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''homemade'' lightmeter


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#1 Jan Weis

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Posted 18 June 2006 - 06:30 AM

The day before I was going to shoot my first scene of my short film I went to visit the ''set'' actually its nice tunnel in the center. Since I didnt have my own light meter I decided to just rely on the one built in on my Beaulieu R 16, unfortunetly that was one of the biggest mistakes I could possibly do since my light meter broke. the needle in the tachometer didnt even flinch.
The next day I started to do some research on light meters and unfortunetly the light meters on ebay (the good ones like sekonic) cost a fortune to purchase, this made me look else were... I went to the local hardware store and found this neat light meter that measure light intensity in LUX. So i bought it for around 30 euros. Afterwards I did my reasearch till I found a nice table that shows how to set the appeture on lens at the amount of light avalable in footcandles. This of course caused some trouble, since the light meter didnt measure the light intensity in Footcandles but in LUX. So I did even more reasearch and found that 1 foot candle = 10.764 LUX, so i converted the table, well just on two sensitivities 64 ASA & 80 ASA because I'm using plus-x film and this is what got:

Posted Image
As you guys can see this is a table of number of LUX needed for each appeture setting. oh yeah this table only works of your shooting 24/25 fps

heres a nice picture of the light meter:
Posted Image

So what do you guys think?


//Jan
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#2 John Pytlak RIP

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Posted 19 June 2006 - 02:13 PM

Of course you can calibrate photometers that were not designed for photographic use, as you did. The risk is that the calibration may not be valid for other light sources or illumination geometries. For example, some inexpensive meters have a spectral response that is not near the standardized "photopic" response usually used for photography. So calibrating for a tungsten source may not track when you use a daylight or a discontinuous source like fluorescent lighting. Many incident light meters used for cinematography use an integrating "dome" to properly weight lighting coming from a variety of directions (key, fill).

Bottom line: calibrate against a known meter, but realize the calibration may not be exact for all conditions.

Better yet, look for a used meter that was designed for cinematography. Even with professional calibration, you may be able to save subtantially over the cost of a new meter, but it may not have all the features of a new meter.
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#3 Jan Weis

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Posted 19 June 2006 - 02:41 PM

Thank you form bringing this problem up, Mr Pytlak. According to the manual, the light meter is calaborated to a ''regular'' light bulb ( 40W is my guess) so its caliborated to 2856 Kelvin.

Will this be a problem ?
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#4 John Pytlak RIP

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Posted 19 June 2006 - 02:50 PM

Thank you form bringing this problem up, Mr Pytlak. According to the manual, the light meter is calaborated to a ''regular'' light bulb ( 40W is my guess) so its caliborated to 2856 Kelvin.

Will this be a problem ?


It depends on what the spectral response of the meter is. Does it say it has a "photopic" response, or is calibrated specifically for photographic use? If not, there may be an offset as other light sources are used, especially ones that have a discontinous spectra.
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#5 Jan Weis

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Posted 19 June 2006 - 03:03 PM

Thanks for tha answers, Mr Pytlak!
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#6 Jan Weis

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Posted 01 February 2007 - 03:39 PM

Thanks for tha answers, Mr Pytlak!


Just a quick update to show you guys my results using this home made light meter
so people will stop wasting loads of cash on proffesional ones

Posted Image

Posted Image

Posted Image

Posted Image

Edited by Jan Weis, 01 February 2007 - 03:40 PM.

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#7 Phil Rhodes

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Posted 01 February 2007 - 04:08 PM

Hi,

I bough a light meter for not much more than that from the local photographic store. It agrees with every top-grade one I've ever tried it against, and has shot several thousand feet of 16 and 35 without issue.

Man, that's grainy. What stock?

Phil
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#8 Jan Weis

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Posted 02 February 2007 - 03:34 AM

its Plus-x 7231 shot wide open, it looks better in motion ;)
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#9 Mike Rizos

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Posted 02 February 2007 - 07:51 AM

Hi
Here in the US you can find plenty of decent light meters for that price at any photo swap meet. Your meter looks like requires two handed operation, can only meter down to 200 Lux, has limited range, looks like is only incident and not reflective, requires calibration, and requires conversion which will make it a complete hassle to use. Plus it won't look too cool if you drape it around your neck. ;)
BTW, Lux is the metric equivalent of foot candles.
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#10 Chris Keth

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Posted 04 February 2007 - 08:17 PM

Hi
Here in the US you can find plenty of decent light meters for that price at any photo swap meet. Your meter looks like requires two handed operation, can only meter down to 200 Lux, has limited range, looks like is only incident and not reflective, requires calibration, and requires conversion which will make it a complete hassle to use. Plus it won't look too cool if you drape it around your neck. ;)
BTW, Lux is the metric equivalent of foot candles.


That's painfully grainy. Intentional?

If you're intending to make filmmaking or photograpy your livlihood, consider a real meter. A couple hundred bucks or even a thousand (I don't know any lightmeter costing that much) would be worth it for the tool you rest your entire way of life on.
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#11 Dory Breaux DP

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Posted 18 February 2007 - 07:06 PM

Or, you can just use a 35mm SLR still camera ;)
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#12 Jan Weis

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Posted 18 February 2007 - 07:28 PM

Or, you can just use a 35mm SLR still camera ;)


interesting I have thought of it but I always considered it to be too difficult.
I mean wont there be problems due to the shutter? Please elaborate, I'd
love to try it


/Jan


That's painfully grainy. Intentional?

If you're intending to make filmmaking or photograpy your livlihood, consider a real meter. A couple hundred bucks or even a thousand (I don't know any lightmeter costing that much) would be worth it for the tool you rest your entire way of life on.


well It wasnt intentional, I think its simply due to the nature of the stock and the low key lighting... But then again I did shoot some of scenes in the middle of the day, cloud free and it still turned up rather grainy... I guess youre all spoiled with the modern vision2 stock ;-)

/Jan
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#13 Jan Weis

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Posted 19 February 2007 - 05:25 PM

Just a little bump...
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#14 Joe Turrentine

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Posted 19 February 2007 - 06:10 PM

interesting I have thought of it but I always considered it to be too difficult.
I mean wont there be problems due to the shutter? Please elaborate, I'd
love to try it
Jan


Well, theoretically, if you set the ISO/ASA rating control for the still camera as the same as your stock, set the shutter speed the same as the big boy's, then it should be go. Then make adjustments to your aperture on the movie camera according to the readings from the still camera and then it should work. At least, I think it should work.

Oh, and focal length would get in the way. If you had a wide prime lens on your still, and then a telephoto on the movie camera, even if they were at the same aperture, a light source wouldn't be able to expose the film because of the telephoto lens.

That seems like a hell of a lot of work, but I guess I'd be inclined to do it too if I was having to spend 200 on a light meter. But I mostly do digital... and when I do film, I can borrow a nice incident meter from a friend!

My two cents. I hope that was helpful.

Joe
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#15 Dory Breaux DP

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Posted 19 February 2007 - 09:03 PM

Well, if you were shooting 35mm I would assume that you could use the same lens, as long as the mount was the same. Or, use a zoom lens on both the 35mm still and the movie cam.
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#16 Dory Breaux DP

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Posted 15 March 2007 - 10:41 AM

Well, if you were shooting 35mm I would assume that you could use the same lens, as long as the mount was the same. Or, use a zoom lens on both the 35mm still and the movie cam.


Hate to quote myself, but I am going to try this when I get my K-3... And thats soon. I'll post resuilts.
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