Ilford Contrast Filters

Discussion in 'Darkroom Equipment' started by panchromatic, Mar 17, 2005.

  1. panchromatic

    panchromatic Member

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    I know this is a novice question here but I would like to ask it anyway...

    If you print an image without any filter at all you have a certain time to create a proper exposure, if you desire more contrast then you can throw say a #3 filter to make it more punchy, but since you filter some light you have to change your exposure to again make a proper exposure. I remember in High School the teacher had a chart that had your exposure (in seconds) and then what your new exposure would be if you used any give filter. I was wondering if anyone had such a chart they would be willing to share with me. Also ilford say thats from 00-3 1/2 that you use 1X the exposure and from 4 and up use 2X the exposure but that seems to yield imperfect results.

    any help or comments would be appreciated.
     
  2. Jeremy

    Jeremy Member

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    With Ilford's filters they are assuming you are always filtering the light. Let's say you standardize on using their grade 2.5--you can change between any of their filters 0-3.5 and not have to change your exposure when changing the grade. Once you hit grade 4+ you have to double the exposure. This is of course what they say, but I once had a filter set where grade 3 was 2x grade 2 and it double again from 3 to 4 and again from 4 to 5. It was weird.
     
  3. Max Power

    Max Power Member

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    Ryan,
    I understand where you're coming from...I believe that there is a Kodak polycontrast exposure meter that does this...It's a dial made out of cardboard.

    Last year I bought a Paterson CdS exposure meter for about $5 on eBay. It doesn't work with filters, so what I do is use it unfiltered and then adjust to take the filter into consideration. It's usually about double the time from unfiltered to filtered. Of course, I would imagine that this would vary from one enlarger to another.

    I hope that this helps,

    Kent
     
    Last edited by a moderator: Mar 18, 2005
  4. ann

    ann Subscriber

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    Some where on all manufactor's directions there seems to appear the message , "must test for personal results" and they "ain't " kidding.

    When using filters the literature indicates that the time remains the same until you reach grade 4. This may or maynot be true for you.

    In our lab for we rarely double the time at grade 4, usually adding about 50 % or 60% of the suggested recommend times, why ; who knows, but under our conditions and environment that is what works for us.

    Try making a print with out a filter, which for most papers, means the grade will default to grade 2, then make a print with a grade 2 filter. DOn't be surprised if they don't look the same.

    MC papers are also created to be used with filters, so it is best to print using them as you will get better results.

    I would like to encourage you to become consistence in your negative making , so they print on basically the same grade of paper. Creating the proper contrast IMHO is better served with the negative rather than switching paper grades.
     
  5. Bob Carnie

    Bob Carnie Subscriber

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    Ryan
    A really simple test for you to do that will answer this queston is to make a grade 2 print, try to keep the printing time at 10 seconds at any given fstop.

    Then make 4 other test prints with the different filters, you will find that you have to change your time to balance the prints do not change the apeture. record these time differences for each filter. if you based your test print at 10 and a 4 filter is 25 seconds then you know that a good starting point in the future when changing from a 2 to a 4 filter is 2.5X

    I hope this makes sense and is of some help to you
     
  6. panchromatic

    panchromatic Member

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    so your saying make a print with each filter and adjust time each print to make the prints look the same? then from there you should be able to figure out the percentage difference? Am I understanding you correctly?
     
  7. GeorgesGiralt

    GeorgesGiralt Member

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    Hi !
    This behavior is quite normal.
    If you look at the paper's datasheet, and look for the Iso paper speed, the figure will be consistent from grade to grade, and halve at the extremes. But, how do you measure your exposure ? At what particular grey tone ? This speed is constant at only one grey, say, from memory .6 above B+F. If you look at the curves, it will became obvious that you will have to twist the exposure a bit around the double value for your particular shade of grey which is important for your print. This has to be like that because "there are far less shades of grey availlable at grade 5 than at grade 3" between ful white and full black... This last sentence is technically wrong but will show you what you're going to get.
    If you buy an RH Designs Analyser pro, it will automagicallly compensate for this and you will be able to get the grey YOU want at any grade YOU like. But it will need to be calibrated to incorporate all YOUR personal variables (enlarger, bulb, filters, paper, print treatment ....)
    Have a nice day !
     
  8. Bob Carnie

    Bob Carnie Subscriber

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    Hi Ryan

    yes that is what I am saying, just try to make the initial grade 2 print at 10 seconds, the math becomes pretty easy .
    You will find that 0 may become 8 seconds
    1 may become 9 seconds
    3 may become 13 seconds
    4 may become 25 seconds
    5 may become 30 seconds
    good luck , do not change the apeture and do these prints in ones session, does not matter what paper you use as you are just trying to find filter/time relationships