Photography stops

Vincent

Senior Member
I was looking into light meters and came to the topic of correct exposure. (working with an old camera fearing the battery might run out and where only the light meeter stops in this camera)
It clarified what a stop was for me, I wanted to share.

When we look at a scene we can now what the light is, we do not need a meter for that. OK it takes some exercise, but humans are not bad at it.

Now depending on the light you need to adapt your ISO, shutter speed or aperture.

I learned by heart: Normal sunlight is EV15 ISO100 1/1000s f5.6

from that you can change 2 parameters in opposite direction and you still have correct exposure (change the same number of stops):
For ISO and shutter speed 1 stop is *2 or /2.
For aperture 1 stop is the next in line in the series: 1; 1.4; 2; 2.8; 4; 5.6; 8; 11; ... (this is 1; 1.4; 2*1; 2*1.4; ....)

So normal sunlight is also EV15 ISO200 1/2000s f5.6 or EV15 ISO100 1/500s f8.

When you see clouds the light is a bit less, that is about a stop: EV14 ISO100 1/500s f5.6; ...

I tried it on different scenes at lunch (under tree, skyline exposure, different sides of the tree, cars, sun/cloudy, etc...) and even if I do still miss 20%; 80% of the time this allowed me to manually set my camera in a position where I have maximum 1/3 of a stop of deviation without using the internal meter to set the parameters.
Obviously you can also work in between stops (on 1/3ds) in this way.

It seems very useful to me to check what your (internal) light meter states by looking at the light yourself and maybe correct (EV+-) and to evaluate material purchases, when knowing the relationship between capabilities and the effect in stops.

P.S. some use the sunny 16 rule, this should work similarly.
 

Horoscope Fish

Senior Member
I was looking into light meters and came to the topic of correct exposure. (working with an old camera fearing the battery might run out and where only the light meeter stops in this camera)
It clarified what a stop was for me, I wanted to share.

When we look at a scene we can now what the light is, we do not need a meter for that. OK it takes some exercise, but humans are not bad at it.

Now depending on the light you need to adapt your ISO, shutter speed or aperture.

I learned by heart: Normal sunlight is EV15 ISO100 1/1000s f5.6

from that you can change 2 parameters in opposite direction and you still have correct exposure (change the same number of stops):
For ISO and shutter speed 1 stop is *2 or /2.
For aperture 1 stop is the next in line in the series: 1; 1.4; 2; 2.8; 4; 5.6; 8; 11; ... (this is 1; 1.4; 2*1; 2*1.4; ....)

So normal sunlight is also EV15 ISO200 1/2000s f5.6 or EV15 ISO100 1/500s f8.

When you see clouds the light is a bit less, that is about a stop: EV14 ISO100 1/500s f5.6; ...

I tried it on different scenes at lunch (under tree, skyline exposure, different sides of the tree, cars, sun/cloudy, etc...) and even if I do still miss 20%; 80% of the time this allowed me to manually set my camera in a position where I have maximum 1/3 of a stop of deviation without using the internal meter to set the parameters.
Obviously you can also work in between stops (on 1/3ds) in this way.

It seems very useful to me to check what your (internal) light meter states by looking at the light yourself and maybe correct (EV+-) and to evaluate material purchases, when knowing the relationship between capabilities and the effect in stops.

P.S. some use the sunny 16 rule, this should work similarly.
That's called Exposure Reciprocity and it's one of the basic rules that used to be taught to photographers some years ago. The concept seems to baffle many but as you correctly point out once we establish a base-line for proper exposure we can adjust our settings and *know* our exposure is still correct while controlling depth of field (aperture), motion blur (shutter speed) and digital noise/grain (ISO).

Using Sunny 16 as our baseline we know f/16 @ 1/125 (Sunny 16) = f/8 @ 1/250 = f/5.6 @1/500 = f4/@1/1000 = f/2.8 @1/2000 etc. etc. etc.

We can do the same thing with ISO. If use "Sunny 16" at ISO 400 then f/16 @ 1/400 = f/8 @ 1/800 = f5.6 @ 1/1600 = f/4 @ 1/3200 etc. etc. etc.

Of course now we all have preview LCD's and histograms so these base skills are becoming a sort of Lost Art.

....
 

aroy

Senior Member
I have seen old timers in film era get the exposure spot on without a meter. Today with the latitude offered by a wide DR in digital sensors I can get away with a stop of over exposure and a few stops of under exposure. But still, knowing the sunny 16 rule does help if the meter in the body starts acting up.
 

WayneF

Senior Member
Latitude is a key point. Sunny 16 said bright sun was a shutter speed of 1/ISO at f/16, and it worked well for negative film, which had wide latitude, so exact exposure was less important for the negative film. It could always be corrected in the dark room. Photo finisher labs did heroic things with exposure and white balance of our film (mostly we not even know about white balance). Overexposure was sort of a virtue for negative film, extra insurance. However, slide reversal film and digital is harder, certainly overexposure becomes a real problem.

I think every roll of Kodak film sold had an instruction sheet that included Sunny 16 (as exposure instruction). Its hard for us to judge degree of overcast and cloudy exactly, but watching the shadows makes it much easier. Sharp shadows, soft shadows, barely visible shadows, no shadows. these were one stop steps. We can see that. And we ought to still always notice it.

Our meters will be much more accurate, but a thought in our head ought to always be, is this a reasonable reading? Comparing to Sunny 16 is a backup. Sunny 16 does not work at all well in partial shade situations, but it is pretty good out in the open, out in the light that exists. The meter is always better (if done right), but it ought not to disagree too much.

Sunny 16 says bright sun is not exactly EV 15, but within 1/3 stop. EV is not based on the sun, but instead the base is that any 1 second f/1 exposure is EV 0.
 
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aroy

Senior Member
The sunny 16 rule is more attuned to the European sun. Here in East the sun is much stronger so one has to adjust for that, may be sunny 32 will be more like it.
 

Vincent

Senior Member
The sunny 16 rule is more attuned to the European sun. Here in East the sun is much stronger so one has to adjust for that, may be sunny 32 will be more like it.

It is absolutely true that you have to adapt to your environment. Your reference might be different, but the principle remains.


I talked to an oldie in the trade and he stated that the diaporama develpment on film did not have a lot of latitude, you needed a meter since being wrong will lead to not usable results.
 

Vincent

Senior Member
A practical application of this.
I have the impression that the Sony A7 II is of no use for me, I have to stay with my idea to get better ISO performance, let us reason in stops.

Sony A7 II
IBIS 4.5 stops improvement on the shutter speed.
ISO 6400 (DXO Mark Dynamic Range EV score of 8 for the original A7)
24 Mpix

better ISO: Sony A7s
ISO 51200 (that is 3 stops better then the A7 II)
12 Mpix
========================
So in overall the A7 II is better due to better resolution and system that makes you gain more stops (1.5 more).
If I want to take a picture with a 50mm I can do 1/2s schutter time hand held normally with good results, with a bit of technique even slower.

Now the A7s has only 12 Mpix, but the strength is that it shows good 12 Mpix at high ISO.

Take a scene which needs flash: 5EV Night home interiors, average light. School or church auditoriums. Subjects lit by campfires or bonfires.
Can you do something without flash with this new technology?
We start from daylight 15EV 1/1000s ISO 200 f5.6.
There is gain of 10 EV needed, we go down to f2.8 so 8EV left to gain.

A7 II: 1/3s ISO 200 f2.8 would be possible and give the picture with a 50mm;
clearly I might choose f5.6 ISO 6400 1/30 s to be able to handle a little movement and have more DOF.

A7s: 1/250s ISO 12800 f2.8 is well possible according to most reports
Clearly I might want to choose: ISO 51200 f5.6 1/250s for a high shutter speed with more DOF.

So now it depends what you want to do.
The A7 II is good for a choir concert ,if their song is not too energetic.
I`ll probably be in a ruin looking at a birds nest with a telephoto and for me the A7 II will be useless at 1/30s, obviously a Df or D3s will do better for me, since the shutter speed is higher due to the stops gained in ISO and not in slower shutter speed.
 
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Stoshowicz

Senior Member
I always wondered why the camera couldn't expressly function as an absolute light meter rather than meter relative to exposure. Thats to say, give a numerical value somewhere above completely dark.
Calibrated to maximum aperture of the lens. Then I imagine one could more easily leap to the settings they might use. As in , this view has an approximate brightness of eight so Ill go with Iso 400.
It seems an increased complication to have the camera compute exposure , and then Ive got to backcalculate exposure compensation or adjustment.
Right now I do a lot of rough rule of thumb guesswork and don't have time to chimp the shot.
Essentially Im thinking it would be a refinement on eyeballing degree of shadow
 
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WayneF

Senior Member
I talked to an oldie in the trade and he stated that the diaporama develpment on film did not have a lot of latitude, you needed a meter since being wrong will lead to not usable results.

Reversal film (slides) don't have much latitude, but negative film had very wide latitude, if given enough exposure. That allowed Sunny 16 to work well for negatives, the dark room processing took care of the rest of it then.

Kodak used to specify the ASA film speed of B&W negative film as half of what it actually was, for greater insurance against underexposure (in regard to Sunny 16). But in 1960, they doubled the speed rating of all their B&W negative film, since light meters were becoming more available, and meters even had started appearing built into cameras (Nikon F had no meter until 1963). No internet then, camera magazines carried most communication, and you should have seen the articles protesting meters in cameras... are we going to let our camera tell us what to do? How could a meter in the camera possibly be accurate? Same old fogy nonsense that accompanies any new technology. :)

I always wondered why the camera couldn't expressly function as an absolute light meter rather than meter relative to exposure.

Camera meters can read reflected light from the subject. It can be absolute in that sense. But the one in a cell phone is not in the same class as the one in a DSLR. DSLR have very special purpose meter cells built- into the viewfinder, designed for the job. Compacts and cellphone (and Live View) can only just look at some pixels in the image.
 

Marcel

Happily retired
Staff member
Super Mod
Of course you can learn to do away without the light meter, the same way as you can drive a car without a speedometer. But I, for sure, wouldn't want to drive from Chicago to Los Angeles without a cruise control.

I really wonder what you are trying to prove.
 

Stoshowicz

Senior Member
Camera meters can read reflected light from the subject. It can be absolute in that sense. But the one in a cell phone is not in the same class as the one in a DSLR. DSLR have very special purpose meter cells built- into the viewfinder said:
Well Im meaning absolute in terms of , ummm, the camera already calculates how much light is coming into a sensor based on a voltage accumulated over a period of time, knowing aperture and ISO,,
Then it calculates whether that would be over or under exposed at the settings you chose.
It seems that it should be able instead to calculate the brightness of the scene and just tell me THAT- instead of changing the output 'relative value' with each click of aperture speed or change of ISO. I could then do a sweep of my circumstance , get a basic idea of how bright the scene is irrespective of my settings , and then I could go right to whatever settings I like to use, I wouldnt have to do clicks up and down from a floating exposure value. Im in accord with the old school guys, almost never use automated exposures and half the time never even consult the meter.

The camera appears to have the data , they just don't program it to inform in this manner.
 
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Horoscope Fish

Senior Member
It seems that it should be able instead to calculate the brightness of the scene and just tell me THAT - instead of changing the output 'relative value' with each click of aperture speed or change of ISO. I could then do a sweep of my circumstance, get a basic idea of how bright the scene is irrespective of my settings...
Are you asking why the camera's meter doesn't measure incidental light, like a hand-held light meter does, as opposed to measuring reflected light?

I ask because the in-camera light meter *does* calculate the "brightness of the scene"; it calculates the brightness of the *entire* scene and then averages everything to expose properly at middle grey.

...
 
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WayneF

Senior Member
Are you asking why the camera's meter doesn't measure incidental light, like a hand-held light meter does, as opposed to measuring reflected light?

I ask because the in-camera light meter *does* calculate the "brightness of the scene"; it calculates the brightness of the *entire* scene and then averages everything to expose properly at middle grey.

...


I am in full agreement. Just elaborating.

Probably very few beginners ever heard of an incident meter, so it seems important to explain. Camera meters are reflected meters (sees light reflected by the subject). Most Sekonic hand held meters can also meter incident light (sees direct light incident onto the subject). There have been early handheld reflected meters, but today, when one says "hand held meter", they most likely infer incident meter.

Incident meters also seek a middle gray level, same as reflected meters do. That is all any light meter can do, they are just a dumb chip with no knowledge of what the subject is, or what the readings mean. No experienced human brain to think it out. That's what we use the photographer for. :)

Reflected meters see very little light is reflected from the black dress, so they boost it to middle (which is overexposure). Reflected meters see a lot of light reflected from the white dress, so they pull it back to middle (which is underexposure). Both dresses come out gray. Neither is correct.

But incident meters read the light directly, which means black dresses come out black, and white dresses come out white, relative to that gray midpoint.

Incident meters are aimed the other direction, away from the subject towards the camera and the light source, so the subjects colors do not affect its reading. It literally measures the light. But reflected meters only see what the subjects colors can reflect.

Surely incident meters could be built into cameras, but incident has to be metered at the subject, to see the specific light actually on that subject. Handheld meters are greatly more convenient for that.

How Camera Light Meters Work
 
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Eyelight

Senior Member
That's called Exposure Reciprocity and it's one of the basic rules that used to be taught to photographers some years ago. The concept seems to baffle many but as you correctly point out once we establish a base-line for proper exposure we can adjust our settings and *know* our exposure is still correct while controlling depth of field (aperture), motion blur (shutter speed) and digital noise/grain (ISO).

Using Sunny 16 as our baseline we know f/16 @ 1/125 (Sunny 16) = f/8 @ 1/250 = f/5.6 @1/500 = f4/@1/1000 = f/2.8 @1/2000 etc. etc. etc.

We can do the same thing with ISO. If use "Sunny 16" at ISO 400 then f/16 @ 1/400 = f/8 @ 1/800 = f5.6 @ 1/1600 = f/4 @ 1/3200 etc. etc. etc.

Of course now we all have preview LCD's and histograms so these base skills are becoming a sort of Lost Art.

....

I can do this quicker with camera in hand, as I'm suspecting you can too. But, I think we missed f/11. Yes??
 

Eyelight

Senior Member
There is a very slight off target in the OP related to the use of EV.

EV is derived by a calculation that does not consider ISO or lighting . It is used to compare camera settings independent of actual light or film ISO (or digital sensor ISO sensitivity). So, aperture/shutter combinations that yield the same EV will yield the same exposure at the same ISO, but EV does not carry up or down ISO sensitivity. An EV of 15 would only be appropriate for bright sun at ISO 100.

So normal sunlight is also EV15 ISO200 1/2000s f5.6 or EV15 ISO100 1/500s f8.

1/2000 @ f/5.6 yields an EV of 16
1/500 @ f/8 yields an EV of 15

These EV values will always be the same whether at ISO 100, 200, 400, etc. And what this tells us is that the two combinations are 1 stop apart. Easier to see here because the shutter speed is 2 stops difference (double-double) and the aperture is only 1 (half).

Just remember EV is about shutter/aperture combinations. EV15, for instance, represents a series of equivalent combinations and only at ISO 100, all these combinations would yield an exposure appropriate for the proverbial Sunny 16 daylight shot. If you changed the ISO to 200 your EV (aperture/shutter combinations) would change to EV16 to yield the same Sunny 16 exposure. If you changed to ISO 800, your EV would change to EV18 (3 stops from EV15) to yield the same Sunny 16 exposure.
 
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