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Why is exposure so confusing?
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Jan 21, 2019 18:37:47   #
Bipod
 
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:

TimeValue + ApertureValue = SensitvityValue + Brightness
E.g., at approx. EV 15:
5 + 8 = 5 + 8

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

Brightness = TimeValue + ApertureValue - SensitivtyValue
8 = 5 + 8 - 5

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

f-number APEX
1 0
1.4 1
2 2
2.8 3
4 4
5.6 5
8 6
11 7
16 8
22 9
etc.

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.

Nominal Sec. APEX
1 1 0
2 1/2 1
15 1/15 2
30 1/30 3
60 1/60 4
125 1/125 5
250 1/250 6
500 1/500 7
1000 1/1000 8
etc.

FILM/SENSOR SPEED


ASA DIN APEX
100 21 5
200 22 6
400 23 7
800 24 8
1600 25 9
etc.


BRIGHTNESS

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


APEX FOOT LAMBERTS
1 2
2 4
3 8
4 15
5 30
6 60
7 125
8 250
9 500
10 1000
etc.

Reply
Jan 21, 2019 18:41:03   #
IDguy Loc: Idaho
 
I believe you are confusing logarithms with algorithms.

Doubling is linear arithmatic, not exponential.

Reply
Jan 21, 2019 18:45:57   #
Bipod
 
IDguy wrote:
I believe you are confusing logarithms with algorithms.

Doubling is linear arithmatic, not exponential.

Log base 2 of 2, 4, 8, 16, 32, 64.....
= 1, 2, 3, 4, 5, 6....

Reply
 
 
Jan 21, 2019 18:54:29   #
Fred Harwood Loc: Sheffield, Mass.
 
Fun read.

Reply
Jan 21, 2019 18:54:51   #
DeanS Loc: Capital City area of North Carolina
 
I have memorized this, when do I get to take the test?😎😎😎

Reply
Jan 21, 2019 18:55:01   #
BebuLamar
 
Back in the old days there was no confusion because one typically had to know about exposure before even took one shot. Today it is confusing because one can take pictures for years before having to think about exposure.
I believe that is the source of confusion. If you learn about exposure on the first time you use a camera it's very simple.

Reply
Jan 21, 2019 18:56:26   #
rmalarz Loc: Tempe, Arizona
 
A fun read. Exposure isn't that confusing. It's actually quite simple, until this sort of thing comes along. Nothing like obsfucating a simple topic.
--Bob
Bipod wrote:
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 ration 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 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:

TimeValue + ApertureValue = SensitvityValue + Brightness
E.g., at approx. EV 15:
5 + 8 = 5 + 8

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

Brightness = TimeValue + ApertureValue - SensitivtyValue
8 = 5 + 8 - 5

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

f-number APEX
1 0
1.4 1
2 2
2.8 3
4 4
5.6 5
8 6
11 7
16 8
22 9
etc.

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.

Nominal Sec. APEX
1 1 0
2 1/2 1
15 1/15 2
30 1/30 3
60 1/60 4
125 1/125 5
250 1/250 6
500 1/500 7
1000 1/1000 8
etc.

FILM/SENSOR SPEED


ASA DIN APEX
100 21 5
200 22 6
400 23 7
800 24 8
1600 25 9
etc.


BRIGHTNESS

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


APEX FOOT LAMBERTS
1 2
2 4
3 8
4 15
5 30
6 60
7 125
8 250
9 500
10 1000
etc.
It time someone talked about WHY exposure is so co... (show quote)

Reply
 
 
Jan 21, 2019 19:06:19   #
mas24 Loc: Southern CA
 
Interesting. It made me go back to my film SLR days. I mostly used Kodak 200 ASA kodacolor film for daylight clicks. And I used 400 ASA for outdoor action sports.

Reply
Jan 21, 2019 19:07:36   #
Just Shoot Me Loc: Ithaca, NY
 
I believe you are on the right track.
Just like pharmists used to write in Latin.
Confusing to those who don’t have the background from 50 years ago, when that’s all we had.
Maybe we can make a difference if we keep talking about it, but getting camera manufacturers to agree...

Reply
Jan 21, 2019 19:16:46   #
AndyH Loc: Massachusetts and New Hampshire
 
I do think it's an interesting read, although I was not familiar with APEX prior to your posts. But there are reasons why it didn't catch on, and not JUST the "we've always done it this way" obstacle. I have a Rollei from the mid fifties with the little locking device that tied the aperture and shutter speed values together, tagged with an EV number. Kind of like a pre-digital "program" mode, no?

Just because it's logical, it doesn't necessarily follow that people will adopt it as the standard.

Thank you for putting this in a separate thread. It's more than some newbies could take!

Andy

Reply
Jan 21, 2019 19:23:56   #
Cany143 Loc: SE Utah
 
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!

Reply
 
 
Jan 21, 2019 19:30:37   #
Bipod
 
rmalarz wrote:
A fun read. Exposure isn't that confusing. It's actually quite simple, until this sort of thing comes along. Nothing like obsfucating a simple topic.
--Bob

Say you own three light meters, Bob: a Nikon, a Pentax and a Gossen.
All are factory calibrated and working perfectly.
The Nikon meter says the EV is 14.
What does the Pentax meter read?
What does the Gossen meter read?

If they are different, can you explain why?
And which one is correct?

Remember: exposure is simple!

Reply
Jan 21, 2019 19:30:50   #
Timmers Loc: San Antonio Texas.
 
I can easily answer your question with a simple response. There are two types of people in the world of photography, one group likes to talk about photography, while the other group wants to make photographs. I'm in the latter category, I make photographs.

F stops are quite simple, learn two neighboring f stops and you will have all f stops. Say f4 and f 5.6 as example. You then simply half or double either to reveal the other f stops. Of course one does not get anal about being 'precise' (double 5.6, that is 5.6+5.6 =11.2, round to f 11). I know, BUT! There is no BUT in the field of practical photography, or just steal that cute phrase, "Just Do It!" We are NOT doing math, we are making images.

Shutter speeds are the same but simpler (along with imaging speed/sensitivity), basic doubling (just like ISO, or the old ASA) 1/2, 1/4. 1/8, 1/15 (Don't be anal, no 1/16).

Yes, you can make it complicated, and loose the image, or make the image and put the camera away and study the math. In the latter I will just wonder away because I'm not here to do math, I'm here to make photographs, that is why people keep thinking that I'm a photographer, silly fools that they are!

Go ahead and ask Bubble about it (he is the guy in the photograph).


(Download)

Reply
Jan 21, 2019 19:32:24   #
sloscheider Loc: Minnesota
 
When you get the above common sense changes to take place your next assignment is to get us Yanks to move on over to the metric system! I’ll support your political party, just say the word. It’s only the US, Burma and Liberia left to go metric...

Reply
Jan 21, 2019 19:36:22   #
Bipod
 
Timmers wrote:
I can easily answer your question with a simple response. There are two types of people in the world of photography, one group likes to talk about photography, while the other group wants to make photographs. I'm in the latter category, I make photographs.

F stops are quite simple, learn two neighboring f stops and you will have all f stops. Say f4 and f 5.6 as example. You then simply half or double either to reveal the other f stops. Of course one does not get anal about being 'precise' (double 5.6, that is 5.6+5.6 =11.2, round to f 11). I know, BUT! There is no BUT in the field of practical photography, or just steal that cute phrase, "Just Do It!" We are NOT doing math, we are making images.

Shutter speeds are the same but simpler (along with imaging speed/sensitivity), basic doubling (just like ISO, or the old ASA) 1/2, 1/4. 1/8, 1/15 (Don't be anal, no 1/16).

Yes, you can make it complicated, and loose the image, or make the image and put the camera away and study the math. In the latter I will just wonder away because I'm not here to do math, I'm here to make photographs, that is why people keep thinking that I'm a photographer, silly fools that they are!

Go ahead and ask Bubble about it (he is the guy in the photograph).
I can easily answer your question with a simple re... (show quote)

For a "strong, silent type" who only takes photographs and doesn't talk about photography,
you just posted four paragraphs, Timmers.

On a photography discussion forum. Ahem.

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