It time someone talked about WHY exposure is so confusing.

It's because of the way manufacture's label camera settings. They don't apply base 2 logarithms
consistently.

There are two reasonable rules:
1. Each detent on a control (aperture, shutter, ISO, exposure compenstation) must be EXACTLY
twice (or half) the exposure of the previous detent; and
2 Each should be labeled in integers: ... -3, -2, -1, 0, 1, 2, 3....

If you do this consistantly, you get the Additive Photographic Exposure System (APEX)
which was standardized way back in 1960 (ASA standard ASA PH2.5-1960) and was used
in industry and by the military (where confusion is not OK).

EC knobs (and menus) generally follow both rules: No compensation is labeled "0". Increasing
exposure by one stop is labled "1". Decreasing exposure by one stop is labeled "-1". Anyone
confused by this? Pretty simple, right?

F-numbers follow Rule 1, but not Rule 2. The sequence 1, 1.4, 2, 2.8, 4, 5.6, etc. is a lot more
complicated than 1,2,3,4,5... And you don't need to know the actual f-stop ratio unless you are
building a camera.

Shutter speeds are a mess. They follow neither rule. This sequence makes sense:
1, 2, 4, 8, 16, 32, 64, 128, 256, 512, .... This one doesn't: 1, 2, 4, 8, 15, 30, 60, 125, 250, 500, .....
What's the rule for latter sequence, pray tell?

ISO speeds are given in two different sysems: ASA and DIN. Both follow Rule 1, but only DIN
follows Rule 2. The ISO "standard" is to use BOTH! (Sure sign of a gutless committee trying to
please everybody.) The ASA number isn't even logarithmic. And ASA 100 is DIN 21 -- why 21?
"Historical reasons".

Finally, Exposure values follow Rule 1 but not Rule 2 -- again for "historical reasons".
"Historical reasons" is a polite way of saying S.N.A.F.U.

Exposure is confusing because of the silly, stupid, inconsitent way in which cameras controls
are labeled.

Here's the "Sunny 16" rule in the traditional Tower of Babel system:

At approx. EV 15 and f/16, use shutter speed 1/ASA speed
for example:
At approx. EV 15 and f/16 and ASA 100, use 1/100th sec

(which of course, isn't even a detent on the shutter dial-it only has 125.)

Here the general rule in APEX:

Does this math confuse anybody? Dang simple, if you ask me.
So by subtracting SensitivityValue from both sides:

As usual, people are willing to update their hardware and software (= buy stuff) but not their thinking.
Picture a cave man holding a Nikon. "Og like take photos. But Og confused by exposure." No wonder!


For reference, here's the basic system, as standardized in 1960.

APEX SYSTEM (per ASA PH2.5-1960)

Note: this may differ from EXIF Version 2.2.

APERTURE

SHUTTER SPEED

The original APEX standard kept the irregular shutter times: 1, 1/2, 1/4,1/8, 1/15, 1/30, 1/60, 1/125....

In fact, some cameras are already calibrated to 1/16, 1/32, 1/64... Shutters are rarely accurate enough
to tell the difference except at 1/15 <> 1/16.

FILM/SENSOR SPEED



BRIGHTNESS

Again, the original standard kept the irregular shutter speeds, so it had to have
irregular brightnesses as well.

If I were trying to understand exposure based on things I read today, I probably wouldn't get close to a reasonably exposed shot. Exposure --and the shutter speed, aperture, ISO/ASA/EI values that determine it-- is not the stuff of convoluted analogies, computational mathematics, or lengthy confabulations. Its the stuff of go-out-and-shoot-it while paying freaking attention to what you aimed the camera at, and what settings you used that worked or the settings you used that didn't work. Jeez!

I who know nothing about the history or the arithmetic designs of camera construction can only cringe after reading this. We lesser types tend to be more intuitive than analytical , let alone judgmental and as such usually remain silent when others speak.

For they usually know of things that we do not and so we learn to be good listeners as a result and hopefully gain helpful knowledge as a result. And that is a good thing indeed.

I never had Logs in school so it's a useless pursuit for me to even attempt to comprehend that discussion with respect to f/stop or ASA or DIN. With the modern DSLR Camera most of that is a waste of hot air for me personally. Exposure is either Up or Down , Aperture is basically wide vs. narrow , Shutter is either faster or slower and ISO is a means of recalibrating the 3 zones up or down with respect the amount of light available to the camera to balance the 3 zones and deliver a proper image.

Everything else not so much. It's kind of like telling Sir Paul Mc Cartney..."you can't be a musician because you don't read music"....which is true BTW in case any of you are curious.

I will say this ,however, this discussion has prompted me to delve into the history of these items and I should educate myself further so for this I thank you.

What others have said , I can only hope to one day be Worthy of Fellowship among the Hogs. Thank You for tolerating my presence.


Jimbo

It time someone talked about WHY exposure is so confusing.

It's because of the way manufacture's label camera settings. They don't apply base 2 logarithms
consistently.

There are two reasonable rules:
1. Each detent on a control (aperture, shutter, ISO, exposure compenstation) must be EXACTLY
twice (or half) the exposure of the previous detent; and
2 Each should be labeled in integers: ... -3, -2, -1, 0, 1, 2, 3....

If you do this consistantly, you get the Additive Photographic Exposure System (APEX)
which was standardized way back in 1960 (ASA standard ASA PH2.5-1960) and was used
in industry and by the military (where confusion is not OK).

EC knobs (and menus) generally follow both rules: No compensation is labeled "0". Increasing
exposure by one stop is labled "1". Decreasing exposure by one stop is labeled "-1". Anyone
confused by this? Pretty simple, right?

F-numbers follow Rule 1, but not Rule 2. The sequence 1, 1.4, 2, 2.8, 4, 5.6, etc. is a lot more
complicated than 1,2,3,4,5... And you don't need to know the actual f-stop ratio unless you are
building a camera.

Shutter speeds are a mess. They follow neither rule. This sequence makes sense:
1, 2, 4, 8, 16, 32, 64, 128, 256, 512, .... This one doesn't: 1, 2, 4, 8, 15, 30, 60, 125, 250, 500, .....
What's the rule for latter sequence, pray tell?

ISO speeds are given in two different sysems: ASA and DIN. Both follow Rule 1, but only DIN
follows Rule 2. The ISO "standard" is to use BOTH! (Sure sign of a gutless committee trying to
please everybody.) The ASA number isn't even logarithmic. And ASA 100 is DIN 21 -- why 21?
"Historical reasons".

Finally, Exposure values follow Rule 1 but not Rule 2 -- again for "historical reasons".
"Historical reasons" is a polite way of saying S.N.A.F.U.

Exposure is confusing because of the silly, stupid, inconsitent way in which cameras controls
are labeled.

Here's the "Sunny 16" rule in the traditional Tower of Babel system:

At approx. EV 15 and f/16, use shutter speed 1/ASA speed
for example:
At approx. EV 15 and f/16 and ASA 100, use 1/100th sec

(which of course, isn't even a detent on the shutter dial-it only has 125.)

Here the general rule in APEX:

Does this math confuse anybody? Dang simple, if you ask me.
So by subtracting SensitivityValue from both sides:

As usual, people are willing to update their hardware and software (= buy stuff) but not their thinking.
Picture a cave man holding a Nikon. "Og like take photos. But Og confused by exposure." No wonder!


For reference, here's the basic system, as standardized in 1960.

APEX SYSTEM (per ASA PH2.5-1960)

Note: this may differ from EXIF Version 2.2.

APERTURE

SHUTTER SPEED

The original APEX standard kept the irregular shutter times: 1, 1/2, 1/4,1/8, 1/15, 1/30, 1/60, 1/125....

In fact, some cameras are already calibrated to 1/16, 1/32, 1/64... Shutters are rarely accurate enough
to tell the difference except at 1/15 <> 1/16.

FILM/SENSOR SPEED



BRIGHTNESS

Again, the original standard kept the irregular shutter speeds, so it had to have
irregular brightnesses as well.