Foot candle to aperture and ISO.

[Grandpa Ron]

I looked up light meters on Amazon and was surprised to find that most read out in foot candles.

I suppose photographic meters are a thing of the past in the age of digital.

So the question is does anyone know how to convert foot candles to F stops and ISO values.

Both are measuring the same light intensity.

[Michael R]

-Foot candle is an illuminance quantity (think of it is as the amount of light falling onto something)
-F stops have to do with lens aperture
-ISO values are standard measures of emulsion speed

There are relationships between these things in the context of photographic exposure (EV numbers for example) depending on whether you are using an incident or reflected meter etc.

What are you trying to do specifically? For example, find a camera setting (f stop and shutter speed) for an exposure based on an incident meter reading in foot candles?

[RichSBV]

I had saved an old web page that had tables for light and exposure conversions. I couldn't get the page into a pic to attach so I printed it to a PDF file. You can't see it here but you can download it to view it. It has direct conversions in a table for f-stop, shutter speed and foot candles. Maybe this will help?

Alternately, I would just buy a decent used exposure meter that does the work for you...

[maltfalc]

there's a ton of photo light meters on amazon. just search for sekonic or other specific brands to WEED out the ones for indoor gardening, or try keh.

[Tin Can]

Trial and error by narrowing your plot to a good image

No devices needed

nor

[Michael R]

There are simple formulas we can use to find EVs for luminance or illuminance values. Once you have an EV you can decide on your exposure settings (aperture, shutter speed). We just need to know a little more about what type of meter OP has in mind or make some assumptions to estimate. Need some clarity in the original question.

But on balance I agree with the Maltese Falcon - just get a regular incident or reflected exposure meter which does this for you.

[BrianShaw]

… or get a meter that does both, like a Weston Master III (reflective mode only).

[ic-racer]

I suppose photographic meters are a thing of the past in the age of digital.

.

https://www.bhphotovideo.com/c/buy/Lightmeters-Accessories/ci/900/N/4077634543

[Grandpa Ron]

I have an old Dejur selenium light meter which I am checking the against some of my old camera light meters. The problem is some of the the old film camera meters are through the lens meters of unknown field of view.

For $20.00 or so I can get an inexpensive light meter that reads in Foot Candles, then match the reading to the conversion chart I down loaded. A gray card reading should do the trick.

[sharktooth]

If you already have a gray card you can use that with your through the lens camera meter. Just fill the frame with the gray card, and it won't matter what the field of view of the meter is.

[EarlJam]

"Basic exposure rule", as taught in film school back in the day:

For ISO 100: 100 foot-candles = 1/50 @ f2.8

We used incident meters, but sharktooth's recommendation of a gray card and reflective meter should yield the same results.

[Bill Burk]

Ansel Adams tells how to convert foot candles to f/stops and shutter speeds in your head.

Use the square root of the film speed for the f/stop and use the footcandles for the shutter speed.

[John Layton]

There was a very well known local (Woodstock, Vt.) photographer, John Doscher, who started and ran a very well regarded photography school - who would always evaluate exposure (and express this to others) in terms of foot candles.

John D. is long gone...but I seem to remember that many photographers - those born in the late nineteenth/early twentieth century, when evaluating or even thinking about a scene...both thought and spoke in terms of foot - candles, which a bit later transitioned to EV's...and then as simply f/stop shutter speed combos.

Many photographers back in those days could also think and speak in terms of color temperature, and where I might photograph a grey card or color chart as the first snap of a series during a commercial color setup, especially if on location where lighting was iffy and not always in my control...earlier photogs would either whip out a color temperature meter (oh...how I wish I'd owned one!) - or just go by the seat of their pants, and just nail it!

But I think we've lost something in our more recent means of evaluating light and color values - because Foot Candles, EV's, and Color temperature values all exist prior to interpretation, and thus could become more closely alloyed and more naturally ingrained during the life of a practitioner.

Makes me think of the old polynesian navigators...standing on the foredecks of their boats - watching and feeling...interpreting what the seas were telling them, guiding them home. Sad that those times, and those practitioners, are leaving us.

[Tin Can]

Yes, and when did your location get the infernal wires

Rural was last to wire and lamp

Before we did use candles

My local Grid ia all spindly poles and a web of wires

I named this 'Wires' last week shot from my gravel driveway, I am letting it go to grass
https://live.staticflickr.com/65535/51672414823_6c68aa4218_z.jpg (https://www.flickr.com/gp/tincancollege/bPT1cE)Wire Support (https://www.flickr.com/gp/tincancollege/bPT1cE) by TIN CAN COLLEGE (https://www.flickr.com/photos/tincancollege/), on Flickr

[John Layton]

Ha! But among the ironies of this infernal technology...that with a few clicks of the clone stamp - those wires are gone! :cool: (or maybe :eek:?)

[Drew Wiley]

Meters that read in footcandles are typically called Lux meters, and are mainly used for things like architectural lighting, not photographic applications, although some incident film meters do both.

Going back to the Polynesian navigators, they did use instruments. Just because those were made of sticks, and floated in the water detecting subtle variations in wave patterns doesn't mean they weren't real instruments. They certainly got them remote places prior to anyone else.

And just a few clicks of a pair of insulated pliers will get those wires down out of the scene too. But then you'll have to contend with some angry neighbors and perhaps electrocution burns too, or a dry pile of leaves and then your house on fire. But at least infernal Photoshop would be disabled in the process, so that's something to commend the manual method. The Polynesians didn't need PS either.

[esearing]

I did a conversion from EV to Lux to FC and created this exposure chart. It even has reciprocity time adjustments for Ilford. Its based on 100 ISO and large format shutters normal working speeds and fstops. For ISO 400 move 2 spaces in either fstop or time.

221526

[BrianShaw]

https://perfesserkev.kevinmoloney.com/miscellany/in-praise-of-the-weston-master-6-light-meter/

[Neal Chaves]

"Basic exposure rule", as taught in film school back in the day:

For ISO 100: 100 foot-candles = 1/50 @ f2.8

We used incident meters, but sharktooth's recommendation of a gray card and reflective meter should yield the same results.

At the start of my career, modern office interiors and industrial workplaces were illuminated by systems designed by lighting engineers. Whenever you photographed in one of these locations, you could bet that there was 100 FC on the desktop or workbench. That was the OSHA standard. The exposure with EI400 Tri-X was usually 1/60 at f5.6. Top light is not very flattering, so auto electronic flash was often used for fill.

[r.e.]

One consequence of the widespread use of LED lights for cinematography and still photography, and the abandonment of tungsten, is that watts are no longer a reliable indicator of light output. In my view, this makes understanding Lux essential to evaluating light sources. Foot candles is a U.S. thing that I suspect is used less and less frequently. When I'm purchasing or using artificial lights, I want to know Lux, not watts (except to determine how much energy the fixture/light draws) or foot candles.

[Neal Chaves]

One consequence of the widespread use of LED lights for cinematography and still photography, and the abandonment of tungsten, is that watts are no longer a reliable indicator of light output. In my view, this makes understanding Lux essential to evaluating light sources. Foot candles is a U.S. thing that I suspect is used less and less frequently. When I'm purchasing or using artificial lights, I want to know Lux, not watts (except to determine how much energy the fixture/light draws) or foot candles.

A new LED technology rated in brightness, or lumens as most are now, will be introduced on Dec. 9th that could be a game-changer, and not just for lighting.

https://ecat.com/

[r.e.]

A new LED technology rated in brightness, or lumens as most are now, will be introduced on Dec. 9th that could be a game-changer, and not just for lighting.

https://ecat.com/

See this Wikipedia article on that company's cold fusion claims: https://en.wikipedia.org/wiki/Energy_Catalyzer

This is the Wikipedia article on CEO Andrea Rossi: https://en.wikipedia.org/wiki/Andrea_Rossi_(entrepreneur)

[C. D. Keth]

One consequence of the widespread use of LED lights for cinematography and still photography, and the abandonment of tungsten, is that watts are no longer a reliable indicator of light output. In my view, this makes understanding Lux essential to evaluating light sources. Foot candles is a U.S. thing that I suspect is used less and less frequently. When I'm purchasing or using artificial lights, I want to know Lux, not watts (except to determine how much energy the fixture/light draws) or foot candles.

Footcandles are still used frequently when lighting sets for films and TV.

[reddesert]

One consequence of the widespread use of LED lights for cinematography and still photography, and the abandonment of tungsten, is that watts are no longer a reliable indicator of light output. In my view, this makes understanding Lux essential to evaluating light sources. Foot candles is a U.S. thing that I suspect is used less and less frequently.

Most likely true.


When I'm purchasing or using artificial lights, I want to know Lux, not watts (except to determine how much energy the fixture/light draws) or foot candles.

Foot candles measure the same thing as lux - they're both surface brightness. 1 foot candle = 1 lumen per square foot, and 1 lux = 1 lumen per square meter. So one foot candle is about 10.8 lux, or about a factor of 10 to the accuracy needed for general photography.

[Drew Wiley]

All this new E-lighting is ruinous for my eyes. Most of these are sheer junk bulbs anyway, very deceptively rated for both color characteristics and bulb longevity. To hell with it. So I just dropped some bucks and ordered up some of the real deal architectural-quality 5000K LED floods from Waveform Lighting for my old studio area display wall at about $30 per bulb. Completely different story - did what was advertised, and best of all, no more eyestrain. Guess I should grab my ole lux meter and see what it says, just out of curiosity.

[Neal Chaves]

Zero Point Energy is not cold fusion and Wikipedia is not a reliable source for information. Here is Dan Winter presenting some of the new technology.

https://www.youtube.com/watch?v=pHj8PP4XBp8

[Tin Can]

Nobody knows yet

There must be many things we all don't know


Zero Point Energy is not cold fusion and Wikipedia is not a reliable source for information. Here is Dan Winter presenting some of the new technology.

https://www.youtube.com/watch?v=pHj8PP4XBp8

[r.e.]

Zero Point Energy is not cold fusion and Wikipedia is not a reliable source for information. Here is Dan Winter presenting some of the new technology.

https://www.youtube.com/watch?v=pHj8PP4XBp8


It's fine that you're a believer, but neither your post #21 nor your link reveal the history of Mr. Rossi and his company. To put it mildly, there are reservations about Mr. Rossi's claims over the years. People should read the Wikipedia links in post #22 before they get on this particular bandwagon and fork over money, as they are invited to do in your link. Apparently you don't like what the Wikipedia articles say. A search will pull up many sources.

[Tin Can]

I read

I hope

I gave no $$$

Science Fiction sometimes comes true

I am a Dreamer, where my real life is, I have wonderful imagination

[Neal Chaves]

It's fine that you're believer

Faith and belief have nothing to offer science which could be at the service of the biosphere rather than the self-destructive folly that prevails now.

[Neal Chaves]

Those 10,000 lumen LEDs that are offered for pre-order are only $25. You won't be charged until the lights are shipped. B&H does business the same way.

[Jerry Bodine]

Ansel Adams tells how to convert foot candles to f/stops and shutter speeds in your head.

Use the square root of the film speed for the f/stop and use the footcandles for the shutter speed.

Not so, Bill. His Exposure Formula requires readings in candles/sq.ft. (not foot candles) and then the shutter speed is the reciprocal of candles/sq.ft. Other than that you're correct.

[Bill Burk]

Not so, Bill. His Exposure Formula requires readings in candles/sq.ft. (not foot candles) and then the shutter speed is the reciprocal of candles/sq.ft. Other than that you're correct.

Right. Since a Weston Master indicates that:

Take the square root of the film speed and use that for your f/stop.
When you have taken an average reading with a Weston Master light meter...
Set the Shutter speed to the number the needle points at.

[Jerry Bodine]

...
Set the Shutter speed to the number the needle points at.

Set the shutter speed to the reciprocal of the number the needle points at; e.g., if it points to 25 c/sq.ft. set the shutter to 1/25 sec. Having established the combo of shutter speed and f/stop, it's a simple matter to adjust the shutter speed for any other f/stop.

[BrianShaw]

If using a Weston master why not just transfer the reading to the exposure calculator?

[Bill Burk]

It is the reciprocal, and you want the square root of the arithmetic film speed. And right Weston meters indicate candela per square foot. Shutters mostly leave off the 1/ . If there is time the exposure calculator is useful.

But the exposure formula is easy to use in a pinch:

Set the f/stop at the square root of film speed and set the shutter to whatever the meter needle points at.