Who says “Use half box speed for ZS”?

[BrianShaw]

Well, it's just film speed after all. However at issue is the rule of downrating relative to ISO speed. In that context it can potentially be somewhat illuminating for one to learn a little about where the ISO standard comes from.

Where these numbers come from is ALWAYS worth knowing and understanding but the science and maths seem to prevent from understanding.

Ironically I just bought some PanF for my first use of that film. It is marked both ISO 50 and EI 50 with an explanation in the data sheets that the rating is subjective and not based on ISO measurement. I wonder which is best and how different the individual ratings would be. Not much, I’d bet.

 

[DREW WILEY]

Different films are engineered differently for distinct reasons. For example, an amateur color neg film is likely to have low contrast and an extremely long toe to accommodate gross exposure errors. In black and white films all kind of toe strategies can be found. And with some films, the shape of the toe can be significantly altered by how the film is specifically developed. If I'm out on a walk on an especially rainy day with a Nikon or 6X9 RF tucked under my parka ready for spontaneous quickie use, I might choose a film with a long toe like Delta 3200 due to its forgiveness factor or exposure "latitude". Try that with TMax, and unless you're very familiar with the exact lighting conditions, you risk a bellyflop; it's steeper native straight line way down into the toe mandates more careful metering down there, unless its a low contrast scene to begin with. FP4 has somewhat more toe, then a long straight line, for sake of it being an easy to use versatile film still capable of exceptional results, and HP5 still longer a toe. Delta 100 is somewhat nearer to the TMax concept, but not quite there by any means. It's like having all kinds of flavor choices in the ice cream shop. I love em all, but for different reasons.

The nice thing about large format sheet film is that one doesn't have to be so concerned about fine grain, so can prioritize film choices for other qualitative reasons. But conspicuous grain isn't necessarily a bad thing. Depends on the subject matter and your personal style. Ironically, I don't mind visible grain in 35mm work because I shoot that tiny size for sake of hinted-at poetic content rather than detail. In MF work, I generally seek a print rich and detailed enough to be comfortable in the same portfolios as my large format prints, and that's a more stringent task requiring high-acutance films.

 

[Doremus Scudder]

View attachment 274339

I notice that there is still a peak in quality to the right of the "first excellent print" point (i.e., more exposure). That peak of even better quality wouldn't happen to be about 2/3-stop more exposure than box speed, would it?

FWIW, for all the films I've worked with for longer periods of time and for which I've honed my personal E.I., the best results are all 1/3 - 2/3-stop slower than box speed.

Developers make a difference too...

Doremus

 

[BrianShaw]

Ilford then goes on to talk about how the film may be exposed at EI 25-50.

Specifically, and paraphrased: the rating of PanF is 50 and that renders best performance or you could rate it at half speed and accept lower performance.

https://www.freestylephoto.biz/pdf/product_pdfs/ilford/Ilford_PanF.pdf

 

[Doremus Scudder]

I wish more people realized that. Most of his really good stuff succeeds despite “poor” negative quality for one reason or another. The other thing you find is “well controlled” negatives which nevertheless were not easy to print.

In reality, as long as exposure is sufficient to record what you need, there is not much else in the way of true control in the making of negatives that translates to high print quality. You make great prints with printing technique work. Printing (or editing in digital/hybrid) is where we have the real control.

I don't know Michael... (just musing here)

While I agree that printing technique is the path to great prints, I sure find well-exposed and well-developed negatives a lot easier to print than under-exposed and under-developed ones.

Yeah, I can print through a #47 blue filter to get maximum contrast and dodge shadows up to get some "substance" there, but usually those prints don't fall in the "excellent" category.

I think many people miss that the ZS isn't as precise as we think. As far as exposure goes, it's only purpose is to get "exposure sufficient to record what you need."
Given the variation in metering equipment, etc. when the ZS was developed, doing a personal E.I. test was important. These days, using box speed plus a fraction of a stop safety factor and then adjusting as needed depending on trends in the results seems an equally viable and easier approach.

We seem to take for granted that using box speed and any old meter will get us sufficient exposure now, so we don't have to test. I think, however, that there are a whole lot of beginners' problems that would simply go away if one did a quick test for "sufficient exposure."

Just because AA managed to make some good prints from less-than-ideal negatives is no reason to toss the baby out with the bath water. Sure, a well-exposed and developed negative doesn't guarantee a good print, or and easy print for that matter, but I'll sure take one of those as a starting point instead of a poorly-exposed and developed one.

And, despite the versatility of VC papers, I'm still going to develop N+ and N- for appropriate subjects. Yes, if I need N-3, I'll just develop N-1 and deal with the rest when printing and vice-versa, but tailoring development to SBR still has a place.

Best,

Doremus

 

[Stephen Benskin]

and color theory too!

He was the chairman of the Subcommittee of Colorometry. They determined that color was psychophysical and they had something to do with the development of CIE. I was going to mention it but didn't want of come off as a fan boy. I also have a picture of him somewhere at home.

 

[Craig75]

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.

thats the reason there are far more lenses that aim to be as sharp as possible as opposed to soft lenses because thats what market demands.

 

[BrianShaw]

He was the chairman of the Subcommittee of Colorometry. They determined that color was psychophysical and they had something to do with the development of CIE. I was going to mention it but didn't want of come off as a fan boy. I also have a picture of him somewhere at home.

I’m a long-time fanboy... since graduate school some 40+ years ago, but don’t have an autographed picture. You are very lucky, in a nerdy sort of way!

 

[Stephen Benskin]

I notice that there is still a peak in quality to the right of the "first excellent print" point (i.e., more exposure). That peak of even better quality wouldn't happen to be about 2/3-stop more exposure than box speed, would it?

FWIW, for all the films I've worked with for longer periods of time and for which I've honed my personal E.I., the best results are all 1/3 - 2/3-stop slower than box speed.

Developers make a difference too...

Doremus

The steps are a stop of exposure apart. The wave maybe an illusion as the increase in quality was hard to distinguish for the judges.

The old ASA and today's ISO is based on the fractional gradient speed point but not the shadow exposure derived from the speed rating. The fractional gradient speed represents the limiting gradient. It's used so all speed determinations are identical. The the speed equation is implemented. I will post the pre-1960 equation later.

 

[Doremus Scudder]

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."

Not a bad strategy if you don't care about grain and you don't have to worry about shutter speed/aperture to optimize depth of field vs subject movement. For any of those cases, a faster film rating helps.

Note that the whole "first excellent print" test is based on the minimum exposure needed to achieve that goal. A bit more exposure may gain even more quality (according tot he table posted by ic-racer) and even more exposure will still yield excellent prints. I overexpose 320 Tri-X by a couple stops at times to get shadows up onto the straight-lie portion of the curve and can easily make what I consider to be excellent prints from them.

Striving to hit that minimum exposure point is important with small film and with subject movement, otherwise, as bit of an exposure buffer seems a good idea to me.

Doremus

 

[DREW WILEY]

Brian - I don't give a damn what Freestyle says about Pan F. As usual, Ilford itself is over-optimistic about the speed. I've gone to a lot of hard work optimizing results with this film, just like numerous others. But I'll withhold any details for the next dedicated Pan F thread. It's a somewhat peculiar film, a fact which can either work for you or against you, depending.

 

[DREW WILEY]

Good ole Tri-X - what a fountain of obsolete advice has sprung forth from it's addictees! The old school contact printers like "thick negatives", way overexposed to get shadow separation way up onto the straight line, and with excess density for sake of the characteristics of contact papers. Now I see that same custom applied to enlargements, and lo and behold, the film has shouldered off, and the highlights are blown out in the print. Duuuh. When it comes to proper threshold exposure, NO, one shoe size does NOT fit all. It never really worked that way anyway.

 

[DREW WILEY]

I stated later, Michael; or you could simply look up my former posts on Pan F per se. I don't mean to sound rude, but I really need to finish my late breakfast and get into the shop and complete my new baseboard easel. Kinda tired and lazy today due to the long drive a couple days ago.

 

[Doremus Scudder]

I think all we usually disagree on a little when if comes to this stuff is what a well exposed and well developed negative means in terms of procedure. I started out with the relative complexity and implied control of the Zone System, but then after going down some rabbit holes, came out the other end with a simplified view of what a good negative is. For me it is just a recording when it comes to exposure, and development is basically "normal" almost all of the time, including exposures made under extreme contrast conditions.

I realized when it came to making prints, as long as the negative had enough exposure, the rest of it was largely a zero-sum game. Changing the gradient would replace one problem with another.

I also found when I did the rabbit hole tests of developers, processes etc. most of the time the assumptions people make were incorrect. In fact I would feel pretty comfortable in saying many people who think they are making finely tuned, controlled negatives are not. People who are good printers can often subconsciously work around this when they print, and then assume the negative had properties it didn't have.

I agree wholeheartedly. I think most ZS users expect a precision from the system that simply doesn't exist. That, however, doesn't make it unusable; just use the tool for what it does.

When I do film-speed testing (rarely now), I judge the tests from final prints in order to get the whole tone-reproduction mechanism in place before I make any evaluations. Same for development tests. My test negative gets placed in a negative carrier with a bit of nothing showing on one edge and I adjust print exposure till the rebate blacks just blend into the max paper black from the clear area under what I consider "normal" gallery-type lighting. Yep, all subjective, but so were the "first excellent print" tests if you look at them on an individual basis (and who was making those prints anyway? A good printer, we hope... )

I don't really know what the exact density range is on my negatives, nor the C.I. nor where Zones I and VIII fall on the densitometer. I do know that my Zones III and VIII look like I want them to at a middle contrast setting on the paper I use most and that I have a depth of shadow detail below Zone III that I can dig for if I need to and even more detail above Zone VIII that can get burned in if I want.

The visualization part of the ZS is what I consider the most helpful, and it mostly informs me about what the medium will do, not how I should manipulate it. Knowing that I should try a filter or leave some room for dodging shadows or that printing a scene is going to be a real PITA in advance, or knowing not to bother making the photograph in the first place is what I use the ZS for mostly. Once you get some kind of working "normal" exposure and development, you don't have to worry much about it after that.

On the subject of EI specifically, what I would say is that the printing is what matters, and therefore that if a great printer finds he consistently has a better time printing when he sets his exposure meter to a speed different than ISO, makes perfect sense to me. But I think that is really the only way to determine a practical EI. The rest of the EI testing is basically arbitrary, and not related with tone reproduction.

That about sums it up. I couldn't express it more succinctly or eloquently.

Best,

Doremus

 

[BrianShaw]

Brian - I don't give a damn what Freestyle says about Pan F. As usual, Ilford itself is over-optimistic about the speed. I've gone to a lot of hard work optimizing results with this film, just like numerous others. But I'll withhold any details for the next dedicated Pan F thread. It's a somewhat peculiar film, a fact which can either work for you or against you, depending.

Dude... did you just look at the URL or look at the document? That is the Hartman/Ilford data sheet. Has little to do with Freestyle except they made it easily available. Not sure what that emotional over-reaction is about...

 

[Renato Tonelli]

I expect this thread to go onfor several pages

In the early eighties I tested 4x5 Tri-x and HC-110; Densitometer readings showed my new ASO at 250 (Zone VI did the densitometer reading). A few decades later the film was 'improved' ; I tested it again, (same camera and lens; shutter was tested) but this time with XTOL 1+1 Densitometer readings showed ABOVE BOX SPEED!

I didn't trust it for one main reason: I was new at using my newly acquired densitometer. I sent the batch of test films to Richard Ritter. ABOVE BOX SPEED!

Go ahead: give it your best shot.

 

[DREW WILEY]

Now that I've finally got a break let me clarify my statement about Pan F. What Ilford published on their tech sheet is correct with respect to their own conventions, which factor how to best navigate an especially narrow passage between the Scylla of the toe and Charybdis of the shoulder using common typical developers, especially their own. Hence a compromise box speed of 50, just to statistically protect from shipwrecks. Pan F has just about the shortest straight line and most exaggerated S-curve of any film I can think of since old Kodak Recording (detective) Film. It's almost the antithesis of TMax, and in our present discussion, is Exhibit A why rubber stamp exposure models, whether via Zone theory or anything else, simply don't work very well.

So for sake of replying to Michael, and to assure Brian that I've known the Pan F spec sheet very well for many years, I'll briefly divulge how I handle it. I didn't come up with this. Jim Galvin, who invented and built the especially compact line of Galvin view cameras, was fond of roll film backs and loved what he termed the "wire sharpness" of Pan F, but had a difficult time dealing with its very short scale in comparison to films available in 4X5 sheet size. Around that time, a friend of his, Gordon Hutchings, popularized staining pyro development with his PMK formula. Put two and two together. By reining in the highlights via the stain, that realistically allowed a whole zone of extra exposure to improve shadow gradation without boosting content excessively onto the shoulder - hence preferred exposure at 25. Modern VC papers do not pre-empt the need to do that, but just provide yet another layer of control. Then PMK's ordinary ingredient ratios get specially tweaked for Pan F only. I won't give all the details; they're pretty well known in large format circles among those using roll film backs. Or you can read one of the later editions of Hutchings' PMK book. So this does seem to get the most out of Pan F, but nothing will turn it into FP4 or TMax or seemingly any other Pan film. It will always have a very limited scene contrast range, and it's own special look.

 

[BrianShaw]

So this does seem to get the most out of Pan F, but nothing will turn it into FP4 or TMax or seemingly any other Pan film. It will always have a very limited scene contrast range, and it's own special look.

That’s very interesting. But how does that make the Ilford data sheet “wrong”? If I process using the recommended chemistry will PanF perform as advertised? I will be developing in DD-X 1+4. Should I use ISO 50 or use half box speed, 25?

 

[DREW WILEY]

I directly stated that they are right within the context of their own given parameters, which does not factor in variables like proportional image stain. If you use 25 but overdevelop in common developers, your risk overexposing the highlights; but if you use 50 you risk blank shadow gradation. Just depends on how much contrast is in the scene and what you are willing to sacrifice. Pan F responds well to the same scene contrast range as most slide films. But if you switch to pyro development, it gives you more room to maneuver, and 25 is the appropriate speed for that.

 

[BrianShaw]

Thanks Drew. I was still trying to figure out what you were saying in post 70.

 

[DREW WILEY]

I would also recommend 25 for any semi-compensating developer like Perceptol.

 

[RalphLambrecht]

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

It is the result of empirical testing of a large photographic community and quite reasonable advise in MHO

 

[wiltw]

It is the result of empirical testing of a large photographic community and quite reasonable advise in MHO

So, to affirm OP oriiginal hypothesis, 'everybody says...' is the origin, rather than one specific individual or photographic organization

 

[Stephen Benskin]

Not a bad strategy if you don't care about grain and you don't have to worry about shutter speed/aperture to optimize depth of field vs subject movement. For any of those cases, a faster film rating helps.

Note that the whole "first excellent print" test is based on the minimum exposure needed to achieve that goal. A bit more exposure may gain even more quality (according tot he table posted by ic-racer) and even more exposure will still yield excellent prints. I overexpose 320 Tri-X by a couple stops at times to get shadows up onto the straight-lie portion of the curve and can easily make what I consider to be excellent prints from them.

Striving to hit that minimum exposure point is important with small film and with subject movement, otherwise, as bit of an exposure buffer seems a good idea to me.

Doremus

The fractional gradient method is simply a sensitometric methodology that agreed best with the print judgement prints. Once Jones established the print judgement speeds, he tested various speed criteria comparing the results to the print judgement speeds. Fractional gradient doesn't dictate the actual film speed. It establishes the conditions of the minimum useful exposure, then a constant is added to determine the shadow exposure. The resulting ASA standard had the shadow exposure fall to the right of the fractional gradient speed point.

The Pre 1960 speed equation is Exposure Index = Fractional Gradient Speed / 4Es or Exposure Index = 1 / 4Es Where Es is the exposure meter candle seconds (also lxs) at the fractional gradient speed point and the 1/Es is the ASA fractional gradient speed.

In other words, EI is two stops above the fractional gradient speed point. The approach is not much different than how the current ISO b&w speed standard uses the fractional gradient speed point as a basis to determine film speed.

 

[BrianShaw]

So, to affirm OP oriiginal hypothesis, 'everybody says...' is the origin, rather than one specific individual or photographic organization

LOL... just another stereotype that is either blindly believed or true enough times that folks consider it universally true.