Who says “Use half box speed for ZS”?

[Stephen Benskin]

I sez it.

I went through the whole rigmarole back in the 70's and ended up with Tri-X at somewhere around 250-300. I found I am not alone - it seems everyone comes up around a stop short. So why not save an awful lot of film and chemistry and buy the wife something nice with the money you would have thrown away on a densitometer?

In any case a stop of safety margin and a stop's more shadow detail are nice things to have. I don't always meter to a gnat's backside of shadow detail. In my take the ASA/ISO speeds are the highest speed you can rate the film and still bring back Mr. Jones' "First Excellent Print." Going at the highest rated anything is something I have found to be a generally bad idea.

For color transparency it is a whole 'nuther matter.

I think it all started with the Illuminati.

It's a common misconception that the ASA speed was actually at the fractional gradient point. The fractional gradient point determined the minimum point of exposure that would yield an excellent quality print, but the film speed rating of the pre 1960 standard is actually an EI that was calculated based on the fractional gradient speed. Film speeds doubling after the 1960 standards proves the previous rating wasn't at the fractional gradient point, as does a number of papers.

Jones' testing didn't conclude that the Fractional Gradient point was the exposure aim, it concluded that exposure shouldn't fall below it. And that the method had the highest degree of agreement with the print judgement speeds.

 

[Stephen Benskin]

"EXPOSING THE FILM
"He claims, all B&W film manufacturers fake (?) their ISOs. So (?), you should
always halve the ISO (i.e. shoot at 200 if you buy ISO 400, and then develop
at 20% less time than the manufacturer's recommended time.) "Everyone knows
and does this", he said... Use Zone System to expose the film."

Probably also a climate science denier. The reason so many people had the same results is because they were all using the same testing method. The reason why ISO is used before a speed rating or CI before a gradient value is to communicate that certain conditions were followed in determining those values.

I also believe the 20% less development time comes from people who used condenser enlargers and didn't realize the manufacturer numbers are based on diffusion, but it's only an assumption.

How do urban myths and legends start? We're living in an age with the greatest access to information in history, but are the most misinformed.

 

[wiltw]

How do urban myths and legends start? We're living in an age with the greatest access to information in history, but are the most misinformed.

My sentiment exactly, every time I hear 'bokeh' so commonly abused for 'everything outside the zone of focus'

For a term not in the English language before 1997, it was readily twisted in the wildfire of the internet.

 

[Stephen Benskin]

That was the reason that was officially given. Not to promulgate a conspiracy theory, but maybe the film lobby had the safety factor removed so as to give the impression that films of the era were faster than practically speaking. The pragmatists simply adopted a 'divide box speed by 2' practice, to get them back to the results they used to get before the 1960 standard adoption! And the rest is unrecorded history.

The reasoning came from a paper by C.N. Nelson in Photographic Science and Engineering in 1960 titled Safety Factors in Camera Exposures. I've attached the first two pages that covers the overview.

I was thinking that it's possible for people to decide to make an informed decision to keep the ratings they were familiar with, but they probably don't account for the whole. How about the ones that propagated the conspiracy theories. Now those can't be informed decisions. Something like that has to be associated with the Kruger Dunning effect.

 

[wiltw]

It's a common misconception that the ASA speed was actually at the fractional gradient point. The fractional gradient point determined the minimum point of exposure that would yield an excellent quality print, but the film speed rating of the pre 1960 standard is actually an EI that was calculated based on the fractional gradient speed. Film speeds doubling after the 1960 standards proves the previous rating wasn't at the fractional gradient point, as does a number of papers.

Jones' testing didn't conclude that the Fractional Gradient point was the exposure aim, it concluded that exposure shouldn't fall below it. And that the method had the highest degree of agreement with the print judgement speeds.

So how did the '1/2 box speed' widespread belief arise, to get us back to OP question?

 

[john_s]

......The reason so many people had the same results is because they were all using the same testing method. ....

I got the same result using a different method. Maybe both methods were good?

 

[foc]

 

[radiant]

 

[radiant]

Here let me help you:

ISO 400 -> 238
ISO 200 -> 119
ISO 100 -> 59 and half

 

[Craig75]

View attachment 274339

first excellent print is just a cultural point of view though.

culture A could define it as it is defined now, culture B could define it in what we would call 8 stops overexposed and 100% development, culture C could define it as what we would call 4 stops underexposed and -50% development.

Similarly anyone in any one culture could define it entirely differently from the consensus.

Its not an objective fact.

 

[Stephen Benskin]

first excellent print is just a cultural point of view though.

culture A could define it as it is defined now, culture B could define it in what we would call 8 stops overexposed and 100% development, culture C could define it as what we would call 4 stops underexposed and -50% development.

Similarly anyone in any one culture could define it entirely differently from the consensus.

Its not an objective fact.

The First Excellent Print test is psychophysical.

 

[Craig75]

The First Excellent Print test is psychophysical.

My thinking would be that yes I could see it being that - but only because "the excellent print" was judged in a nominally christian society where "accurate representationarts" of the human figure was of importance for the culture.

In a society where that was not the case (eg islam or african arts where the human body was presented in abstracted term) then it is theoretically possible an entirely different point could be drawn

Secondly as photographers we can see a massively overexposed or underexposed negative made into a print and hail it as much (or even more) an excellent print as one defined by a collection of members of the public

 

[BrianShaw]

The First Excellent Print test is psychophysical.

Amen... and statistical too.

 

[Sirius Glass]

I use an alternative approach particularly in large format work. This is to give MAXIMUM USABLE exposure.

No, not maximum possible exposure but rather that exposure which fills the film with as much information as it can hold without blocking highlights where I want tonal gradation. A negative full of information offers the greatest versatility and expressive possibilities.

In modern times the role of N+. N, and N- development is worth discarding to be replaced by changing paper grades on the superb variable contrast papers now available. A change from paper grade #2 to grade #3 is remarkably equivalent to a N+1 development change, for example.

The possibility of split grade burning and dodging on variable contrast paper can achieve results the classic zone system cannot do.

I'll say the zone system is now effectively obsolete in terms of making the best possible black and white prints.

And in pursuit of maximum usable exposure I often find my light meter is set to half box speed.

I discarded the N, N+, N- and only use the metering part based on spot meter readings using box speed.

 

[Vaughn]

Since it all seems to based on an subjective decision of what a good print looks like, I'll sticking to using that as my guide and leave the cobblygook to you tech folks. It is really not that difficult.

"Box Speed", FEP, -- Add those to our list of photographic religious terms..

Edited -- changed objective to subjective -- I get a little dyslexic at times. I'll blame it on decades of changing black to white and white to black, looking at images on GG that are either upside down (LF) or backwards (Rollei).

 

[BrianShaw]

Most psychophysics studies involve a series of “forced choice” decisions. Of these two, which do you feel is better. An example: optometrist visit where a series of “of these two lenses, which looks best” tests are used to refine the individual prescription. The answer is specific to the individual. studies to determine “population preference “ will involve a large number of subjects and statistical data processing. The results will be generally consistent (correct) but individual differences (opinions) will still exist. But overall the “answer” will be, more often than not, “correct”.

 

[Craig75]

The print studies were not as haphazard as that in asking observers to choose something "excellent". If I remember correctly the observers were specifically asked to choose prints that most accurately reproduced the subject values. The purpose after all, was emulsion speed. If a print is filled with featureless black wherever light in the scene was low, while clearly such an aesthetic might be subjectively deemed excellent or not from an artistic perspective, one would expect less diversity of opinion if observers are asked to judge prints based on how "realistic" they look. Obviously it's not at all perfect.

If a speed method is based on the minimum exposure required to record all the detail one typically sees in a scene, I would argue under all but extreme cases it allows for the broadest possible interpretation of the negative. It won't necessarily be ideal for everyone but no standard is.

Just some thoughts.

Yes my words are just thoughts to throw out too just for discussion

If a culture believes that we are all shadow puppets controlled by extraterrestrial beings (and i have met someone, a top photographer too, who believed that) it would be "accurate" that the human body was what we would call underexposed 4 stops to reflect the beliefs.

Or if a culture believed that we were all going to fry in a supernova then you could see massively overexposed shots being an accurate representation of the belief system.

Even in western art you see in medieval paintings the size of the person in the picture is an accurate representation (of their status) and accuracy of the person proportial to geometric space is of no concern. So accuracy is a very relative term according to belief

 

[Craig75]

Most psychophysics studies involve a series of “forced choice” decisions. Of these two, which do you feel is better. An example: optometrist visit where a series of “of these two lenses, which looks best” tests are used to refine the individual prescription. The answer is specific to the individual. studies to determine “population preference “ will involve a large number of subjects and statistical data processing. The results will be generally consistent (correct) but individual differences (opinions) will still exist. But overall the “answer” will be, more often than not, “correct”.

Yes that is very well expressed. I would say though that as people's literacy in a discipline increases (be it whatever art form), they understand and become more receptive to the opposite of what they would initially choose. The concensus on a lens is always that the sharper the better but equally a lot of us enjoy soft pictures too once we become exposed to them and understand what we are looking at and how the technique can be used.

 

[Vaughn]

I do not think 'consensus' has ever been reached on this forum...

 

[Stephen Benskin]

Let me just add the findings from the First Excellent Test and others are the basis of Tone Reproduction Theory.

 

[wiltw]

Since it all seems to based on an subjective decision of what a good print looks like, I'll sticking to using that as my guide and leave the cobblygook to you tech folks. It is really not that difficult.

The dogmatically rigid interpretations all forget the ISO rating is merely a GUIDE. My own examples of 'the guide' principle put to use...

• I shoot color neg at -2/3EV from box speed. to improve color rendition and reduce muddiness in the shadows
• I shoot color transparency at box speed to not lose details in the highlights, but I would shoot the original Velvia (box speed 50) at EI 40

I have not shot B&W routinely in so very long, I have no rule of thumb for that. My metering methods also change with film type. No single rule covers all.

But, back to OP question, where/when did the universalized 'half of box speed' rule of thumb come from?1

 

[DREW WILEY]

When starting out with any new or unfamiliar film, I'll shoot it in 120 roll film version first to save money, use a gray target, and will indeed cut the box speed in half, and then bracket exposures upward from there. Leftover frames will be used for the same kind of test with my favorite contrast filters. I think that kind of custom is common, reasonable, and a quick way to get to first base. So it's probably been stated in that manner many times before. Just makes sense. But any hard rule doesn't make sense. If you want the practical truth, you have to test each film yourself, under your own parameters.

Box speeds are sometimes trustworthy on a general basis, especially for color films, and sometimes they're not. I think many b&w films are labeled overoptimistic, and a few products downright deceptive. Marketing is generally part of the mantra. But as we all know, different developers can affect film speed differently, along with different degrees of development. There is no silver bullet generic equation for how to best expose film , and never will be. Anyone who teaches otherwise is a snake oil salesman.

I partially disagree with Maris because I think the Zone System is still helpful to at least understand in principle because it's contains a common-denominator vocabulary quite useful in a multi-generational sense on forums like this one. It's also a helpful introduction to practical sensitometry versus the more technical aspects. But like Maris, I don't pay attention to it during my own workflow.

Wilt - your habit of overexposing color neg film is based on moth-eaten old advice which can be counterproductive nowadays, especially with a more contrasty and saturated version like Ektar. People are often astonished to learn that many of my color prints are enlarged from color neg film. They look more like chrome results - clean, vibrant, un-muddy colors.

 

[Vaughn]

Michael_r, I would call it a suggestion that never got to 'rule' status. But what caught my attention was the idea that there was ever an actual consensus here that a lens must be a sharp as possible.

 

[radiant]

As quality films characteristic curve is pretty linear, why even put anything on toe. Just overexpose heavily on the straight line which continues to the moon on many films.

"How many stops is the usable range on this film?" "Yes."

 

[BrianShaw]

Let me just add the findings from the First Excellent Test and others are the basis of Tone Reproduction Theory.

and color theory too!

Do you know what the sample size is, approximately, in these studies. I understand the Power Test and confidence intervals but never saw the original studies to see the actual subject pool constituency. If that’s in the first two pages previously posted, please forgive me as o can’t read them on my phone. Must wait for a bigger display... thanks to presbyopia and cataracts not ready for fixing yet.