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Defining correct exposure
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Jun 13, 2018 09:54:07   #
Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)
 
SusanFromVermont wrote:
"Correct exposure" is determined by your objectives in taking a particular photograph. There is no clear-cut definition that covers any situation. You can use middle gray all you want, but that does not solve problems of high dynamic range, where there are multiple levels of exposure that will capture the image, so which one would be correct? Also, if your intent is to capture a scene and put a certain "mood" into it, you might decide that a bit of under- or over-exposure will accomplish that. There are more factors to take into consideration for determining exposure than how the colors turn out!
"Correct exposure" is determined by your... (show quote)


Ah, but shooting raw is the game changer - you don't need to shoot over or under for a "mood" since you can adjust the exposure level in post. At the end of the day is when you capture the information in the image that allows whatever expression you want in the image. In my experience, exposing to the right always gives me that - so my take on a "correct" exposure is capturing as much detail and tonal value as possible without overexposing (clipping) anything important. If the shadows are too dark, then you have to resort to exposure merging of multiple bracketed shots -

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Jun 13, 2018 09:59:36   #
selmslie Loc: Fernandina Beach, FL, USA
 
rmalarz wrote:
That is quite simple. The f-stop is determined by taking the square root of the ISO. The shutter speed is the reciprocal of the number of foot candles of light measured from the middle grey object.

Thus, if one is using an ISO of 100 and the light reflected from the middle gray object is 250 foot-candles, the exposure will be 1/250 at f/10.
--Bob

Not so simple if you don't have a foot candle meter - hardly anyone does. They measure incident light, usually for an indoor space like an office or museum.

To make matters worse, different sources give you different values for broad daylight foot candles. I have seen values of 250 fc (your meter), 7600 fc (Seconic) and 10000 fc (Wikipedia).

Nearly all meters used for photography provide exposure value (EV) and they have dials or internal calculations to give you shutter speed and f-stop adjusted for ISO without any additional calculations.

Sunny 16 is just as simple as your formula: 1/ISO seconds at f/16 for broad daylight. That's the same as your 250 fc calculation.

There is plenty of information available at Exposure Value.

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Jun 13, 2018 10:03:25   #
boberic Loc: Quiet Corner, Connecticut. Ex long Islander
 
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's "correct"? It depends. Is a partially blurred image "correct"? There is even a word for it, and it's presence is valued. Bokeh. If you like it, it's correct, if you don't, it aint. It depends

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Jun 13, 2018 10:13:24   #
DanielB Loc: San Diego, Ca
 
Hard to say since we can't download to have a better look but to me it looks a little washed out.
Gene51 wrote:
I'll ask a question back at you. Do you consider this contact print right out of the camera to be a good exposure?

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Jun 13, 2018 10:16:18   #
selmslie Loc: Fernandina Beach, FL, USA
 
DanielB wrote:
Hard to say since we can't download to have a better look but to me it looks a little washed out.

Are you not familiar with the final version? Didn't it make a good print?

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Jun 13, 2018 10:18:30   #
rmalarz Loc: Tempe, Arizona
 
You realize that the example I used was fictitious. I could have used any value for the light reflected from the grey surface. So, you using my 250 fc (your meter) is a somewhat bogus statement.

The meter I used years ago, and still use at times now, provides measurements in ft-lamberts. Since I carry a notebook with me when photographing, I have the necessary tables to convert ft-lamberts, or EV, to ft-candles. So, it's very simple, at least for me. And, it works.

Additionally, the sq-root of the ISO and reciprocal of the ft-candles combination for photographic exposure comes from "The Negative" - Ansel Adams. Too bad he's not still around so you could argue with him.
--Bob

selmslie wrote:
Not so simple if you don't have a foot candle meter - hardly anyone does. They measure incident light, usually for an indoor space like an office or museum.

To make matters worse, different sources give you different values for broad daylight foot candles. I have seen values of 250 fc (your meter), 7600 fc (Seconic) and 10000 fc (Wikipedia).

Nearly all meters used for photography provide exposure value (EV) and they have dials or internal calculations to give you shutter speed and f-stop adjusted for ISO without any additional calculations.

Sunny 16 is just as simple as your formula: 1/ISO seconds at f/16 for broad daylight. That's the same as your 250 fc calculation.

There is plenty of information available at Exposure Value.
Not so simple if you don't have a foot candle mete... (show quote)

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Jun 13, 2018 10:19:23   #
DanielB Loc: San Diego, Ca
 
This one I like more because it has more contrast and it's moody. As far as the exposure question - in example #1 slightly over exposed & #2 slightly under. That's just what my eye is telling me...that somewhere in between would be a more accurate exposure. But what the heck - I don't shoot film anymore and it's been a long time since I've been in the darkroom, so what do I know.
Gene51 wrote:
If you thought that exposure was terrible, then what would you say about this image?

The point I am making is that a proper exposure is less about how "nice" an image is when you view it on the preview screen or look at the jpeg on your computer screen or print, and has a mid-gray object in it that looks like it does in reality. But more about recording the important parts of the scene, with detail, in such a way that with some manipulation you can extract all of the details, tones and colors to make a complete image. Mnay photographers are proud to state that they do not spend any time manipulating their images. I say that they are "leaving money on the table" by not taking their images and improving contrast, sharpening, dodging and burning, as the photographer who took the picture below did, in order to create a better image. So the first image is a correct exposure, and the ultimate result bears that out.
If you thought that exposure was terrible, then wh... (show quote)

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Jun 13, 2018 10:23:43   #
rmalarz Loc: Tempe, Arizona
 
Gene, like yourself, I use The Zone System 99% of the time. For film, I use it as explained by AA in his books. For digital, I use it just the opposite. Instead of metering for the shadows, I meter for highlights and place them in the Zone I wish. The two are 180 degrees apart from one another, but they work.
--Bob
Gene51 wrote:
I use the zone system all the time - but in reverse - I don't concentrate on retaining shadow detail, but I do work on keeping highlight detail. Same zone system, different focus.

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Jun 13, 2018 10:28:36   #
rmalarz Loc: Tempe, Arizona
 
The only reason he considered bracketing was that he couldn't find his exposure meter. However, he did remember the luminance of the moon and used that for his exposure setting. This was explained in one of his books.
--Bob
BebuLamar wrote:
With all due respect Gene, Adams didn't consider that he got the best exposure possible for that image. He would have bracketed but he had time for only one exposure so he had to make the best out of that negative.

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Jun 13, 2018 10:29:38   #
CatMarley Loc: North Carolina
 
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?


That exposure which results in an image that mat accurately displays the shape, texture and tonal values of the subject.

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Jun 13, 2018 10:48:11   #
selmslie Loc: Fernandina Beach, FL, USA
 
rmalarz wrote:
You realize that the example I used was fictitious. I could have used any value for the light reflected from the grey surface. So, you using my 250 fc (your meter) is a somewhat bogus statement. ...

I guess your recommendation is also bogus since you don't expect anyone to be able to measure fc. But you didn't pull the 250 out of the air - see below.

As you know, I am quite familiar with The Negative and all of the esoteric ways that you can express luminance and all of the convoluted ways that you can convert the measurements.

But like Adams, I am pragmatic. He used modern meters once they became available. Modern photographic meters do not read out in foot candles or lumens and force you to do additional calculations.

Your suggestion to calculate exposure from fc is not helpful.

Your 250 fc example
Your 250 fc example...

My sunny 16 example
My sunny 16 example...

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Jun 13, 2018 10:58:34   #
rmalarz Loc: Tempe, Arizona
 
Damn, I keep forgetting that you are the Oracle of UHH.

As a matter of fact, I did pull 250ft-candles out of the air.
--Bob
selmslie wrote:
I guess your recommendation is also bogus since you don't expect anyone to be able to measure fc. But you didn't pull the 250 out of the air - see below.

As you know, I am quite familiar with The Negative and all of the esoteric ways that you can express luminance and all of the convoluted ways that you can convert the measurements.

But like Adams, I am pragmatic. He used modern meters once they became available. Modern photographic meters do not read out in foot candles or lumens and force you to do additional calculations.

Your suggestion to calculate exposure from fc is not helpful.
I guess your recommendation is also bogus since yo... (show quote)

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Jun 13, 2018 10:59:26   #
selmslie Loc: Fernandina Beach, FL, USA
 
rmalarz wrote:
... he did remember the luminance of the moon and used that for his exposure setting. ...

And that is, in fact, where you got your 250 fc number from. It's the gray card reading in broad daylight.

In fact, he placed the moon on Zone VII because he knew he was going to need to pull (water bath) the development and the moon would have been almost the brightest part of the image. Almost, that is, except for the sunlit clouds which recorded even brighter.

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Jun 13, 2018 11:07:39   #
Kozan Loc: Trenton Tennessee
 
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?


Correct exposure would be whatever you wanted it to be assuming not a lot of the highlights are blown out. Some photographers say to expose using the histogram and expose for the right edge. But that means shooting in RAW and doing post production to get the "correct" exposure. Take a look at the covers of Professional Photographer Magazine. The right edge of the histogram would have NO white pixels.

The correct exposure depends on the mood of the picture-- not what the histogram shows!

I used to expose by the histogram. That is, have the light pixels bump up against the right side of the histogram, but then I would have to go to Photoshop or Camera Raw, and drop the exposure by two stops. I was doing that a lot.
Now I don't worry so much about the histogram.

That's my story and I'm sticking to it.

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Jun 13, 2018 11:08:30   #
rmalarz Loc: Tempe, Arizona
 
Scotty, believe what you wish. I pulled that 250 out of thin air when I was writing the initial reply to the OP. It was totally unrelated to anything other than being a reasonable number.
--Bob
selmslie wrote:
And that is, in fact, where you got your 250 fc number from. It's the gray card reading in broad daylight.

In fact, he placed the moon on Zone VII because he knew he was going to need to pull (water bath) the development and the moon would have been almost the brightest part of the image. Almost, that is, except for the sunlit clouds which recorded even brighter.

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