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#41
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Try to think as if contrast filtration doesn't exist and you may get my point.
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#42
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I think the point is that it is a combination of BOTH negative contrast and filtration which results in overall print contrast.
That means you can use a soft neg with hard filtration OR hard neg with soft filtration and the result can be the same overall contrast. And this is totally irrespective of which type of enlarger you are using. However, whilst the overall contrast can be the same there is a difference and that is the shape of the curve, particularly at the toe and shoulder and generally it is desirable (IMO) to keep the toe and shoulder as short as possible because that provides better separation in the shadows and the highlights. And that is usually obtained by a negative with a short toe and as hard a paper grade as you can get away with. And the negative overall contrast needs to fit the paper exactly. So there is an argument for using grade 3 as standard but it certainly isn't one that I adhere to although I often end up at grade 3 having started at 2. |
#43
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Quote:
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Your response is to a follow-up post that I made in response to questions from the OP relating to my earlier post outlining a testing procedure for roll film users. Sure you can calibrate your negatives to Multigrade paper with no filters (or to fixed grade papers for that matter) BUT this is only practical when you:
By using the tests that I outlined, you fix your Exposure Index (or put another way the ISO rating for the film when using your equipment, your way of metering, your developer of choice and your chosen printing time), placement of dark shadows in which you wish to retain detail, placement of highlights in which you wish to retain detail and the minimum exposure for the print to ensure a full black in the print. This fixes a great number of variables and ensures that you have consistent negatives. The reason for suggesting these tests be done at #3 are:
Bests, David. www.dsallen.de
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David, d.s.allen, fotograf dsallenberlin@gmail.com http://dsallen.carpentier-galerie.de |
#44
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BTW, is there a standard for grades?
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#45
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Hi Miha
I researched this last year and found that ISO 6846:1992 is the only current standard referring to paper contrast. It does not mention the contrast grades 00...5 that we are familiar with. The Standard text states: "Each manufacturer has established a unique system for grading of papers and designations which makes it extremely difficult for users to identify products which are comparable for printing characteristics. The ISO range number is introduced to reduce this source of confusion." It defines paper contrast as ISO Range in the form, for example, "ISO R140". I found the following table of range/grade equivalents for Multigrade IV RC paper and Multigrade filters on the Ilford/Harman website: http://www.ilfordphoto.com/Webfiles/...1231142522.pdf page 2 Filter 00 R180; 0 R160;1 R130; 2 110; 3 R90; 4 R60; 5 R40 |
#46
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#47
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Joe is correct but to expand on this see attached chart.
This is made by printing a transmission step wedge onto paper and then measuring reflection densities of the paper for each step of the transmission wedge (0.1 LogD transmission steps in my case). The standard for ISO(R) states that the paper density is measured from between 0.04 LogD and 90% of max logD for this test and paper. The two horizontal red lines are those two containing limits. So the ISO(R) is calculated only on the data between those upper and lower limits. The ISO(R) is the transmission range (the R in ISO(R)) between those two limits as read off the bottom axis in logD and multiplied by 100 (just to provide an integer value instead of demical places values) So taking grade 2 filter, the red curve, the lower point where it crossses red line reads off 0.63 and the upper point it crosses red line reads off 1.72. The range difference between two points on bottom axis is therefore 1.09 and that multiplied 100 is 109 so the ISO(R) I got for my test is 109. So when you see the little chart that Joe pointed you to saying that grade 2 is ISO(R) 110 it means that the negative density range required to produce G2 with G2 filter is 1.1 LogD Remember of course that you will need a bit more density range to hit pure white and pure black in the print. And from my tests I have determined that the optimum density range target of any negative is 1.3LogD or thereabouts which will result in very easily printable negative on G2 (or no filtration) on MGIV paper. |
#48
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Thanks. But for a negative with an effective density range of 1,32 log a grade 1 is needed, says Ilford. Go figure. I have the reference negative made by Ilford (FP4 in ID11), it should print nicely on unfiltered MGIV. I'll make a test during the weekend.
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#49
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If you look at my chart the range between upper and lower for G1 is on or about 130. Last edited by Argentum; 11th September 2014 at 01:33 PM. |
#50
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As a bit of a generalisation you can add 20 (0.2 LogD) to the ISO(R) value of any grade to find what your overall negative density range should be for any specific grade. So for a grade 1 then you get 150 which is 1.50 LogD.
All these numbers are pretty useless in real world photography from day to day. However, if you do own a densitometer and have been through the learning curve it makes testing a new film developer combination a breeze. You know what the target is and can see from a single test how close you are to it. So much so that at most you can nail it with two tests or be close enough with a single test to be able to make intuitive adjustment and go straight into using new film dev combination with a high degree of confidence that you will get it spot on first time out. |
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