Exposure Triangle

[o hey tyler]

Sure, Buckster. Everyone thinks of the numerical designations for apertures as the denominator of a fraction, ESPECIALLY newbies.

Well, the faster that one understands that, the faster one understands that a larger f/stop is technically a larger number. Leads to less confusion in the long run.

 

[timor]

AAAAAA

I do understand exposure, people. Please stop assuming that I don't.

I like your declaration or self description on your blog.
Just to add some confusion: in film photography term "perfect exposure" does not exist. There is only an approximation of an exposure.

 

[BRN1]

I like dogs. Hot dogs and corn dogs too.

 

[table1349]

This thread is the biggest waste of bandwidth in quite some time around here.

 

[Derrel]

This thread is the biggest waste of bandwidth in quite some time around here.

No...no way...there are several other current threads that are equally, or even MORE-worthless than this one. Give some of the other posters here some credit! lol

 

[Fred Berg]

I use a bucket analogy:

You want to fill a bucket with light. Aperture is hose size, shutter speed is how long to stand there filling, and ISO is how big the bucket is.

The meter tells you how to fill the bucket up halfway. If you want it less full, that's the same thing as darker. If you want it more full, that's lighter.

Aperture is dumb and goes backwards, smaller numbers mean a bigger hose.

DONE.

Words. They work.

Hedgecoe used a very similar analogy to explain the relationship between aperture and shutter speed. His beaker/bucket didn't change size to account for the DIN value, though. I like your model and also the idea of the see-saw/weighing scales. If the fulcrum is shown as DIN, it could be very useful to demonstrate/explain the relationship between this, aperture and shutter speed, I think.

I agree that the exposure triangle is confusing, especially for people new to photography.

 

[bratkinson]

Having always been mathematically inclined, I "picture" (pun intended) the exposure triangle as a mathematical formula something like:

A x B x C = P

Unfortunately, P is an 'indefinite' or non-specific number that I think of as ‘the Perfect Picture’, and depends on the eye of the beholder.

Let me explain:
If A x B x C = 1000 (a constant value), then it’s easy to see that as A increases, then B and/or C must decrease to compensate to get the result of 1000. Likewise, decreasing B, for example, would require an increase in A and/or C. Unfortunately, the exposure triangle not this ‘simplistic’ of a math formula, and there’s intended and sometimes unintended consequences to altering any of the values.

Let’s say A = f-stop value. If a larger f-stop (aperture) is used (numerically smaller value), then, increasing f-stop increases the exposure and therefore shutter speed and/or ISO must be lowered to get the same result. Similarly, if B = Shutter Speed, increasing the shutter-open time (1/x th second, where x is numerically smaller) requires that ISO be decreased and/or aperture must be decreased as well to get the same result.

So, for you mathematicians out there, the formula would actually be something like:

(100 - f/stop) x (1000 - shutter speed expressed without the fraction) x ISO speed = P

Note: I chose 100 as a max f-stop value as I don’t know if f/100 is possible (pinhole, perhaps?). Similarly, I chose 1/1000[SUP]th[/SUP] second as a ‘max’ shutter speed, but in reality it is probably more like 32,000 or something equally as large. 1000 used here for simplicity sake.

The 100 - f/stop calculation is there to give a larger number from smaller f-stop numbers. f 22, for example, would result in a value of 88, and so on. Shooting at f 4 (96 value in the calc) instead of f 22 will result in more light hitting the sensor if nothing else is changed.

Similarly, 1000 - shutter speed is used to give a smaller number the faster the shutter speed (eg, 1/100 sec speed would use only the 100 number in the calculation, giving a result of 900). Longer shutter open times result in larger numbers in this calculation. Decreasing shutter open time (eg, 1/30[SUP]th[/SUP] to 1/100[SUP]th[/SUP]) would therefore result in a smaller number in this calculation, lowering the total exposure value “P”.

Lastly, increasing ISO speed would necessitate a reducing one of the other numerical values in my equation, but in actuality, you'd be increasing the shutter speed (less time open) or going to a smaller f-stop like f 16 or f 22 to still get a good exposure.

Before everybody’s head starts spinning, know that I don’t do any of these ‘complex’ calculations in my head when I go to take a picture. I’m too old for that kind of stuff. Instead, I simply think of it in the simplistic A x B x C = P. Changing any of the three will require compensating (opposite) changes in either or both of the other two to get the same result. I’m not really saying ‘A = f/stop, etc.’ It’s simply A x B x C, without assigning meanings or values of any kind to them.

As mentioned at the top, there’s additional, intended and non-intended consequences when changing ANY of the values.

On the intended side, simply increasing the aperture size and changing nothing else will result in a ‘brighter’ picture, due to more light hitting the sensor. But there’s a limit to how bright is ‘right’. If the picture gets too bright, the highlights wash out. And at the other extreme of under exposure, what’s in the darker areas have no visible details recorded.

Increasing aperture size also DECREASES the depth of field, that portion of the picture where everything is in focus. At f 32 (smallest aperture), almost everything will be in focus (depth of field) that’s farther away from the lens than its closest focal distance. At f1.2, the depth of field is frequently measured in inches, even fractions of an inch for some lenses. Note that narrower depth of field is desirable in some shooting situations to ‘bring out’ the subject of the photo, while making everything else a little or a lot fuzzy, also known as bokeh. Some lenses produce better bokeh than others, depending on their construction and quality (and price). Of course, increasing aperture size requires decreasing either/or shutter open time or ISO.

Making shutter speed adjustments either increases or decreases the total amount of light hitting the sensor. Shutter speed variations are good for making long (often, minutes!) night exposures when the camera is on a tripod. But in most situations, long shutter open times are more like ¼ or 1/10 or 1/30 of a second. The long open time lets in more light, and is useful in situations where nothing is moving. People shots are almost always blurred at these speeds, even if they are sitting down and smiling. Yours (and mine, too) hands will move slightly with every heartbeat as well, and at 1/30[SUP]th[/SUP], there could be a blur. Speeding things up to 1/60[SUP]th[/SUP] can stop ‘slower’ human movement (like holding a pose), but for most people pictures, 1/100[SUP]th[/SUP] or faster is required to stop them for sure. Indianapolis race cars, on the other hand, need shutter times of 1/500[SUP]th[/SUP] second or even faster to ‘freeze’ them in the picture. So, by increasing shutter open time, more light hits the sensor. But subject movement can end up in a blur if too slow. Too fast, and the pictures get dark, unless compensating increases are made to aperature and/or ISO. Shutter speed synchronization with flash units is a lengthy subject in itself, has various added effects, and not a part of this epistle.

ISO is probably the easiest to understand. Think of a bird pecking at seeds on the ground. Some birds peck seeds faster than others. Of course, me armed with a Shop-Vac can clear the ground of all the seeds in a heartbeat or three. ISO is the same. Lower ISO settings are like birds pecking away to gather the necessary light to make the picture. With a Shop-Vac (high ISO setting), all the light is gathered in less than a heartbeat. The problem with using a Shop-Vac in the above example is it also picks up a lot of dirt with the seeds. This is comparable to noise, ie, odd, multi-colored pixels in the resultant picture, mostly visible in darker areas. Slower ISO speeds closer to 100 or 200 rather than 3200 reduces the ‘dirty’ noise in the pictures. How high is ‘high ISO’? It varies from camera maker to camera maker, and even from camera model to model, as well. Generally, the newer the camera, the better the handling of faster ISO speeds…How big is YOUR Shop-Vac?

Of course, there’s even more to the ‘exposure triangle’ adjustment consequences than discussed above, like color density, edge focusing, and other generally pro-level issues. But for me, and for most non-professional photographers, I suspect, the simple A x B x C = P and the consequences described above is more than enough to keep our heads spinning!

 

[unpopular]

That explanation is on an order of magnitude more complicated than it needed to be.

 

[Tee]

You (everyone who likes) should, of course, feel free to use my word (picture) as you see fit. I think it's pretty decent myself!

I think Byran Peterson did in his "Understanding" volumes. Like almost word for word.

 

[Ballistics]

Sure, Buckster. Everyone thinks of the numerical designations for apertures as the denominator of a fraction, ESPECIALLY newbies. Denominators, for reference, are dumb and go backwards. Bigger numbers mean smaller fractions, as you so wisely point out. Thanks for backing me up.

Wow. Haha. This has to be one of the greatest things I have heard someone say on here in a long time.

Denominators are dumb lmfao!

They don't go backwards.
Do you really need to have fractions explained to you?

Newbies don't think like that? Is everyone new to photography in 1st grade?

 

[unpopular]

f-stops are counter-intuitive. It's hard to say a translation of f/5.6 to f/4 is half of anything. Sure, it makes optical sense, but people are not used to dealing with exponential fractions on a daily basis. Still, hardly anything people can't overcome.

 

[Fred Berg]

I think most people normally think of 22 as bigger than 2. Understanding how to handle aperture settings is a bit like learning to steer a boat.

 

[JAC526]

Sure, Buckster. Everyone thinks of the numerical designations for apertures as the denominator of a fraction, ESPECIALLY newbies. Denominators, for reference, are dumb and go backwards. Bigger numbers mean smaller fractions, as you so wisely point out. Thanks for backing me up.

Wow. Haha. This has to be one of the greatest things I have heard someone say on here in a long time.

Denominators are dumb lmfao!

They don't go backwards.
Do you really need to have fractions explained to you?

Newbies don't think like that? Is everyone new to photography in 1st grade?

You give people too much credit.

 

[Solarflare]

Just to add some confusion: in film photography term "perfect exposure" does not exist. There is only an approximation of an exposure.

Why, thanks for adding more confusion. :mrgreen:

Why does perfect exposure not exist ? Its when the brightest pixel is almost at its maximum. I would have thought thats a quite well defined state.

Sure, Buckster. Everyone thinks of the numerical designations for apertures as the denominator of a fraction, ESPECIALLY newbies. Denominators, for reference, are dumb and go backwards. Bigger numbers mean smaller fractions, as you so wisely point out. Thanks for backing me up.

Wow. Haha. This has to be one of the greatest things I have heard someone say on here in a long time.

Denominators are dumb lmfao!

They don't go backwards.
Do you really need to have fractions explained to you?

Newbies don't think like that? Is everyone new to photography in 1st grade?

Um.

ISO is 100, 200, 400, 800, 1600, ... (and sometimes ISO 50)

Aperture is f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, ...

Shutter Speed is 1/15 sec, 1/30 sec, 1/60 sec, 1/125 sec, 1/250 sec, 1/500 sec, 1/1000 sec, ... (and of course also 1/8, 1/4, 1/2, 1, 2, 4, 8, 15, 30 sec and Bulb mode)

Why is it not obvious that these numbers may look very confusing to a newbie ?

 

[KenC]

Why does perfect exposure not exist ? Its when the brightest pixel is almost at its maximum. I would have thought thats a quite well defined state.

There are many creative images with quite a bit of pure white in them and also many with nothing even close to white.