Film testing

BrianShaw · Feb 11, 2007

David A. Goldfarb said:
I don't know, but from now on, I will refer to all spot meters as "bananas," and just claim that it's one of those colorful terms they use on film sets.

Didn't the Marx Brothers make a movie about spot meters?

or was that Woodie Allen??

Roger Hicks · Feb 12, 2007

sanking said:
Donald Miller used the term SBR to discuss measuring subject brightness range in a very specific way that persons who understand BTZS would immediately understand.

Dear Sandy,

Precisely. And as it is completely unreasonable to expect anyone except users of BTZS to understand BTZS jargon, I make absolutely no apologies for my lack of knowledge of BTZS, nor for calling it nonsense to point out that you cannot measure subject brightness range with an incident light meter.

IF he had said "I accept that you are not measuring the actual subject brightness range, but merely inferring it" (which I addressed in post 56), or even if he had had the honesty to answer my simple question posed in my thought experiment, as you did, none of this would have happened.

The only 'multiple meaning' here is one apparently invented by Phil Davis, and understood only by those few thousands who have managed to chew their way through his book. I repeat: the only way to measure an actual subject brightness range, which is known to everyone except devotees of BTZS as the range of reflected brightness (or more accurately luminance) of the subject, is to measure it with a reflected light meter, most conveniently a spot meter (or perhaps banana). To assert that you can measure it directly (or even indirectly) with an incident light meter is, therefore, nonsense, and misleading nonsense at that.

So I'm not picking and choosing -- you are.

Cheers,

R.

Steve Smith · Feb 12, 2007

I did a few prints over the weekend and although I can't add anything scientific to this thread, I can say that I greatly prefer the prints I made with HP5+ at EI 160 than those at EI 400. As expected, they show better shadow detail but with no discernable (to me) loss to the highlights.

As for my experiment to determine exposure by finding minimum time for maximum black using a blank piece of the same film - It worked to a point but I found I needed to use a little bit extra exposure to get a pleasing print.

And just to add my opinion to the incident metering 'discussion' (without wanting to antogonise it any further) I would say that an incident reading can only tell you what the maximum and minimum light values could be, not what they are. The meter does not know if the subject is a piece of grey card or a chess board.

Steve.

sanking · Feb 12, 2007

Roger,

Whatever.

Sandy

BBarlow690 · Feb 12, 2007

Steve Smith said:
I did a few prints over the weekend and although I can't add anything scientific to this thread, I can say that I greatly prefer the prints I made with HP5+ at EI 160 than those at EI 400. As expected, they show better shadow detail but with no discernable (to me) loss to the highlights.

As for my experiment to determine exposure by finding minimum time for maximum black using a blank piece of the same film - It worked to a point but I found I needed to use a little bit extra exposure to get a pleasing print.

Steve.

That's cuz HP5 has never tested for me anywhere close to ISO400. More like 200, so 160 ought to be delightful, too. Ain't gonna tell you what I use it at, 'cuz you need to test fer yerself.

But then yes, HP5 is probably a little overexposed at 160, so while min-time-max-black is good for proofs to see exactly what you've got, it will almost never work for making the best expressive print. An overexposed neg will need a little more enlarger light to make it right. So all-in-all it sounds like you're right on target. Nice shadow separation, though, huh?

We need a new rant here: PREVISUALIZATION, which I saw here a while back. Would someone please tell me what precedes "visualization"? I can visualize the final print when I look at the scene, but before that I'm probably parking the car. I can't find "previsualization" in any of my dictionaries. I got edited by a professional editor for far too long to let such a barbarism as "previsualization" pass, and I don't care if my fave photog Edward Weston used it. Just pass me his girlfriends and hold the ketchup.

So I don't get the "pre-" and find it an horrendous use of our otherwise equally horrendous language. I don't permit anyone to use it in our workshops, unless it's after dinner over a beer or three and they're trying to tease me.

Chuck_P · Feb 12, 2007

Steve Smith said:
As for my experiment to determine exposure by finding minimum time for maximum black using a blank piece of the same film - It worked to a point but I found I needed to use a little bit extra exposure to get a pleasing print.

Steve.

Steve,

I suggest using the MTMB to produce a straight, unmanipulated print only. I often let it serve as a guide to how much (by percentage basis) dodging and burning is called for.

Chuck

David A. Goldfarb · Feb 12, 2007

Well, it is dreadful, but I think Adams's idea of emphasizing the "pre-" was to reinforce the idea that B&W photographers should think about how the world will be rendered in the print when making the image with the camera, rather than trying to visualize it after looking at the proof sheets, but you already knew that.

The curious thing to me is that the idea of "previsualization" is in tension with AA's other famous dictum--"the negative is the score, and the print is the performance." So the message seems to be: previsualize, but don't be afraid to change your mind.

Chuck_P · Feb 12, 2007

I cannot find the word "previsualization" in any of AA's pubs that I have. All references are to "visualization" as far as I can tell. I think the word "previsualization" is a misconception by ZS practitioners over many years. Although I think I did here it used by John Sarkowski in the PBS American Experience documentary on AA that I have.

Chuck

Steve Smith · Feb 12, 2007

BBarlow690 said:
HP5 is probably a little overexposed at 160

That's just me being lazy! I was out with my Olympus XA set to ISO 400 and took one shot as normal and another at it's +1.5 stop setting. I should have alternated between ISO setting 200 and 400.

Shadow separation is certainly better and I intend to use HP5 at EI 200 now as I think that will be about right.

Steve.

Michel Hardy-Vallée · Feb 12, 2007

BBarlow690 said:
We need a new rant here: PREVISUALIZATION, which I saw here a while back. Would someone please tell me what precedes "visualization"? I can visualize the final print when I look at the scene, but before that I'm probably parking the car. I can't find "previsualization" in any of my dictionaries. I got edited by a professional editor for far too long to let such a barbarism as "previsualization" pass, and I don't care if my fave photog Edward Weston used it. Just pass me his girlfriends and hold the ketchup.

Earlier versions of The Negative use "pre-"; later editions (the blue book) include a notice by Adams that someone pointed to him how redundant was the prefix. Don't worry too much about that. After all, this thread has shown that photographers are not always the best masters of the linguistic medium.

David Brown · Feb 12, 2007

David A. Goldfarb said:
The curious thing to me is that the idea of "previsualization" is in tension with AA's other famous dictum--"the negative is the score, and the print is the performance." So the message seems to be: previsualize, but don't be afraid to change your mind.

Perfect!

Jean Noire · Feb 12, 2007

Bob F. said:
Ah well, at least this has somewhat resolved my confusion over the "add five" concept, so not all was wasted...

Cheers, Bob.

Perhaps I could suggest that you read Roger's post number 56 in this thread to clear this matter for you further, he explains the concept clearer than I.
Regards
John

Helen B · Feb 12, 2007

I quite like incident metering but, as this thread shows very well, to make something work you have to know when it won't work. With spot metering you have to know when the colour of the metered object will cause a problem, for example. A while ago there was some discussion on the use of incident metering for reflections off metal objects etc. It is (there was a url link here which no longer exists) for anyone interested. If this has already been referenced, I apologise. I didn't see it in my quick scan through the thread.

At the risk of sounding like a cracked record, the use of incident light readings to estimate subject brightness range for the Zone System predated BTZS: Minor White covered it in one concise page of his Zone System Manual.

Best,
Helen

sanking · Feb 12, 2007

Helen B said:
At the risk of sounding like a cracked record, the use of incident light readings to estimate subject brightness range for the Zone System predated BTZS: Minor White covered it in one concise page of his Zone System Manual.

Best,
Helen

Helen,

I have a reprint (1994) of Minor White" 1967 Zone System Manual.

I asssume you refer to Chapter 8, which is a one-page chapter entitled "Short Cut Exposure Development Calculations." On this page White describes a quick sysem for determing N times based on a reflected reading of the palm of the hands in the shadow (or turned away from the light), and in sunlight. This works conceptually much like Phil Davis' BTZS and is the equivalent of an incident reading, though he uses a reflectance meter. However, the N values for contraction and expansion don't correspond exactly to the SBR values one would derive from sunlight and shadow readings with an incident meter.

Sandy

symmar_man · Feb 12, 2007

If you are interested in the math behind BTZS, here is enough to keep you busy for a while. . .

http://www.bobwheeler.com/photo/Surveys/Survey.pdf

. . . look at page #39

Have fun,

B Dalton

jgjbowen · Feb 12, 2007

BBarlow690 said:
We need a new rant here: PREVISUALIZATION, which I saw here a while back. Would someone please tell me what precedes "visualization"? I can visualize the final print when I look at the scene, but before that I'm probably parking the car. I can't find "previsualization" in any of my dictionaries. I got edited by a professional editor for far too long to let such a barbarism as "previsualization" pass, and I don't care if my fave photog Edward Weston used it. Just pass me his girlfriends and hold the ketchup.

So I don't get the "pre-" and find it an horrendous use of our otherwise equally horrendous language. I don't permit anyone to use it in our workshops, unless it's after dinner over a beer or three and they're trying to tease me.

Note to self.....at the May Fine Focus Workshop be sure to ask Bruce about Previsualization after a few beers, then be prepared to duck....

Roger Hicks · Feb 12, 2007

symmar_man said:
If you are interested in the math behind BTZS, here is enough to keep you busy for a while. . .

http://www.bobwheeler.com/photo/Surveys/Survey.pdf

. . . look at page #39

Have fun,

B Dalton

Thanks. A nice summary of the assumptions -- and a clear and appropriate statement that they ARE (legitimate) assumptions, not actual measurements.

Cheers,

R.

Michel Hardy-Vallée · Feb 12, 2007

symmar_man said:
If you are interested in the math behind BTZS, here is enough to keep you busy for a while. . .

http://www.bobwheeler.com/photo/Surveys/Survey.pdf

. . . look at page #39

Nice summation, it's important to note the following:

"If one assumes a range of reflectance for the subject, then one need only measure the illumination to discover the subject luminance range. . . . A five stop range of reflectance is assumed, and Davis argues both that this is normal, but that even if it is not, '. . . camera exposure should generally provide for all the tones, from black to white, whether they are actually present in the subject or not.' "

I concur with Roger on the importance of knowing what assumptions are taken.

Paul Howell · Feb 12, 2007

What excapes me is how by using the BTZS you can place a value without a reflective meter. If use we the distant barn in a pasture for an example, you measure yourself as the fully lite side of the barn, your shadow and the open shadow of the shadow the barn casts, but not the shadow of the interior though the door which I want to fall in zone 3 rather than zone 2. With only 2 reading how you know where the values will fall? Do you guess by holding your hand over the meter to minic the deeper shadows?

Roger Hicks · Feb 12, 2007

Paul Howell said:
What excapes me is how by using the BTZS you can place a value without a reflective meter. If use we the distant barn in a pasture for an example, you measure yourself as the fully lite side of the barn, your shadow and the open shadow of the shadow the barn casts, but not the shadow of the interior though the door which I want to fall in zone 3 rather than zone 2. With only 2 reading how you know where the values will fall? Do you guess by holding your hand over the meter to minic the deeper shadows?

Dear Paul,

See the last few posts, and post 56, now oft-cited. A key word is 'assumption'. Almost as important is the word 'unstated', as in 'unstated assumption'. Apparently, the relevant assumptions for BTZS are stated in The Book. True devotees of BTZS assume that everyone has read The Book. Anyone who has not is an arrogant fool with an uncertain command of the English language.

Yours arrogantly (and foolishly),

Roger

Jean Noire · Feb 12, 2007

mhv said:
Nice summation, it's important to note the following:

"If one assumes a range of reflectance for the subject, then one need only measure the illumination to discover the subject luminance range. . . . A five stop range of reflectance is assumed, and Davis argues both that this is normal, but that even if it is not, '. . . camera exposure should generally provide for all the tones, from black to white, whether they are actually present in the subject or not.' "

I concur with Roger on the importance of knowing what assumptions are taken.

It would appear then, to lay it on the line, that subject brightness range cannot be read with an incident meter.
Regards
John

Michel Hardy-Vallée · Feb 12, 2007

jonjonho said:
It would appear then, to lay it on the line, that subject brightness range cannot be read with an incident meter.
Regards
John

This thread should be remembered for this fact, insofar as "subject brightness range" is meant to be the brightness of the different constituents of a subject, as seen from the position of the camera.

Roger Hicks · Feb 12, 2007

jonjonho said:
It would appear then, to lay it on the line, that subject brightness range cannot be read with an incident meter.
Regards
John

Dear John,

To use the technical legal term, this is an embarrassing truth. Or as we used to say in the days when I wrote technical advertising material for mainframe software (which shows you how long ago it was), 'not as such'.

Cheers,

R.

jstraw · Feb 12, 2007

"A five stop range of reflectance is assumed..."

Why?

Roger Hicks · Feb 12, 2007

jstraw said:
"A five stop range of reflectance is assumed..."

Why?

'Cos empirically, that's pretty typical. It's actually a perfectly reasonable assumption, if you can't be assed actually to measure it and don't mind under-rating (i.e. over-exposing) your film to compensate for the few times when you're wrong. That's one clever part about BTZS: it works WITH the flexibility of neg/pos photography. The other is that it gives you remarkably consistent negs.

Cheers,

R.

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