The current packaging says ISO 400. Anyway, if you set your meter at 2/3 ISO you will probably get a higher percentage of good printable negatives than if you use the ISO setting. I rarely meter anyway. Most of the time the exposure is based on the light conditions, so long as the light is not frequently changing. I shoot at about 1/500 @ f/8 in the sun, and about 1/250 @ f/5.6 in open shade, with ISO 400 films. I do mostly "candid" photography, quick captures of events, not tripod photos of rocks and trees. Metering off grass is a good practice.
Film Developing Cookbook - Does one really need to overexpose T-grain film by 1-2 stops and pull process to get satisfactory results?
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The current packaging says ISO 400. Anyway, if you set your meter at 2/3 ISO you will probably get a higher percentage of good printable negatives than if you use the ISO setting. I rarely meter anyway. Most of the time the exposure is based on the light conditions, so long as the light is not frequently changing. I shoot at about 1/500 @ f/8 in the sun, and about 1/250 @ f/5.6 in open shade, with ISO 400 films. I do mostly "candid" photography, quick captures of events, not tripod photos of rocks and trees. Metering off grass is a good practice.
I'm glad that you took a second look at my previous post, poor wording on my part. Yes, I was primarily asking about how those negatives were actually printed to be included in the psychophysical testing for an "excellent" print. Given that the printing process is a personal and very subjective interpretation of the information on the negative, it seems the two hundred observers would be basing "excellent" print quality on someone else's very subject points of view regarding a negative. Were any print manipulations allowed or were they all straight prints, etc.....Perhaps it's not a valid concern, but I will try to check out the paper you mentioned. Thanks.
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Such angst! 
Its a wonder they ever got a good photograph in the old days...
Its a wonder they ever got a good photograph in the old days...Well, after searching for the article, and I didn't search greatly, it is behind a pay wall on the first link and would cost me $25 bucks to read it. Sometimes things come at a cost, I understand, but not this time
........I'll stand on Stephen's summarization of it in his posts.What you’re describing is essentially a safety factor. A safety factor of 1 stop was removed from the standard in 1960 (which put black and white negative films in line with color film). At the time the increasing use of smaller formats placed an increasing importance on image structure, while the reliability/accuracy of exposure meters/equipment had also improved a lot, so the change made sense. See Nelson, Safety Factors in Camera Exposure, 1960, which is a short, straight forward paper.
Since then, films have evolved to be sharper and finer grained, and generally there is more overexposure latitude so there is less of a penalty if one chooses to put a safety factor back into an EI. Said another way, there isn’t really anything to lose by setting your EI to half the ISO speed, which is also conveniently only 1/3 stop slower than the Zone System EI.
Well, after searching for the article, and I didn't search greatly, it is behind a pay wall on the first link and would cost me $25 bucks to read it. Sometimes things come at a cost, I understand, but not this time
And there are two parts. There's another way. Theory of the Photographic Process 1st edition is free online somewhere. It covers the first excellent testing in some detail. While the summary I used is from the 3rd edition, the graphics are from the 1st if that is any indication.
Maybe here:
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I believe what Milpool has been suggesting is that there are many potential experimental errors involved with testing for a personal film speed, such as unknown variables, poor control variables, and incorrect assumptions. Consequently, the results are no better than simply applying a safety factor to the ISO speed and evaluating the outcomes in the field.
For instance, Zone System testing has become almost ubiquitous within certain groups of photographers, but has anyone stopped to evaluate the legitimacy of the methodology? It's apparent from a cursory glance that the Zone System didn't change its methodology when the ASA standard changed, removing most of its safety factor. Personal Zone System speeds before the change produced EIs approximating the ASA speed setting, but they were consistently lower after. Whether good, bad, or neutral, one changed and the other didn't, which undermines any direct comparison of the results.
It shouldn't need to be said, but as we know, people obtained excellent results before the change in the ASA rating, and a reasonable safety factor has little to no effect on the quality of the resulting images. In fact, the additional exposure might be more conducive to Zone System metering. Upon deeper investigation, it is apparent that the ISO standard and Zone System have different ratios between the metered exposure point (Hg) and the sensitometric exposure (speed point) (Hm). This discrepancy has resulted in almost universally slower EI speeds of 2/3 to 1 stop when using general-purpose developers with Zone System testing. Additionally, film speed is related to the degree of processing. How many Zone System practitioners complete the second part of the testing to determine normal development, without which any resulting speeds are questionable even within the Zone System methodology?
When I said that personal testing results may be no better than just applying a safety factor, I left out it can easily be worse. The unknown variables in poorly conducted testing can create a false sense of accuracy, sometimes to the point where people accuse scientifically derived standards of being wrong or even part of a conspiracy. It's no different from science deniers in areas like evolution, climate science, and vaccinations. A lack of understanding of how the ISO standard for film speed and the underlying theory works is a big part of the misunderstanding.
I've seen accounts of development times to the exact second based on personal testing. Times like 7:23. As if using 15 or 30 second intervals was too loose a criteria. As if variations in dozens of processing variables or small differences in scene luminance range or flare wouldn't overwhelm any such attempt at precision. Worse yet, the processing time was probably derived from a single test.
Dunn and Wakefield, in their book "Exposure Manual" (4th edition, page 214), state: "This is the situation at the time of writing, and it may be regarded as wholly satisfactory as after the removal of the larger safety factor included in earlier days it is now left to the photographer himself to apply any safety factor he may consider desirable for the work he is doing. Using a large format camera he can, if he wishes, play safe and revert to a safety factor of 2 of even 4 without endangering print quality. If on the other hand he is working with a 35mm camera and is seeking negatives capable of big enlargement he can follow his exposure meter intelligently with only such modifications as may be suggested by unusual scene contrast or unbalanced luminance distribution."
For instance, Zone System testing has become almost ubiquitous within certain groups of photographers, but has anyone stopped to evaluate the legitimacy of the methodology? It's apparent from a cursory glance that the Zone System didn't change its methodology when the ASA standard changed, removing most of its safety factor. Personal Zone System speeds before the change produced EIs approximating the ASA speed setting, but they were consistently lower after. Whether good, bad, or neutral, one changed and the other didn't, which undermines any direct comparison of the results.
It shouldn't need to be said, but as we know, people obtained excellent results before the change in the ASA rating, and a reasonable safety factor has little to no effect on the quality of the resulting images. In fact, the additional exposure might be more conducive to Zone System metering. Upon deeper investigation, it is apparent that the ISO standard and Zone System have different ratios between the metered exposure point (Hg) and the sensitometric exposure (speed point) (Hm). This discrepancy has resulted in almost universally slower EI speeds of 2/3 to 1 stop when using general-purpose developers with Zone System testing. Additionally, film speed is related to the degree of processing. How many Zone System practitioners complete the second part of the testing to determine normal development, without which any resulting speeds are questionable even within the Zone System methodology?
When I said that personal testing results may be no better than just applying a safety factor, I left out it can easily be worse. The unknown variables in poorly conducted testing can create a false sense of accuracy, sometimes to the point where people accuse scientifically derived standards of being wrong or even part of a conspiracy. It's no different from science deniers in areas like evolution, climate science, and vaccinations. A lack of understanding of how the ISO standard for film speed and the underlying theory works is a big part of the misunderstanding.
I've seen accounts of development times to the exact second based on personal testing. Times like 7:23. As if using 15 or 30 second intervals was too loose a criteria. As if variations in dozens of processing variables or small differences in scene luminance range or flare wouldn't overwhelm any such attempt at precision. Worse yet, the processing time was probably derived from a single test.
Dunn and Wakefield, in their book "Exposure Manual" (4th edition, page 214), state: "This is the situation at the time of writing, and it may be regarded as wholly satisfactory as after the removal of the larger safety factor included in earlier days it is now left to the photographer himself to apply any safety factor he may consider desirable for the work he is doing. Using a large format camera he can, if he wishes, play safe and revert to a safety factor of 2 of even 4 without endangering print quality. If on the other hand he is working with a 35mm camera and is seeking negatives capable of big enlargement he can follow his exposure meter intelligently with only such modifications as may be suggested by unusual scene contrast or unbalanced luminance distribution."
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The simplest way to "test" (assuming the use of a 35mm camera with focal-plane shutter) is to put the camera on a tripod and take a 36 exp roll, using an aperture of f/8 or so on a first-class 50mm lens, running a sequence from 1/30 to 1/2000 second (or 1/1000 if that's your top speed), over and over till the roll is complete. This is best done on a sunny day with no clouds. Be sure that there are areas of shadow and white (typical white houses make a good test subject).
Then, in the darkroom, snip the roll into thirds, then process each strip separately, one at normal, one at 15% less, and the last at 25% less time. Keep records of the exposures! Then make enlargements of the negatives on your usual paper (grade 2.5 or 3 is what I use with Ilford's latest Multigrade). Compare the results with the value your meter gave you. Don't be surprised if your best print comes from the negative given a stop more exposure and 25% less development. I have tested dozens of times, with many films, and the results are always less than ISO speeds. My cameras are Leicaflex SL2s, maintained well.
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What do you guys mean by "Zone System EI"? The ZS is just like a rubber band which anyone can expand or contract as they please. The only difference is that they think in terms of segments, like a centipede. You make your own decision where the first segment belongs, as well as the last segment, and even the middle. Nor are all the segments equal, given the fact that some of the film curve involved will not be on the straight section, and that the character of the curve itself can vary by specific film as well as specific development.
And lets not forget that the quality control of films has significantly improved from the old days. That fact should alleviate some of the need for a "safety factor". As far as I'm concerned, if the film does have extra usable real estate lower down the curve, I'll use it. And T-Max films do; they're my go to films for high contrast scenes.
"Safety factor" - Humbug! Instead of reading an old book containing theory, let's talk a walk on a gleaming glacier adjacent to dark pitted volcanic rock, and see who can bag the full textural range in the print or not. The Zonies will try to compress the high values using minus development, and end up with a certain amount of blaah, while paranoid "safety factor" types will overexpose the film and shoulder off the highlights and kill all the sparkle up there in that manner. I'd rather strategize with an appropriate film in the first place, and expose with it specifically in mind, and not some generic idea what film supposedly is.
And it makes no difference whether we're talking about small format roll film or large format sheet film, except that with sheet film, you can assign different degrees of development to each image if you need to.
And lets not forget that the quality control of films has significantly improved from the old days. That fact should alleviate some of the need for a "safety factor". As far as I'm concerned, if the film does have extra usable real estate lower down the curve, I'll use it. And T-Max films do; they're my go to films for high contrast scenes.
"Safety factor" - Humbug! Instead of reading an old book containing theory, let's talk a walk on a gleaming glacier adjacent to dark pitted volcanic rock, and see who can bag the full textural range in the print or not. The Zonies will try to compress the high values using minus development, and end up with a certain amount of blaah, while paranoid "safety factor" types will overexpose the film and shoulder off the highlights and kill all the sparkle up there in that manner. I'd rather strategize with an appropriate film in the first place, and expose with it specifically in mind, and not some generic idea what film supposedly is.
And it makes no difference whether we're talking about small format roll film or large format sheet film, except that with sheet film, you can assign different degrees of development to each image if you need to.
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There was a time when people relied on exposure calculators. Perhaps not ideal by today's standards but a lot of photographers got by with them.
As Stephen Benskin alludes to above, metering technique plays a large role in the decision of a personal E.I. Metering shadows with a spotmeter and placing them à la Zone System yields a different effective film speed than using your TTL matrix meter on your smart SLR. Incident metering following Beyond the Zone System guidelines may give yet another E.I. ISO remains the same in any case.
When I started out, I did all the laborious ZS testing; even made Zone Rulers à la Minor White, et al. for all my films and development schemes and carried them in the field with me (I still have a few lying around). These latter were great tools for learning to visualize, since the compressions at the ends of the scale was readily visible as was the greater separation in steeper portions of the films' curves. I think these helped me more than any of the other exercises I went through.
What I've learned over time is that a constant monitoring of actual results in comparison with exposure records and then making adjustments as necessary is as, or more, important than the initial testing. I often find I have to tweak development time for something as simple as having mixed a new batch of developer. Chemical strength and purity variations often result in a developer with different activity, even if the formula was meticulously followed.
Finding some reliable way to meter, expose and develop that yields consistently usable results was (and is) the aim of any exposure/development system. That, coupled with the required (or desired) degree of precision (think BZTS) determines the relative complexity of the system (whether or not such precision is even practical in the field).
I'm a ZS practitioner because I find the metering method helpful in visualizing my final results and because I use sheet film and a spot meter. My E.I.s for most film are 2/3 stop slower than ISO simply because of the metering technique. However, I don't bother with the ZS at all when using a camera with a sophisticated built in meter, nor do I use the same E.I. for a given film; the metering techniques require different approaches to exposure.
Coming up with a way to consistently avoid underexposure is important, If it can't be achieved with precision and accuracy of the equipment being used, or the photographer is not skilled enough to consistently derive a successful amount of exposure from the meter data, then a safety factor is a practical and very usable work-around. As is erring on the side of overexposure in tricky situations. This plays into the choice of a personal E.I. as well.
All this discussion of the "First Excellent Print" seems to fail to mention that there is a large exposure/development range between the "First" and "Last" Excellent Prints that provides the photographer with a more or less wide margin of error if they can simply stay within the limits. Overexposing film a bit helps here, especially if one uses larger film and/or isn't making extreme enlargements. Some of us try to hang out in the middle of this exposure range instead of trying to stay as close to the bottom threshold as possible. While this latter might be great for small roll film, especially if one brackets exposure in tricky situations, the assurance that one's metering and development schemes are sufficient to guarantee a very high percentage of printable negatives is not only reassuring, but saves time and money with larger film. If the cost is a bit lower E.I., or a safety factor, in practice (which, if one is aware of what one is doing, can always be done away with when necessary), then that is a small sacrifice.
As far as testing goes: Nowadays, I just rate a film 2/3-stop slower than box speed, make a few negatives of a subject with a full range of easily-metered tones and develop them to a few different contrasts. I then choose (or extrapolate) where my "Normal" development should be by comparing proper proof prints made with my enlarger (no contact prints here; I want to include flare from my enlarger in this too) and go from there. I'm not striving to pinpoint an absolute minimum exposure and exact development to print the perfect range of tones on X paper with a #2 filter. Rather, I want a "Normal" negative with enough information to print somewhere in the middle contrast range with my enlarger's color head and diffuse light source. That's a pretty large window, so I can get good results immediately by starting with more generous exposure than minimum and a development time that hits somewhere between #1.5 and #3.5 filtration. Refinements can be made later, based on field notes.
The point of this entire ramble is that metering technique and consistency of results and the attendant reduction of the risk of getting an underexposed negative should be the determining factors in deciding on an E.I. The amount of testing that is actually needed to achieve this goal can be quite small. It need be no more than what is required to get printable negatives somewhere in the window between "First" and "Last" Excellent Prints. This, guided by careful note-taking and adjustments as necessary should ensure consistently good results.
Best,
Doremus
When I started out, I did all the laborious ZS testing; even made Zone Rulers à la Minor White, et al. for all my films and development schemes and carried them in the field with me (I still have a few lying around). These latter were great tools for learning to visualize, since the compressions at the ends of the scale was readily visible as was the greater separation in steeper portions of the films' curves. I think these helped me more than any of the other exercises I went through.
What I've learned over time is that a constant monitoring of actual results in comparison with exposure records and then making adjustments as necessary is as, or more, important than the initial testing. I often find I have to tweak development time for something as simple as having mixed a new batch of developer. Chemical strength and purity variations often result in a developer with different activity, even if the formula was meticulously followed.
Finding some reliable way to meter, expose and develop that yields consistently usable results was (and is) the aim of any exposure/development system. That, coupled with the required (or desired) degree of precision (think BZTS) determines the relative complexity of the system (whether or not such precision is even practical in the field).
I'm a ZS practitioner because I find the metering method helpful in visualizing my final results and because I use sheet film and a spot meter. My E.I.s for most film are 2/3 stop slower than ISO simply because of the metering technique. However, I don't bother with the ZS at all when using a camera with a sophisticated built in meter, nor do I use the same E.I. for a given film; the metering techniques require different approaches to exposure.
Coming up with a way to consistently avoid underexposure is important, If it can't be achieved with precision and accuracy of the equipment being used, or the photographer is not skilled enough to consistently derive a successful amount of exposure from the meter data, then a safety factor is a practical and very usable work-around. As is erring on the side of overexposure in tricky situations. This plays into the choice of a personal E.I. as well.
All this discussion of the "First Excellent Print" seems to fail to mention that there is a large exposure/development range between the "First" and "Last" Excellent Prints that provides the photographer with a more or less wide margin of error if they can simply stay within the limits. Overexposing film a bit helps here, especially if one uses larger film and/or isn't making extreme enlargements. Some of us try to hang out in the middle of this exposure range instead of trying to stay as close to the bottom threshold as possible. While this latter might be great for small roll film, especially if one brackets exposure in tricky situations, the assurance that one's metering and development schemes are sufficient to guarantee a very high percentage of printable negatives is not only reassuring, but saves time and money with larger film. If the cost is a bit lower E.I., or a safety factor, in practice (which, if one is aware of what one is doing, can always be done away with when necessary), then that is a small sacrifice.
As far as testing goes: Nowadays, I just rate a film 2/3-stop slower than box speed, make a few negatives of a subject with a full range of easily-metered tones and develop them to a few different contrasts. I then choose (or extrapolate) where my "Normal" development should be by comparing proper proof prints made with my enlarger (no contact prints here; I want to include flare from my enlarger in this too) and go from there. I'm not striving to pinpoint an absolute minimum exposure and exact development to print the perfect range of tones on X paper with a #2 filter. Rather, I want a "Normal" negative with enough information to print somewhere in the middle contrast range with my enlarger's color head and diffuse light source. That's a pretty large window, so I can get good results immediately by starting with more generous exposure than minimum and a development time that hits somewhere between #1.5 and #3.5 filtration. Refinements can be made later, based on field notes.
The point of this entire ramble is that metering technique and consistency of results and the attendant reduction of the risk of getting an underexposed negative should be the determining factors in deciding on an E.I. The amount of testing that is actually needed to achieve this goal can be quite small. It need be no more than what is required to get printable negatives somewhere in the window between "First" and "Last" Excellent Prints. This, guided by careful note-taking and adjustments as necessary should ensure consistently good results.
Best,
Doremus
I don't think we should presume that the OP is doing the same kind of work you do. I am surprised how often ZS aficionados do this on forums. Most people use 35mm cameras and take photos of various things in various situations: sports, concerts, kids, people on the street, etc. The ZS is impractical for this. If you want to help, don't presume that your kind of work applies here.
It may not be the simplest, but it is one of the best, especially for those without expensive testing equipment. In fact, the ring-a-round is pretty much the same approach as the first excellent print test. Personally, whatever works for you is all that matters. What I've been attempting to convey is there is a difference between film speed and exposure. Many people tend to confuse the two, and then mistakenly blame the standards if their personal experiences don't match. I believe it's best to properly describe a situation so it can be more effectively worked.
I do have a pet peeve with something in your second paragraph. Process 15% and 25% less time from what? Even if the assumption is the manufacturer's recommended development time, what about those who process for printing with a condenser enlarger vs those who print with a diffusion enlarger. I just think the information is more instructional if it's placed in context.
You're right, but I was not sure how to explain that. Film mfrs' times do not always include that info. Some people scan B&W negatives, not knowing that this exaggerates grain and does not lead to the same results that wet printing does.
In any event, every time I have done this I get the same results: films are best exposed at 2/3 stop more than I get from metering at ISO speeds. My Leicaflex cameras have a spot in the center of the viewfinder that allows for selective metering. It takes a while to learn how to use this system (you must avoid very light or dark items to measure), but it works flawlessly when I point it at the right area, and use +2/3 stop exposure (e.g., 250 instead of 400 for ISO 400 films).
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Augustus - First of all, I am not a Zone System aficionado. But I do understand its range of possibilities, and was simply pointing out its ability to be custom tailored to personal expectations. It is be made either as simple or as complicated as one wishes. Many people ridiculously overcomplicate it, especially beginners. The Zone System isn't a silver bullet anyway, but just another helpful tool kit.
What I more strongly object to is the kind of generalization which expects every film to behave more or less the same, especially with respect to TTL metering, such as you have expressed in the last paragraph of the previous post. That formula pretty much limits one's success rate to relatively modest contrast subjects, that is, if taken dogmatically.
Of course, all kinds of approaches can be intuitively tweaked given enough practical experience with both one's own meter and their own typical subject matter. But isn't that the whole idea? - to get so comfortable with your gear and methodology, that you don't even need to get bogged down thinking about it anymore when out shooting. It becomes second nature.
What I more strongly object to is the kind of generalization which expects every film to behave more or less the same, especially with respect to TTL metering, such as you have expressed in the last paragraph of the previous post. That formula pretty much limits one's success rate to relatively modest contrast subjects, that is, if taken dogmatically.
Of course, all kinds of approaches can be intuitively tweaked given enough practical experience with both one's own meter and their own typical subject matter. But isn't that the whole idea? - to get so comfortable with your gear and methodology, that you don't even need to get bogged down thinking about it anymore when out shooting. It becomes second nature.
Precisely. I hardly ever meter in familiar conditions. Slows me down. But, I have found that +2/3 stop gives good results with every film I have "tested", when developed to about the same contrast: Neopan 400, 1600, Acros, Pan-F, FP4, HP5, Delta 400, Tri-X, T-Max 400 and 3200.
The missing phrase here is "for me". It works consistently well for me. On the other hand, I use the ISO speed and it works for me. I do have a rather situational metering technique though. There is no wrong if the exposure works for you. However, from sensitometric speed standpoint, I own a EG&G Mark VI sensitometer that was calibrated by the manufacturer. It's out of calibration now, but it had a known illuminance and I used a Kodak calibrated step tablet. I've also worked in a number of high end photo labs so I've seen a lot of film. For the most part, the films were around their ISO speeds and that was in a seasoned developer.
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Well, there is another way of metering, which is to use the open shadow method. For this, I rate the film at 1/3 stop higher, and point the meter at the darkest part of the scene that is an open shadow. The shadow detail is always captured this way. I used to use this method when I was working with a Nikkormat, which had a center-weighted meter system. Measuring the scene as a whole, I would get slight underexposures, every time. I did well with FP4 rated at 160 using this method, but you must meter the darkest open shadow!
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The light source of the enlarger has an effect on the required contrast of the negatives too.
Condenser enlargers generally produce a higher contrast print than a diffuser enlarger and shorter film development times are needed compared with films developed for a diffuser enlarger to obtain the same print contrast.
Condenser enlargers generally produce a higher contrast print than a diffuser enlarger and shorter film development times are needed compared with films developed for a diffuser enlarger to obtain the same print contrast.
Yes, and let's not forget the contrast of the taking lenses and enlarging lenses!
Can Hm be in units other than lux seconds when using the equation: 0.8/Hm. The major divisions on my x-axis with my curves is using the log10 of 2 or 0.3 units of log exposure for each one step up or down in log exposure. This is so I can more easily view the x-axis in zones, that's how I am accustomed to looking at the x-axis. The Hm point for my normal curve puts it at a log exposure of 0.28. But 0.8/.28 = 2.86. Is there any validity to that, is there a conversion factor. Thanks.
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Sounds like you're working with relative log exposure. Sorry, you do need to use mcs or lxs to calculate the speed. When plotting, log-H is just the log of meter candle seconds.
To determine the exposure when using a step tablet first identify the point of density where you want to ascertain the transmitted illuminance. The density of the step tablet where the resulting film density is at 0.10 for instance.
This is where having a precise measurement of the incident illuminance comes in handy and an accurate density value (calibrated step tablet). Although, a relative speed value can be determined and then used as a comparison against future tests. Finding the necessary lxs for any speed is simply 0.8/EI.
0.80 / 400 = 0.0020 lxs
0.80 / 125 = 0.0064 lxs
0.80 / 100 = 0.0080 lxs
Transmittance = 1 / 10^Density
Transmitted light = Incident Illuminance * Transmittance.
2.76 step table density has a Transmittance of 0.0017
If the incident illuminance is 1.18 lxs, the transmitted illuminance is 1.18 * 0.0017 = 0.0020 lxs
0.08 / 0.0020 = 400
Here's something fun. The value of Hg or the metered exposure is 8/Speed Value. 8/400 = 0.020
The relationship between Hg and Hm can be expressed as Hg / Hm. It can also be expressed by the constants of Hg and Hm or 8 / 0.8 = 10 or 1.0 logs, or 3 1/3 stops. Not the 4 stops of the Zone System and the explanation as to why they are usually 2/3 stop difference in EI.
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Speeds were designed to enable photographers to get consistent results with minimal effort, with the introduction of meters. It was never supposed to require elaborate measurements. That seems to be lost in this discussion. As I have claimed, the doubling of speeds in the 1960 revision of the standards was a mistake, in that it rested on evaluation of exposures and negative densities that were rapidly becoming obsolete. Films were becoming faster, and the leaf-shutter roll film cameras were being supplanted by 35mm focal-plane-shutter cameras. The older cameras, when loaded with faster films than had been available before the war, tended to create slight overexposure (when stopped well down to accommodate the faster films), but this did not matter greatly because the negatives were usually contact-printed by photo-finishers. I have seen such photos of my relatives taken in the 1940s. The photos came bound in a group, like a book. Some of the photos show the cameras, and they are the large folding models with leaf-shutter lenses.
Just when the new ASA standard finally was put into effect, these cameras were already being supplanted by Japanese 35mm SLR models with focal-plane shutters that were better able to handle the new faster films. The result is that almost every user of 35mm focal-plane shutter cameras will do well to use a little more exposure.
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Speeds are designed to make it easier for users. Easier for users, yes, but they still needed to be determined.
The adjustment in film speed was partially due to smaller 35mm cameras but not for the reason you suggested. From Safety Factors, "If a large safety factor is used, the negatives obtained will, on the average, be much denser than is required for making a high-quality print. A small safety factor means thinner negatives. The main advantages of negatives resulting from the use of a small safety factor are:
1. Easier focusing of enlargers
2. Shorter printing times
3. Less graininess in enlargements
4. Sharper pictures
a. Greater depth of field
b. Reduced subject-motion blur
c. Reduced camera-motion blur "
"If a large safety factor is undesirable at the present time, why was it thought to be necessary when the American Standards for film ratings and exposure meters were first adopted in the 1940's? The first reason is that exposure meters, camera shutters, and lens apertures were not as accurate in the 1940's as they are in 1959. The second reason is that the camera-exposure latitude of black-and-white films was effectively greater in those earlier years, largely because the increase in print graininess with increase, in camera exposure was not as evident with the large cameras, large negatives, and small degree of enlargement or contact printing then commonly used. The great increase in the number of small cameras in recent years and the increase in the degree of enlargement has made the graininess problem more acute."
Ok, I was just wondering if there was a way to convert the log exposure value to a lux second value that would satisfy Hm for that speed equation you had referenced. Thanks.
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