Exposure control in a raw developer: misnomer?

Started Jan 30, 2013 | Discussions
jcharding Senior Member • Posts: 2,306
A thought

Many of the posts are confusing two different processes, including the original post.  The original photographic triangle referred to the process of taking a photo, and the compromises or attributes a photographer chose.  Those three points were ISO (or film speed), lens aperture and shutter speed, and they affect noise, depth of field and motion blur.

What many posts are confusing, including perhaps me, is these variable as they affect the ultimate image.  The proposed term by the OP to add is scene luminescence or scene brightness.  The problem is that the proposed new trilogy has an output factor now combined with two input variables, which irritated me greatly  because it just doesn't work with the other two input variables.

I think what the OP is really trying to discuss is the output trilogy, which is depth of field in the screen image (or print), brightness in the image, and sharpness of the image (unless the photographer has chosen to have it unsharp, such as waterfall motion blur).

These two trinities IMHO do not mix.  As the original trinity is about the process of taking a photo while the second trinity is about what people ultimately see. So I agree with the OP that scene brightness is part of a trinity, it should not be lumped with shutter speed and aperture.

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Great Bustard Forum Pro • Posts: 39,910
Re: Absolutely correct.

dosdan wrote:

Great Bustard wrote:

It's funny, 'cause if you ask someone who considers ISO part of exposure, and you ask them if f/2.8 1/100 ISO 100 and f/5.6 1/100 ISO 400 result in the same exposure for a given scene, it's exceedingly rare that the answer to this simple yes or no question will take the form of "yes" or "no".

GB, ask them this: if they consider these 2 exposures to be equivalent, what about the 2x worse shot noise SNR in the ISO400 shot due to the 1/4x smaller total number of photons collected during the exposure period?

For many, "exposure" = "brightness".  Here's another conundrum for you:  does f/2.8 1/100 ISO 1600 on a 5D have the same exposure as f/2.8 1/100 ISO 1600 on a 6D?  After all, the noise is most certainly not the same.

OP dosdan Contributing Member • Posts: 509
Re: Absolutely correct.

The answer is yes, they are the same exposure. QE is not part of it. It's the photons falling on the unit area of the sensor that are the same, not the photo-electronics produced. Since only scene luminance, shutter speed and f-number are involved with determining the amount of light/unit area arriving, for the same scene luminance, f/5.6 & 1/100s results in the same exposure on APS-C AA-less, FF Foveon & MF cameras. (Assuming the same lens transmittance.)

So while I use the phrase "photons captured" (OK if considering different settings on the same camera), exposure is really about "photons arriving" rather than"photons converted".

In the two exposures with different shot noise figures, I was assuming the same camera.

Dan.

For many, "exposure" = "brightness". Here's another conundrum for you: does f/2.8 1/100 ISO 1600 on a 5D have the same exposure as f/2.8 1/100 ISO 1600 on a 6D? After all, the noise is most certainly not the same.

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RedFox88 Forum Pro • Posts: 27,319
Re: Exposure control in a raw developer: misnomer?

dosdan wrote:

the rendered output? If so, it has nothing to do with exposure and is a misnomer.

What does it matter what it's called when the result doesn't change?!

OP dosdan Contributing Member • Posts: 509
Re: Absolutely correct.

While I usually think of exposure as the result, it's better to think of it as "exposure to".

Dan.

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robert1955 Veteran Member • Posts: 3,328
Re: There's lots of misnomers, multiplication is another one!

Focal length has for a long time been used as the number to describe what is really angle of view. But unlike AoV it needs a sort of fixed point and because of the fact that most of the first generation digital shooters came from 35mm  that became the fixed point. That's when people started using the cropping word. Not really accurate, but not something that can lead tio misunderstandings like the exposure syndrome that the main part of the thread tries to deal with.

When I was a Canon user (DX is a Nikon label, we did not use that term, you really should accept that they are no the same thing) I only had EF lenses that were designed for what I called full frame back then. But the 17-40 mm was for my 10D at the time the best option for a sort of standard zoom, with 27-68 being the shorthand description that was understandable for those still on silverhalide. Yhere are even those who think it was really designed to be mainly that. But designed for is not really interesting, what ciunts is what it can do for you.

Using the term multiplication factor is just as inaccurate as crop, the only difference that it gvies a more positive framing. I've seen enough Panoly users proudly proclaiming their 200mm to be really a 300mm to realize that they like that more positive way of looking at things.

Maybe when i encounter my first Nikon1 user I should ask: 'so how small is your sensor?"


BTW:

And what happens when you compare a larger format camera, do you then have a NEGATIVE crop factor?

Did you know most medium format digital cameras have smaller sensors than the original film format and so could be called crop cameras?

And did  you know that in German the word 'Kleinbild' [small format] is still in regular use for 35mm?

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Great Bustard Forum Pro • Posts: 39,910
Absolutely correct -- again!

dosdan wrote:

For many, "exposure" = "brightness". Here's another conundrum for you: does f/2.8 1/100 ISO 1600 on a 5D have the same exposure as f/2.8 1/100 ISO 1600 on a 6D? After all, the noise is most certainly not the same.

The answer is yes, they are the same exposure. QE is not part of it. It's the photons falling on the unit area of the sensor that are the same, not the photo-electronics produced. Since only scene luminance, shutter speed and f-number are involved with determining the amount of light/unit area arriving, for the same scene luminance, f/5.6 & 1/100s results in the same exposure on APS-C AA-less, FF Foveon & MF cameras. (Assuming the same lens transmittance.)

So while I use the phrase "photons captured" (OK if considering different settings on the same camera), exposure is really about "photons arriving" rather than"photons converted".

Winner!  Yes, you are absolutely correct.  Exposure is simply the density of light falling on the sensor while the shutter is open, not the total amount of light used for the photo:

Total Light Collected = Exposure x Effective Sensor Area x QE

where the QE (Quantum Efficiency) is the proportion of light falling on the sensor that is recorded (e.g. if QE = 50%, then half the light falling on the sensor is recorded).

However, in terms of the noise in the photo, we must also include the read noise (the amount of additional noise added by the sensor and supporting hardware).  So, we can phrase the situation thusly:

Photos made from the same total amount of light will have the same noise if the sensors are equally efficient.

So, what we have is:

  • Exposure
  • Total Light
  • Total Light Collected
  • Brightness

which are all related, but mean different things, and are discussed in detail here:

http://www.josephjamesphotography.com/equivalence/index.htm#exposure

In the two exposures with different shot noise figures, I was assuming the same camera.

In the case of using the same camera, then the same exposure results in the same total light which results, the sensors are equally efficient, which means the same total light is recorded and the read noise is also the same, thus the same noise.

In other words, for a given format, we can use the words "exposure" and "total light" interchangeably, and for the same format and sensor efficiency, the noise differential between two systems is purely a function of the exposure.

OP dosdan Contributing Member • Posts: 509
Re: Exposure control in a raw developer: misnomer?
1

I think the problem with the term "exposure" came about like this:

In the days of film, you would take "an exposure" by exposing film to light. Later you would "develop" it, with the possibility of making various adjustments to the final rendered image. The only time these two processes were tightly coupled was with the Polaroid Land system.

Along came digital cameras. With JPEG shooting, exposing and developing seemingly occurred together.  So users started to think that "exposure" equates to shooting & producing an JPEG image, with printing producing a hard copy.

Then some digital cameras provided raw image storage, so that users could again decouple the two processes. But the concept of "exposure" had loosened sufficiently in the thinking of typical digital camera users, that the producers of raw developer programs used the label "Exposure" in a rendering control in the development process, even though I'm sure they knew it was incorrect.

Dan.

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Detail Man
Detail Man Forum Pro • Posts: 16,688
Re: Exposure control in a raw developer: misnomer?
1

dosdan wrote:

I think the problem with the term "exposure" came about like this:

In the days of film, you would take "an exposure" by exposing film to light. Later you would "develop" it, with the possibility of making various adjustments to the final rendered image. The only time these two processes were tightly coupled was with the Polaroid Land system.

Along came digital cameras. With JPEG shooting, exposing and developing seemingly occurred together. So users started to think that "exposure" equates to shooting & producing an JPEG image, with printing producing a hard copy.

Then some digital cameras provided raw image storage, so that users could again decouple the two processes. But the concept of "exposure" had loosened sufficiently in the thinking of typical digital camera users, that the producers of raw developer programs used the label "Exposure" in a rendering control in the development process, even though I'm sure they knew it was incorrect.

Exactamundo.

To even further muddy the waters, Adobe's "Brightness" control (in LR through versions 3.x, and Camera RAW through versions 6.x) modified an applied gamma-correction constant (as opposed to amounting to a straightforward linear scaling of the output image-data).

Thus, the Empire of 1,000 Years painted themselves into a non-reversible rhetorical corner with those choices - and their faithful followers' heads might possibly have exploded upon discovering those facts along with discovering the facts surrounding the hue-twisting that accompanied the adjustment of their "Exposure" and "Highlight Recovery" control-sliders.

It is unknown (to me) whether LR 4.x and CR 7.x "Exposure" continues the hue-twisting behavior.

Ron Poelman
Ron Poelman Veteran Member • Posts: 5,950
Not really, the exposure has come and gone ...

so to adjust it, is not too bad a way of putting it;
no different to "adjusting" the seasoning of a dish.

That said, if we're going to wrong-turn at Albuquerque and head off down the Semantic Trail,
was exposure noun or verb or was it present or past tense ?

Output brightness level or brightness is fine with me,
it's a command in a RAW processor, so in context, what else could it refer to ?

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Jack Hogan Veteran Member • Posts: 6,207
Re: Not really, the exposure has come and gone ...

Ron Poelman wrote:  it's a command in a RAW processor, so in context, what else could it refer to ?

gain?

Ron Poelman
Ron Poelman Veteran Member • Posts: 5,950
Re: gain?

Jack Hogan wrote:

gain?

Indeed, think it'd catch on ?
I can hear the screams now, " how can you have negative gain ?"
(No pun intended, more's the pity.)

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richarddd
richarddd Senior Member • Posts: 2,982
Re: Exposure control in a raw developer: misnomer?

The goal of the authors of raw development programs is to communicate clearly with users so that they can sell more product and cut down on technical support questions. For that purpose. "exposure" is likely the best term. I doubt there is anyone who doesn't understand what the exposure slider in a raw development program is intended to do.

A goal of photographers is to understand how to get the best picture quality from their cameras, which includes understanding the effects of varying the amount of light on the sensor, the effects of varying ISO, the effects of changing shutter speed, etc.

A goal of someone trying to help photographers understand how to get the best picture quality from their cameras should be to communicate clearly with those photographers. Compare "amount of light on the sensor" (or "density of light" you're so inclined) with "exposure". Which is more likely to get the thought across rather than result in confusion or arguments with most people?

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Great Bustard Forum Pro • Posts: 39,910
So...

richarddd wrote:

The goal of the authors of raw development programs is to communicate clearly with users so that they can sell more product and cut down on technical support questions. For that purpose. "exposure" is likely the best term. I doubt there is anyone who doesn't understand what the exposure slider in a raw development program is intended to do.

A goal of photographers is to understand how to get the best picture quality from their cameras, which includes understanding the effects of varying the amount of light on the sensor, the effects of varying ISO, the effects of changing shutter speed, etc.

A goal of someone trying to help photographers understand how to get the best picture quality from their cameras should be to communicate clearly with those photographers. Compare "amount of light on the sensor" (or "density of light" you're so inclined) with "exposure". Which is more likely to get the thought across rather than result in confusion or arguments with most people?

...a "brightness adjustment" slider would be confusing?

richarddd
richarddd Senior Member • Posts: 2,982
Re: So...

Great Bustard wrote:

richarddd wrote:

The goal of the authors of raw development programs is to communicate clearly with users so that they can sell more product and cut down on technical support questions. For that purpose. "exposure" is likely the best term. I doubt there is anyone who doesn't understand what the exposure slider in a raw development program is intended to do.

A goal of photographers is to understand how to get the best picture quality from their cameras, which includes understanding the effects of varying the amount of light on the sensor, the effects of varying ISO, the effects of changing shutter speed, etc.

A goal of someone trying to help photographers understand how to get the best picture quality from their cameras should be to communicate clearly with those photographers. Compare "amount of light on the sensor" (or "density of light" you're so inclined) with "exposure". Which is more likely to get the thought across rather than result in confusion or arguments with most people?

...a "brightness adjustment" slider would be confusing?

Yes

LR3 had both an exposure slider and a brightness slider.  The exposure slider in LR4 is essentially the same as the one in LR3. They made many changes to the brightness slider in LR3 and called a new LR4 slider highlights.  The exposure slider moves the entire tone curve.  The brightness and highlight sliders control the right portion.

Given the history, it would be confusing to call the exposure slider "brightness adjustment".

Do you believe anyone is confused by a slider called exposure (or, at least, anyone who is not being willful)?

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jcharding Senior Member • Posts: 2,306
Re: Exposure control in a raw developer: misnomer?
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Joofa Senior Member • Posts: 2,332
Re: Exposure control in a raw developer: misnomer?

richarddd wrote:

A goal of someone trying to help photographers understand how to get the best picture quality from their cameras should be to communicate clearly with those photographers. Compare "amount of light on the sensor" (or "density of light" you're so inclined) with "exposure". Which is more likely to get the thought across rather than result in confusion or arguments with most people?

I agree with you. While I can appreciate that people want to introduce technically correct lingo in photography, however, ad hoc terms such as "density of light", etc., without proper qualification, are confusing, in IMHO. I'm not even sure that the proponents of such terms fully understand what they are trying to say.

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Mike_PEAT Forum Pro • Posts: 12,922
That's a MARKETING thing...

sherwoodpete wrote:

I think I've seen at least one Olympus four-thirds lens actually marked with both the actual focal length, and also having in large letters the 35mm equivalent focal length displayed on the side too.

When manufacturers do things wrongly, its difficult to expect people to not be follow their lead.

Olympus puts a REMOVABLE sticker on their consumer lenses to let the uneducated know the equivalent range of the lens when they buy it.  It only describes the range of te lens...it doesn't indicate the actual zoom positions, like a speedometer marked in km and miles.

The first thing I do (after testing a lens) is remove that sticker!

John Sheehy Forum Pro • Posts: 19,229
Re: So...

richarddd wrote:

LR3 had both an exposure slider and a brightness slider. The exposure slider in LR4 is essentially the same as the one in LR3. They made many changes to the brightness slider in LR3 and called a new LR4 slider highlights. The exposure slider moves the entire tone curve. The brightness and highlight sliders control the right portion.

Given the history, it would be confusing to call the exposure slider "brightness adjustment".

Do you believe anyone is confused by a slider called exposure (or, at least, anyone who is not being willful)?

IMO, the most logical thing would be to have a slider called "gain" which would be a purely linear treatment of the RAW data, and along with that controls for contrast, shoulder, knee, etc, for the rendered tone curve.  Most converters don't even give a homogenous gain with the "exposure" slider; the curve changes along with the gain.

richarddd
richarddd Senior Member • Posts: 2,982
Re: So...

John Sheehy wrote:

richarddd wrote:

LR3 had both an exposure slider and a brightness slider. The exposure slider in LR4 is essentially the same as the one in LR3. They made many changes to the brightness slider in LR3 and called a new LR4 slider highlights. The exposure slider moves the entire tone curve. The brightness and highlight sliders control the right portion.

Given the history, it would be confusing to call the exposure slider "brightness adjustment".

Do you believe anyone is confused by a slider called exposure (or, at least, anyone who is not being willful)?

IMO, the most logical thing would be to have a slider called "gain" which would be a purely linear treatment of the RAW data, and along with that controls for contrast, shoulder, knee, etc, for the rendered tone curve. Most converters don't even give a homogenous gain with the "exposure" slider; the curve changes along with the gain.

Are you suggesting "gain" would be easier to understand than "exposure"?

Do you want to redesign LR's tone controls as well as relabel them?

I'll ask you the same question as above, "Do you believe anyone is confused by a slider called exposure (or, at least, anyone who is not being willful)?"

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