2006

Oh cool, cheers for that Hal

Jake Kerber · December 2, 2006

Another thing you can do to see how the color temps of your various sources are registering is to take some some reference stills with a digital camera. It is not going to tell you exactly how the film is going to read the scene, but I've found it to be effective in many scenarios.

Stick to HMI safe fps & shutter angle combinations for 50HZ and you should be fine as long as the power going to these sources is reliable/constant. If you can get your hands on a frequency meter you can check the cycle to be completely confident.

The sources you mentioned--mercury vapors, commercial fluorescents, etc.--in general have a lower CRI (color rendering index) than say, a tungsten light and even if you time out the green or blue, skin tones, for example, won't render quite the same. It's a certain look and while not neccessarily 'bad', it's just something to be aware of.

-Michael Jacob Kerber

D.P. / L.A.

December 4, 2006

Thanks for the replies so far guys! I'll check out the rosco link to find out more about correcting practicals/film stock.

Exposure

Thanks for the reply concerning the exposure scenario I had. Yes, I'm shooting on Vision2 500T. This information gives me the confidence to shoot with the lighting package the budget can provide me and also make a few changes here and there.

I hope this is not too much to ask but are they any framegrabs off the Internet which I can reference to that shows the exact/similar exposure situation as the one I've mentioned. Seeing real world grabs can only cast aside my "fears" even further lol.

Practicals

I do have a chroma meter with me when I went around the shooting location but the problem is, I did not know how to translate those meter readings into the type of lights they are.

Also, the readings that I got from most of them were not consistent, they range for e.g. from 2400K to 2600K for each practical. While I believe that gives me an orange look, will I see slight shifts in colour temperature?

Frequency meter - which kind is suitable for use or it's the usual type you can get from a normal hardware store? So for example, when I check for the power cycle of any type of practical and it gives me 50 Hz, it is "flicker safe" to shoot at 25fps right?

Is there any particular practical that gives a lower power cycle than 50Hz?

Lastly, is there anywhere else I can read up about practicals and its usage in film so that I can arm myself with better technical and creative knowledge about them.