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Defining correct exposure
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Jun 12, 2018 08:58:23   #
BebuLamar
 
Gene51 wrote:
Ah, Bebu, I guess you hadn't read Ansel Adams' own words on this:

"I was at a loss with the subject luminance values, and I confess I was thinking about bracketing several exposures, when I suddenly realized that I knew the luminance of the moon—250 c/ft2. Using the Exposure Formula, I placed this luminance on Zone VII; 60 c/ft2 therefore fell on Zone V, and the exposure with the filter factor o 3x was about 1 second at f/32 with ASA 64 film. I had no idea what the value of the foreground was, but I hoped it barely fell within the exposure scale. Not wanting to take chances, I indicated a water-bath development for the negative."

I interpreted this as nailing the exposure by using a known EV for the moon in the scene, and using his knowledge and experience and the Zone System to ensure a proper exposure. As he said, he was thinking of bracketing but given the circumstances, there was no time.

It's funny how two people can read the same words and come up with a different take. I think he was very precise and knew exactly what he needed to do to make it work. Bracketing was a passing thought until he realized he had a known luminance level he could base his exposure on. But you made it sound like there was a bit of guesswork, and that Adams had some regret that he did not make the best exposure and would rather have relied on bracketing. I'm pretty sure that by the time AA pressed the shutter, he knew he was going to get what he wanted.

Do you have anything that I can read that supports his unhappiness with the exposure, other than the fact he did not have enough time to take a second one?
Ah, Bebu, I guess you hadn't read Ansel Adams' own... (show quote)


I read that paragraph many times and in my opinion he wasn't sure of his exposure. He based his exposure on the moon but he had no idea how bright the foreground was. He did the water bath development because he wasn't sure.

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Jun 12, 2018 09:04:27   #
selmslie Loc: Fernandina Beach, FL, USA
 
canadaboy wrote:
Discounting special effects such as high or low key etc, if asked how I might define correct exposure I could say something like "were it a scene that includes a mid Grey object, correct exposure would be settings that make the object appear as a similar tone in the completed image".

How would you define it?

Forget about where gray ends up. It depends on whether your camera is going to provide the final image straight out of the camera (SOOC) or if you are going to develop the image from the information in the raw file.

A correct exposure is one that gives you a useful record of the tones you want to use in the final image.

That might mean letting the highlights disappear into pure white if you don't care about them. It can also means letting the shadows disappear into total black if they don't contribute to the image.

But it also means getting the tones in which you want to show some color, details and texture to record close enough to middle gray that you end up with something you can work with.

But if you want an image to look good SOOC you will need to be more careful with your exposure and you might need to bracket.

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Jun 12, 2018 09:12:12   #
selmslie Loc: Fernandina Beach, FL, USA
 
BebuLamar wrote:
I read that paragraph many times and in my opinion he wasn't sure of his exposure. He based his exposure on the moon but he had no idea how bright the foreground was. He did the water bath development because he wasn't sure.

If you read what Adams wrote about how he determined the exposure you will see that he knew very well how well the foreground and everything else was going to record.

The way he developed the negative was part of his plan to control the overall contrast. That's what the Zone System is all about - to mate the exposure with the appropriate development.

What is just as interesting is how he changed the appearance of the final print over several decades. His later prints ended up darker and with more contrast while still using the same developed negative.

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Jun 12, 2018 09:18:11   #
dsmeltz Loc: Philadelphia
 
canadaboy wrote:
Discounting special effects such as high or low key etc, if asked how I might define correct exposure I could say something like "were it a scene that includes a mid Grey object, correct exposure would be settings that make the object appear as a similar tone in the completed image".

How would you define it?


What if you subject is not anywhere near the mid grey object?

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Jun 12, 2018 09:22:08   #
bpulv Loc: Buena Park, CA
 
canadaboy wrote:
Discounting special effects such as high or low key etc, if asked how I might define correct exposure I could say something like "were it a scene that includes a mid Grey object, correct exposure would be settings that make the object appear as a similar tone in the completed image".

How would you define it?


Proper exposure is the exposure at which both the maximum possible highlight and shadow details are maintained along with a linear relationship throughout the grey scale portion of the black to white continuum for the medium being used. That means that the whitest white and blackest black possible are present or inferred along with a full grey scale.

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Jun 12, 2018 09:26:56   #
BebuLamar
 
selmslie wrote:
If you read what Adams wrote about how he determined the exposure you will see that he knew very well how well the foreground and everything else was going to record.

The way he developed the negative was part of his plan to control the overall contrast. That's what the Zone System is all about - to mate the exposure with the appropriate development.

What is just as interesting is how he changed the appearance of the final print over several decades. His later prints ended up darker and with more contrast while still using the same developed negative.
If you read what Adams wrote about how he determin... (show quote)


He was hoping that the foreground would fall into the range. He did the water bath to reduce contrast in hope that his foreground isn't too dark.

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Jun 12, 2018 09:54:00   #
selmslie Loc: Fernandina Beach, FL, USA
 
BebuLamar wrote:
He was hoping that the foreground would fall into the range. He did the water bath to reduce contrast in hope that his foreground isn't too dark.

He actually knew that the foreground would record. He also knew that in the time it took him to flip the holder over for a second shot the light changed enough that the opportunity for a bracketed image was gone.

But he exposed based on experience. He didn't even have time to find his meter.

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Jun 12, 2018 09:59:07   #
selmslie Loc: Fernandina Beach, FL, USA
 
bpulv wrote:
Proper exposure is the exposure at which both the maximum possible highlight and shadow details are maintained along with a linear relationship throughout the grey scale portion of the black to white continuum for the medium being used. That means that the whitest white and blackest black possible are present or inferred along with a full grey scale.

That only means something if you want to record highlight and shadow detail. You might not want to (see my earlier post).

As for any linear relationship, you can't control that at the time of exposure with digital like you can when developing film. But linearity is gone as soon as you start to adjust the tones in post processing.

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Jun 12, 2018 10:24:09   #
bpulv Loc: Buena Park, CA
 
selmslie wrote:
That only means something if you want to record highlight and shadow detail. You might not want to (see my earlier post).

As for any linear relationship, you can't control that at the time of exposure with digital like you can when developing film. But linearity is gone as soon as you start to adjust the tones in post processing.


You don't need to record highlight and shadow detail if your subject does not have that detail, however for a full tone print, the grey scale should be placed as if you were recording shadow and highlight detail. I.e., the proper exposure will account for the entire grey scale spectrum whether those shades of grey are in the subject matter or not.

White on white, black on black and other extreme lighting situations are a completely different subject. The original question was a general one regarding what constitutes proper exposure and I took that to mean for the "normal" subject.

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Jun 12, 2018 11:21:33   #
selmslie Loc: Fernandina Beach, FL, USA
 
bpulv wrote:
You don't need to record highlight and shadow detail if your subject does not have that detail, however for a full tone print, the grey scale should be placed as if you were recording shadow and highlight detail. I.e., the proper exposure will account for the entire grey scale spectrum whether those shades of grey are in the subject matter or not. ...

I don't want to quibble over semantics but the subject might actually have detail that you don't care about or want to record. And a proper print (or digital image) does not necessarily need to contain a full complement of shades from maximum black to pure white.

The zones being described in the Zone System are found in the print (or the final image). They are not necessarily in the same place they were recorded in the original exposure. You may or may not choose to place whatever you metered as middle gray when capturing the image in the middle of Zone V in the final print. That depends on how you decide to modify the tone curve or dodge and burn during analog printing or during digital raw development.

When it comes to applying the Zone System to color digital images, here is a very good article: Understanding & Using Ansel Adam's Zone System.

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Jun 12, 2018 11:58:25   #
dsmeltz Loc: Philadelphia
 
canadaboy wrote:
Discounting special effects such as high or low key etc, if asked how I might define correct exposure I could say something like "were it a scene that includes a mid Grey object, correct exposure would be settings that make the object appear as a similar tone in the completed image".

How would you define it?


There is no one definition of correct exposure. It really depends on what qualities you want in your final image. This, unfortunately, means thinking about the final outcome before you push the shutter and choosing your settings accordingly.

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Jun 12, 2018 13:13:23   #
bpulv Loc: Buena Park, CA
 
selmslie wrote:
I don't want to quibble over semantics but the subject might actually have detail that you don't care about or want to record. And a proper print (or digital image) does not necessarily need to contain a full complement of shades from maximum black to pure white.

The zones being described in the Zone System are found in the print (or the final image). They are not necessarily in the same place they were recorded in the original exposure. You may or may not choose to place whatever you metered as middle gray when capturing the image in the middle of Zone V in the final print. That depends on how you decide to modify the tone curve or dodge and burn during analog printing or during digital raw development.

When it comes to applying the Zone System to color digital images, here is a very good article: Understanding & Using Ansel Adam's Zone System.
I don't want to quibble over semantics but the sub... (show quote)


First of all, what makes you think that I use the Zone System. I have used sensitometry (Macbeth TD-102 densitometer) for film since the 1960's to match the grey scale of the film to that of the paper I am using. The entire process is controlled by precise transmission density measurements of processed film samples and the reflected density of the paper on which the print is made. Adams started this with his popularized Zone System, but it advanced to a scientific/mathematical system in following Adams. It is much more exacting than the Zone System and results in consistent full tone prints.

It is true that not all subjects contain every shade of grey from black to white, but exposing and processing as if it did results in consistent high quality prints. The same rules apply to color. The grey scale is integral to every color photograph and must be considered. Professional photo labs do not use the Zone System, they use some form of measurement (sensitometry) to insure consistent quality.

Once you have your properly exposed image, you can manipulate the print any way you like depending on your skill. Don't limit yourself to one method of thought. Although Ansel Adams methods of control and teaching are outstanding and easy to understand, they are not the only or necessarily the best if you are willing to examine methods that use mathematics and measurement as apposed to general rules.

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Jun 12, 2018 15:16:59   #
selmslie Loc: Fernandina Beach, FL, USA
 
bpulv wrote:
First of all, what makes you think that I use the Zone System. I have used sensitometry (Macbeth TD-102 densitometer) for film since the 1960's. ...

Almost nobody uses the Zone System the way it was originally defined for sheet film. It is a stretch to attempt to apply the original Zone System to roll film or to color or digital imaging.

However, as a common frame of reference a particular part of the Zone System is very useful. We can refer to the scale (0, I, II ... VIII, IX, X) used to define the tones in an image or print with Zone 0 representing maximum black, Zone X as maximum white and Zone V as being right in the middle.

That does not mean we are actually "using" the Zone System, just a particular part of it that is actually common to all images and prints - even to painting, tapestry and other forms of two-dimensional art.

Anyone who has worked with film and sensitometry is following the work of Hurter and Driffield whether they use the same methods or tools that were used originally to plot film curves.

Even the statement attributed to Newton (1643-1727), "If I have seen further it is by standing on the shoulders of giants" is a good example since the sentiment can actually be traced back to the twelfth century and probably goes back much further.

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Jun 12, 2018 15:19:34   #
mwsilvers Loc: Central New Jersey
 
canadaboy wrote:
Discounting special effects such as high or low key etc, if asked how I might define correct exposure I could say something like "were it a scene that includes a mid Grey object, correct exposure would be settings that make the object appear as a similar tone in the completed image".

How would you define it?

The proper exposure is the one that meets my intended goals. Very often it's the same as the camera would give me automatically, but just as often it isn't. The proper exposure for my photography can change on a shot by shot basis.

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Jun 12, 2018 15:19:58   #
Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)
 
BebuLamar wrote:
I read that paragraph many times and in my opinion he wasn't sure of his exposure. He based his exposure on the moon but he had no idea how bright the foreground was. He did the water bath development because he wasn't sure.


Yeah, but he knew exactly what he wanted from the luminance of the moon, and where he wanted to place the value of the moon in his scene. The rest is using his expertise in developing, which often included custom developer formulas, temperatures and development times, to extract every last iota of tonality from the negative. I doubt that he "wasn't sure" about how it would turn out. From his words I am sure that he dismissed the idea of bracketing once he decided to use the correct exposure for the moon to determine the exposure for the shot - which he pretty much stated.

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