R.G. Loc: Scotland

Light meters that give lux values can be got for $20-$30. Exposure meters, on the other hand, are typically in the hundreds. It seems to me that the main difference between a modern light meter and an exposure meter is that the exposure meter can calculate appropriate values for aperture, shutter speed and ISO. That capability comes with a considerable price premium.

Is there some way to relate lux values from light meters to LVs (or EVs) for camera use? If there was, I'm sure there are relatively inexpensive ways to calculate camera settings for any given LV or EV. I don't personally know of any, but I wouldn't be surprised if there are calculators of the plastic wheel variety for just that purpose. I know that the Sunny 16 rule (and others) can do that, but there's mental arithmetic involved (), and it would be handy to have a method that applied to all light conditions, not just sunny days.

I'd do a search for calculator/converters but I don't know the proper terminology. A search of "Exposure calculator" produces lots of apps but I don't have a smartphone so I can't evaluate them. "Exposure calculator wheel" didn't lead me to any specific products.

Converting lux to LV shouldn't be too hard. It didn't take me long to find the following:-

Examples of light levels:-

Very Bright Summer Day - 100,000 Lux

Full Daylight.................. - 10,000 Lux

Overcast Summer Day... - 1,000 Lux

Very Dark Day.............. - 100 Lux

Twilight....................... - 10 Lux

Full Moon.................... - < 1 Lux

(The Full Moon value refers to ambient light strength - which has nothing to do with the values required to photograph the moon itself).

I get the impression that there's probably a relatively simple way to translate lux values to camera settings. Any suggestions?

BebuLamar

Yes

Log (Lux/2.5)/Log (2)=LV

If you have Log to the base 2 function (like in Excel) then
Log2 (Lux/2.5)=LV

That if you measure using a flat diffuser. With a dome use 3.3 instead of 2.5.

R.G. Loc: Scotland

Thanks for the info. I was hoping for a simpler connection. I suppose if an exact conversion is going to be that complicated, an alternative is to carry a table of values around. If it went something like

100,000 lux > LV 15

10,000 lux > LV 14

etc etc

would that be sufficient for getting reliable camera settings?

BebuLamar

Yes wii do shortly

R.G. Loc: Scotland

Thanks.

Found this for equating EV to lx -
.

(Download)

BebuLamar

The chart you have based on a K factor of 12.5 and C factor of 250 (with a flat diffuser). Which is the calibration factor used by Sekonic. Minolta uses K=14 and the same C=250 when using the flat diffuser.
When using the dome diffuser the C factor is 330 for Minolta and 340 for Sekonic. I post the chart for C=330 which agrees with your statement that LV15=100,000 Lux.

Attached file:
(Download)

DirtFarmer Loc: Escaped from the NYC area, back to MA

.

(Download)

R.G. Loc: Scotland

Thanks. The list I posted in the original post has steps of one decade whereas your list has steps of one octave (one stop). Your list puts 10,000 lx between LV11 and LV12. Thanks again for your contribution.

I'm still hoping that there's some sort of pocket exposure calculator still available somewhere. It's not that I can't do mental arithmetic.......

R.G. Loc: Scotland

Thanks for the post. It's interesting, but probably more information than is needed for my simple lux to LV translation.

bleirer

The second calculator here lets you enter lux and returns exposure value, but once ev is known there are many combinations of shutter speed, f stop, and ISO possible. https://www.translatorscafe.com/unit-converter/en-US/illumination/1-10/lux-lumen/foot%C2%B2/

Chart of common values http://www.fredparker.com/ultexp1.htm#EXPOSURE%20FACTOR%20RELATIONSHIP%20CHART%20B

BebuLamar

Once you know the LV (EV for ISO 100) you can figure out any combination of shutter speed, aperture and ISO without using any tools. Just need to memorize a bit. After a while it's easy.

rook2c4 Loc: Philadelphia, PA USA

Just write up a conversion chart on a business card size paper and place it in your wallet. That's what I did.

R.G. Loc: Scotland

Thanks for the links. That calculator should make it easy to run up a table.

I notice the author is one of those who think all you ever need is Sunny 16 plus a bit of arithmetic. I think I'll work my way up to that one .

R.G. Loc: Scotland

I'll take your word for it .

R.G. Loc: Scotland

Good idea. Thanks for the suggestion.