Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 71,949   Posts: 1,585,940   Online: 997
      
Page 4 of 4 FirstFirst 1234
Results 31 to 32 of 32
  1. #31
    Rudeofus's Avatar
    Join Date
    Aug 2009
    Shooter
    Medium Format
    Posts
    1,833
    Images
    10
    Quote Originally Posted by dpgoldenberg View Post
    Here is another function that does include a shoulder:

    f(x) = a1*log(1+exp(a2*x+a3))/(a4+log(1+exp(a2*x+a3)))
    David, your curve implies that the shoulder is as abrupt as the toe, which is generally not the case. It also requires that you catch the complete shoulder region with your measurement data points or you risk numerical instability in your curve fit.

    For these reasons I strongly advise against this model and recommend you take another look at my square model.
    Trying to be the best of whatever I am, even if what I am is no good.

  2. #32
    Rafal Lukawiecki's Avatar
    Join Date
    Feb 2006
    Location
    Co. Wicklow, Ireland
    Shooter
    Multi Format
    Posts
    737

    CI Calculator Now Plots Dev/CI Chart and New Delta 100 DDX Charts

    Following Bill's suggestion, I have added a Development Time/CI plot. It highlights, with horizontal lines, the CIs I would presently associate with different N-times. If your CI-N relationship is different, and if you use my R code, you can just pass those as a parameter, it is explained in the comments in the file.
    Click image for larger version. 

Name:	Delta 100 4x5 DDX 1+4 Dev Time-CI-N.png 
Views:	21 
Size:	62.0 KB 
ID:	73791
    As for real darkroom stuff, I have just run another test, at 4 min in DDX 1+4, to get the lowest contrast curve, which I was missing earlier. This is what my Delta 100 seems to be doing, I wonder how different it may be from others on the forum (I've only seen Michael 1974's plots):
    Click image for larger version. 

Name:	Delta 100 4x5 DDX 1+4 4-24 min.png 
Views:	18 
Size:	88.1 KB 
ID:	73792
    Attached Files
    Rafal Lukawiecki
    See rafal.net | Read rafal.net/articles

Page 4 of 4 FirstFirst 1234


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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