DPR Glossary revisions

GeorgianBay1939 · Aug 9, 2015

It seems that DPR contributes to the propagation of errors in the correct understanding and use of the terminology and principles basic to the practice of photography.

As a relative neophyte I now use Wikipedia and known authorities in the field instead of using the various "expert" websites. Unfortunately, even Wikipedia suffers from inadequacies in spite of an attempt at "peer review". There appears to be no such attempt in the DPR Glossary.

Lately I've been reviewing a number of topics to squeeze a bit more out of my gear and have tried to use the DPR Glossary (which would be more obvious if listed under the "Features" pull-down menu.)

My trials began when I decided to look up the following: Dynamic Range , Noise , Sensitivity , etc --- leading me eventually to Exposure :

_____________________

DPR Glossary Definition: "The exposure is the amount of light received by the film or sensor and is determined by how wide you open the lens diaphragm (aperture) and by how long you keep the film or sensor exposed (shutterspeed). The effect an exposure has depends on the sensitivity of the film or sensor.

The exposure generated by an aperture, shutterspeed, and sensitivity combination can be represented by its exposure value "EV". Zero EV is defined by the combination of an aperture of f/1 and a shutterspeed of 1s at ISO 100[1]"

______________________

Compare to the Wikipedia definition of Exposure (Photographic) :

______________________

Wikipedia Definition: "In photography, exposure is the amount of light per unit area (the image plane illuminance times the exposure time) reaching a photographic film or electronic image sensor, as determined by shutter speed, lens aperture and scene luminance. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance in a specified region."

______________________

1 All of the experts that I trust use amount of light / unit area in discussions of exposure (and total light when considering noise and other factors.)

2 I believe that (Photographic) Exposure is determined by only 3 factors: Scene luminance, shutter interval (speed) and f/ (T-stop to be more precise). Exposure is unaffected by ISO Speed. Exposure Metering is affected by ISO Speed and, if it is followed, will affect the camera's EV setting, and therefore the exposure.

3 Both definitions should use the phrase aperture ratio or f/ instead of "aperture" in such a critical application.

4 "The exposure generated by an aperture, shutterspeed, and sensitivity combination can be represented by its exposure value "EV" is very misleading as it implies that exposure is a function of sensitivity (ISO Speed) which it isn't. The use of "EV" here is also problematical.

5 Exposure value, by definition, only depends on f/ (T-stop) and shutter interval (speed).

6 Exposure value (ISO Speed 100) , can be used as a measure of scene lighting conditions.

It appears that the DPR Glossary is in need of an update since much of it appears to be written about 10 years ago. Perhaps it is also time to improve the vocabulary and principles described in the work.

On the other hand, perhaps Amazon, prefers the confusion propagated by the current Glossary as a stimulant for endless forum arguments about sensor size/performance, equivalence, noise, ad nauseam.

--
Tom
The best part of growing old is having the opportunity to do so.
https://brtthome.wordpress.com/

quadrox · Aug 9, 2015

I agree completely, but I believe this forum is not the best place to get their attention. Maybe you should post in the site feedback forum?

D Cox · Aug 10, 2015

quadrox said:
I agree completely, but I believe this forum is not the best place to get their attention. Maybe you should post in the site feedback forum?

Or is there a religion forum it could go in ? ;-)

GeorgianBay1939 · Aug 10, 2015

quadrox said:
I agree completely, but I believe this forum is not the best place to get their attention. Maybe you should post in the site feedback forum?

I don't think that DPR has the leadership to invite folks to review/revise their aging (decade?) DPR Glossary. Rather, I suspect that the initiative has to come from the helpful folks who contribute to this forum (and others) with corrections and authoritative posts.

I hope that some of these folks will engage by suggesting particular revisions to the DPR Glossary. Perhaps, after some discussion, the results could be used to fix the obvious errors in it.

Perhaps a good start would be to review/revise the entry for Exposure , since it is so fundamental to the practice of photography.

In any event a discussion of the meaning/use of the phrase "Photographic Exposure" might in itself be quite revealing! :-D

GeorgianBay1939 · Aug 10, 2015

D Cox said:
quadrox said:

I agree completely, but I believe this forum is not the best place to get their attention. Maybe you should post in the site feedback forum?

Click to expand...

Or is there a religion forum it could go in ? ;-)

Good question, one that I followed up:

I HAD thought that Photography was an application of science to capturing and modifying images, in the tradition of James Clerk Maxwell , a hero of mine. So I googled "Science of Photography" and found this curious result at the top of the list:

https://en.wikipedia.org/wiki/Science_of_photography#Law_of_Reciprocity

"Exposure ∝ Aperture Area × Exposure Time × Scene Luminance"

"The law of reciprocity describes how light intensity and duration trade off to make an exposure—it defines the relationship between shutter speed and aperture, for a given total exposure. Changes to any of these elements are often measured in units known as "stops"; a stop is equal to a factor of two."

"Aperture Area"???!!!!!!

"a stop is equal to a factor of two" ???!!!!!!

_____________________________

So I googled "Religion" and found the Wikipedia definition to be quite fitting to the practice of photography:

"A religion is an organized collection of beliefs, cultural systems, and world views that relate humanity (photography??) to an order of existence. ..........

....... Religions may also contain mythology."

____________________________

Unfortunately, Googling "Religion of photography" didn't turn up anything useful.

Aaaargh. :-( :-(

(In the meantime I, for one, really appreciate the efforts of those patient photographers who contribute good, reliable, science-based discussion to these forums.)

--
Tom
The best part of growing old is having the opportunity to do so.
https://brtthome.wordpress.com/

Iliah Borg · Aug 10, 2015

I would love to see a glossary and explanation of common errors (something like they have for translators in 'faux amis du traducteur' dictionaries).

ISO = sensitivity

dynamic range in highlights

exposure triangle

exposure = brightness = G-d knows what else

2 greens make for the raw file green look

a 14-bit raw contains 2^14^3 colours

megapixel wars lead to more noise

Company nnn colours

etc

--
http://www.libraw.org/

GeorgianBay1939 · Aug 10, 2015

Iliah Borg said:
I would love to see a glossary and explanation of common errors (something like they have for translators in 'faux amis du traducteur' dictionaries).

My french being mainly oral, I had to google (and translate) "faux amis du traducteur " indicating that the subject of photography is rich in "false friends".

Iliah Borg said:
ISO = sensitivity

"Authoritative" explanation here , with this kernel of "truth" according to Nikon USA:

"Each time you double the ISO (for example, from 200 to 400), the camera needs only half as much light for the same exposure."

Iliah Borg said:
dynamic range in highlights

Whaaaat? decibels or stops?

Iliah Borg said:
exposure triangle

What a relief: The iPhone shooters have been brought into the flock by another good shepherd:

"Even after all these years of shooting commercial photography with almost every camera known to man, I am still intrigued and infatuated by the photographic concept of exposure. The science of photography, over the years, hasn’t really changed that much. Optimum exposure has been and always will be a delicate combination of aperture, shutter speed and ISO. And while the technology hasn’t changed, the art of photography surely has. Learn how to express your art through exposure. Click away!"

Iliah Borg said:
exposure = brightness = G-d knows what else

Ah! The joys of jpegs in our EVFs and in our outputs.... and the magick of Lightroom sliders.

I could never figure out how Lightroom could retroactively change either Scene Luminance, or EV (f/ and shutter speed camera settings ). Magick?

Please correct all those RAW shooters who don't believe that Exposure = Brightness, especially this fellow: http://www.dpreview.com/articles/8148042898/exposure-vs-brightening

(Ooops. The cat is out of the bag!)

Iliah Borg said:
2 greens make for the raw file green look

I always thought that 2 greens is 2/18 of a course. .... or maybe 1/4.5 of a 9-hole course.

Iliah Borg said:
a 14-bit raw contains 2^14^3 colours

4,398,046,511,104 bits? 550 GB? hmmm. How fast is the burst rate in raw? This "fact" almost decides me to shoot 8 bit JPEGS from now on.

Iliah Borg said:
megapixel wars lead to more noise

Related to ISO wars? Religious wars? Pixel SNR vs Sensor SNR?

Iliah Borg said:
Company nnn colours

Speaking of colour ..... http://www.cambridgeincolour.com/tutorials/camera-exposure.htm

Iliah Borg said:
etc

--
http://www.libraw.org/

Thank goodness J C M kept his vocabulary under control. I understand that a firm diet of good single malt keeps the technobabble of the artistic muse under control.

--
Tom
The best part of growing old is having the opportunity to do so.

Brtthome's Blog

photos, prose, prattle and possibilities

brtthome.wordpress.com

quadrox · Aug 11, 2015

GeorgianBay1939 said:
GeorgianBay1939 said:

exposure = brightness = G-d knows what else

Click to expand...

Ah! The joys of jpegs in our EVFs and in our outputs.... and the magick of Lightroom sliders.

I could never figure out how Lightroom could retroactively change either Scene Luminance, or EV (f/ and shutter speed camera settings ). Magick?

Please correct all those RAW shooters who don't believe that Exposure = Brightness, especially this fellow: http://www.dpreview.com/articles/8148042898/exposure-vs-brightening

To be quite fair, the intent of the exposure slider is clearly not to change the exposure, but to simulate what the photo would look like if the original exposure had been X stops higher or lower - all other settings being equal.

To my mind "brightness" and similar terms do not accurately reflect what the slider does, since the slider respects the tone curve etc.

Iliah Borg · Aug 11, 2015

quadrox said:
GeorgianBay1939 said:

quadrox said:

exposure = brightness = G-d knows what else

Click to expand...

Ah! The joys of jpegs in our EVFs and in our outputs.... and the magick of Lightroom sliders.

Please correct all those RAW shooters who don't believe that Exposure = Brightness, especially this fellow: http://www.dpreview.com/articles/8148042898/exposure-vs-brightening

Click to expand...

To be quite fair, the intent of the exposure slider is clearly not to change the exposure, but to simulate what the photo would look like if the original exposure had been X stops higher or lower - all other settings being equal.

To my mind "brightness" and similar terms do not accurately reflect what the slider does, since the slider respects the tone curve etc.

In raw converters exposure compensation sliders are usually linear, seldom they attempt to emulate film shoulder.

quadrox · Aug 12, 2015

Iliah Borg said:
quadrox said:

GeorgianBay1939 said:

Iliah Borg said:

exposure = brightness = G-d knows what else

Click to expand...

Ah! The joys of jpegs in our EVFs and in our outputs.... and the magick of Lightroom sliders.

Please correct all those RAW shooters who don't believe that Exposure = Brightness, especially this fellow: http://www.dpreview.com/articles/8148042898/exposure-vs-brightening

Click to expand...

To be quite fair, the intent of the exposure slider is clearly not to change the exposure, but to simulate what the photo would look like if the original exposure had been X stops higher or lower - all other settings being equal.

To my mind "brightness" and similar terms do not accurately reflect what the slider does, since the slider respects the tone curve etc.

Click to expand...

In raw converters exposure compensation sliders are usually linear, seldom they attempt to emulate film shoulder.

I am not sure if I understand you correctly - it's sometimes hard for me to express technical matters that I understand intuitively in clear and correct terms. So let me try again:

Based on my experience with Bibble/AfterShotPro/RawTherapee/Darktable, the exposure compensation is processed before any tone curve is applied. This means that brightness of each pixel will be equivalent to what you would get if you had taken the shot with a different exposure (although noise, motion blur, DOF and similar characteristics will not be equivalent to that exposure).

I understand the term linear brightening to take effect *after* the tone curve has been applied and to *not* result in an image that is equivalent to one having been taken with different exposure settings.

Iliah Borg · Aug 12, 2015

quadrox said:
the exposure compensation is processed before any tone curve is applied.

Often, so. It is non-photographic and in that sense incorrect, however.

quadrox said:
This means that brightness of each pixel will be equivalent to what you would get if you had taken the shot with a different exposure

Yes.

quadrox said:
I understand the term linear brightening

This is a non-standard term, no meaning guarantee.

GeorgianBay1939 · Aug 12, 2015

quadrox said:
GeorgianBay1939 said:

quadrox said:

exposure = brightness = G-d knows what else

Click to expand...

Ah! The joys of jpegs in our EVFs and in our outputs.... and the magick of Lightroom sliders.

Please correct all those RAW shooters who don't believe that Exposure = Brightness, especially this fellow: http://www.dpreview.com/articles/8148042898/exposure-vs-brightening

Click to expand...

To be quite fair, the intent of the exposure slider is clearly not to change the exposure, but to simulate what the photo would look like if the original exposure had been X stops higher or lower - all other settings being equal.

This is very interesting and new to me. I checked a pair of bracketed (4/3 of a stop apart in EV) images in Lightroom and the shape of the histogram stayed quite similar when adjusted in Lightroom 5.6:

[ATTACH alt="1/400 sec, no movement of "Exposure" slider."]1018965[/ATTACH]
1/400 sec, no movement of "Exposure" slider.

[ATTACH alt="This image was shot -4/3 exposed (compared to the upper one) and then "compensated for" by increasing the "Exposure" slider by 1.3 stop."]1018966[/ATTACH]
This image was shot -4/3 exposed (compared to the upper one) and then "compensated for" by increasing the "Exposure" slider by 1.3 stop.

Is this a good test of the degree of "simulation" that you refer to?

quadrox said:
To my mind "brightness" and similar terms do not accurately reflect what the slider does, since the slider respects the tone curve etc.

How do you define "brightness"?

_______________________________________

I had a devil of a time finding a usable definition of "photographic brightness". After rummaging around on various "expert blogs/sites" I realized that "brightness" has a wide variety of meanings to folks. I finally went here: https://en.wikipedia.org/wiki/Brightness

"Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light. In other words, brightness is the perception elicited by the luminance of a visual target. This is a subjective attribute/property of an object being observed and one of the color appearance parameters of color appearance models. Brightness refers to an absolute term and should not be confused with Lightness."

... which seems to be independent of HOW the brightness is achieved.

________________________________________

So I went to my "go-to man " on the subject of brightness and exposure and found this:

"With the preceding model in mind, we make the following definitions of basic concepts:

Exposure: the amount of light falling per unit area on a sensor: it is determined by the scene luminance, the f-ratio (more properly the t-ratio), and the shutter speed.

Brightness: the perceived lightness of an image resulting from amplification of any form applied to a given exposure either in-camera (including ISO), or by "pushing" or "pulling" in a raw processor or image editor, or by adjusting appropriate controls on the output medium. This term applies only to an image as viewed on a chosen medium: print or monitor.

Brightening: increasing the brightness of an image by any means (in-camera, in the computer, or in the output medium) other than those determining exposure (scene luminance, f-ratio, and shutter speed)."

__________________________

Although I wish that gollywop had not used the term "lightness " in his definition, I think that he has the guts of a definition for Brightness right, in that:

Brightness is one of the characteristic parameters of visual perception.

Changes in brightness can be the result of changing Exposure, ISO Speed, in-camera processing, raw conversion, post processing, etc.

__________________________

So, I agree that "Brightness" is not a good title for that slider.

But "Exposure" further conflates the differences between Exposure and Brightness leading to the grossly misleading idea that Exposure depends on ISO Speed.

So what is a better title for that slider???

IF Adobe agrees that the slider shifts the apparent EV by plus or minus stops, (thus preserving the tone curve?) maybe "EV shift"? or maybe "Simulated EV compensation"? I am sure that there are competent wordsmiths out there who could suggest something better! :-D

( I haven't even thought about the use of that slider on a JPEG! What is involved there?)

--
Tom
The best part of growing old is having the opportunity to do so.

Brtthome's Blog

photos, prose, prattle and possibilities

brtthome.wordpress.com

GeorgianBay1939 · Aug 12, 2015

Iliah Borg said:
quadrox said:

GeorgianBay1939 said:

Iliah Borg said:

exposure = brightness = G-d knows what else

Click to expand...

Ah! The joys of jpegs in our EVFs and in our outputs.... and the magick of Lightroom sliders.

Please correct all those RAW shooters who don't believe that Exposure = Brightness, especially this fellow: http://www.dpreview.com/articles/8148042898/exposure-vs-brightening

Click to expand...

To be quite fair, the intent of the exposure slider is clearly not to change the exposure, but to simulate what the photo would look like if the original exposure had been X stops higher or lower - all other settings being equal.

To my mind "brightness" and similar terms do not accurately reflect what the slider does, since the slider respects the tone curve etc.

Click to expand...

In raw converters exposure compensation sliders are usually linear, seldom they attempt to emulate film shoulder.

Iliah Borg · Aug 12, 2015

GeorgianBay1939 said:
How do you define "brightness"?

CIE defines brightness as "the attribute of a visual sensation according to which an area appears to emit more or less light".

Brightness is a complex phenomenon, and CIE recommends a substitute that can be more readily and accurately computed, luminance. It is that Y in XYZ colour model, cd/m^2; or it can be normalized to viewing conditions, in which case the luminance of white reference is considered as 100%, and actual luminance is in percents of the luminance of the white reference. The idea of white reference and the brightness of surroundings that both affect perception are included in "reference viewing conditions".

Reference viewing conditions are explicitly stated for sRGB https://en.wikipedia.org/wiki/SRGB#Viewing_environment and used to be included as comments right in sRGB profiles.

As viewing conditions are an important part of colour management, X-Rite offer a pdf https://www.xritephoto.com/documents/literature/en/StandardViewingNTK_EN.pdf

More on the subject is here: Digital Color Management: Encoding Solutions, Edition 2

By Edward J Giorgianni, Thomas E Madde (both - Kodak).

Relevant chapters are nearly fully available for free through google books.

GeorgianBay1939 · Aug 13, 2015

Thanks Iliah!

Iliah Borg said:
Iliah Borg said:

How do you define "brightness"?

Click to expand...

CIE defines brightness as "the attribute of a visual sensation according to which an area appears to emit more or less light".

Another definition using attribute/characteristic of a visual sensation/perception of an area emitting/radiating/reflecting varying amounts of light. (A long ways away from "Exposure").

Iliah Borg said:
Brightness is a complex phenomenon, and CIE recommends a substitute that can be more readily and accurately computed, luminance. It is that Y in XYZ colour model, cd/m^2; or it can be normalized to viewing conditions, in which case the luminance of white reference is considered as 100%, and actual luminance is in percents of the luminance of the white reference.

Thanks for this. Relating brightness to luminance is huge and helps me a lot!

It seems natural that the aim of any faithful optical system is to reproduce the luminance of a subject by constructing the appropriate brightness , (the subjective response to luminance ), in the output (screen or print).

This concept helps to validate gollywop's flow diagram:

Brightness as one of the perceived attributes of light emitted from the output medium (screen or print).

Iliah Borg said:
The idea of white reference and the brightness of surroundings that both affect perception are included in "reference viewing conditions".

Reference viewing conditions are explicitly stated for sRGB https://en.wikipedia.org/wiki/SRGB#Viewing_environment and used to be included as comments right in sRGB profiles.

As viewing conditions are an important part of colour management, X-Rite offer a pdf https://www.xritephoto.com/documents/literature/en/StandardViewingNTK_EN.pdf

More on the subject is here: Digital Color Management: Encoding Solutions, Edition 2

By Edward J Giorgianni, Thomas E Madde (both - Kodak).

Relevant chapters are nearly fully available for free through google books.

--
http://www.libraw.org/

All very useful to the neophyte bogged down in the morass of confusing terminology. The xrite pdf was nice! The other articles were a bit too advanced for me.

The DPR Glossary does not include the term "Brightness". Since the word is used so often it would be useful to include it in any revision to the Glossary.

Here is another use of the word: http://www.cambridgeincolour.com/tutorials/histograms1.htm

"Each pixel in an image has a color which has been produced by some combination of the primary colors red, green, and blue (RGB). Each of these colors can have a brightness value ranging from 0 to 255 for a digital image with a bit depth of 8-bits. A RGB histogram results when the computer scans through each of these RGB brightness values and counts how many are at each level from 0 through 255."

_____________________

It is clear that experienced photographers have the context to make sense of the terminology. Experienced photographers don't need to use Glossaries.

It is the beginners, the students of the art/science, that need authoritative definitions of the terms used, especially when there is some dispute about their meanings when relating to technique.

It seems useful to have a Glossary Discussion Forum where you and others (including the originators of existing Glossary entries) can revise the Glossary. It would serve as an instrument to keep the Glossary up-to-date and authoritative. Perhaps it could be moderated by the more technically adept editors at DPR. A go-to Glossary for the subject would be a significant attractant for students of photography.

--
Tom
The best part of growing old is having the opportunity to do so.

Brtthome's Blog

photos, prose, prattle and possibilities

brtthome.wordpress.com

Iliah Borg · Aug 13, 2015

GeorgianBay1939 said:
Here is another use of the word: http://www.cambridgeincolour.com/tutorials/histograms1.htm

"Each pixel in an image has a color which has been produced by some combination of the primary colors red, green, and blue (RGB). Each of these colors can have a brightness value ranging from 0 to 255 for a digital image with a bit depth of 8-bits. A RGB histogram results when the computer scans through each of these RGB brightness values and counts how many are at each level from 0 through 255."

Calling data numbers "brightness" is very wrong. Brightness appear when there is a light source.

Suppose, you have a DAT tape, containing a sound recording; or an MP3 file. Can you call data numbers on the media "volume"? No, right?

mostlyboringphotog · Aug 20, 2015

GeorgianBay1939 said:
It seems that DPR contributes to the propagation of errors in the correct understanding and use of the terminology and principles basic to the practice of photography.

As a relative neophyte I now use Wikipedia and known authorities in the field instead of using the various "expert" websites. Unfortunately, even Wikipedia suffers from inadequacies in spite of an attempt at "peer review". There appears to be no such attempt in the DPR Glossary.

Lately I've been reviewing a number of topics to squeeze a bit more out of my gear and have tried to use the DPR Glossary (which would be more obvious if listed under the "Features" pull-down menu.)

My trials began when I decided to look up the following: Dynamic Range , Noise , Sensitivity , etc --- leading me eventually to Exposure :

_____________________

DPR Glossary Definition: "The exposure is the amount of light received by the film or sensor and is determined by how wide you open the lens diaphragm (aperture) and by how long you keep the film or sensor exposed (shutterspeed). The effect an exposure has depends on the sensitivity of the film or sensor.

The exposure generated by an aperture, shutterspeed, and sensitivity combination can be represented by its exposure value "EV". Zero EV is defined by the combination of an aperture of f/1 and a shutterspeed of 1s at ISO 100[1]"

______________________

Compare to the Wikipedia definition of Exposure (Photographic) :

______________________

Wikipedia Definition: "In photography, exposure is the amount of light per unit area (the image plane illuminance times the exposure time) reaching a photographic film or electronic image sensor, as determined by shutter speed, lens aperture and scene luminance. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance in a specified region."

______________________

1 All of the experts that I trust use amount of light / unit area in discussions of exposure (and total light when considering noise and other factors.)

2 I believe that (Photographic) Exposure is determined by only 3 factors: Scene luminance, shutter interval (speed) and f/ (T-stop to be more precise). Exposure is unaffected by ISO Speed. Exposure Metering is affected by ISO Speed and, if it is followed, will affect the camera's EV setting, and therefore the exposure.

3 Both definitions should use the phrase aperture ratio or f/ instead of "aperture" in such a critical application.

4 "The exposure generated by an aperture, shutterspeed, and sensitivity combination can be represented by its exposure value "EV" is very misleading as it implies that exposure is a function of sensitivity (ISO Speed) which it isn't. The use of "EV" here is also problematical.

5 Exposure value, by definition, only depends on f/ (T-stop) and shutter interval (speed).

6 Exposure value (ISO Speed 100) , can be used as a measure of scene lighting conditions.

It appears that the DPR Glossary is in need of an update since much of it appears to be written about 10 years ago. Perhaps it is also time to improve the vocabulary and principles described in the work.

On the other hand, perhaps Amazon, prefers the confusion propagated by the current Glossary as a stimulant for endless forum arguments about sensor size/performance, equivalence, noise, ad nauseam.

GeorgianBay1939 · Aug 24, 2015

Iliah Borg said:
Iliah Borg said:

Here is another use of the word: http://www.cambridgeincolour.com/tutorials/histograms1.htm

"Each pixel in an image has a color which has been produced by some combination of the primary colors red, green, and blue (RGB). Each of these colors can have a brightness value ranging from 0 to 255 for a digital image with a bit depth of 8-bits. A RGB histogram results when the computer scans through each of these RGB brightness values and counts how many are at each level from 0 through 255."

Click to expand...

Calling data numbers "brightness" is very wrong. Brightness appear when there is a light source.

Suppose, you have a DAT tape, containing a sound recording; or an MP3 file. Can you call data numbers on the media "volume"? No, right?

GeorgianBay1939 · Aug 24, 2015

Big SNIP

mostlyboringphotog said:
Even though DPR caters to more of the gear head, it's not a highly technical site. That may explain your dissatisfaction.

I'd be interested in learning what the characteristics are of the DPR readership. Any data?

I suspect that a lot of folks are referred to DPR for camera reviews ------ where this caution is clearly presented:

"If you're new to digital photography you may wish to read the Digital Photography Glossary before diving into this article (it may help you understand some of the terms used)."

My dissatisfaction has nothing to do with who DPR caters to.

It has everything to do with DPR's contribution to the propagation of errors into the photographic vocabulary. Especially so since DPR suggests that its glossary is authoritative for folks "new to digital photography".

There are several highly technical authors who contribute to this DPR. I am encouraging them to get involved in revising the Glossary, to everyone's benefit, including Amazon's.

Great Bustard · Sep 3, 2015

GeorgianBay1939 said:
It seems that DPR contributes to the propagation of errors in the correct understanding and use of the terminology and principles basic to the practice of photography.

As a relative neophyte I now use Wikipedia and known authorities in the field instead of using the various "expert" websites. Unfortunately, even Wikipedia suffers from inadequacies in spite of an attempt at "peer review". There appears to be no such attempt in the DPR Glossary.

Lately I've been reviewing a number of topics to squeeze a bit more out of my gear and have tried to use the DPR Glossary (which would be more obvious if listed under the "Features" pull-down menu.)

My trials began when I decided to look up the following: Dynamic Range , Noise , Sensitivity , etc --- leading me eventually to Exposure :

_____________________

DPR Glossary Definition: "The exposure is the amount of light received by the film or sensor and is determined by how wide you open the lens diaphragm (aperture) and by how long you keep the film or sensor exposed (shutterspeed). The effect an exposure has depends on the sensitivity of the film or sensor.

The exposure generated by an aperture, shutterspeed, and sensitivity combination can be represented by its exposure value "EV". Zero EV is defined by the combination of an aperture of f/1 and a shutterspeed of 1s at ISO 100[1]"

______________________

Compare to the Wikipedia definition of Exposure (Photographic) :

______________________

Wikipedia Definition: "In photography, exposure is the amount of light per unit area (the image plane illuminance times the exposure time) reaching a photographic film or electronic image sensor, as determined by shutter speed, lens aperture and scene luminance. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance in a specified region."

______________________

1 All of the experts that I trust use amount of light / unit area in discussions of exposure (and total light when considering noise and other factors.)

2 I believe that (Photographic) Exposure is determined by only 3 factors: Scene luminance, shutter interval (speed) and f/ (T-stop to be more precise). Exposure is unaffected by ISO Speed. Exposure Metering is affected by ISO Speed and, if it is followed, will affect the camera's EV setting, and therefore the exposure.

3 Both definitions should use the phrase aperture ratio or f/ instead of "aperture" in such a critical application.

4 "The exposure generated by an aperture, shutterspeed, and sensitivity combination can be represented by its exposure value "EV" is very misleading as it implies that exposure is a function of sensitivity (ISO Speed) which it isn't. The use of "EV" here is also problematical.

5 Exposure value, by definition, only depends on f/ (T-stop) and shutter interval (speed).

6 Exposure value (ISO Speed 100) , can be used as a measure of scene lighting conditions.

It appears that the DPR Glossary is in need of an update since much of it appears to be written about 10 years ago. Perhaps it is also time to improve the vocabulary and principles described in the work.

Yep. Also, a link to Gollywop's excellent article on Exposure vs Brightening would be good to include.

GeorgianBay1939 said:
On the other hand, perhaps Amazon, prefers the confusion propagated by the current Glossary as a stimulant for endless forum arguments about sensor size/performance, equivalence, noise, ad nauseam.

Heh! I'm pretty certain that they'd love to see discussions move on to other topics. ;-)

DPR Glossary revisions

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