Is there such thing as a universal brightness measurement?

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I don't mean Kelvin or Candles or this kind of thing. I mean:

Let's say you're in a room and it's fairly dim and so you say to yourself, "This is about 20% bright."
Then you go outside and it's almost night time so it's quite dark out, and you decided that there's about as much light as there was in your room, so you also attribute it this "20% brightness."
Is this a reasonable comparison?

Now in this hypothetical situation, 0% brightness would be pitch blackness and 100% brightness would be light that would blow out any picture.
I came to this question by reading a textbook that used a technique where the photographer would give "brightness" measurements to differently lit areas of his photograph, and then expose for the average brightness of that aggregate.
For example, if it was dark in the foreground (30%), and light in the background (70%), he would expose for "50% brightness." (Let's say in this hypothetical, there was no main subject so it wasn't a matter of deciding what you wanted to expose more).

Is this a legitimate way of deciding exposure?
When you walk into a room, do you think in your head "I have to expose for 30%"?
If you're getting 30% light from a lamp and you walk out and you get 30% light from the ambience, do you expose them the same way?

If this is a legitimate way of deciding exposure, do you guys have different exposure combinations and their equivalent exposure settings (for different f-stop/shutter speed combos) ready to switch to?

The main reason I'm asking this is because I still have trouble walking into a room and determining the brightness level and where to start with my settings. Where I'm at right now is that I'll walk into a room or outside and say, "Oh it's kind of dark in here," then I'll open up my aperture and lower my shutter speed in a sort of wild guess, then adjust it by resorting to the light meter.

I wanna stop wildly guessing and want to know how to get to the proper settings, or close to it a bit more methodically.

Kind of a long winded question, but thanks to any who answer.
 
You cannot use your eyes because they are too adjustable to light. Why on Earth do you want to ignore the light meter that your camera supplies?

You do need to be able to improve the right meter reading - snow needs more exposure than he camera will want, very dark scene need less - but only a fool ignores the meter altogether.

Sent from my A1-840 using Tapatalk
 
Are you trying to describe tonal range?

The concept is clearer in B&W photography because light level (luminosity, or "brightness") is all you're looking at. It applies to color photography just the same, though, because generally you don't want to lose dark areas to solid black, and you don't want light areas to be completely blown out.

But it's not quite as simple as just averaging out a couple of spots in the scene.

Your process is flawed: make a guess, try some settings, and finally, "resort to the light meter." The light meter is the only useful reference you have for luminosity of a scene. It is impartial, not self-adjusting, and it has no bias as to what a scene "should" look like. None of those apply to the human eye and mind.

Experience will teach you when you need to adjust from the meter readings. Learning to use the metering modes is important, as well. Spot-metering may well produce a completely different image from matrix metering.
 
I don't mean Kelvin or Candles or this kind of thing. I mean:

Let's say you're in a room and it's fairly dim and so you say to yourself, "This is about 20% bright."
Then you go outside and it's almost night time so it's quite dark out, and you decided that there's about as much light as there was in your room, so you also attribute it this "20% brightness."
Is this a reasonable comparison?

Yes.

Now in this hypothetical situation, 0% brightness would be pitch blackness and 100% brightness would be light that would blow out any picture.
I came to this question by reading a textbook that used a technique where the photographer would give "brightness" measurements to differently lit areas of his photograph, and then expose for the average brightness of that aggregate.
For example, if it was dark in the foreground (30%), and light in the background (70%), he would expose for "50% brightness." (Let's say in this hypothetical, there was no main subject so it wasn't a matter of deciding what you wanted to expose more).

Is this a legitimate way of deciding exposure?
When you walk into a room, do you think in your head "I have to expose for 30%"?
If you're getting 30% light from a lamp and you walk out and you get 30% light from the ambience, do you expose them the same way?

If this is a legitimate way of deciding exposure, do you guys have different exposure combinations and their equivalent exposure settings (for different f-stop/shutter speed combos) ready to switch to?

As Derrel noted, I think in terms of EV, but yes what you're doing is identifying constant levels of ambient light intensity. Using EV values we do that by selecting the range of shutter-f/stop combinations that would expose correctly.

The main reason I'm asking this is because I still have trouble walking into a room and determining the brightness level and where to start with my settings. Where I'm at right now is that I'll walk into a room or outside and say, "Oh it's kind of dark in here," then I'll open up my aperture and lower my shutter speed in a sort of wild guess, then adjust it by resorting to the light meter.

I wanna stop wildly guessing and want to know how to get to the proper settings, or close to it a bit more methodically.

Kind of a long winded question, but thanks to any who answer.

Time for a story: When I became seriously interested in photography it was the 1970s and I was a student at Saint Louis University. The city's local camera store was just on the edge of campus and I used to hang out there. One day in the store I met old man Bob Arteaga -- old man meaning neither of his two sons Eldon and Wayne who were also in the business. Bob Arteaga had been a photographer for a long time by then. Here in St. Louis he is best remembered as the person who photographed the construction of the Gateway Arch -- wonderful photographs.

One day I was walking between classes and there was Bob Arteaga with his camera. It was a big old camera with a bellows. The camera was on a tripod and he was looking at the ground glass with a black rag over his head. He was photographing one of the campus buildings for the college. I introduced myself and asked if I could watch him work. When he had the camera ready he inserted a film holder, pulled the slide and made an exposure. Then he shot another one; I guess as a backup. I then asked him this question: "Excuse me Mr. Arteaga but I never saw you take a meter reading. How'd you know what the proper exposure was?" To which he answered as he pointed skyward: "For heaven's sake, the bleep bleep sun's shining. I was doing this before they invented light meters. I didn't need one then and I don't need one now."

What Bob had done was learn a range of reasonably constant lighting conditions -- he had trained himself to identify them with pretty good accuracy. Using EV values makes that process possible because you don't have to remember shutter speeds and f/stops -- only a single number.

This chart is on the back of one of my antique cameras:

expose.jpg


Those are EV numbers. Exposure on this camera was set by setting the EV value. The shutter speed and f/stop dials on the camera were locked together so that changing one changed the other.

EV vlaues

equation.jpg


Another story: I remembered my encounter with Bob Artega and decided to train myself to do the same. This came in very handy when I started to do a lot of canoeing. I didn't want to take the expensive cameras with me on canoe trips and what I had that I was willing to take were some older camera's made in the 60's that took great photos but didn't have light meters. Like this one:

retina.jpg


Not a problem setting the correct exposure without a meter -- like Bob said, "the bleep bleep sun is shining."

Joe
 
Outside, the Sunny 16 rule, and variations, works well. Indoors, which is what the OP mentioned, it is much harder. Photographers took to meters for a reason.

Sent from my A1-840 using Tapatalk
 
Outside, the Sunny 16 rule, and variations, works well. Indoors, which is what the OP mentioned, it is much harder. Photographers took to meters for a reason.

Sent from my A1-840 using Tapatalk

The OP mentioned both, "Where I'm at right now is that I'll walk into a room or outside..." For many decades before meters existed photographers managed to successfully take photos both outdoors and indoors. Erich Salomon's Ermanox wasn't equipped with a light meter in the 1920s. It is likewise possible to train oneself to reasonably judge the level of interior brightness, but yes it is more difficult than doing the same outside.

Not suggesting abandoning a meter if you have one -- just answering the OP's question.

I applaud the OP for the question and the effort to learn. There's advantage to having a good understanding of the photographic process. Another story: Again early in my career I worked selling Pro gear. I remember a fashion photographer who had to spend a lot of money paying for a re-shoot because he blew the original shoot. He brought me his light meter which we determined was at fault for his debacle. It had broken as was reading more than 5 stops off. How do you miss an equipment failure like that?

Joe
 
The short answer to your question... is there a way to measure universal brightness? The answer is 'yes'.

But then as you reword the question to ask if you can represent this on a scale where 0% is complete blackness and 100% is the point that blows out the exposure... the answer is no.

Camera sensors have something called "dynamic range" -- which is a measure of the tonal range of the camera sensor. This gets complicated... but each "stop" of light represents either a halving or doubling of the amount of light from the previous stop. So if I double the amount of light on a subject then I've improved the lighting by one "full" stop. Also... if I cut the amount of light in half, then I've reduced by one "full" stop. As I reduce the light, there will come a point where the amount of light is technically non-zero... but the camera is no longer able to detect that the light is half the previous amount and it's hit the limit of the range in the dark direction. Similarly, there will be a point at which the exposure is blowed (clipped) and the camera can no longer detect that you've doubled the light on the high range. If you then count the stops from dark to bright, that's your "dynamic range".

Except... as you boost ISO, you raise the floor value on the range, but given the limits of the chip, you cannot also raise the ceiling. This means each time you boost ISO, your camera loses dynamic range.

Camera manufacturers don't publish the "well depth" of their sensors, but astrophotography CCD cameras do. "Well depth" is a much more meaningful measure of dynamic range. A good DSLR might have about 32000 wells (while the manufacturer doesn't "publish" these values, we are able to do enough testing to derive the approximate limit of the camera.) A decent astro-imaging CCD camera would have about 100,000 wells (quite literally about triple what a good DSLR camera has). A scientific research grade CCD camera would probably have about 500,000 wells (if only our DSLRs could do that!)

Anyway... considering that each camera will have a different "dynamic range" and even the SAME camera will have it's range changed as you alter the ISO, you can see why you can't find an absolute definition of "100% light".

While it's easy to scientifically quantify the concept of absolute darkness in the same way you can quantify temperatures such as "absolute zero"... you can't quantify "absolute light" in the same way you can't quantify "absolute heat" -- no matter how much light you have, there's always a way to get even more light.

You can still have a standard measure of light... generically a non-photographic light meter would usually measure this in lumens. A photographic light meter can measure the light and convert it either to exposure settings... or it can display it in a bit more of an absolute value called Ev (Ev = Exposure value.)

Here's an exposure value table:

Av 0 12345678910
Tv1.01.42.02.84.05.6 8 11162232
01s012345678910
11/21234567891011
21/423456789101112
31/8345678910111213
41/154567891011121314
51/3056789101112131415
61/60678910111213141516
71/1257891011121314151617
81/25089101112131415161718
91/500910111213141516171819
101/10001011121314151617181920
[TBODY] [/TBODY]

Ok, so I'm not going to bother to color every cell in the table... but here's how it works.

The very easy formula is: Ev = Av + Tv

You use a light meter to meter the room in "Ev" (exposure value). An outdoor sunny day will typically meter at about Ev 15.

Look at the table and you'll notice that every Aperture value as an integer number assigned to it (counting 0 through 10 at the top of the columns).

Also, notice that every Time value (Time value = shutter speed setting) has an integer number assigned to it (also counting 0 through 10 at the front of each row.)

If you've metered the outside light at Ev 15 then you can use ANY combination of "Aperture value" plus "Time value" where they add up to "15". You can see in the table that there are lots of cells with "15" in them... and if you look to the left of the row and top of the column you'll notice (let's just pick f/16 and 1/125th) that the f/16 is Av 8 and 1/125th is Tv 7... and 8+7=15.

If you look at the colors you'll notice they run in diagonal stripes on the tables... all the cells with "7" (colored blue) form a diagonal stripe... that's because you can trade off one stop of aperture for one stop of time and get the same sum -- so these are all considered "equivalent" exposures.

One last thing... notice that there's no ISO?

That's because this was created in the film days and based on ISO 100. You'd need a table that's really a 3-dimensional cube to add in ISO.
 
I don't mean Kelvin or Candles or this kind of thing. I mean:

Let's say you're in a room and it's fairly dim and so you say to yourself, "This is about 20% bright."
Then you go outside and it's almost night time so it's quite dark out, and you decided that there's about as much light as there was in your room, so you also attribute it this "20% brightness."
Is this a reasonable comparison?

Now in this hypothetical situation, 0% brightness would be pitch blackness and 100% brightness would be light that would blow out any picture.
I came to this question by reading a textbook that used a technique where the photographer would give "brightness" measurements to differently lit areas of his photograph, and then expose for the average brightness of that aggregate.
For example, if it was dark in the foreground (30%), and light in the background (70%), he would expose for "50% brightness." (Let's say in this hypothetical, there was no main subject so it wasn't a matter of deciding what you wanted to expose more).

Is this a legitimate way of deciding exposure?
When you walk into a room, do you think in your head "I have to expose for 30%"?
If you're getting 30% light from a lamp and you walk out and you get 30% light from the ambience, do you expose them the same way?

If this is a legitimate way of deciding exposure, do you guys have different exposure combinations and their equivalent exposure settings (for different f-stop/shutter speed combos) ready to switch to?

The main reason I'm asking this is because I still have trouble walking into a room and determining the brightness level and where to start with my settings. Where I'm at right now is that I'll walk into a room or outside and say, "Oh it's kind of dark in here," then I'll open up my aperture and lower my shutter speed in a sort of wild guess, then adjust it by resorting to the light meter.

I wanna stop wildly guessing and want to know how to get to the proper settings, or close to it a bit more methodically.

Kind of a long winded question, but thanks to any who answer.




So you walk into a room and you decide the brightness level? Does that brightness level change in a few minutes as your eyes have adapted to the relative brightness of the room? If not, you should be seeing an ophthalmologist.

Like the others, I think you're confusing terms and usage. It sort of sounds as though you are describing the zone system. That system though is working with the photographic subject and not the photographic environment (walking into a room). If you were standing inside a close to completely dark room but shooting a photo of a distant sunlit horizon, your camera settings wouldn't be concerned about the room you were standing in.

Not sure though why you would bother to make such wild guesses before you've checked either your light meter or your camera's metering system. They are far more accurate than your eyes/brain/perception train.

The best way to stop wildly guessing at stuff is to go cold turkey - just stop - and learn to look at your metering system prior to adjusting your camera.
 
The short answer to your question... is there a way to measure universal brightness? The answer is 'yes'.

But then as you reword the question to ask if you can represent this on a scale where 0% is complete blackness and 100% is the point that blows out the exposure... the answer is no.

Camera sensors have something called "dynamic range" -- which is a measure of the tonal range of the camera sensor. This gets complicated... but each "stop" of light represents either a halving or doubling of the amount of light from the previous stop. So if I double the amount of light on a subject then I've improved the lighting by one "full" stop. Also... if I cut the amount of light in half, then I've reduced by one "full" stop. As I reduce the light, there will come a point where the amount of light is technically non-zero... but the camera is no longer able to detect that the light is half the previous amount and it's hit the limit of the range in the dark direction. Similarly, there will be a point at which the exposure is blowed (clipped) and the camera can no longer detect that you've doubled the light on the high range. If you then count the stops from dark to bright, that's your "dynamic range".

Except... as you boost ISO, you raise the floor value on the range, but given the limits of the chip, you cannot also raise the ceiling. This means each time you boost ISO, your camera loses dynamic range.

Camera manufacturers don't publish the "well depth" of their sensors, but astrophotography CCD cameras do. "Well depth" is a much more meaningful measure of dynamic range. A good DSLR might have about 32000 wells (while the manufacturer doesn't "publish" these values, we are able to do enough testing to derive the approximate limit of the camera.) A decent astro-imaging CCD camera would have about 100,000 wells (quite literally about triple what a good DSLR camera has). A scientific research grade CCD camera would probably have about 500,000 wells (if only our DSLRs could do that!)

Anyway... considering that each camera will have a different "dynamic range" and even the SAME camera will have it's range changed as you alter the ISO, you can see why you can't find an absolute definition of "100% light".

While it's easy to scientifically quantify the concept of absolute darkness in the same way you can quantify temperatures such as "absolute zero"... you can't quantify "absolute light" in the same way you can't quantify "absolute heat" -- no matter how much light you have, there's always a way to get even more light.

You can still have a standard measure of light... generically a non-photographic light meter would usually measure this in lumens. A photographic light meter can measure the light and convert it either to exposure settings... or it can display it in a bit more of an absolute value called Ev (Ev = Exposure value.)

Here's an exposure value table:

Av 0 12345678910
Tv1.01.42.02.84.05.6 8 11162232
01s012345678910
11/21234567891011
21/423456789101112
31/8345678910111213
41/154567891011121314
51/3056789101112131415
61/60678910111213141516
71/1257891011121314151617
81/25089101112131415161718
91/500910111213141516171819
101/10001011121314151617181920
[TBODY] [/TBODY]
Ok, so I'm not going to bother to color every cell in the table... but here's how it works.

The very easy formula is: Ev = Av + Tv

You use a light meter to meter the room in "Ev" (exposure value). An outdoor sunny day will typically meter at about Ev 15.

Look at the table and you'll notice that every Aperture value as an integer number assigned to it (counting 0 through 10 at the top of the columns).

Also, notice that every Time value (Time value = shutter speed setting) has an integer number assigned to it (also counting 0 through 10 at the front of each row.)

If you've metered the outside light at Ev 15 then you can use ANY combination of "Aperture value" plus "Time value" where they add up to "15". You can see in the table that there are lots of cells with "15" in them... and if you look to the left of the row and top of the column you'll notice (let's just pick f/16 and 1/125th) that the f/16 is Av 8 and 1/125th is Tv 7... and 8+7=15.

If you look at the colors you'll notice they run in diagonal stripes on the tables... all the cells with "7" (colored blue) form a diagonal stripe... that's because you can trade off one stop of aperture for one stop of time and get the same sum -- so these are all considered "equivalent" exposures.

One last thing... notice that there's no ISO?

There's no need or reason for ISO. EV 14 is EV 14 regardless of what's on either end of the shutter speed -- f/stop combination.

That's because this was created in the film days and based on ISO 100. You'd need a table that's really a 3-dimensional cube to add in ISO.

No, it's not based on ISO 100 from the film days. It's just an EV table. You're over-thinking it. EV values are simply the constant produced by a reciprocal set of shutter speeds and f/stops. They don't change relative to ISO. The EV value we use when setting an exposure changes relative to both the ambient light level and ISO.

Joe
 
Ysarex said:
Outside, the Sunny 16 rule, and variations, works well. Indoors, which is what the OP mentioned, it is much harder. Photographers took to meters for a reason.

Sent from my A1-840 using Tapatalk

The OP mentioned both, "Where I'm at right now is that I'll walk into a room or outside..." For many decades before meters existed photographers managed to successfully take photos both outdoors and indoors. Erich Salomon's Ermanox wasn't equipped with a light meter in the 1920s. It is likewise possible to train oneself to reasonably judge the level of interior brightness, but yes it is more difficult than doing the same outside.

Not suggesting abandoning a meter if you have one -- just answering the OP's question.

I applaud the OP for the question and the effort to learn. There's advantage to having a good understanding of the photographic process. Another story: Again early in my career I worked selling Pro gear. I remember a fashion photographer who had to spend a lot of money paying for a re-shoot because he blew the original shoot. He brought me his light meter which we determined was at fault for his debacle. It had broken as was reading more than 5 stops off. How do you miss an equipment failure like that?

Joe

Joe,
Do you recall the circular calculator system that was sold for a time, mail-order mostly, in which lighting levels and exposures were tied to a simple X-value system, which began with the Sunny 16 rule as the Zero-X baseline, and then added exposure in one-stop or one-X increments? I read about it in Popular Photography magazine, but it never got off the ground really. Sort of similar to Fred Parker's Ultimate Exposure Computer, but a bit different, and I would say, better conceptualized. Parker's Ultimate Exposure computer is shown as an EV value chart that is directly associated with real-world lighting scenarios, like EV 16 which is light that is one exposure value brighter than Sunny 16, meaning EV 16 is "Subjects in bright daylight on sand or snow". The Sunny 16 rule means light that is E.V. 15 in brightness.

The EV System is fine as a framework, but it is almost always presented merely as a charted set of numbers and f/stop and shutter speed times, with no verbal or illustrated linkage to actual shooting scenarios or common types of scenes. We can say "EV 14! EV 15!", but without a kind of scene, a type of location, or some kind of general description, the saying of the two words, "EV fifteen" means...nothing to most people.

The X-System, as it was called (to the best of my recollection) began as I said, at Sunny 16 at let's just say, ISO 100 film speed, so f/16 at 1/100 second. Keep in mind, the Sunny 16 settings refer to an EV light value rating of 15. The X-system began there, as "O-X", or Baseline. As the light level grew dimmer, another "X" was added, meaning the lens was opened up one more stop, or the shutter slowed by one stop value, or any combination of both.

So...beginning at Zero-X,the X-system was like this:
The Full moon or weak, hazy sunlight was +1-X.
Cloudy-bright with no shadow light was +2-X.
Heavy Overcast or Open Shade lighting was +3-X.
Sunsets and Deep Shade was +4-X.
Landscapes and City Skylines just after sundown was +5-X.
Neon Lights,Landscapes, Skylines, 10 mins after sunset +6-X
Las Vegas, TImes Square,campfires,bonfires,ice shows, baseball, football, bright interiors with florescent light +7-x.
Indoor sports, circuses, bottom of rainforest canopy, +8-x.

This continued to Moonlight, at +20-X for moonlit landscapes, and ended at +21-X, starlighted landscapes.

The Minus-X stuff was all crazy-bright stuff, like "Welding Arc flame at work surface" and so on.
This system had basically 21 different scene brightness levels to work with in normal, everyday situations. The advantage it offered was that it began right at the Sunny 16 rule, and was based on the simple idea like, okay, some light clouds come out, I need to go Plus-1 "X". A little bit darker but still daylight, plus 2-X. Heavy Overcast or Open Shade, plus 3-X. So, basically, there are about 21 different exposure brightness values that a person could use for most of a lifetime, and only 12 of them which take you down in brightness (but "up" in X-value) to "Fireworks".
 
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Now in this hypothetical situation, 0% brightness would be pitch blackness and 100% brightness would be light that would blow out any picture.

So 0% would be zero photons a minute? You can increase this brightness quite a bit before any consumer camera will be able to detect anything. But it's easy to define.
100% is MUCH more difficult, I've used shade 14 welding glass to photograph sun-spots The camera wasn't blown out at all, but if it was I could easily have added another bit of welding glass. Even defining 100% to exclude ND filters, you can use a pinhole 'lens' (usually ~f/128) and choose a camera with different dynamic range (possibly even one not yet available).

Defining the scale to set 100% to be bright daylight, and allow the possibly of brightness percentages over 100% could work, but in reality the EV scale is more useful (as are Candles or Lumins which are actual absolute measures of brightness).

Kelvin is a temperature scale and not directly related to luminosity - If the light is produced by black body radiation it can be calculated from the temperature (it's not linear) with other sources of light (like LEDs) the relationship falls down completely. In photography the colour temperature is the equivalent black body temperature to give the same colour but not related to light intensity.
 
Whatever book you're reading sounds like it's discussing the zone system.
Yes. And no. Zone system is a part of general philosophy of exposure, a part with specific application, not really much usable with averaging meters or digital technology.
To OP. You can't rely on your eyes to determine subject brightness. There is no such a thing like 100% brightness, even Sun is not that bright. Only, our tools have limitations thus it seems, that there is. However you're right with 0%, no photons at all. If you want to see the differences in brightness between let say background and something else the universal tool for it is a spot meter.
 

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