You know... I think Bill & Sam would be much happier if they just go out & burn a roll of film without all the freakin' thinking! Sheesh!
(Stop picking on Sam. You will bruise his ego and make him turn to digital photography.)
Sam needs to get an 8x10 - that'll cure him of his slapdash habits...
I see it this way:
Originally Posted by fhovie
Kids in their adolescents feel they know more than their parents and then, by the time they reach the age of 25-30, they wonder how their parents suddenly became smart..
"Pictures are not incidental frills to a text; they are essences of our distinctive way of knowing." Stephen J. Gould
I quite like that attitude. If someone says to me "you can't do it like that...." my immediate reaction is "why? What would happen if I did?".
Originally Posted by fhovie
Here are the pictures.
The pictures came from Todd and Zakia, they were showing results from a similar experiment and published it in the book.
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Maybe Sam should try that on Bergger 200 instead on TMY.
Mine is about to explode - I must log out.
Originally Posted by Christopher Walrath
Sam's Determination of EI
There are two issues addressed by Sam's technique. One is "determination of EI" and the other is "determination of development time." I'll address each separately.
An explanation of Sam's Determination of EI:
Short answer: He used the method for determining an exposure index for REVERSAL (slide) film.
Longer answer: He used the SHOULDER of the HD curve as a basis of his exposure, rather than the FOOT of the HD curve.
What difference does it make if you use the SHOULDER or the FOOT of the curve?
Short answer: Negatives based on the SHOULDER (of modern films) will be denser.
Long answer: There are a lot of permutations here and I will bring up a few. Exposure based on the foot of the curve (the common way) causes the shadows to fall on the foot of the HD curve, and the rest of the image falls on the middle (sometimes, straight-lined) portion of the curve.
An exposure of negative films based on the SHOULDER causes the HIGH values to fall on the curved shoulder and the low and middle values to fall on the sometimes straight middle part of the curve.
Something else to think about. Imagine a film with a short density scale, for example 8 stops. In this case the exposure index will be the same or similar, irrespective of if you use the shoulder or the foot. In real life, most films have many more than 8 stops range, so the exposure based on the shoulder is going to be much denser than the other.
For example, a long scale film like TMY used in the story, puts the exposure determination based on the SHOULDER way out at 5 to 6 stops more exposure than the EI based on the FOOT.
So, SAM overexposed his TMY by 6 stops. The thing is, he tested accurately. For example, he did not overexpose by 9 stops because he tested for the 'end of the shoulder' with the densitometer (0.1 log below maximum film density). So he showed us the 'Maximum exposure you can make on TMY and still get an acceptable print.'
This is in contrast to Bill who showed us the more conventional 'Minimum exposure you can make on TMY to still get an acceptable print.'
The two pictures from Todd and Zakia show a "Normal" exposure (based on the foot of the HD curve) whereas the other picture shows the best print from an over exposure of 6 stops.
T&Z describe a method of EI determination based on a series of pictures like these. That is, viewers rated pictures from negatives with varying exposure. The EI was based on the best print from the negative with LEAST exposure. These negatives with least exposure have been analyzed and ultimately this forms the basis for the popular use of 0.1 log in EI determination.
The bottom line here is that knowing about how to use 0.1 log above film base plus fog saves you from having to make a bunch of pictures and show them to a group of observers for exposure rating. The work was already been done. So the 0.1 log is a incredibly useful, shortcut. But, as Sam showed us, its not the only way!
If anything does not make sense, ASK don't FLAME. This is supposed to be amusing and entertaining and encourage 'thinking outside of the box.'
Next, the explanation of Sam's determination of development time. (Einstein, really??:o)
Didn't Mortensen’s 7-Derivative technique use the principle of expose for the highlights and develop for the shadows? Mortensen certainly made some nice photographs.
"The secret to life is to keep your mind full and your bowels empty. Unfortunately, the converse is true for most people."
To me, the key word is "HAVE". Neither I. you, or anyone else HAS to do a damned thing; IF anyone chooses to wring out and spend a lot of time and energy "dealing" with the quest for a 'perfect' exposure (whatever that may be ...), all well and good. More power and luck to them.
For me, I'll contemplate the incredible beauty and majesty of this world, try to stay light and cool, so as not to miss anything (or at least not the important stuff), and make my not-so-perfect exposures (system: experience, mainly).
There is always the darkroom. dodge and burn, pre-flash ... multi-grade paper...
Ed Sukach, FFP.