# EC - adds or subtracts light?



## monkey44 (Dec 18, 2014)

OK, got a bet on this one, if I win it, she buys lunch, if I lose it, I buy lunch. It's always difficult for anyone to "get it" -- larger number f-stop means LESS light, a contraction in math, usually, except in photography, same with SS, smaller number means MORE light ... 1/250s is more light than 1/500s, a contradiction to most people unfamiliar with how a camera and lens functions.

When we open or close f-stop, the sensor gains or loses light. Opening f-stop means the number gets smaller. a f-4 lets in MORE light than an f-8 at same SS and ISO ... 4 is a smaller number in math than 8 ... so we think 8 is larger, so lets in more light. Obviously, incorrect in photography.

So, when we say f-4.0 w "EC + 1/3," and write it as a calculation, it would be 4.0 + .333 -- so the immediate implication here is LESS light, because we're now mathematically adding 1/3 to a number, and in photography, larger is LESS light -- therefore, f-4.333 would be smaller aperture than f-4 ... So, if we read it as 4.0 + 1/3 stop, we imply we land BETWEEN f-4.0 and f-4.5 ... and if we move in a larger number direction, then the f-stop lets in LESS light.

SO, the bet is: True or False --- f-4 and EC + 1/3 means LESS light hit the sensor ... because f-4 plus a third = f-4 plus one third lands between 4 and 4.5 ---

So, please do NOT guess, or say "I think" blah, blah, blah (I think, means I guess, not I know, right?)-- explain how the mechanics of this function works, so I can show it and win lunch. Merely saying -- + 1/3 adds light, or - 1/3 subtracts light will not help (or the reverse). I need to prove it from the technical standpoint, what actually happens to the shutter when we plus or minus a stop fraction. I'm not stating my opinion here, on purpose -- just assume I know, and need support to win the bet. And, believe me, winning this bet is totally worth it ... hehehe ... but even if I lost, the lunch hour will be worth it !!


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## jrista (Dec 18, 2014)

You are misunderstanding what exposure compensation does. When you adjust EC, your are NOT adjusting your priority setting. If your Av, that means aperture is your priority setting. YOU control Aperture, the camera controls shutter (let's assume fixed ISO for the moment.) If your Tv, that means shutter is your priority setting. YOU control Shutter, the camera controls aperture. When you compensate, your compensating the *OTHER setting*,* not *the one you control. So, it isn't f/4 +1/3 -> 4.0 + Aperture 0.3333. That's fundamentally wrong. You CHOSE f/4, the camera cannot compensate your exposure by adjusting aperture..._it has to adjust shutter_. So, it/s f/4 + 1/3 -> 4.0 & ShutterSpeed One Third Stop SLOWER. In other words...MORE LIGHT! 


For more specificity:


EV +1/3 means ADD one-third light. This is obvious, as when you adjust EC positive, it shifts the metered exposure indicator to the left. If your shooting Av, that results in a SLOWER shutter speed; if your shooting Tv, that results in a WIDER aperture (if possible...obviously you've got a problem if your already at max ap.) If you adjust EC negative, that shifts the metered exposure indicator to the right. If your shooting Av, that results in a FASTER shutter speed (if possible, if you hit 1/4000 or 1/8000 or whatever your camera max is, you've got a problem); if your shooting Tv that results in a NARROWER aperture (if possible, if you hit min aperture, you've got a problem.)


SLOWER shutter/WIDER apeture = MORE light
FASTER shutter/NARROWER aperture = LESS light



Exposure compensation should be very easy to understand...you "compensate your exposure by adding or subtracting light." So, +1/3 means ADD a third stop light, and -1/3 means SUBTRACT a third stop light. This is easy to verify...just look at what your EC adjustments do to the automatic exposure setting (the other one, the one you are not controlling yourself).


This explanation assumes your using a priority mode on the camera. In manual mode, EC often does not do anything on many cameras. Some cameras, like Canon's 1D X, will allow you to use EC to adjust ISO, while you control both aperture and shutter. It's the same deal, though, +1/3EC means increase ISO to increase the exposure.


Sorry bub! Gotta tell the truth here. Sounds like *your buying* lunch! ;P


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## tolusina (Dec 18, 2014)

+EV compensation = more light through larger aperture (smaller f/) or slower shutter (1/smaller) and/or an increase in sensitivity (do show increased sensitivity at lunch, whoever wins) higher ISO.

-EV = less light or ISO.
---
From Wikipedia.....
_"In optics, the f-number (sometimes called focal ratio, f-ratio, f-stop, or relative aperture[1]) of an optical system is the ratio of the lens's focal length to the diameter of the entrance pupil."_ 

So, the larger the physical opening of the lens, the closer it is to the lens' focal length, the lower the ratio.


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## bbb34 (Dec 18, 2014)

*smaller number - LESS light!*

Besides the confusion what exposure values (EV) are, and how exposure correction (EC) works, you got the basic maths wrong.

1/250 is larger than 1/500 ! They are fractional numbers. Maybe it is more obvious in decimal numbers:

1/250 s = 0.004 s > 0.002 s = 1/500 s

-> Bigger exposure time gives more light. It's logic, or not?


The trouble with the f-stop is that nobody pronounces what they are: fractional numbers! (But they are written correctly at the front of your lens)

When people say f/4 or f/8, they really mean the ratio between the focal length (f) and the diameter of the lens entrance (D). 

For instance, if you have a 80 mm lens: 

f/4 = 80 mm / 4 = 20 mm

f/8 = f / N = 80 mm / 8 = 10 mm

Therefore, f/4 is bigger than f/8 ! Bigger aperture gives more light. 


regards,
bbb


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## Joey (Dec 18, 2014)

*Re: smaller number - LESS light!*



bbb34 said:


> 1/250 is larger than 1/500 ! They are fractional numbers. Maybe it is more obvious in decimal numbers:
> 
> 1/250 s = 0.004 s > 0.002 s = 1/500 s
> 
> ...


Neat, accurate, clear explanation. Couldn't have said it better myself.


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## jrista (Dec 18, 2014)

The problem isn't the math, though, even though it was wrong. 


The problem the OP has is that his understanding of what EC changes is incorrect. Adjusting EC does not change the priority setting. If you are in Av and change EC, you aren't going from f/4 to f/4.5. You stay at f/4, and SHUTTER changes. Conversely, if you are in Tv and change EC, you aren't going from 1/250th to 1/320th. You stay at 1/250th, and APERTURE changes. 


Exposure compensation is designed to allow you to influence the metered exposure. You have to think the right thing. You want to "compensate the metered exposure by +1/3rd stops"...if you think like that, then EC +1/3 means something, whatever it is as determined by your camera mode, has to change in order to make the exposure BRIGHTER, not dimmer.


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## neuroanatomist (Dec 18, 2014)

monkey44 said:


> 1/250s is more light than 1/500s, a contradiction to most people unfamiliar with how a camera and lens functions math



There, I fixed that for you. 



bbb34 said:


> ...you got the basic maths wrong



Indeed. However, the concept does have some personal relevance, as my daughter is just now learning that a larger denominator means a smaller number...in *first grade* math.


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## monkey44 (Dec 19, 2014)

Well, as I review the post -- I did get some things backwards, that's what I get for writing with my fingers and not my brain ... and multi-tasking at the same time.

In any event - yes, I get it. My position is: When you add + 1/3 (thinking in terms of AV priority) then the shutter will slow down and allow MORE light (open longer) to hit the sensor. 

My "Opponent" says the fraction becomes smaller (adding 1/3 to the f-stop in her example) means the aperture gets smaller and lets in less light (she says). But even if I wrote it backwards, the actual fact is: + 1/3 means you (the camera) either slows shutter or opens aperture, depending on which is priority (and assuming it has the room to make the change) ... and the sensor has more light to work with when exposing + 1/3 ... That was my point in the bet.

Also, should not have used f-4 in example, as many lenses will not open wider than f-4 ... using f-8 would have made more sense -- so an f-4 lens could go either direction. Blah!! 

So, in fact - I win the bet!! Lunch will taste great ! Too bad I can't share it with you all -- Have a great holiday, and enjoy the new year ... Thanks for the tech explanations -- 

In fact, what began the 'discussion' was my original comment to her. I said: When you set AV priority and you set +1/3, the shutter slows 1/3 of a stop in time value (shutter speed). She disagreed ... and said, " + 1/3 makes the aperture read f-4.333 instead of f-4.0 ... and that's how it started. Course, couple wine's helped the confusion   

To admit my own personal case tho too -- I began my career with film/slides years ago, and so when I try to compute or understand the technology in DSLR - I get lost pretty quickly. My brain does not wrap around an electron and the technology that controls it. I get what it does, not how it does it ... have no wish here to jump on the benefits of technology nor the difference it brings to the image table -- technology changes too quickly for me to keep up, and with limited background in the tech world, it's even worse when a change makes me "study more and shoot less" ... <laughing at myself> Great forum here, lots of knowledge and willingness to share ...


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## BozillaNZ (Dec 19, 2014)

First, thanks for the good laugh!

Second, if you can't grasp the fact that 1/250 is bigger than 1/500, or 1/4 bigger than 1/8, I suggest you read 1st Grade Math, Chapter Fractional Numbers :

If a f/1 lens with 1 second shutter gives you 1 dose of light

then a f/2 lens with 1/2 second shutter gives you a quarter dose of light, since 1/2 * 1/2 = 1/4, how magical is that?!


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## dcm (Dec 19, 2014)

Perhaps an example from my film days will help. Here's the exposure compensation dial on my trusty old A1 in the photo below to help illustrate. Note it is on the ASA/ISO dial because that is what it directly affects. The exposure compenstation 1/4,1/2,1,2,4 affects how the camera meters the scene as a delta from the current ISO of 400 at EC=1 as in the middle image. The EC numbers refer to the amount of light relative to 1 that will be metered, not the number of stops. So a 4 (+2 stops) in the top image means to meter like the camera was loaded with ISO 100 to overexpose while a 1/4 (-2 stops) in the bottom image means to meter like the camera was loaded with ISO 1600 to underexpose. 

How this affected the camera depended on the mode you are using. In P it would follow the program up or down, possibly changing both the shutter speed and aperture. In Av it would change the shutter speed to compensate while in Tv it would change the aperture to compensate. In manual it had no affect on either shutter or aperture, you controlled them both and ISO was fixed.

DSLRs operate similarly, EC affects the metering of the scene which determines the settings. But in recent DSLRs you can set the aperture and shutter manually, then let the camera vary the ISO to obtain the correct exposure. Exposure compensation doesn't change either the aperture or shutter in this case, it just modifies the ISO that will be selected to control exposure thereby underexposing or overexposing the image. 

Hope this helps.


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## monkey44 (Dec 19, 2014)

I know, I know -- I wrote the math backwards -- that's why I put <laughing at myself> We sit here and try to make sense of all the technology, technique, settings, light, frame, composition, and everything that goes with it, then make a bonehead reverse of what we really want to say / ask ... and then every one laughs, and tomorrow we all wake up and go capture something interesting and all the talk and chatter goes away ...   

Until the next time -- but I'm glad to supply today's dose of laughter because we often don't get enough of that. I think I'll go camping this weekend, and try out a few plus and minus shots !!! ;D ;D ;D


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## bbb34 (Dec 19, 2014)

@monkey44: Your attitude and how you are dealing with the laughter is just great. A lot of forum user have a lot to learn from you!

Then, be assured that *most* photographers understand as much of the physics and circuitry of a digital camera as they did understand of the chemistry of photographic film. Close to nothing. Anyway, what we have discussed above has nothing to do with how the film or sensor works. It is only about the optics, just to the point where the light hits the light sensitive whatever.

cu,
bbb


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## monkey44 (Dec 19, 2014)

QUOTE: ">>> It is only about the optics, just to the point where the light hits the light sensitive whatever."

Yes, correct - it's the same thing that happens when light hits film/slide, and for how long, and whether the film gets over / under or proper exposure. 

I'm not so certain it happens exactly the same way, as in digital cameras or film cameras that is, but the result is the same when you "see" an image either on screen or printed. The mini-computer may do some of the 'action' that creates exposure -- I'm not exactly sure that the shutter and the f-stop mechanism work in the same way in a digital camera as in a film camera, particularly the old manual camera before EOS appears.


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## bbb34 (Dec 19, 2014)

Both, film and sensors have plenty of peculiarities and artefacts.

- Film chemistry is complicated and highly non-linear.
- Sensors depend on incident angle, there might be micro-lenses and filters, and certainly post-processing. 

But for the basics of photography, shutter, aperture and sensitivity are controlled in exactly the same way.


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## bbb34 (Dec 19, 2014)

BozillaNZ said:


> If a f/1 lens with 1 second shutter gives you 1 dose of light then a f/2 lens with 1/2 second shutter gives you a quarter dose of light, since 1/2 * 1/2 = 1/4, how magical is that?!



Almost, but you are missing a square. Aperture is measured as a diameter, but the light that gets through is proportional to the area of the aperture.

Therefore going from f/1 to f/2 gives only a quarter of the light.
From f/1, 1 s to f/2, 1/2 s would give an eighth of light.


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## Joey (Dec 20, 2014)

bbb34 said:


> BozillaNZ said:
> 
> 
> > If a f/1 lens with 1 second shutter gives you 1 dose of light then a f/2 lens with 1/2 second shutter gives you a quarter dose of light, since 1/2 * 1/2 = 1/4, how magical is that?!
> ...


Yes indeed. Twice as bright as f/2 is f/1.4. The formula is SqRoot(2) which is 1.4142 and a few more decimals, simplified to f/1.4. Interestingly, photography has always rounded the numbers around the shutter dial and aperture dial. Half of 1/8 is 1/16 but the next shutter speed (Time value) on the dial is 1/15, for instance. Also Twice as bright as f/16 is actually f/11.313 but it's always written as f/11.


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## monkey44 (Dec 20, 2014)

YEAH, it's kinda like PI ... 3.14 is close enough, but mathematicians have been trying to get the absolute forever. Not sure what that will change in our world if someone ever gets that final decimal figure. The only people that care are other math folks -- the rest of us grab the numbers we're given and go out and push a shutter button.

What do we have then? An image. What to the PI seekers have? An enigma and no reward. Which door do you choose?


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## Marsu42 (Dec 20, 2014)

monkey44 said:


> YEAH, it's kinda like PI ... 3.14 is close enough, but mathematicians have been trying to get the absolute forever. Not sure what that will change in our world if someone ever gets that final decimal figure.



Hasn't it been proven that irrational numbers like pi have no end, and if you translate the numbers into chars every book ever been written and will-be-written in the future is contained in it (if you look at the right decimal place)?


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## monkey44 (Dec 20, 2014)

Marsu42 said:


> monkey44 said:
> 
> 
> > YEAH, it's kinda like PI ... 3.14 is close enough, but mathematicians have been trying to get the absolute forever. Not sure what that will change in our world if someone ever gets that final decimal figure.
> ...



Yeah - right, like the chimpanzee banging on the keyboard to infinity (He once banged on a typewriter, but the chimp upgrades to keep up with the Jones family) and writing out the complete works of Shakespeare ...

The engineers already did the numbers -- and all these reviewers are simply copying those numbers in a more personal way - and people that continue finding infant-sized infringements on the math potential of this 7D2 just waste a lot of time. It's not gonna change, ever. It's done, designed, and taking it out into the field and capturing images should now be the only criteria for judging its merit.

A little bit ago, I was reading a thread where a guy posted an image he really, really likes. And someone else started negatively popping off about the 'tech details' -- how far off it is, and what it needs to be "perfect" in the technical sense -- but the problem with that package?? The guy who shot it might (shouldn't tho') change his image to suit "MR TECH PERFECTION", but then he might lose (probably will lose) the artistic character the image presents, and what appeals to the guy most about the image as it exists now. I didn't care for the image much personally -- but it did have a sense of intrinsic beauty about it regardless, although I'd never buy it.

We are artists, not technicians (at least not specifically) and we create images to enjoy in an artistic sense ... or maybe even in a documentary sense (every image we create is one piece of history, a spit second in time that will never exist again -- and knowing the "rules" and then breaking them artistically separates artists from mechanics in the photography field.

Just my opinion, of course. But given a choice between taking a 7D2 out in the field and maybe breaking the rules creating an image I like wins hands-down to sitting at a table with a pen and paper, figuring out the next step in the PI equation ... Believe it!


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## bbb34 (Dec 21, 2014)

Some people need to sit down at a table with pen, paper and a firm grip on science. Some of them build cameras. You depend on them. A bit more appreciation would be nice. Believe it!


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## monkey44 (Dec 21, 2014)

bbb34 said:


> Some people need to sit down at a table with pen, paper and a firm grip on science. Some of them build cameras. You depend on them. A bit more appreciation would be nice. Believe it!



Yes absolutely -- I appreciate the engineers that make my photography life easier and more creative -- that was not my point. Point is, once the engineers design it, and manufacturers build it, the arguments about how good or how poorly the math works simply become less effective or interesting after the camera fills my paws. 

But some guys spend a lot of time here stating engineering facts over and over, which means absolutely nothing until you go out an capture an image -- and even if the math is perfect and accurate, the image might still suck because of framing or composition etc. (Or the light can change in a few seconds, and make an image great, or blow it out) -- which has little to do with math and everything to do with artistic vision.

Nothing will change the math those engineers did after production. So, most of the reviews regurgitate the same numbers Canon posts in its advertising and spec sheets. So, to post those spec figures again and again, and again, call it a review becomes nonsensical after awhile. The real world images it produces become the true test of any camera (based on the photographer and skill level) ... so, to state the math over and over as if it makes a difference ?? It doesn't ... 

We constantly read complaints from guys simply reviewing the math (and bashing Canon) and the real information comes visually from the actual IMAGE itself after we capture it. And to evaluate an image mathematically instead of artistically makes less sense. Because one person thinks pulling information up out of the shadows makes a more interesting image may work for that one person, but not for everyone. Some actually LIKE the shadows and the darkness for effect ...

So, to tell on artist the his image sucks because it has too much red, or too much green, or looks soft or dark in one corner or edge (unless that indicates a problem with equipment, maybe?) does not do justice to any one. Unless that person is asking for that advice.

Personally, I care less if a camera or lens can make a wall chart with circles in it look sharp -- I never shoot wall charts, nor would we have much luck selling one. What I want to see is its ability to track, its ability to point-focus on a flitting bird, its ability to create a great seascape or landscape, or some other artistic vision that only the photographer sees in his/her mind until it becomes an image s/he can share with others ... when it makes that bird's eye tack-sharp amongst a surrounding collection of leaves all interfering with focus ... those abilities are what make me appreciate a camera. 

So Yes -- absolutely, a heartfelt thanks to all the engineers with pencils who make this possible -- but, once it's built and the images engage our emotions -- let an image judge its success or failure, not math equations.

Someone earlier posted the "most expensive photographs ever sold" -- so, maybe, just maybe someone took all the measurements of light, color, sharpness, composition, etc. and said: "Wow, perfect photograph." But I gotta tell you, I wasn't impressed with the images (Billy the Kid, the exception for its historic value, and its artistic sense as well) nor were a lot of other folks on here impressed. But a lot of other folks will flame this comment - stating people that don't like those images have no understanding of ART and can't appreciate it ... a real mistake. But I also believe those image sales for that kind if money is pretentious, contrived, and a lot of hogwash from the art perspective. Of course, from the financial perspective, it ranks right up there at the top of the list, and nothing would please me more than some rich person buying one of my images (even my favorite image) for a million bucks. But that would not change my opinion of all the above tho'...  :


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## jrista (Dec 21, 2014)

I understand that to some people, the only thing that matters is the creative aspect of photography. That said, having a proper understanding of the technical nature of the device in your hands can only benefit those creative endeavors. 


Not misunderstanding how to use exposure compensation, for example, can mean the difference between underexposing by 4 2/3rd stops, when you wanted to compensate by +2 1/3rd stops (yes, think about that...if you accidentally compensate by -2 1/3rd stops when you actually needed to compensate by +2 1/3rd stops, the error is 4 2/3rd stops!! ) Understanding what increasing ISO will do to your photo, vs. opening the aperture or reducing the shutter, can affect not only the quality of your photograph...but also it's characteristic. Increasing ISO can result in higher apparent noise. Opening the aperture reduces your depth of field. Reducing shutter increases the amount of subject motion blur. These are not just technical aspects...they affect the creative aspects as well, they change the nature of the art. 


Personally, I think that, even if you solely pursue the creativity of your photography, it is important to understand how the device that let's you create those works of art operates. Having that understanding means you, the artist, can make more effective use of the tool(s) at your disposal. It means you make fewer mistakes (like not under-exposing when you misunderstand what exposure compensation means), and therefor have more creative "hits"...successful photos that might indeed actually turn into true works of art in the end...instead of another dud that gets tossed into the digital trash bin.


Don't underestimate knowledge. This place, CR, has far too many technical wars. I've been party to them myself in the past, and I've tried very hard to extract myself from them these days. They are pointless. However that's quibbling over minutia, which is different than becoming educated about the technology. I strongly encourage you to learn the specifics about the technology, so you know how it works, how it affects your art, so you can better employ the camera filling your paws to produce the creative works of art you want to.


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## Don Haines (Dec 21, 2014)

For those somewhat less technically or mathematically inclined...

Put camera in live view.... push compensation button, turn thumbwheel. One direction (+) the exposure gets brighter, the other direction (-) it gets darker...


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## monkey44 (Dec 22, 2014)

jrista said:


> I understand that to some people, the only thing that matters is the creative aspect of photography. That said, having a proper understanding of the technical nature of the device in your hands can only benefit those creative endeavors.
> 
> 
> Not misunderstanding how to use exposure compensation, for example, can mean the difference between underexposing by 4 2/3rd stops, when you wanted to compensate by +2 1/3rd stops (yes, think about that...if you accidentally compensate by -2 1/3rd stops when you actually needed to compensate by +2 1/3rd stops, the error is 4 2/3rd stops!! ) Understanding what increasing ISO will do to your photo, vs. opening the aperture or reducing the shutter, can affect not only the quality of your photograph...but also it's characteristic. Increasing ISO can result in higher apparent noise. Opening the aperture reduces your depth of field. Reducing shutter increases the amount of subject motion blur. These are not just technical aspects...they affect the creative aspects as well, they change the nature of the art.
> ...



When this monkey takes the camera in his paws, he understands exactly how it works - at least he knows what to do when it 'needs something' to set or adjust, and create the image he wants. Then, it's up to the physics, and the physics is far beyond my need or requirements. The fact that adding EC on the plus side adds more light on the sensor and exposes the image in the manner the photographer means is enough -- the math behind the technology that allows it to work is irrelevant to in the 'create the image' component.

But, after a few people had fun (we all did, laughing, remember) this original thread began about a bet, which I won, and some folks here think the 'inaccurate side' emerged from this side of the table, when in fact the question was asking for support so my partner at lunch would 'get it' in the way I explained it to her ... then, when I wrote it, I got some of it backwards, confusing myself as I wrote it, because I was giving her side and my side all rolled into one, -- yes, gimme some more of that wine, or whatever it was  -- instead of only one side -- letting my fingers write the words instead of my brain -- altho', the brain did pick up and deposit some new knowledge as well during this adventure ... 

All of us should be in favor of learning and educating (and sharing that knowledge) ourselves about our craft -- but more often than not, the arguments or discussions here whither on the side of math and technology and ignore the artist side completely, when in fact it's always both. 

We all need to accept great technology that has emerged in DSLR's and in photography in general allows us to better express that artistic side - which is what it's all about in the end. Sharing a vision with others to the enjoyment of all parties, no matter what process it take to get to that moment.


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## monkey44 (Dec 22, 2014)

Don Haines said:


> For those somewhat less technically or mathematically inclined...
> 
> Put camera in live view.... push compensation button, turn thumbwheel. One direction (+) the exposure gets brighter, the other direction (-) it gets darker...



And one interesting fact follows here too -- thinking about the "original image creating theory", for the moment - in a darkroom.

Adding into the mix -- the sometimes convoluted way we measure exposure -- in general, public thinking says when we 'up a number' the value increases 1+ 2+ 3+ etc ... but when we up the number in aperture, the value (light source) decreases. A confusing fact, I'll bet, when each of us first heard it. And, in the darkroom, when we add light to photo paper, instead of "lightening" the paper, it darkens the paper (in areas where the negative allows that light to pass, it's backwards again.) So, adding light in effect increases darkness. So, when we - or anyone - turns that wheel, + 1/3 and the image gets darker, we again find a conflict in terms, where adding light darkens the image. So, one could draw the conclusion that darkening in the viewer is actually under-exposing the image because it lightens the image view ... we first need to KNOW that intuitive thoughts often lead to the opposite effect in imaging ... and turning that wheel enough in one direction will blow out the image completely, and make it too light, whereas, the same process (adding light to photo-paper in a darkroom will turn that paper black) An interesting dichotomy in any world.

Then, add in one other factor, just for the fun of it -- when we expose film, we create a negative image of that visual, and in slides, we create a positive of that visual. Then, when we process each, we reverse that exactly. No wonder some of us artists get confused. Food for thought anyway, while we wait for Santa to bring us the very inventions that make all this happen, provided we can figure out how it works   ... Happy Holidays to you all ...


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## Valvebounce (Dec 26, 2014)

Hi Monkey. 
I suggest your best bet is to actually grab your camera, select aperture priority or shutter priority, set an ISO, pick a subject, wind on all the plus you have, +3 on my 7d take the shot, wind on the -3. 
Now view the images, lighter and darker respectively, look at the exif to see the net result of adding the exposure compensation, i.e. what it did to the non fixed value, there you have your answer without bogging down in maths and fractions. 
This removes the problem of having two people with their own "expertise and interpretation" of fractions! ;D

Thanks for making the grey matter work, by the time I had finished reading your post I was confused and had to resort to the above method to reaffirm my knowledge!

Have a good one.

Cheers, Graham.


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## sanj (Dec 26, 2014)

You daughter won.


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## jrista (Dec 26, 2014)

monkey44 said:


> YEAH, it's kinda like PI ... 3.14 is close enough, but mathematicians have been trying to get the absolute forever. Not sure what that will change in our world if someone ever gets that final decimal figure. The only people that care are other math folks -- the rest of us grab the numbers we're given and go out and push a shutter button.
> 
> What do we have then? An image. What to the PI seekers have? An enigma and no reward. Which door do you choose?




LOL. Well, it entirely depends on the precision of the math your doing, whether 3.14 is enough. For a lot of mathematics work, that isn't close to enough precision. Now, we don't need precision out to thousands of decimal places, but neither is two decimal places enough for every use case.


I don't see photography as any different. Either you plateau and are simply ok with that, or you are always striving to do better, go farther, create more incredible art. At some point, you have to push the envelope, and part of that means learning more about your equipment. Just barely good enough (like Pi == 3.14) is just that, just barely good enough. It's limiting. It'll always hold you back and limit your capabilities if you simply settle for that and never strive for more. Your acceptance of the first limitations you reach will show up in your work as well, and you will forever be...ok. Never great, nor excellent, nor a "genious"...just ok. 


Some people are ok with that. Which is perfectly fine. Other people are not.  Pi = 3.14 is simply not enough for some people, those who push the limits...


BTW, there is no "final decimal figure" with Pi...it's an irrational number, which means it's precision is infinite...we can keep calculating Pi to ever more decimal places, and there will always be something left to discover. Beyond simply precision, Pi is an endless number, it contains discrete strings of digits that can, and do, represent...anything, possibly everything. There are mathematicians who have searched for keys to genetic code in Pi, rendered parts of it as images (some think the Mona Lisa is in a sequence in there somewhere), played out sequences of it's decimal places as music, and many other things. It is an infinitely complex number...all that precision isn't "needed" per-se, however if no one ever looked for more than two decimal places, we wouldn't have pondered the implications of such a complicated number, nor tried to play it back as music (and some sequences can be quite beautiful when rendered with the proper notes), nor rendered it as images (there have been some incredible images rendered from bits of Pi as well), nor any of the other things we've done with Pi. 


Personally, I have a hard time simply stopping once I've achieved the minimal amount of skill required to barely succeed at something: Set everything to automatic, switch to Av or Tv, press the shutter. Hmm. You can be successful with that, but it will only take you so far. You are going to run into limitations, improper exposures, too much noise, too much blur, not enough DOF, something. Photography isn't a purely creative endeavor...it is a technical endeavor as well, and understanding the technical side if things can only make you a more effective photographer. It'll help you discover more levels of skill or talent within yourself, empowering you to do more, see more, create more. Just like all the things we've done with Pi...despite the supposed "lack of necessity" of having more precision than 3.14.


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## dcm (Dec 26, 2014)

Three digits of precision was about all most of us could expect using slide rules before the advent of pocket calculators in the 70s. Still have mine. Much of the world was built on that basis. I might have a greater appreciation of the big picture as a result.

On the other hand, I computed Pi to thousands of digits for fun back in the day. Current record is over 13 trillion digits by a couple of college students using an algorithm one of them designed. The hardware involved is a not as large as you might think: 2 x Xeon E5-4650L @ 2.6 GHz, 192 GB DDR3 @ 1333 MHz, 24 x 4 TB + 30 x 3 TB. It takes a couple of hard drives to hold one copy of the result. http://www.numberworld.org/y-cruncher/

Unsolvable problems like this are a good way to get started in serious numerical computation, particularly with the creation of new algorithms - there are many ways to compute Pi. It also forces you to figure out ways to get the most out of your relatively limited hardware. Advances in systems and algorithms result from these types of efforts and spill over into other areas. My own research involves machine learning and combinatorial optimization problems where compute time grows exponentially with N - all of the computers on the planet working together cannot put a dent in the problem, my focus is on newer and better algorithms.

I prefer to keep my photography simpler.


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## jrista (Dec 27, 2014)

dcm said:


> Three digits of precision was about all most of us could expect using slide rules before the advent of pocket calculators in the 70s. Still have mine. Much of the world was built on that basis. I might have a greater appreciation of the big picture as a result.
> 
> On the other hand, I computed Pi to thousands of digits for fun back in the day. Current record is over 13 trillion digits by a couple of college students using an algorithm one of them designed. The hardware involved is a not as large as you might think: 2 x Xeon E5-4650L @ 2.6 GHz, 192 GB DDR3 @ 1333 MHz, 24 x 4 TB + 30 x 3 TB. It takes a couple of hard drives to hold one copy of the result. http://www.numberworld.org/y-cruncher/
> 
> ...




However if you understand that much about PI, I highly doubt you would ever confuse what EC does, or how it works, or what the side effects of aperture, shutter, and ISO are, or any other technical facet of your camera.  You already understand your camera, there probably isn't much, if anything, left to learn about it. Utilizing it's technology would be second nature, and therefor quite simple. Learning the technology of a DSLR isn't some kind of P vs. NP or NP-complete problem. 


That's the thing about learning...once you have, it isn't complicated anymore. 8)


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## dcm (Dec 27, 2014)

jrista said:


> dcm said:
> 
> 
> > Three digits of precision was about all most of us could expect using slide rules before the advent of pocket calculators in the 70s. Still have mine. Much of the world was built on that basis. I might have a greater appreciation of the big picture as a result.
> ...



Dunno. I sometimes find even my techie peers have trouble understanding things like this. Years of practice starting in my film days helped a lot for me. Still learning everytime I get another body or lens that extends my reach (wide,tele) or features (macro, fisheye, tilt/shift).


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