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  1. #11

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    Quote Originally Posted by jmal View Post
    Roger,

    Thanks for the info. However, as I shot at EI 200 I'm not sure it applies. Ilford gives a time of 6.5 minutes for EI 200. Should I split the difference between 200 and 400? Or, add the same percentage listed above to the 200 time? Thanks.


    Jmal
    Dear Jmal,

    Well, there's no advantage I can see in using DD-X. You've already over-exposed, reducing sharpness and increasing grain, and DD-X will increase grain again. On the other hand, I suppose it might look good tonally. I'd give it 7 minutes and see how it looks.

    Cheers,

    R.

  2. #12

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    Quote Originally Posted by David A. Goldfarb View Post
    A speed increasing developer like Acufine or Microphen lets you expose the film at a higher speed than the box setting (i.e., it lets you "underexpose" in camera, but you're not really underexposing, because the speed is really higher), but still retain good shadow detail and normal contrast at the reduced exposure.

    This differs from what people normally call "pushing" (attempting to increase film speed substantially by extending development time), which usually increases density in the highlights while not really improving shadow detail significantly, and film speed is measured in terms of shadow detail.
    There are several definitions of film speed (ASA, ISA, DIN etc). The film speed can be changed (in a limited way) through the development time.
    In the case of a compensating ( or HD) developer one will observe more detail in the shadows, but this is not the result of a film speed increase. A compensating ( or HD developer) has the ability to show the actual light distribution in the deep shadows. Whether you will observe the actual light distribution in the deep shadows depends on the quality of the camera lens too.
    The film speed change has a chemical origin; the struture in the deep shadows has a physical origin.

    Jed

  3. #13

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    Quote Originally Posted by Jed Freudenthal View Post
    There are several definitions of film speed (ASA, ISA, DIN etc). The film speed can be changed (in a limited way) through the development time.
    In the case of a compensating ( or HD) developer one will observe more detail in the shadows, but this is not the result of a film speed increase. A compensating ( or HD developer) has the ability to show the actual light distribution in the deep shadows. Whether you will observe the actual light distribution in the deep shadows depends on the quality of the camera lens too.
    The film speed change has a chemical origin; the struture in the deep shadows has a physical origin.

    Jed
    Dear Jed,

    Not exactly. First, all speeds are now ISO, which is based on the older ASA and DIN standards. These are now about as relevant as GOST, Scheiner, etc. but may be treated interchangeably with the respective ISO arithmetic and logarithmic speeds, e.g. ISO 400/27 is equivalent to ASA 400 or DIN 27.

    Second, true film speed cannot be changed by varying time. You can get more density at the speed point (0,10 above fb+f) by increasing development, but only at the expense of increased contrast. This is commonly known as 'pushing'.

    Third, true film speed can be affected by developer choice, as noted earlier.

    Fourth, a compensating developer does nothing for the shadows, but decreases highlight contrast, allowing a longer brightness range to be represented without dodging or burning, at the expense of compressing the mid-tones.

    Fifth, compensating and HD developers are completely different creatures, assuming you mean 'high definition' by HD. HD or acutance developers emphasize microcontrast at light/dark borders, at the expense of some sharpness.

    Sixth, shadow detail depends on exposure, and differentiation of shadow detail to some extent on flare. Flare is a function of the lens and camera body -- the latter is often forgotten.

    Seventh, I should be much obliged if you could expand upon your statement about chemical and physical changes as I could not quite understand it.

    Cheers,

    Roger

  4. #14

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    Quote Originally Posted by Roger Hicks View Post
    Dear Jed,

    Not exactly. First, all speeds are now ISO, which is based on the older ASA and DIN standards. These are now about as relevant as GOST, Scheiner, etc. but may be treated interchangeably with the respective ISO arithmetic and logarithmic speeds, e.g. ISO 400/27 is equivalent to ASA 400 or DIN 27.

    Second, true film speed cannot be changed by varying time. You can get more density at the speed point (0,10 above fb+f) by increasing development, but only at the expense of increased contrast. This is commonly known as 'pushing'.

    Third, true film speed can be affected by developer choice, as noted earlier.

    Fourth, a compensating developer does nothing for the shadows, but decreases highlight contrast, allowing a longer brightness range to be represented without dodging or burning, at the expense of compressing the mid-tones.

    Fifth, compensating and HD developers are completely different creatures, assuming you mean 'high definition' by HD. HD or acutance developers emphasize microcontrast at light/dark borders, at the expense of some sharpness.

    Sixth, shadow detail depends on exposure, and differentiation of shadow detail to some extent on flare. Flare is a function of the lens and camera body -- the latter is often forgotten.

    Seventh, I should be much obliged if you could expand upon your statement about chemical and physical changes as I could not quite understand it.

    Cheers,

    Roger
    I thought the filmspeed was determined by the minimum amount light that will expose the film (Expose for the shadows)
    You say that compensating devs does nothing for shadows but only highlights, how about Diafine? Is it both compensating and speed increasing (though not with all films) as two different qualities?
    Can one say that the speed of X film in Y dev depends on a treshold value as in how exposed need the silverhalides to be for the developer to start working on them. Hight treshold (more light) = slow speed and low treshold (less light) = high speed.
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  5. #15

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    Quote Originally Posted by Soeren View Post
    I thought the filmspeed was determined by the minimum amount light that will expose the film (Expose for the shadows)
    You say that compensating devs does nothing for shadows but only highlights, how about Diafine? Is it both compensating and speed increasing (though not with all films) as two different qualities?
    Can one say that the speed of X film in Y dev depends on a treshold value as in how exposed need the silverhalides to be for the developer to start working on them. Hight treshold (more light) = slow speed and low treshold (less light) = high speed.
    Film speed is determined by the amount of light required to give a certain density (NOT a minimum density) AT A FIXED CONTRAST. And at this fixed contrast, the amount of light required will depend on the developer and (believe it or not) the agitation: more agitation = more toe speed at a given contrast.

    Yes, it is possible (I believe) to have a dev that is both compensating and speed increasing, and Diafine lovers claim this for their favourite developer, but I have never done any sensitometric testing of this myself, nor do I know of anything other than anecdotal or distinctly amateurish evidence that it is true -- but I've never looked, so it may well be true.

    Thresholds (the minimum amount of light required to create ANY density) are another matter entirely. They were used in some early speed testing systems but were soon dropped as unreliable, hence the DIN standard of 0,10 above fb+f and the later Kodak fractional gradient system which became ASA and is now integrated surprisingly cleverly with the DIN standard in the Delta X criterion.

    Cheers,

    R.

  6. #16

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    Quote Originally Posted by Roger Hicks View Post
    Dear Jed,

    Not exactly. First, all speeds are now ISO, which is based on the older ASA and DIN standards. These are now about as relevant as GOST, Scheiner, etc. but may be treated interchangeably with the respective ISO arithmetic and logarithmic speeds, e.g. ISO 400/27 is equivalent to ASA 400 or DIN 27.

    Second, true film speed cannot be changed by varying time. You can get more density at the speed point (0,10 above fb+f) by increasing development, but only at the expense of increased contrast. This is commonly known as 'pushing'.

    Third, true film speed can be affected by developer choice, as noted earlier.

    Fourth, a compensating developer does nothing for the shadows, but decreases highlight contrast, allowing a longer brightness range to be represented without dodging or burning, at the expense of compressing the mid-tones.

    Fifth, compensating and HD developers are completely different creatures, assuming you mean 'high definition' by HD. HD or acutance developers emphasize microcontrast at light/dark borders, at the expense of some sharpness.

    Sixth, shadow detail depends on exposure, and differentiation of shadow detail to some extent on flare. Flare is a function of the lens and camera body -- the latter is often forgotten.

    Seventh, I should be much obliged if you could expand upon your statement about chemical and physical changes as I could not quite understand it.

    Cheers,

    Roger
    Sure, film speed nowadays is almost always ISO. But in pictorial photography, this number has the finction of a reference point. Lightmeters are even calibrated in two different ways ( I got two Rolleis back from Rollei, and they were calibrated differently!).

    But now the question on the chemical and the physics side of the problem. I could try to explain this in 'common language', but this is not easy compared to the scientific way.
    Therefore the scientific approach first. But please let me know, if that is not clear.

    The photographic process is a process of image transfer: through the camera lens, through the development process/ negative, through the enlager optics and finally the print on th paper. Each step is described by a Modulation Transfer Function ( describing the transfer of contrast). In this image transfer process, one can recognize physical and chemical contributions.
    When you look at a print in the deep shadows with structure, you should ask what is coming from what. Is this because of the properties of the camera lens, the developer, the film etc. In fact, with a camera lens with a high MTF at the higher spatial frequencies, a compensating or high definition developer, one can observe more than onbe reason that a deep shadow is structured. It requires experimenting to see what influences what.
    I hope, this clarifies my statement a bit more.

    Jed

  7. #17

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    Quote Originally Posted by Jed Freudenthal View Post
    Sure, film speed nowadays is almost always ISO. But in pictorial photography, this number has the finction of a reference point. Lightmeters are even calibrated in two different ways ( I got two Rolleis back from Rollei, and they were calibrated differently!).

    But now the question on the chemical and the physics side of the problem. I could try to explain this in 'common language', but this is not easy compared to the scientific way.
    Therefore the scientific approach first. But please let me know, if that is not clear.

    The photographic process is a process of image transfer: through the camera lens, through the development process/ negative, through the enlager optics and finally the print on th paper. Each step is described by a Modulation Transfer Function ( describing the transfer of contrast). In this image transfer process, one can recognize physical and chemical contributions.
    When you look at a print in the deep shadows with structure, you should ask what is coming from what. Is this because of the properties of the camera lens, the developer, the film etc. In fact, with a camera lens with a high MTF at the higher spatial frequencies, a compensating or high definition developer, one can observe more than onbe reason that a deep shadow is structured. It requires experimenting to see what influences what.
    I hope, this clarifies my statement a bit more.

    Jed
    Dear Jed,

    Thanks for the explanation; I think I now have a better grasp of what you meant. As I said, I do not see that a compensating developer will have any effects on the shadows -- visualize a D/log E curve for both compensating and non-compensating developers and I think you'll agree -- and I am some way from convinced that an HD developer will have any effect on subtle shadow graduations, given that it works only at abrupt light/dark (and of course dark/darker) interfaces. And, as I noted, the MTF must be considered as a system, including camera flare as well as lens flare.

    I'd dispute 'calibrated differently', too, suggesting that the two meters (assuming that they are otherwise identical cameras) are calibrated in the same way and to the same standard, but that the variations are a consequence of tolerances in the calibration process. If the cameras are not identical, they cannot be calibrated in exactly the same way, i.e. the process or referents or both of the calibration process must vary. Nit-picking perhaps, but no evidence that there is any film speed standard other than ISO.

    I fully take your point about about ISO speeds as 'a reference point', but what else could they be? Many photographers habitually give a little more exposure in the interests of tonality, but this normally remains fairly constant, e.g. if you rate Tri-X at 250 you're likely to be happy with HP5 at 250 too.

    Cheers,

    Roger

  8. #18

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    Quote Originally Posted by Roger Hicks View Post
    Dear Jed,

    Not exactly. First, all speeds are now ISO, which is based on the older ASA and DIN standards. These are now about as relevant as GOST, Scheiner, etc. but may be treated interchangeably with the respective ISO arithmetic and logarithmic speeds, e.g. ISO 400/27 is equivalent to ASA 400 or DIN 27.

    Second, true film speed cannot be changed by varying time. You can get more density at the speed point (0,10 above fb+f) by increasing development, but only at the expense of increased contrast. This is commonly known as 'pushing'.

    Third, true film speed can be affected by developer choice, as noted earlier.

    Fourth, a compensating developer does nothing for the shadows, but decreases highlight contrast, allowing a longer brightness range to be represented without dodging or burning, at the expense of compressing the mid-tones.

    Fifth, compensating and HD developers are completely different creatures, assuming you mean 'high definition' by HD. HD or acutance developers emphasize microcontrast at light/dark borders, at the expense of some sharpness.

    Sixth, shadow detail depends on exposure, and differentiation of shadow detail to some extent on flare. Flare is a function of the lens and camera body -- the latter is often forgotten.

    Seventh, I should be much obliged if you could expand upon your statement about chemical and physical changes as I could not quite understand it.

    Cheers,

    Roger
    Dear Roger:
    I use High Definition in the way it is used nowadays: high MTF values over the relevant range of spatial frequencies. In the 1960 ties high defintion has been used for high acutance. This gives sometimes confusion. As a matter of fact, you will see the term high definition in many areas (TV and audio, although the term high fedelity is still common)

    The flare is an example ehere a reduction of the MTF will show up.

    High defintion developers are compensating. A compensating developer is not necessarily High Definition.

    Jed

  9. #19

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    Quote Originally Posted by Jed Freudenthal View Post
    Dear Roger:
    I use High Definition in the way it is used nowadays: high MTF values over the relevant range of spatial frequencies. In the 1960 ties high defintion has been used for high acutance. This gives sometimes confusion. As a matter of fact, you will see the term high definition in many areas (TV and audio, although the term high fedelity is still common)

    The flare is an example ehere a reduction of the MTF will show up.

    High defintion developers are compensating. A compensating developer is not necessarily High Definition.

    Jed
    Dear Jed,

    Fair enough, though I'd suggest that as applied to developers, 'acutance' and 'high definition' are still all but synonymous.

    I am not convinced that high definition developers (in any sense of 'high definition') are necessarily compensating, but perhaps you would care to say more about your definition of 'compensating'. Or perhaps you would be kind enough to refer me to the relevant passages in one of the authorities such as Haist or Glafkides.

    To me, 'compensating' means 'with reduced developer activity (and therefore film density) in the highlights, normally achieved via dilution and reduced agitation'. Or as Mike Gristwood so graphically put it, "It pushes over the top of the D/log E curve." An acutance developer relies on edge exhaustion, again achieved via dilution and reduced agitation, so I can see the parallel between them, but, for example, some of Geoffrey Crawley's formulations are famed for their acutance at 1+9 but he suggests using them at lower dilutions (1+14 or even 1+19, from memory) for a compensating effect.

    Then again, the more I think about it, the harder I find it to understand your definition of 'high definition'.

    What are 'the relevant spatial frequencies'? High MTF at low frequencies creates 'sparkle', as research by both Ilford and Zeiss confirms: Ilford quantifies it in lp/mm, Zeiss in frequencies across the image area.

    At high frequencies, any developer still offers the age-old trade-off between resolution, sharpness and grain. What is your definition of 'High Definition' if not 'a pretty good balance between resolution, acutance and grain'?

    From the way you use all these terms, it sounds as if you know more about the subject than I, but I have not hitherto been so confused by things I was reasonably confident I understood.

    Cheers,

    R.

  10. #20

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    Quote Originally Posted by Roger Hicks View Post
    Dear Jed,

    Fair enough, though I'd suggest that as applied to developers, 'acutance' and 'high definition' are still all but synonymous.

    I am not convinced that high definition developers (in any sense of 'high definition') are necessarily compensating, but perhaps you would care to say more about your definition of 'compensating'. Or perhaps you would be kind enough to refer me to the relevant passages in one of the authorities such as Haist or Glafkides.

    To me, 'compensating' means 'with reduced developer activity (and therefore film density) in the highlights, normally achieved via dilution and reduced agitation'. Or as Mike Gristwood so graphically put it, "It pushes over the top of the D/log E curve." An acutance developer relies on edge exhaustion, again achieved via dilution and reduced agitation, so I can see the parallel between them, but, for example, some of Geoffrey Crawley's formulations are famed for their acutance at 1+9 but he suggests using them at lower dilutions (1+14 or even 1+19, from memory) for a compensating effect.

    Then again, the more I think about it, the harder I find it to understand your definition of 'high definition'.

    What are 'the relevant spatial frequencies'? High MTF at low frequencies creates 'sparkle', as research by both Ilford and Zeiss confirms: Ilford quantifies it in lp/mm, Zeiss in frequencies across the image area.

    At high frequencies, any developer still offers the age-old trade-off between resolution, sharpness and grain. What is your definition of 'High Definition' if not 'a pretty good balance between resolution, acutance and grain'?

    From the way you use all these terms, it sounds as if you know more about the subject than I, but I have not hitherto been so confused by things I was reasonably confident I understood.

    Cheers,

    R.

    High definition, as it is defined nowadays, (not just in photography) has an MTF close to 100% over the entire range of relevant spatial frequencies. In practice, the MTF will fall off somewhat at higher spatial frequencies. A developer for scientific applications should always be high defintion ( image distortion as small as possible). For developer/film combinations see publications of Kodak, Agfa/Gevaert and FOMA . Ilford never published their measurements.
    In the case of high acutance, the MTF is higher than 100%, in particular at the lower spatial frequencies. It is often obtained, using adjacency effects in the development process.
    High Definition and high acutance are two different things in the current terminology. Although, sometimes, high defintion has been used for high acutance, 40 years ago. Grant Haist is using that in his book. This terminology leads to some confusion.
    Anyway, I follow the current use of the word. Resolution and sharpness are not in the current vocabulary anymore. Resolution has been replaced by MTF, and sharpness disappeared all together. The MTF description replaced all that.
    I have a Kodak publication of 1976, and at that time already, the developer/film characteristic is given through the MTF representation.

    We often talk about 'compensating developers'. I rather would talk about a developer with a compensating effect, as has been done in the 1930's ( by Hans Windisch). This means an extension of the contrast range in both directions (highlights and shadows). In the past, the extension in the direction of the highlights was very clear. Nowadays with some modern lenses, with good MTF characteristics, the extension into the shadows is very important. This is not just theory. I made photographs to prove this.


    Jed

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