BebuLamar

R.G.! Now that we have your question answered I am wondering why would you need the conversion? Do you have a meter that measure in Lx and try to use it as exposure meter or do you remember the illuminance of a lot of scenes?

R.G. Loc: Scotland

I like the thought of having incident metering as an option and I looked at some of the options. Exposure meters are to my mind prohibitively expensive, but £25 or so for a light meter seems more acceptable. As I said before, the main difference between a light meter and an exposure meter is the ability to calculate appropriate camera settings. If I can do that myself using a table of values and some mental arithmetic (I was hoping for an exposure calculator wheel), I've found a way to make incident metering affordable.

I wouldn't rank myself among those who can assess light levels by eye. Perhaps that comes with time, but my untrained eye is too susceptible to the tricks that my brain plays with my perceptions.

BebuLamar

It's irony that cheap light meters are significantly less expensive than exposure meters yet good light meters are significantly more expensive than the most expensive exposure meter. They range in the several thousands dollars range.

R.G. Loc: Scotland

I've been seeing values of 3% - 5% accuracy for the cheap ones. That's good enough for me . I'm left wondering what justifies the hundreds of dollars/pounds that they charge for exposure meters.

E.L.. Shapiro Loc: Ottawa, Ontario Canada

https://www.scantips.com/lights/evchart.html

The link, posted above, might be of use. Also, the chart on the back of my old exposure meter may be of interest.

BebuLamar

I don't know but I am not sure if I should trust the 3-5% specification. A good Lux meter that costs several thousands dollars only has an accuracy of 2%. The best exposure meter only has the resolution and repeatabilty of 1/10 which is about 7%. We only need 1/3 stop accuracy which is about 25%.
Any how I think using one of the chart to convert Lx to LV and then using this chart to help in picking the combination of aperture, shutter speed and ISO.

After getting the LV value you would add the ISO value to the LV to get the EV.
Once you get the EV you would subtract the shutter or aperture value you choose from it. The resulting value is the value of the other parameter. Once you know the full stop value you can easily figure out the 1/3 stop value as the number is quite intuitive. For example if you get the value of 7 and 2/3 then the shutter speed for 7 is 125 and 2/3 more is 320. Or if the value of the aperture is 7 and 2/3 you get the aperture value of 7 which is f/11 and 2 /3 more is f/14.
After a while you actually will remember these values by heart.

R.G. Loc: Scotland

Quite a lot to take in there . I notice the author is happy to refer to ISO as one of the exposure variables. Not sure what "fc appr." means.

R.G. Loc: Scotland

That was the plan. Since I'd be making up my own chart I could simplify it by using values I'd be likely to use. If I listed values for f/8 and f/11, that would give me references for stops and half stops. That reduces the mental arithmetic to a level that I'd be comfortable with .

All of the meters that I looked at (including the cheap ones) were quoting accuracies of 3, 4 and 5%. Sounds close enough. However, none of them mention long term stability and drift......

E.L.. Shapiro Loc: Ottawa, Ontario Canada

I think "FC"= foot.candles.

I have used a LIGHT meter used by interior lighting designers to measure display lighting of prints that I make for my customer's displays where "foot.candles" are specified by the display designer. That way I can judge the printing density as I produce the prints as per the lighting environment. Sometimes print competition judging light levels are indicated in the rules for submission. Folks who design stage lighting also refer to "foot.candles.

The meter I used to read foot.candles was made by Weston- the now-defunct manufacturer of the famous Weston Master series of exposure meters of Zone System and Ansel Adams fame. There were Zone System conversion stick-on labels for the old Weston meter's calculating dial to assign zones and range to numerical aspects of the dial. I did find, however, that my old Weston f.c meter was consistent and accurate in moderate to high light levels but did not do well in low existing light. I don't know of any meters that express their readouts in LV that are not EXPOSURE meters.

The line of high-end Spectra brand exposure meters, favoured by cinematographers, do read out in foot. candles but also can convert readings to various f/stop and specific fps rates.

I haven't paid much attention to the LV values on my meters since I don't use my Hasselblad film system very often. All the Hasselblad/Zeiss lenses had an LV scale so it was easy to set the LV and all the aperture and shutter speeds would track along unless I disengaged the feature.

bleirer

If you are going for low cost, there are plenty of article on the internet about metering a grey card to approximate incident light. The light is incident on the grey card and so it doesn't vary from scene to scene, and you know or learn how your camera spot meter reads the card and where that value falls in raw.

BebuLamar

Which model of meter is it?

R.G. Loc: Scotland

I see that some light meters are designed specifically to work with LED lighting and other lighting that gives a narrow spectrum. Apparently LED lighting can give false readings with standard light meters. I suppose that would apply to camera meters as well.

R.G. Loc: Scotland

Since you mention it, that would definitely be another alternative that would be worth having.

E.L.. Shapiro Loc: Ottawa, Ontario Canada

It is model #614. The nameplate is marked, Weston Electrical Instrument Company, Frelinghuysen, New Jersy.

E.L.. Shapiro Loc: Ottawa, Ontario Canada

Perhaps that is possible. I remember a time when older reflected-light- selenium cell, photoelectric exposure meters, prior to silicone cell technology, would render false readings if the reading was sampled from areas of certain colours. I recall that yellow would produce a higher reading than says blue, even of both colours were of the same reflectivity. In the old meters, the cell generated an electrical current that produced the meter's deflection whereas in the selenium cell models, a constant current was supplied by a battery and the cell provided variations in resistance- the more light, the less resistance and the higher deflection. The newer meters worked better in low light and did not seem to show a bias for various colours.

LED light is more and more prevalent in interior lighting in homes and offices. I have used my regular Minolta and Sekonic exposure meters to determine exposures in my architectural work and have not noticed any serious errors in the readings. It would be difficult for me to notice any small errors or fluctuations in that I always bracket exposures and select the best file. As of yet, I don't use LEDs as main light sources in the studio- mostly electronic flash and occasionally tungsten (hot) lights. I might purchase a few LED units to provide fill light for existing LED lighting.

Frankly, I am not very familiar with the spectral quality of LED lighting. I do know that various kinds of high-pressure sodium lamps and many kinds of fluorescent lamps have discontinuous spectrums that used to require elaborate filtration with colour films. In digital, I have never had any difficulty in achieving a decent white balance with all kinds of what was formerly "the lighting from hell" and again I don't recall any inaccurate readings with my handheld or in-camera meters.

Exposure wise, I consider myself a careful worker, however, I am happy if my meters get me well into the ballpark. In my studio and many routine and static conditions, my exposure is pretty well standardized. In less controlled circumstances. I will oftentimes second-guess my meters and come away with good files. The more you shoot the more instinctive you become and every time you solve a bizarre lighting or exposure issue, the solution remains in your "toolbox" for the next time and you say "....oh..., that again"!