stephen_benskin

<p>Better yet, why not dictate to the lab what you want. Do a couple of tests, determine what works, and make that your normal. Refremas can process in 15 sec intervals. If they are a professional lab, they should accommodate you. Don't forget to ask questions to ascertain the extend of their knowledge. </p>

<p>I may have approached things differently, but if someone wanted to do a development test, I'd do it for free. If they wanted us to match the contrast they obtained using a different lab, chemistry, or at home, I'd expose a few sensitometric strips for them to test using the their old method and then match that and make it their normal.</p>

<p>It doesn't hurt to try. How they respond may tell you a lot about the type of business you're dealing with.</p>

<p>I've run B&W lines at a number of high end labs in LA. Pro labs tend to have greater consistency but most have little idea about processing. When I started at each of the labs, their development chart was almost non-existent and none of them had any idea how to do a decent film test. Generally they determine their processing by tweaking the development time based off an averaging of what generally comes out. Generally they tend to over process and not consistently between film types. Some labs will process all 100 speed films at one time and all 400 speed films at another. Kodak did a lab survey in the 90s and the results were very discouraging. <br>

I once toured a "pro" lab that would make guesstimates with the processing time to compensate for differences in the temperature of the developer instead of attempting to stabilize the developer. Another lab I tested processed their Tri-X at +3 when asked for normal processing. It wasn't a choice. They didn't know how to measure the processing.<br>

My advice is to test any lab before letting them process anything important.</p>

 

<p>The almost universal tenet that ISO film speeds are faster than in practice is most likely attributed to a flawed concept with the Zone System. While the statistical shadow placement falls 4 1/3 stops below the meter reading, the ISO speed point falls 3 1/3 stops. Why? Flare. Average flare adds at least a stop to the speed of the film. The Zone System doesn't factor this in and its assumption that the shadow falls four stops under the meter reading creates a 2/3 stop difference in speed. When you consider experimental error and a slight influence of flare from the testing (80 percent of flare is produced from the subject), this can make for a difference from 1/2 to 1 stop slower film speeds than the ISO speed. Since this discrepancy is almost universally observed with ZS testing, the difference between the ISO speed and the "personal speed" can't be attributed to laboratory verses practical testing. In fact, because of the consistent difference, it actually verifies the validity of the ISO speed. <br /> <br /> ZS testing actually produces results comparable with the pre 1960 speed standards which produced film speed one stop slower than the current standard. Films such as Tri-X were rated at 200 and Plus-X was rated at 50. Without any changes to the films and only a change in the standard, film speed doubled over night. According to the “first excellent print” test which was the psychophysical test that established the criteria for modern film speeds, the perceived quality of the results increased with increased exposure up to a certain point than there was no increased perception of quality with increased exposure. The practical conclusion was to pick the point where the minimum of exposure produced the best results or the first excellent print. This would produce faster film speeds allowing for faster shutter speeds and shorter printing times. It doesn’t mean that any “over exposure” wouldn’t produce equally good looking prints (although it will tend to increase grain and decrease sharpness). So, any slight “over exposure” like that produced with the flawed ZS concept will still produce excellent results. BTW, the reason why the speeds dropped by one stop after 1960 is because there was a safety factor attached to the prior standards. There still is a slight safety factor but it is dependent on the degree of flare from a given scene.<br /> <br /> In addition, another misconception of film speed comes from a misinterpretation of the ISO standards fixed density method. Although the ISO standard uses a fixed density point as the speed point (0.10 over fb+f), it is only valid when the contrast parameters of the standard are followed. This is because under those conditions, the fixed density point fits into a formula that will approximate the fractional density method, which is considered to be the most accurate speed determination method. If the contrast conditions are different than the delta 0.80 density differences at a range of 1.30 log-H from the speed point, then an additional equation must be used to calculate the film speed. This method is known as the Delta-X Criterion. The reason the Delta-X Criterion isn’t discussed in the ISO speed standard is because standards don’t generally deal with theory. The ISO speed standard is designed to instruct how to determine the ISO speed of black and white film and a discussion on why a certain method was chosen or how to determine speeds that don’t adhere to the chosen method aren’t pertinent. Generally, a paper will be published concurrently with the new standard that contains all the background.<br /> <br /> According to the Delta-X Criterion and in accord with the fractional gradient method, density isn’t the primary factor in the determination of the quality produced. The contrast or curve’s gradient is the most important factor. It was determined that most consistent results producing the highest quality reproductions were produced when the speed point was at a gradient of .3 times the overall curve gradient. Using the Delta-X Criterion incorporated into the ISO standard, when adhere to the standards conditions, this point will fall 0.28 log-H units below the 0.10 fixed density point. As the processing changes, this will change the overall curve gradient as well as the gradient of the shadow. This tends to change the relationship between the fixed 0.10 density point and the Delta-X Criterion point. This, in effect, tends to negate film speed changes associated with developmental changes. In other words, within a certain range of development (approximately -1 to +2), there is only a single film speed. The variability that most people experience using the fixed density method of 0.10 over fb+f without the incorporation of the Delta-X equation doesn’t exist.<br /> <br /> Let me be clear, I am making a distinction between film speed and pragmatic method of making an exposure. What most people attribute to film speed is more about personal working methods. Film speed is about scientific methodology. When it comes to making an exposure, you do what works for you.</p>

<p>"First, manufacturers' film speeds are determined according to a rather arcane testing procedure prescribed by the ISO standards institute. They are there so you can compare films, but have little relevance to what your "actual" film speed should be (kind of like mileage figures for new cars...)."<br>

I have to disagree with this part of Doremus' response on principle. While a primary aspect of the ISO standardization is film to film comparison, it is also based on real world results. The change in the standard in the 1990s changed some of the more questionable practices in order to reflect real world use. In addition, the ISO standard was founded on psychophysical testing which unquestionably reflect real world conditions.<br>

How you use your light meter and other personal working methods have a higher degree of influence to how you expose than the actual film speed. I agree with Doremus that you should find what works for you based on your personal methods. Before coming to any conclusions, you must first carefully investigate all the potential variables that can influence the final results. Many people misinterpret such things as over processing as over exposure. Confirm what your lab is doing.</p>

<p>That is correct.</p>

<p>Meter's don't read reflectance but luminance. However, if you compare the illuminance from which incident exposure meter are calibrated to to the luminance that reflected exposure meters are calibrated to, then the reflectance is 12%. 297*pi / 7680 = 0.121. You can also do it with their K factors. 1.16*pi / 30 = 0.121. </p>

<p>So, it you are shooting in a front lit scene, if you want to obtain similar exposures using both an incident light meter and a reflected light meter (assuming they are being used properly, ie angled correctly), you will have to open up 1/2 stop from the reflected light reading. If you read the instructions that comes with the Kodak 18% card, it states just that.</p>

While not the Peak filters, try the Mole Richardson site.

 

http://extranet.mole.com/public/index.cgi?cmd=view_category&parent=1434-1547&id=1021

Hi Roger,

 

Long time. I would like to second your well said statement and add I happen to have an article in the current issue of PHOTO Techniques that deals with this very topic. It's titled <i><u>Flare and Accurate Film Speeds</i></u>. My premise is the discontinuity between the ISO speeds and speeds from Zone System testing originate from a fundamental misconception within Zone System methodology. If you follow the traditional ZS method of film speed testing, you will produce speeds more in line with the pre 1960 standards. The basic premise is that the film speed point isn't necessarily the point of desired exposure, but only a point to define the film speed (explained in more detail in the article). If you think about it, Zone I is four stops under the meter reading or meter calibration point. ISO speed is determined at 3 1/3 stops under and also assumes a certain amount of flare.

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I'm also currently working on an article that describes the contrast parameters of the ISO standard as a version of the fractional gradient method masquerading as a fix density method and not a capitulation to those who found the fractional gradient method too difficult. As you know, any fixed density method will tend to overrate film developed to higher CIs and underrate film developed to lower CIs. The interesting part that I discovered is that film speed based on the frational gadient method changes very little with development. Yes, the overall densities change. Higher CIs will produce a negative with an overall higher density, but since the fractional gradient method is based on gradient and not density, the film speeds don't change much. (This tends to negate the just noticable black concept of standardized printing time.) This is probably why the original fractional gradient method didn't specify a degree of development. It only stated that the film be developed to an average gradient in excess of 0.50. Anyway, the contrast parameters of the current ISO standard are really variables in an equation that defines the difference between the fixed density speed point and the fractional gradient speed point. I feel that if this weren't the case, there would never have been international agreement on a film speed standard. Very interesting stuff.

It's about the interconnection of the scene, film, processing, paper, and enlarger (among other factors). This is called Tone Reproduction. It's too big of a subject to attempt to cover on this board. There are a number of books that cover this subject well such as Photographic Materials and Processes.

The ultimate decisive moment.

IMO, most of the "personal" film speed methods just give a false sense of accuracy. Take for instance the method of stopping down X stops and opening up the lens of adjusting the shutter speed in small increments. First, how accurate is the f/stop? The f/stop indication is a mathematical value and not a tested value for that lens. You will need T/stops for that. Then there is the accuracy of the shutter. It may not only be giving you a shutter speed different from indicated, but the variance between different settings can be different.

 

Let's say you only change the f/stop. This method could eliminate the relevance of any practical difference between the f/stop and t/stop. You are, in effect, incorporating this difference into your "personal" speed. This is all fine and good only if you use this lens. Use another lens and you have a whole new f/stop, t/stop relationship which negates your test. Now, you have to do film tests for each and every lens. Also, are you really pegging 1/3 stop increments on the lens. Most lenses don't have click stops for third stops.

 

Then there's the shutter speed. You did all your tests using the same shutter speed. What about the other ones? Your test is only truly valid for that shutter speed. You will have to determine a personal film speed to each and every shutter speed in order to have absolutely accurate results.

 

Don't forget general testing variations. In order to eliminate a random variation from influencing the results, you will need to run dozens of tests and average the results for each and every step mentioned above. No body wants to do that.

 

And all this is an example of only one set of variables. What about the light source, color temperature, meter calibration, photo cell spectral biases, metering techniques, variations in emulsion batches, or dozens of other variables that may crop up under the testing conditions but will be different in actual use?

 

This is not to say that you shouldn't test. I personally have a sensitometer which I do my test exposes on. While it is more accurate than almost any other method, I know that there are so many other variables at work in real world conditions. Know the conditions, understand the realities, and see what works for you. Use the test as a starting point. Understand what film speed is and how it works. Understand the roll of film speed in relation to exposure. This is the best possible approach.

You really can't compare motion picture criteria with still, or even color (especially transparency) with B&W. As for incident metering, it will sacrifice the high and low ends for the middle tones for higher contrast scenes. Quality in B&W is defined by the shadows. Under average conditions, however, incident meter will produce high quality results with any general photographic material.

 

I don't really understand Jay's statement on how light meters are a luxury because he uses VC paper. An exposure meter places the scene's luminance onto the film. VC paper's LER can be adjusted to match the film's DR. Now, the film's DR will change if you lose the low end because of bad meter, but that is a mistake with meter and not considered a positive result. Mostly, the film's density range has more to do with the subject's luminance range and the subsequent film processing than with metering.

 

The eye is really a bad meter. It adapts to what ever condition it is in. A meter doesn't. My advice is to learn what works for you, whether it is a reflected or incident meter, and then make adjustments to fit your needs. I use a number of different metering techniques depending on the scene and results desired.

Looks like fogging to me. The multiple sprockets indicate that the film was moving around. The fog is probably from a low light level over a period of time. I'm thinking sometime in the loading of the film reel or during processing.

John, do you have the color temperature for the lightsource?

Hasn't anyone wondered about MacGregor's printing conditions? What paper and what grade / filter is he using. Plus, let's not forget the perceptual aspects of viewing a gray scale. The lower tones will look more compressed than they really are.

I'm looking at a table that compares a number of different speed methods. This was published before 1960 so it is the old standard.

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Weston 100 = ASA 125

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Weston 400 = ASA 500

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Looks like a third of a stop difference.

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John Painter Photo.net Patron, mar 13, 2004; 06:47 p.m.

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<b>Don't forget to take pictures :)</b>

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jmp</i>

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John, O.K., maybe you're not one of the major transgressors, but not totally innocent either. This is a pet peeve with me, and maybe I jumped on you too hard. But let this be a lesson to all those others.;>) At least I'm not yet at the point where I'm out walking around the streets spouting something about socialism.

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About temperatures, it's best to keep them close together to avoid shock to the emulsion causing reticulation. There's less chance of reticulation after a hardening fix. Some people might argue, but plus or minus five degrees for the stop and fix from the dev. temp shouldn't cause too much trouble. I've never tried going from normal dev temp to ice water, but can't see how it could be good. So, I guess the general rule should be don't have extreme changes in bath temperatures.

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According to LP Clerc's <i><u>Photography, Monochrome Processing</i></u>, <i>In general,reticulation is liable to be caused by any circumstance tending to cause very rapid swelling or shrinkage of the gelatin.</i>

John, err, I was just giving you some of your own medicine. You always seem to add the "just shoot" statement in the more technical threads. I've always found that extremely rude, contemptuous, and ignorant. Where do you get the nerve to reject out of hand something like sensitometry when you don't even know about the importance of temperature consistency? Someday you may realize there's more than your limited perspective.

John, why waste your time thinking about such things? Just get out there and shoot! :>)

<i>So color affects contrast, even if the subject contrast is the same.</i>

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It's called the Gamma-Lambda Effect, and it works differently than most people would think. Blue reduces contrast, while green increases contrast, and red generally doesn't make any change.

I had something like this happen. The screws broke off. I took it to a watch repair place and they fixed it for 5 dollars.

Ron, I believe Kirk was talking about ISO R (range and there's that word again) and not ISO paper speed.

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According to the 3rd edition of <i><u>The Focal Encyclopedia of Photography</i></u>, there isn't an entry for "Tonal Scale" or "Tonal Range." The closest term they have is "Tonality" which was written by Stroebel. He defines it as, "The overall appearance of the densities of the component areas of a photograph or other image with respect to the effectiveness of the values in representing the subject." This sounds like Ron's definition of tonal scale.

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<i><u>Photographic Materials and Processes</i></u> uses tonal range in the index, but doesn't use the term in the text. Let's just call these terms what they are, two very general popular photographic terms that have no specific meaning and are essentially meaningless. It's time to pass a law and have the terminology police issue a fine whenever used. All funds generated can go to the upkeep of Photo.net.

<i>To me, exposure range and tonal scale are not the same. Exposure range implies the length of the straight line portion of the H&D curve, and tonal scale implies the overall shape and contrast of that curve.</i>

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Fine, but most sources don't seem to define it. To me, they are the same. Jones used to use the term scale for everything, brightness scale, exposure scale, etc. I've seen scale used in papers up through the 50s. Now it's luminance range, exposure range, etc.

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Kirk's question was not really what a particular person thinks it means, but how it is used in so many different ways in literature. Scale or range, I've seen tonal scale / range used to refer to both the exposure range of a material and the density range of a material, and those are two different things in any bodies' book.

<i>just reducing development and contrast doesn't turn short range materials into long range materials</i>

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Sorry Conrad, I have to disagree with you here. I do agree with you about changes to local contrast.

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The term tonal scale or tonal range is just too nonspecific. It's like saying "gutsy development." IMO, the term is used most often because there wasn't any quantitative testing.

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If we are talking about films, isn't contrast index, density range, or log-H range more informative and specific. "The film has a long tonal range" doesn't mean as much as saying "at a CI 0.60, there are no signs of the film shouldering off within a scene's average log-H range."

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When discussing papers, why not use reflection density range, or log exposure range? I just think the tonal scale / range term is so ubiquitous that most people don't stop and think how weak a term it really is.

Looks like subtle facetiousness just doesn't play well in type. And since a real devotee of sarcasm would never use the smiley face :-), it may never work.