Testing for Relative ISO Range Numbers

Chuck_P

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I completed a test today for the relative ISO RN's for Oriental Seagull VC II FB paper. I find "my" results to be interesting. Parameters are:

-LPL 4550 XLG enlarger (quartz halogen light source)
-Stouffer 21 step calibrated step wedge, projected
-exposure 10 sec at f/8
-Dektol 1:3, 3 min development
-TF4 fixer
-selenium toned 1:10, 4 minutes

The test carried out precisely as described in Anchell's Variable Contrast Printing Manual for testing the relative ISO Range Number for each filtration setting. The main purpose of the test, of course, is to see what contrast grade is actually produced given any filtration setting I use with my LPL light source, developer, and toner regimen. And, also, to help conserve paper----because adjacent filtration settings may not produce enough difference in RN to actually increase the contrast as desired. No need to change to a filtration setting of 3 if the RN produced from a 3 does not differ than that from a 2, for example. That, IMO, is the real value in the results.

My results are, and I tested whole grade settings from 00 - 5, which is the filtration channel that is calibrated for Ilford papers on my LPL. RN, Exp Scale Value (ESV), and contrast grade are determined from the chart in Anchell's book, see the attachment.

-No filtration used (white light): RN = 155, Exp Scale Value = 1.55 for a contrast grade of "0"

-"00" filtration setting: RN = 200, ESV = 2.0 for a contrast grade "0", actually Contrast Equivalent Chart does not go above a RN of 170 (the highest RN with a contrast grade "0" on the chart in Anchell's book).

- "0" filtration setting: RN = 170, ESV = 1.7 for a contrast grade of "0"

- "1" filtration setting: RN = 155, ESV = 1.55, same as using no filter, contrast grade of "0"

- "2" filtration setting: RN = 155, same as using no filter, contrast grade of "0"

- "3" filtration setting: RN = 125, ESV = 1.25, for a contrast grade of 1 1/2

- "4" filtration setting: RN = 110, ESV = 1.1 for a contrast grade of 2

- "5" filtration setting: RN = 95, ESV = 0.95; this falls right on the dividing line between contrast grade 2 and 3.

Seems that at a #4 setting, which most of would think of as getting up there in contrast, actually tests as ISO R110, equivalent to a grade 2 paper. In fact, Anchell specifically calls attention this being a distinct possibility with some combinations of paper/light source/dev/toner. And switching from a #4 setting to a #5 will not provide a full grade increase in contrast. It appears that I should not expect to print one of my negatives beyond a contrast paper grade of 3 with dektol and Oriental Seagull VCII FB paper.

I thought these were interesting results and wanted to share.

Chuck
 

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ic-racer

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What??

When you plotted your independent value (the input density) I hope you used an on-easel meter to get your input values. If you didn't then you can't use the indicated values on the step wedge if you are projecting it to determine ISO(R).

You need to contact the step wedge if you want to easily determine ISO(R) of the paper. Otherwise your results are-what-they-are, (they might be close, but we don't know).
 
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Chuck_P

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If I understand your statement, I presume that is why there is a range of "range numbers" within each contrast grade as seen on the chart. After reading the test for the #4 setting on the LPL, I determine the Dmax step and the Dmin step on the paper. While not counting them, I then count the number of steps between them that show tone from just above Dmax to just below Dmin. For the #4 setting there were 8 definable steps of tone. By the test method then, that would be an ISO Range Number of 110. That's the method, but perhaps you don't agree with the method, IDK.
 

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ic-racer

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That is fine methodology but the distance between the steps will not be exactly 0.5 stops if you project it (lens flare etc). You see what I mean? Try contact printing at max (#5) and see what you get.

If you compare your projected and contacted results you have just done a very accurate 'lens flare and scattered fog' test. You can see how much contrast you lose when projecting and how good the coating is on your enlarging lens, or if you need to paint the walls behind your enlarger black etc.
 

Stephen Benskin

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ic-racer said:
You need to contact the step wedge if you want to easily determine ISO(R) of the paper. Otherwise your results are-what-they-are, (they might be close, but we don't know).
Click to expand...

For the ISOR yes, but since an individual's printing conditions tend to remain consistent, it's just as legitimate to determine the paper's LER with projection printing. That way you are hopefully incorporating average flare conditions into the test. Otherwise, flare would have to be independently factored in. Basically, I think this is mostly a question of semantics.

Chuck,
From my understanding different manufacturer's multigrade papers have different spectral sensitivities. That's why they all have their own filter sets. I suspect a smaller LER is possible with the Seagull with the proper filtration.
 
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Chuck_P

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ic-racer said:
That is fine methodology but the distance between the steps will not be exactly 0.5 stops if you project it (lens flare etc). You see what I mean? Try contact printing at max (#5) and see what you get.
Click to expand...

Yes, I understand that and what you mean. However, I performed the test with Anchell's suggestion that it be done by projection if that is how one normally prints---I don't contact print.
 

ic-racer

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If you get the exact same results with the contact print, then you have a very good flare-free system, but still have something else sucking your maximum contrast.

Also, when printing the wedge up in the enlarger, are you masking off all the stray lightf? You can test with it masked and unmasked. You will be surprised at how much all that stray light causes flare even with the best multicoated German lenses.

I spent some time making a bunch of tight-fitting format masks for glass carriers based on tests like you did (well the projected part compared to the contact part)

I'll bet you a beer that you are printing the step wedge un-masked and getting a good deal of lens flare confounding your results.

If I lost the bet, then the next thing to try would be to print through both the #5 setting on the enlarger and an Ilford #5 filter together. If no change there then your enlarger is fine and, then its going to get harder to track down. Maybe a bad box of paper or poor developer or bad safelight etc. Even a bad step wedge.
 
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Chuck_P

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Stephen Benskin said:
Chuck,
From my understanding different manufacturer's multigrade papers have different spectral sensitivities. That's why they all have their own filter sets. I suspect a smaller LER is possible with the Seagull with the proper filtration.
Click to expand...

My LPL has two filtration channels---I'm thinking about doing it with channel 2,which is calibrated for Kodak paper (I realize Kodak doesn't do paper anymore, but they were when this model was made I guess). Perhaps that channel would provide more consistent results.
 
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Chuck_P

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I don't know that it is necessarily a problem if the ISO Range and spacing between each filtration setting is not constant---my reading so far does not at all indicate that it should be, in fact, it may very well not be given the light source/filtration setting/developer/toner system. This is a big reason for doing the test. It's all interesting.
 

ic-racer

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I'd be interested if you do have a flare issue in the test, but either way, you are really exploring your system to the max. Thanks for sharing.
 

Stephen Benskin

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Attached is the data from two series of paper tests. I was helping a photograph evaluate their set-up. Their darkroom had two different enlargers with two different types of colorheads. So the results in the attachment are from the two different enlargers with everything else remaining the same - the same darkroom (safelight, ambient light, etc), the same chemicals (temp, time, washing, drying).

The difference in the LERs for the grade setting can only be attributable to the colorhead.
 

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ic-racer

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The table is a little jumbled but one enlarger goes to 0.64 max contrast and the other goes to 0.45 max contrast right? The filters were swinging in all the way OK and all that, right?
 
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Stephen Benskin

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ic-racer said:
The table is a little jumbled but one goes from 190 to 70 and the other from 190 to 60, right?
Click to expand...

I believe I entered the grade 0 out of order. Looks like there are two zeros in the ISOR column too. Wow, old program, sorry. The important column is the LER column. Just line it up with the grade column.
 
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ic-racer

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I have been playing around with using a color meter's M and Y channels to correlate my step wedge tests at max magenta and yellow. Its a little non-intuitive because you need to compare the enlarger's filter to its own white light (so you can't detect any difference in two enlarger's white light color) but I got it down so I think I can estimate an unknown enlargers performance at maximum magenta or maximum yellow with just the meter (why?? well just to see if I could do it ).
 
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Chuck_P

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ic-racer said:
I'd be interested if you do have a flare issue in the test, but either way, you are really exploring your system to the max. Thanks for sharing.
Click to expand...

You're right, I'm not masking. Anchell's test method did not discuss it but perhaps the flare is being accounted for as mentioned by Mr. Benskin---I tend to think it is but I don't really know for sure. The lens I'm using is a 150mm Schnieder Compnon-S. I do know that the whole purpose of the test is to determine if the contrast range and spacing between contrast settings is accurate on the paper given the totality of the system used to produce it. I have calibrated step tablet that I checked for accuracy with my densitometer--it checks out ok.
 
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Stephen Benskin

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Don't over mask either. You want a certain amount of extraneous light to reflect a normal negative's influence in the enlarging process.
 

Ken Nadvornick

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FWIW, I performed the same series of tests from the Anchell text to determine custom settings using my Aristo VCL4500 light source.

My results* for both FB and RC Ilford MGIV were eerily on the mark. I was easily able to achieve the midpoints of each ISO contrast range from grades 0 through grade 5. (A grade 6 was not reachable for me.)

Then, using the exact same setup during the same darkroom session, I opened a box of Oriental Seagull VC FB and performed a boundaries test. Meaning I first tested at the lowest and highest contrast settings available from the light source.

The lowest setting produced a RN175 for an extra-soft grade 0. But the highest setting (which gave a grade 5 with both MGIV FB/RC) produced a RN115 for only a grade 1.5.

I promptly closed the box of Oriental paper and have not opened it since.

My safelight for all testing consisted of 6-635nm red LEDs bounced off a white ceiling. The DIY safelight fixture is fortified with a covering of Rubylith, since earlier tests showed minor residual blue and green light still being generated. After adding the Rubylith, both Ilford papers had earlier tested perfectly safe out to at least 60 minutes in prefogged tests.

I had not specifically performed a safelight fog test on the Oriental paper, so there is always the chance that its reduced contrast range was somehow related to safelight fogging. But if this is true with red light, the point is moot.

Ken

* Contact prints, Stouffer 31-step calibrated, Ansco 130 (1+1) at 68F/20C, 4 minutes dev time, Schneider 150mm f/5.6 Componon-S lens, red safelight.
 

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I have found the new Oriental VC FBII to be easy to fog with 0C safelights. It gave me fits one time during the printing of a series earlier this year, with fresh paper right off the shelf at Freestyle. I used to use it with 0C all the time with no issues, but had not used it in a few years when I tried this new batch. I only use it with red safelights now, and the problems have gone away. I do still find that it can be hard to get extreme contrast on grade 4 and 5 (using Ilford MG filters in my B-22's filter drawer). I use Ilford PQ or MG developers, and add some 10% carbonate solution if needed to raise contrast.

Not to go too much off topic, but can someone explain what "RN" means, and how the numbers relate to contrast?
 
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Chuck_P

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This is an interesting finding that you have with the Oriental paper-----I'm going to perform a safelight test this evening when I get home from work. I am under the impression that my distance from my light is such that fogging could not be an issue as my work with MGIV FB absolutely has no fogging issues with my safelight. But, perhaps it's an assumption that I should not be making with the Oriental paper.
 
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Mike Wilde

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The Oriental I have rough calibrated as others discuss in this tread does almost all of it's contrast adjustment in the yellow ranges, with the hardest contrast found with about 20CC of magenta. It was old paper, but a second old box from an independent source acted the same way.
 

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Chuck_P

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2F/2F said:
Not to go too much off topic, but can someone explain what "RN" means, and how the numbers relate to contrast?
Click to expand...

Since I generated the post, I'll answer it the best I can.

If doing paper sensitometry, graphing the paper curve and such, the Range Number is found by measuring the width of the paper's Exposure Scale Value (ESV or I believe otherwise stated by Mr. Benskin as the LER for Log Exposure Range, although I have not seen that acronym before, I believe that is what that is, seems to make sense).

The width is measured by subtracting the Log Exposure Minimum (Emin) for reaching the highlight density limit from the Log Exposure Maximum (Emax) for reaching the shadow density limit. Those limits, according to Anchell, are set by the ISO at 90% of Dmax for Emax and .04 over the Dmin for the Emin of the paper.

The difference multiplied by 100 equals the paper's ISO Range Number. That ISO Range Number correlates to an equivalent contrast paper grade. For example, for a manufacturer to sell a paper as a grade 2, then it must have a RN between R95 and R115. Divide that R# by 100 and you will have the width of the paper's ESV on the log exposure scale of the paper curve.

A different RN can be associated (with your printing system i.e., paper, light source, filter, developer, toner) with each contrast filter or filtration setting in your arsenal. The RN is then bounced against a Contrast Equivalent Chart established by the ISO, according to Anchell. That's how it is related to paper contrast grade as I understand it. I included a graph from the book I'm using as an illustration; sorry for the blurry scan.

Why do I feel this is important? Because I use the ZS as my method of film and development testing and I test very strictly with it (whether one agrees with that method or not, I don't find it relevant). I want to know with the paper I'm using in my printing "system" what contrast filtration available to me provides a standard grade 2 paper contrast. Just because you have a #2 contrast filter does not mean you are getting a paper contrast grade of 2, although it could if found by testing your printing "system".

I discovered that it is not a filtration setting of 2, but rather a setting of 4 that provides a paper contrast grade of 2 (R95 to R115) with the Oriental paper I tested. The filtration setting of 4 produced an ISO RN of R110.

Now, I don't know if there are multiple ways to determine the RN and quite frankly, I don't really care as I don't have time or materials to carry on a battery of tests. I understand this fully and don't have any inclination to test a multitude of different ways to determine it or to see that another method is better or more right. I find this test method to be very easy to carry out and understand.
 

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Ken Nadvornick

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Here's a quick table relating log exposure range (LER) values to range number (RN) values to standardized paper contrast grades. This is the same information provided by the attachment scan in CPorter's first post, just more precisely broken down.




The listed RNs are the exact midpoints of defined ranges. If your filtration matched these values, your contrast grades would be perfect. In practice, just getting reasonably close is fine. Because my VCL4500 allows for infinitely variable filtration I was able to hit these values pretty closely - at least up to grade 5.

Ken
 
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