Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,700   Posts: 1,549,004   Online: 1167
      
Page 20 of 23 FirstFirst ... 1014151617181920212223 LastLast
Results 191 to 200 of 228
  1. #191
    markbarendt's Avatar
    Join Date
    May 2008
    Location
    Ignacio, CO, USA
    Shooter
    Multi Format
    Posts
    5,757
    Blog Entries
    3
    Images
    19
    Quote Originally Posted by AndreasT View Post
    You guys are running away leaving me behind.
    You are not alone.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  2. #192
    markbarendt's Avatar
    Join Date
    May 2008
    Location
    Ignacio, CO, USA
    Shooter
    Multi Format
    Posts
    5,757
    Blog Entries
    3
    Images
    19
    Quote Originally Posted by CPorter View Post
    I like to equate it to pre-exposure to film,
    And that is what I was trying to equate it to. Trying to use a concept that I think or at least thought I understood to understand the affect of veiling flare. By saying generalized, which is probably a bad choice of word, I meant to say flare affects the film all over or at least in areas where it is not intended to affect, much like pre-exposure does.

    Pre-exposure, as I understand the concept, allows us to bring more shadow detail up into our printable range without increasing or affecting the rest of our image significantly, the higher values remain essentially pegged, they don't slide up the curve significantly. Pre-exposure allows us to minimize the image exposure to protect highlight separation. The only way I know to get a wider SBR to print straight onto a given grade of paper is by reducing the film's CI somewhere. Pre-exposure as I understand it, reduces the contrast in the shadows/flattens the toe to do this. This is what Dunn & Wakefield and Adams seem to be saying.

    Is that understanding of pre-exposure true or false?
    Last edited by markbarendt; 01-29-2013 at 06:43 AM. Click to view previous post history.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  3. #193
    Stephen Benskin's Avatar
    Join Date
    Jan 2005
    Location
    Los Angeles
    Shooter
    4x5 Format
    Posts
    1,218
    Mark, you've got it. Pre-exposure is essentially the same as flare, effective film speed is increased and overall contrast reduced.

  4. #194
    CPorter's Avatar
    Join Date
    Feb 2004
    Location
    West KY
    Shooter
    4x5 Format
    Posts
    1,662
    Images
    24
    That's it Mark, what Stephen said.

  5. #195

    Join Date
    Feb 2010
    Location
    Montreal, Canada
    Shooter
    Multi Format
    Posts
    4,775
    That's not the point I'm challenging though. I'm saying that reducing exposure under these conditions is detrimental.

    I think Stephen agreed with me earlier so I'l try to present this argument against reduced exposure again. I might be wrong but I don't think so. CPorter has said he's interested in practicality. I'm simply challenging the logic of something he's occasionally doing in practice under high subject flare conditions.

    Given a film, zero flare and fixed processing procedures, a characteristic curve is generated for the film. That is the curve under those conditions. It is independent of the exposure we decide to give. If we have a subject under these hypothetical conditions (say a grey scale), more exposure moves the subject up the curve. Less exposure moves the subject down the curve. But the curve does not change.

    Repeat this under a high flare scenario. The effect of subject flare is reduced contrast. The lowest negative densities are affected most. All other things being equal, compared with the zero flare curve, non-image forming light (ie flare) causes both an increase in density, and reduced contrast for exposure values below around Zone V. That is now the characteristic curve we have to work with. It is independent of the exposure we decide to give the film. As in the no-flare scenario, giving more exposure moves the subject (suppose it is the grey scale again) up the curve. Less exposure moves it down the curve. The shape of the curve doesn't change. So, if we reduce exposure, all we are doing is moving more of the subject into the lower part of the curve - where contrast is lower. It's not helping anything. It's just reducing local contrast for more of the subject values.

    I'm simplifying here, but perhaps the key point that's being lost is that the flare light that "lifts" the shadow values is non-image forming light.

    So I'll ask again - what is the purpose of giving less exposure? You might have a shorter print exposure time, but reduced local contrast in the shadow values in the negative - not a good thing from a Zone System perspective.

    So I actually disagree with the notion effective speed is increased by flare effects. Perhaps the speed "point" is increased, but local contrast in the shadows is decreased. If speed is a means to an end (ie sufficient local contrast in the shadows), we've lost more than we've gained, and this is compounded by reducing exposure.

    Andreas - you are not alone. I'm getting a little better at this (slowly) but I still often get lost in the various charts, diagrams etc. Stephen and Bill are much better at this than I am. I need to take a few days and slowly go through Stephen's stuff (not just this thread but several others).
    Last edited by Michael R 1974; 01-29-2013 at 07:40 AM. Click to view previous post history.

  6. #196
    AndreasT's Avatar
    Join Date
    Sep 2006
    Location
    Berlin
    Shooter
    Multi Format
    Posts
    355
    If flare / pre-exposure raises density more on the low density areas, then surely the density leat of the speed point would be raised more than the speed point resulting in less speed. No, Yes??

  7. #197
    Stephen Benskin's Avatar
    Join Date
    Jan 2005
    Location
    Los Angeles
    Shooter
    4x5 Format
    Posts
    1,218
    Quote Originally Posted by AndreasT View Post
    If flare / pre-exposure raises density more on the low density areas, then surely the density leat of the speed point would be raised more than the speed point resulting in less speed. No, Yes??
    No. Increased exposure in the shadow increases the shadow density and the speed point is reached with less exposure. This equals more speed.
    Last edited by Stephen Benskin; 01-29-2013 at 01:05 PM. Click to view previous post history.

  8. #198
    markbarendt's Avatar
    Join Date
    May 2008
    Location
    Ignacio, CO, USA
    Shooter
    Multi Format
    Posts
    5,757
    Blog Entries
    3
    Images
    19
    Michael, I don't think it is actually less exposure in the shadows, especially with pre-exposure. It's pre-exposure + main exposure = normal shadow point. At the high end though total exposure can be lower.

    With flare there is only one exposure so I'm not sure how that gets any extra.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  9. #199
    Stephen Benskin's Avatar
    Join Date
    Jan 2005
    Location
    Los Angeles
    Shooter
    4x5 Format
    Posts
    1,218
    Quote Originally Posted by Michael R 1974 View Post
    So I'll ask again - what is the purpose of giving less exposure? You might have a shorter print exposure time, but reduced local contrast in the shadow values in the negative - not a good thing from a Zone System perspective.
    Why not just print through any density created by excessive flare.

    So I actually disagree with the notion effective speed is increased by flare effects. Perhaps the speed "point" is increased, but local contrast in the shadows is decreased. If speed is a means to an end (ie sufficient local contrast in the shadows), we've lost more than we've gained, and this is compounded by reducing exposure.
    There's flare and there's excessive flare. All optical systems have flare. We just don't notice it unless it's excessive. Normal shooting conditions have normal flare and flare is part of normal film processing and part of film speed.

    Fun fact about flare and shadow compression. Ever wonder why Tri-X professional, with it's long toe, is considered a "studio" film? There's less flare with interiors and the ability to control lighting. In theory, regular Tri-X shot in daylight would have similar tonal distribution in the toe as Tri-X Pro shot in the studio.

  10. #200

    Join Date
    Feb 2010
    Location
    Montreal, Canada
    Shooter
    Multi Format
    Posts
    4,775
    Quote Originally Posted by markbarendt View Post
    Michael, I don't think it is actually less exposure in the shadows, especially with pre-exposure. It's pre-exposure + main exposure = normal shadow point. At the high end though total exposure can be lower.

    With flare there is only one exposure so I'm not sure how that gets any extra.
    CPorter indicated under these conditions he might give up to 2/3 stop less exposure (I assume this to mean 2/3 stop less exposure than he would otherwise give based on his meter readings and planned development). Pre-exposure + (normal main exposure less 2/3 stop). I'm saying if anything this will result in reduced local contrast through more of the subject range vs Pre-exposure + normal main exposure).

    I think we're all sort of on the same page regarding flare as pre-exposure. I'm just challenging the notion giving less exposure than one normally would, improves anything. If anything it puts more of the subject into the part of the curve that is compressed.

    I guess we'll just agree to disagree on this. I don't want to start pissing people off. The more people who participate in these threads the better.



 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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