Switch to English Language Passer en langue franšaise Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 75,247   Posts: 1,660,197   Online: 890
      
Page 9 of 12 FirstFirst ... 3456789101112 LastLast
Results 81 to 90 of 114
  1. #81
    Bill Burk's Avatar
    Join Date
    Feb 2010
    Shooter
    4x5 Format
    Posts
    4,083
    Images
    51
    Interesting that W speed, Delta X speed and 0.3 gradient all are reasonable. But heck no to 0.1 speed. And I know you've said that the standards get away with using 0.1 - only because they specify conditions that make them fit 0.3 gradient.

    But this is another fun thought for the conclusion...

    Maybe we should be designing "print judgment" tests, since they're the best. And we have all this determination to pick a personal speed...

  2. #82
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    24,463
    Images
    65
    It should be noted here that both "first acceptable print" and the "zone system" are less than quantitative measures due to their very nature. They are "shadows" of real sensitometric tests based on the ANSI standards. And combining the sensitometry with "first acceptable print" (as is done in Mees) one has a really effective method of examination of this problem.

    Having done this sort of thing dozens of times with hundreds and hundreds of "users" and "customers", I can say that "when things are said and done, more things are said than done".

    BTDT. Guys, go out and do about 1000 or so exposures and 3000 or so print tests with about 100 people.

    Sorry for the rant.

    PE

  3. #83
    Bill Burk's Avatar
    Join Date
    Feb 2010
    Shooter
    4x5 Format
    Posts
    4,083
    Images
    51
    Haa, Every once in a while I knuckle down and get something done.

    I have a roll of TMAX 100 to develop that I shot with the new (to me) Kodak Retina I where I thought I calibrated the shutter speeds. But I have my doubts about the shutter test I performed. I'm a little worried. Seems the responsiveness of the sensor in my tester has a bit of lag, which over-estimates the time. So where I thought 1/100 was 1/40, it might really be 1/100. I don't like making mistakes in the underexposure direction so I am going to shoot a test roll - and I rarely do that - just to validate the shutter speeds. I'll include sensitometry exposure and develop the two rolls together so I'll soon find out whether I knew what I was doing all along or if I just thought so.

  4. #84
    Stephen Benskin's Avatar
    Join Date
    Jan 2005
    Location
    Los Angeles
    Shooter
    4x5 Format
    Posts
    1,289
    Quote Originally Posted by Doremus Scudder View Post
    But, for the sake of clarification, when I develop, say N-2 in order to accommodate a rather high subject brightness range, am I not changing the gradient and therefore the effective speed of the film? Or would you say that this is outside the parameters of ISO testing standards and simply does not apply?
    You are asking the wrong question. I’ve already covered it to a degree in other posts so you may already know what I’m about to write. The effective film speed changes with changes in development. The question is how to measure it. As I’ve pointed out, a fixed density method lacks good correlation with the print judgment speeds. The fractional gradient method and the subsequent Delta-X method uses the point on the curve that is 0.3x of the average gradient. This point tends to shift in a inverse relationship to a fixed density point which causes a slower change in the effective film speed than with the fixed density method.

    This example from the Simple Methods for Approx Fractional Gradient Speeds paper shows the inverse relationship between ΔD (contrast) and ΔX (difference between the 0.10 fixed density point and the fractional gradient point). As ΔD decreases, ΔX increase and visa-verse effectively tempering changes in effective film speed with changes in development.

    Click image for larger version. 

Name:	Delta X, inverse relationship.jpg 
Views:	14 
Size:	437.9 KB 
ID:	87260

    The chart shows three sensitometric exposures from the same film type developed to different contrast indexes. One corresponds to the ISO contrast parameters and the others are developed to a less and greater degree. An effective film speed was determined from each of the samples using both the 0.10 fixed density method and the Delta-X method.

    Click image for larger version. 

Name:	Relationship Between Fixed Density Speeds and Delta X Speeds copy.jpg 
Views:	20 
Size:	34.5 KB 
ID:	87261

    Should I really be questioning whether my testing method "is yielding reliable results"? Are the Zone System and BTZS tests unreliable?
    Technically, yes to both questions. Practically, no to both. You don't need this stuff to shoot. I think it's good to know if only to understand the lack of precision with the type of equipment generally available and concern yourself with what's really necessary to produce good images.
    Last edited by Stephen Benskin; 05-03-2014 at 02:20 AM. Click to view previous post history.

  5. #85

    Join Date
    Sep 2002
    Location
    Oregon and Austria
    Shooter
    4x5 Format
    Posts
    952
    Quote Originally Posted by Stephen Benskin View Post
    You are asking the wrong question. ...

    The chart shows three sensitometric exposures from the same film type developed to different contrast indexes. One corresponds to the ISO contrast parameters and the others are developed to a less and greater degree. An effective film speed was determined from each of the samples using both the 0.10 fixed density method and the Delta-X method.

    Click image for larger version. 

Name:	Relationship Between Fixed Density Speeds and Delta X Speeds copy.jpg 
Views:	20 
Size:	34.5 KB 
ID:	87261

    ... You don't need this stuff to shoot. I think it's good to know if only to understand the lack of precision with the type of equipment generally available and concern yourself with what's really necessary to produce good images.
    Stephen,

    First, thanks for taking the time to explain in terms I can deal with. I'm busy digging through the papers you posted. That said, the excursion is a bit on the superfluous side, since my primary concern/goal is to improve my technique in the field. And, although you maintain that, "you don't need that stuff to shoot," I'm finding that much of it is useful, if only in clearing the clutter of accumulated misconceptions and Zone System inaccuracies. I'll continue to use the Zone System, though, since I find it such a wonderful visualization tool, but I'll be trying to refine exposure some now.

    I mentioned earlier a disconnect (for me, anyway) between ISO and personal E.I. This connects somewhat with your discussion on gradient speeds vs. fixed point speed. First, let me say that I'm now convinced that the Delta X or fractional gradient speed based on first excellent print testing is likely a better method than the Zone System fixed-point speed determination. But, if I accept that, then it would seem that much of the exposure compensation that I have been doing for expansions and contractions would be unnecessary. This confuses me a bit, for it really seems to me that when I make a negative of a very contrasty scene that requires, say, N-2 development, that, unless I give substantially more exposure (along the lines of that suggested by the fixed-point speed) to compensate for the reduced development, my shadow values suffer. Conversely, expansion negatives are often overexposed (which doesn't bother me much) if I don't compensate by reducing exposure.

    This is the disconnect I am addressing. And, I don't even really know where to start asking informed questions about it except to fire away and hope you will indulge me yet again. So, did the first excellent print tests include lots of expansion and contraction subjects, or were they more or less concerned with prints of subjects with more "normal" SBRs? If so, then should we expect much different results for similar print tests with subjects with significantly higher or lower SBRs? If not, then why does it seem that in practice I have to compensate exposure for contractions and expansions than the Delta X or fractional gradient speeds would suggest?

    I'll leave it at that for now, as I'm probably asking the wrong questions again

    Looking forward to your answer,

    Doremus

  6. #86
    markbarendt's Avatar
    Join Date
    May 2008
    Location
    Beaverton, OR, USA
    Shooter
    Multi Format
    Posts
    5,984
    Blog Entries
    3
    Images
    19
    Quote Originally Posted by Stephen Benskin View Post
    You don't need this stuff to shoot. I think it's good to know if only to understand the lack of precision with the type of equipment generally available and concern yourself with what's really necessary to produce good images.
    I agree that we don't "need" this stuff to shoot.

    The value I find in building my understanding of these concepts though, and in getting the terminology/language right, is in taking the mis-understandings, myths, urban legends, and magic bullet chasing out of my shooting and processing.
    Mark Barendt, Beaverton, OR

    "We do not see things the way they are. We see things the way we are." Ana´s Nin

  7. #87
    Stephen Benskin's Avatar
    Join Date
    Jan 2005
    Location
    Los Angeles
    Shooter
    4x5 Format
    Posts
    1,289
    I think this example from Simple Methods for Approximating the Fractional Gradient Speeds of Photographic Materials is a rather good illustration of the difference between the print judgment speeds, "S", 0.10 fixed density, "S`", and inertia speed thrown in for good measure, under different curve shapes and changes in gradient.

    Click image for larger version. 

Name:	Simple methods approx fractional gradient.jpg 
Views:	9 
Size:	302.2 KB 
ID:	87263

    I should point out that the graphs are not implying that exposure should fall on S` or S. Only that it they are points where film speed can be determined. More on this later.

    For the clincher on Zone System speed testing is Calibration Levels of Films and Exposure Devices by D. Connelly. Two important take aways are the value of "P", photographic constant, and "k1", ratio between P and the speed constant (also difference between Hg and Hm for B&W).

    Calibration Levels of Films and Exposure Devices, Connelly.pdf
    Last edited by Stephen Benskin; 05-03-2014 at 12:42 PM. Click to view previous post history.

  8. #88
    Bill Burk's Avatar
    Join Date
    Feb 2010
    Shooter
    4x5 Format
    Posts
    4,083
    Images
    51
    Quote Originally Posted by Stephen Benskin View Post
    Basically, the print judgment speed is the most accurate method of determining film speed. It is based directly on the finished prints; however, it is incredibly laborious and therefore impractical to do on a regular basis. The next best method is to find a mechanical approach that will yield speeds similar to the print judgment speeds in the majority of cases. The fractional gradient method is that method. Fixed density methods were evaluated but weren't as consistently accurate. The fractional gradient method was determined by finding the spread between the proposed method and the speeds resulting from the print judgement speeds. Just like the spread example with testing alternative methods to the fractional gradient method. Of the three methods shown, the fixed density 0.10 method had the highest degree of spread and therefore the least consistently accurate to the print judgment speeds.

    Attachment 87258
    I want to point out a quick personal interpretation of this chart... It shows the relative ability of a few of the better speed determining methods... to predict whether the speed used for taking a picture... to predict if that picture will be excellent.

    Notice the spread of the three better methods... A spread of 0.2 density units, or two-thirds of a stop. A way to guarantee a picture will be excellent... is to rate your film using any of the three good methods illustrated... AND THEN set your Exposure Index two-thirds of a stop lower than the speed you determined.

    PE, I think you said you do that. I know I do that.

    Xmas, I tend to always talk about Black and White negative... slides would of course require a different method to guarantee an excellent picture.

  9. #89
    Bill Burk's Avatar
    Join Date
    Feb 2010
    Shooter
    4x5 Format
    Posts
    4,083
    Images
    51
    Quote Originally Posted by Doremus Scudder View Post
    ... N-2 development, that, unless I give substantially more exposure (along the lines of that suggested by the fixed-point speed) to compensate for the reduced development, my shadow values suffer.
    Hi Doremus,

    When you use N-2 to accommodate a long scale subject, your aim is still to print on Grade 2 paper. The shadows are suffering not for lack of any detail, but for lacking enough detail to be revealed on Grade 2 paper. So increasing exposure is a good idea for this case.

    The Delta-X criterion justifies using the same speed according to the fractional gradient method, for a relatively normal scene where the underdevelopment is done for other purposes, say... to maintain high resolution and fine grain. Then the aim would be to print on Grade 4 paper, and the speed could be same and give a similar print as a normally developed negative of the same scene printed on Grade 2.

  10. #90
    Stephen Benskin's Avatar
    Join Date
    Jan 2005
    Location
    Los Angeles
    Shooter
    4x5 Format
    Posts
    1,289
    Quote Originally Posted by Doremus Scudder View Post
    I mentioned earlier a disconnect (for me, anyway) between ISO and personal E.I. But, if I accept that, then it would seem that much of the exposure compensation that I have been doing for expansions and contractions would be unnecessary. This confuses me a bit, for it really seems to me that when I make a negative of a very contrasty scene that requires, say, N-2 development, that, unless I give substantially more exposure (along the lines of that suggested by the fixed-point speed) to compensate for the reduced development, my shadow values suffer. Conversely, expansion negatives are often overexposed (which doesn't bother me much) if I don't compensate by reducing exposure.

    This is the disconnect I am addressing. And, I don't even really know where to start asking informed questions about it except to fire away and hope you will indulge me yet again. So, did the first excellent print tests include lots of expansion and contraction subjects, or were they more or less concerned with prints of subjects with more "normal" SBRs? If so, then should we expect much different results for similar print tests with subjects with significantly higher or lower SBRs? If not, then why does it seem that in practice I have to compensate exposure for contractions and expansions than the Delta X or fractional gradient speeds would suggest?
    Since the effective film speed is based on 0.3x average gradient, you shouldn't expect to match the over all density of negatives with expansion and contraction development to that of a normal negative. The overall negative density will change with development, but the shadow gradient at the speed point remains at 0.3x average gradient (this is why the just black proof is valid only with normal development). Things tend to get more complicated at the extremes. The degree of flare is more of an uncertainty, as is preferred tone reproduction. We haven't even discussed developmental models yet. I'd like to show you a four quadrant example, but my program is down because of a conflict with Internet Explorer and I don't have an example of a N-2 development. I have one of a large subject luminance range with 2 stops flare and compensation with the paper grade, but that might just muddy the waters. Anecdotally, when I shoot scenes that I intend on progressing less than -1, I tend to error on the safe side.

    One of my favorite Jones quotes comes from A Study of Various Sensitometric Criteria of Negative Film Speeds. This is the paper comparing various speed methods to the print judgement speeds. Jones writes, "From the standpoint of tone reproduction theory there seems to be no justification for the adoption of any value of density as a significant criterion of the speed of a photographic negative material. The primary function of the negative material is to record brightness differences existing in a scene. Density, per se, has no significance as an indication of the ability of the photographic material to perform this function. The value of negative density by which any particular object brightness is rendered, as, for instance, the deepest shadow, is of no consequence except insofar as it may have some bearing on the exposure time required to make a print from a negative.

    Tone reproduction theory indicates that there is only one characteristic of the negative curve that is significant in expressing the capacity of the material to reproduce brightness (luminance) differences, and it is upon the way in which brightness differences are reproduced that the quality of the film positive must depend. This characteristic of the D-log E relationship to the gradient or slope, since this determines the magnitude of the density differences by which brightness differences in the object will be rendered in the negative and eventually in the positive made therefrom."

    More specifically, I do have a development chart that uses both fixed density and Delta-X speed determination. In this example, I used a fixed flare model to determine aim contrast index. Fixed flare tends to higher and lower CIs faster as the luminance range moves out from the statistical normal then variable flare.

    Click image for larger version. 

Name:	development chart.jpg 
Views:	14 
Size:	38.5 KB 
ID:	87325

    For a reference, here is a data from one of the images used in the first excellent print test.

    Click image for larger version. 

Name:	Willow Pond.jpg 
Views:	19 
Size:	577.9 KB 
ID:	87326

    To answer your question about terminology. EI or effective film speed seems to be commonly used for any method of determining speed outside of the ISO standard. I prefer effective film speed for sensitometrically tested film because EI has other uses.

Page 9 of 12 FirstFirst ... 3456789101112 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  Ś   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin