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Divided Attention

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Bill Burk

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Bill Burk submitted a new resource:

(there was a url link here which no longer exists) - Divided Attention


(there was a url link here which no longer exists)
 
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Stephen Benskin

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Bill, this is absolutely excellent. It's well thought out, balanced, and factually accurate. You've covered a lot while being concise. While not going into too much detail, you were able to convey the concepts in an understandable manor. Plus you provided additional references for the reader to further investigate the concepts that interest them.

I have only two suggestions. Subject Brightness Range is an outdated term. And I could send you better versions of those development charts if you wish.

It was a pleasure to read. Thank you for sharing it. I hope people take the time to check it out. It's a great primer.
 
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markbarendt

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I like it Bill
 

TheToadMen

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This will be an interesting read during my upcoming holiday.
Thanks!
 
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Bill Burk

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Thanks for the comments!

I see I left out a paragraph I would have liked to include that explains my feelings towards Delta-X Criterion.

In Beyond the Zone System (BTZS), Phil Davis designed a "Power Dial" which you use while metering and planning the scene.

The Power Dial asks you to change your Exposure Index as the development plan changes, BTZS assumes you always want to have the speed point fall on 0.10 density.

Obviously that Power Dial is at odds with my presentation, because I advise testing after the fact. The Delta-X Criterion is an important part of my plan.

Delta-X Criterion demonstrates that speed does not really move along the 0.10 density point, but that as you decrease film development... you change print paper grade as well. With a higher paper grade you can reach down further on the toe to get shadow detail below 0.10 density.

So in the end, Delta-X is as simple to implement as: "Choose an Exposure Index that works for Normal and leave it alone."
 

MattKing

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Stephen:

What is the current replacement for "Subject Brightness Range". I confess that I am a regular user of that phrase.
 

JPJackson

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Really enjoyed reading this; thank you.

I think the "Powerdial" is neat and have used it a good bit; but now, mostly just follow PD's recommendations for the incident metering system and also keep a spot meter handy.
 
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Bill Burk

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I will make a note to replace "SBR" with "SLR." Back when Zone System was being formulated, "SLR" meant one thing, and one thing only: Single Lens Reflex. So the correct term was deliberately avoided.

Dungeons and Dragons had no problem using "Level" to describe spells, depth of dungeon and experience... Players were expected to know what is meant by context.

And not too many people toss "SLR" around as a phrase these days (without a D in front).

So maybe it's time to start using the right term.

Another note to self... Negative Density Range and Paper Log Exposure Range (LER) do not correlate exactly. I jumped from one term to the other with little explanation (I found two benchmark negatives that just work for me). I should give advice how to fit a negative to paper in case you don't have two magic negatives.
 

Stephen Benskin

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From Photographic Materials and Processes:

"Luminance is the photometric quantity that relates closely to the perceptual concept of brightness. The term brightness is used exclusively to describe the appearance of a source and, therefore, cannot be directly measured."

From Encyclopedia of Photography:

"The scientific study of the relationship between the physical attributes of a stimulus and the perceptual response of the viewer. A goal of psychophysics is to be able to predict the appearance of a stimulus on the basis of physical measurements of the stimulus. For example, sodium vapor emits a narrow wavelength band of radiation at approximately 590 nm, and it can be predicted that viewers generally will identify the color of the light as being yellow."

Most aspects of the photographic process are psychophysical, film speed, paper grades, LER, tone reproduction theory, sensitometry, and color.

Oh and you could use LSLR for log subject luminance range.
 
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Bill Burk

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JPJackson said:
Really enjoyed reading this; thank you.

I think the "Powerdial" is neat and have used it a good bit; but now, mostly just follow PD's recommendations for the incident metering system and also keep a spot meter handy.
Click to expand...

Have you seen the instructions how to make a Wonder Wheel? Amazing meticulous graphing and knife-work is required. But the result would be a mile ahead of my simple chips on my Master II meter.

Another note to self... Talking about the Weston Master meter is incomplete without information about its slightly different emulsion speed dial (compared to ASA) and how to tell apart the two variations I've heard about of this meter which differ by 1/3 stop.
 

JPJackson

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Bill,
I have read the instructions on constructing the "Wonder Wheel" and opted to buy the "Powerdial" for $15.
 
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Bill Burk

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As a companion for the graphs in the resource I called "Divided Attention" I have created a Delta-X meter to make it easy to determine "delta X speeds."

The scale of this Delta X Meter is the same as my other graphs referenced in the resource, and is intended to be printed on an overhead transparency sheet.

http://www.beefalobill.com/images/DeltaX_Meter.pdf

NOTE: To find a practical Exposure Index, (relative to ASA/ISO speed) look at the difference between your delta X and the delta X of 0.29 that is approximately what you get when film is developed to ASA/ISO contrast parameters.

Bill
 
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Bill Burk

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The post earlier today is a direct transcription of the "Speed Meter - Model X" as it was drawn in 1955.

The "speed point" it defines is approximately the point at which the characteristic curve has a gradient that is 0.3 times the average gradient.

It illustrates that point very clearly when you use it... but you can't directly enter that value into your exposure meter.

To directly adjust Delta X to ASA/ISO I made this variation of the Delta X Meter.

http://www.beefalobill.com/images/DeltaX_Meter_Shifted.pdf
 
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Bill Burk

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20150812 CallingYourShot-DividedAttention.pdf

https://www.photrio.com/forum/resources/divided-attention.77/

http://beefalobill.com/imgs/20150812 CallingYourShot-DividedAttention.pdf

Updated URLs

An expansion of ideas first introduced in my APUG thread: Working idea - Zone System exposure - Time/CI darkroom
( https://www.photrio.com/forum/threads/working-idea-zone-system-exposure-time-ci-darkroom.84567/ )

Recommended: Photrio
( http://www.photrio.com )

Recommended: Enlarger -----> Sensitometer
( https://www.photrio.com/forum/threads/enlarger-sensitometer.92518/ )

Recommended: Great Sensitometer Shootout
( https://www.photrio.com/forum/threads/the-great-sensitometer-shootout.95837/ )
 
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Bill Burk

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Direct upload of resources for lab notes
 

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  • labnotesnegs.pdf
    808.2 KB · Views: 100
  • labnotesprint.pdf
    808.9 KB · Views: 158
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Bill Burk

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Summary of links:

Choosing a Contrast Index
Recommended: Chart takes SBR and LER to determine CI with fixed flare model
( http://beefalobill.com/imgs/Contrast Indexes - Kodak.jpg )

Recommended: Chart takes SBR and LER to determine CI with practical flare model
( http://beefalobill.com/imgs/Practical Flare Model b.jpg )

WORKSHEETS & EXAMPLES
Recommended: Sensitometry Graph Paper
( http://beefalobill.com/imgs/sensitometry.pdf )
Recommended: Time/Contrast Graph Paper
( http://beefalobill.com/images/TimeCI.pdf )
Recommended: Contrast Index Meter (print onto overhead transparency film)
( http://beefalobill.com/imgs/cntrastindexmeter.pdf )
Recommended: Lab Notes Negs
( http://beefalobill.com/images/labnotesnegs.pdf )
Recommended: Lab Notes Prints
( http://beefalobill.com/images/labnotesprint.pdf )
 
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