Understanding exposure

[Ysarex87 81]

"Ehhhhhhhhhhhhh!!!!!!!!" loud, irritating buzzer sound, indicating Game Over.

Sorry, nice effort, but no sale. I still prefer the old "drinking glass + faucet + clock" illustration concept.

For decades "Exposure" was thought of as being Exposure = Intensity X Time.

Now, in the digital era, some young whippersnapper saw fit to add an unneeded third leg...adding in ISO value.

Exposure is really pretty simple. All one needs to do is to learn that there is an Intensity...as in the flow rate of the water. And a Time, as in the length of time the water is allowed to flow into the vessel (the drinking glass, or the film, or the pixel wells). One can fill the glass in at wide-open in two seconds, or fill the glass in with the faucet at half-open in four seconds, or fill the glasswith the flow at one-quarter flow in eight seconds.

The whole "triangle" concept is relatively new. I'm not sure that adding in ISO sensitivity really helps neophytes understand the idea of equivalent exposure; if anything, I think it might cloud the waters for the less-astute thinkers, at least at the start of their learning process.

Sensitivity can be thought of as the capacity of the drinking glass that we are filling with our pretend water faucet: High-sensitivity film requires very little "water" and is represented by a small glass.

Oh hell...let's just scrap this all and build a bridge instead...and we'll truss it up using some cool triangular-array trusses that we fab outta' recycled railroad rails!!!

Addendum: in the time it took me to type my post, I now see that amolitor has added another post; one with which I agree with in the first point very much: the exposure "triangle" in not a very useful tool for neophytes.

Yep, the old water faucet, glass and clock works well. When I had to teach Photo I students the concept they were sitting around a table in the lab and the processing sink was over against the wall. I had a faucet and an old Gralab timer ready to go. And to cap it off I set out a 64 ounce graduate, a 32 ounce graduate, a 16 ounce graduate and an 8 ounce graduate. Those graduates were ISO 100, 200, 400 and 800 -- I wrote the ISO numbers on pieces of tape and stuck them right on the graduates. If I put the graduates under the faucet and set the clock off to the side you could draw a triangle to connect the three together!

Joe

 

[runnah]

I still think the "filling in the gap" is more apt than a stupid triangle. They triangle doesn't really explain the "why" of it all.

 

[Derrel]

I myself, years ago, developed a teaching method to help newbs understand "exposure". I use something that I, personally developed, because it WORKS, works well, AND this is the critical aspect--it is actually tied properly and logically to the "numbers involved" [in multiple aspects], and it has unique memory cues.

What's the Derrel method of Exposure Illustration????? Simple. I use the concept of one dollar. One US dollar. One-hundred pennies that tally up to one dollar.

My teaching tools are: TWO US half-dollar coins. "fifty Cent pieces", which are quite large in diameter. FOUR US "quarter-dollar coins". TEN United States dimes, ten-cent coins.

The half-dollars represent a lens that is HALF-open. The lens's aperture is f/2. To make up a whole dollar unit, we need only TWO coins. Big coins represent a lens that is 1/2 of the way open.

If we have the lens open to one-fourth, or f/4, we need four coins to make up our dollar. Moderately-sized coins represent a lens that is "1/4 of the way open".

If we have the lens open a very small fractional amount, like say to f/10, we need ten coins to make up our dollar. At f/10, the small-diameter dimes represent a lens that is "1/10 of the way open".

I have used this method to teach a number of people how the f/stop numbering system works: Many people need some kind of memory hints, and the half-dollar coins are BIG, and cool-looking, and do a good job of representing what "f/two" as in f/2, stands for.

The quarter-dollars do a great job of representing what "f/four" stands for in the real world of exposures. The dimes are small, and represent pretty well how how a high numerical value represents a small diameter lens opening.

When a newbie says, "i can never remember if a high number like f/11 is a big hole or a small hole, you can tell them: the f/stop's number represents the fraction of a dollar, so think about the size of the half-dollar, the quarter, and the dime. If it takes only TWO coins to make a dollar, they are "1/2 dollar coins" and the hole in the lens is BIG. If it takes "4" coins to make a dollar, the aperture is not big, and not small, but in-between in size. If the number is high, like f/10 or f/11, the hole is small in diameter, like a dime is.

 

[e.rose]

I drew this because the exposure triangle makes no sense at all and is a worthless pedagogical tool. It seems to help some people who already know how exposure works, but it's a confusing and worthless drawing for people who do not know how exposure works already.

That's an interesting and somewhat bold statement... considering the when *I* first started shooting and had no idea how exposure worked, it clicked when I learned about the exposure triangle.

I'll say it again... I had NO idea how exposure worked... exposure triangle cleared all that up for me.

I've also used it to help explain to friends who are just starting out how exposure works.

And after they get *that*, I then explain to them how back in the day ISO wasn't really a factor because that was a factor of the film itself and move into Derrel's faucet sort of idea...

But that with *digital* cameras ISO *is* something we can adjust, whether or not you want to take that into consideration... thus... the triangle makes sense.

Maybe some people simply don't like it. Maybe for some people it is confusing, and that's fine because people have different ways of thinking, however to say that it makes no sense at all and is useless to anyone who knows nothing... is false. Because that was exactly my case a few years back. I knew nothing... the triangle cleared it up for me.

"Ehhhhhhhhhhhhh!!!!!!!!" loud, irritating buzzer sound, indicating Game Over.

Sorry, nice effort, but no sale. I still prefer the old "drinking glass + faucet + clock" illustration concept.

Again, I agree. This is another clear, easy to understand method of explaining it.

The bridge thing is... I mean like I said, I already understand how exposure works, and you lost me right at the beginning with your metaphor.......

 

[amolitor]

I am at a loss as to how on earth the exposure triangle can cause anything to click, but evidently it's just the thing for some people.

Can anyone pose a single question a newbie might ask which could be answered by carefully examining the exposure triangle?

ETA: And, um, I hope it's obvious, also sketch out just how the answer might be obtained by examining it.

 

[Derrel]

Amolitor is a very smart, crafty fellow...I suspect his post was designed to cleverly lead us, via Google searching, to the famous "Bridge to Nowhere", which was built in 1936.

Bridge to Nowhere - Google Search

or perhaps he was thinking we'd think of that famous Talking Heads song, "Road to Nowhere",and that by us thinking of that old song, we would ourselves be creating our very own "bridge".

 

[amolitor]

Amolitor is a very smart, crafty fellow...I suspect his post was designed to cleverly lead us, via Google searching, to the famous "Bridge to Nowhere", which was built in 1936.

Sadly, I am not so witty today. Today, I am merely filled with despair.

 

[peter27]

I drew this because the exposure triangle makes no sense at all and is a worthless pedagogical tool. It seems to help some people who already know how exposure works, but it's a confusing and worthless drawing for people who do not know how exposure works already. Teaching is something I do, sometimes for money. Pedagogy is a topic of interest to me, therefore, and photography is simply shocking in how poorly it's taught, and how shamelessly all the would-be teachers copy stupid, wrong, and meaningless stuff from one another.

Suppose I am a n00b. I understand that there's a shutter speed, an aperture, and something called ISO. I have them set to 1/125, f/5.6, and 100 respectively and things seem to be working pretty good.

My friend says I could "stop the action" better with a faster shutter speed, which with a little thinking, I decide means 1/500.

Now I consult the exposure triangle. It says that shutter speed, aperture, and ISO are inter-related, somehow. So, I guess I have to adjust aperture or ISO somehow. Can I just adjust one of them, or do I need to adjust both? And in what direction? Help me, exposure triangle! Help me!

The exposure triangle provides zero intuition into how any of this stuff work. It literally just says 'there are three things, related to one another, somehow'

And yet, for me at least, the triangle analogy works well because the internal angles always have a total of 180°, so if you change one of these at least one of the others has also to be adjusted to compensate.

 

[amolitor]

And yet, for me at least, the triangle analogy works well because the internal angles always have a total of 180°, so if you change one of these at least one of the others has also to be adjusted to compensate.

And this, right here, is a great example of why I am filled with despair. This worthless bit of chartjunk seems to somehow crystallize things for people, and then they write things like this that almost make sense, but not quite.

If you had an exposure circle with three variable sized wedges or something, this sentence would make perfect sense (and, as an aside, you'd be back to the bridge, except now it's wrapped around in a circle). The "exposure triangle" is always drawn as an equilateral triangle, though, and the internal angles are always all 60 degrees. If you dig around slightly, you'll even find "explanations" that explain how you have to make your adjustments so as maintain the equilateral triangle shape.

However it is, it seems to work well enough to be this self-propagating object, and really, who the hell am I to judge? Apparently there's some bizarre alchemy that makes it work for some people.

 

[480sparky41 40]

......and is a worthless pedagogical tool. ....... Pedagogy is a topic of interest to me, .....'

And truth be told, how many people will know what these words mean?

 

[amolitor]

I pretty much assume people can handle vocabulary like "pedagogy", and if they can't, that they know where a dictionary can be found.

 

[Overread17 5]

The triangle itself is just a visual representation that helps people to see that 1 Stop of Aperture = 1 Stop of Shutter speed = 1 Stop of ISO and that if you change the value of 1 of those values by any number of stops then you have to compensate either either or both of the other two to return to the balanced exposure you had before.

Yes looking at the triangle on its own won't teach it, that is why its a visual aid not an entire guide book on a diagram.

 

[Turbo]

 

[EIngerson]

Does anyone else keep looking for Dora in that map?

 

[amolitor]

It's always interesting to get into a situation where you and the other chap are both pretty sure that the other fellow is a complete moron. If you're intellectually honest, you gotta wonder if maybe the other chap has it right.