Question about determining actual paper grade

[weasel]

I just started shooting a new film and developer combo, and have been doing testing to determine film speed and developing times. The method I have used for years is a pretty standard visual test, no densitometer, very similar to lots of other peoples published tests.
Here is my question, and i dont know why I have never really thought about this before, but this testing system is based on using one particular paper, and one particular contrast grade. I have always just used a number 2 filter if im using variable contrast paper. My negatives will now be tailored to that. But how do I know that that filter grade is getting the full range of what the paper can give me? Is a grade 2 really a grade two?
Should I be figuring that out before I even start, and if so, how? Or does it really matter?

 

[Craig75]

I always test filters or colourheads with a new enlarger or new materials simply because my experience was that i could not replicate the results given in datasheets that came with papers.

I just contact print a stepwedge and count the visible squares. Then i can use that to adjust general development times for negatives if enlarger is printing softer

 

[pentaxuser]

The simple but also instructive way is to print the same scene at say grades 1.5, 2.5, 3 and 3.5 on small sheets say 6x4 and examine which gives the best rendition of your negative.

Sometimes and this can depend on both the negative, scene and your own taste the best grade is not always the "conventional /standard" grade 2

pentaxuser

 

[distributed]

But how do I know that that filter grade is getting the full range of what the paper can give me?

What do you mean by the "full range of what the paper can give"? If you mean the range between white and the darkest black, then I'd say that every grade should be able to produce it. The difference is in how much exposure range the different grades require to produce the full white to black range.

If you have standardized your negative exposure and development such that said negatives print well on grade 2, your process is working. In the confines of your question, I don't think it matters what exposure range your grade 2 corresponds to if you are satisfied with your results. An important point however is that depending on the brightness range of the scene, and also depending on subject matter and stylistic preferences, a different grade than 2 might be the right choice for some of your images.

As @pentaxuser has pointed out, it might be instructive to print the same negative(s) at several different grades and see what that changes. To judge contrast in a test strip read from lightest to darkest part I go by SERC, "shadows early, reduce contrast". That is if the shadows seems right earlier, i.e. in a less exposed part of the test strip, than the highlights, you have to reduce contrast/choose a lower grade. If the highlights seems right earlier than the shadows, you have to increase constrast/choose a higher grade.

 

[koraks]

If you mean the range between white and the darkest black, then I'd say that every grade should be able to produce it.

Quite, but not quite. At the lowest grades, it may not always be possible with all papers to get the same dmax as on higher grades. I quite painfully ran into this when building a led exposure head where I found I had to mix in just a tiny bit of blue with the green of grade 0 in order to hit dmax (most testing was done with Adox MCC110).

But how do I know that that filter grade is getting the full range of what the paper can give me? Is a grade 2 really a grade two?

Those are two different questions.

1: Does the filter give the full tonal scale the paper has to offer? Actually, not a very pressing matter, but if you want to make sure, expose a test strip without any filter and observe the tonal range the paper can make. The compare with your filter of choice, and, if you so desire, start working on finding non-linearities of the response curve etc. BUt I'd say, keep an eye on what you want to achieve. It's surprisingly easy to get lost in very interesting technical matters that turn out to have relatively little practical implications for 99.9% of the printing you're likely to do.

2: Is filter #2 really grade 2? For this you'll have to compare a set of test strips you make using a known-accurate step wedge and compare the outcome against the Iso_R grade plots of the paper. Note that not all paper manufacturers list detailed information on ISO-R grade and curves in their datasheets. Note also that there is no agree-upon definition of what constitutes 'grade 2'. Ilford's 'grade 2' may be slightly different from Adox's etc. They will be fairly close, but not necessarily an exact fit. Again, ask yourself: how important is this to you? How important is it really to be able to say "my negatives are optimized for grade 2" if you realize that (1) probably only you will print your own negatives, under your own and self-determined conditions & requirements, and (2) your paper's grade 2 may not be the exact same grade 2 of someone else's paper (from their preferred brand, with their light source, in their preferred developer etc.)

Imagine you are actually optimizing your negatives for grade 1.5 or 2.5 without knowing it. What's the impact of this? At some point you may change what paper you prefer to print on, replace your old and trusty contrast filter/enlarger head, switch developers or change whatever parameter you can think of. You then find out that your negatives all of a sudden require just a little more punch (let's say half a grade) or they are just a bit too contrasty (by, let's say, half a grade) for your new printing process. So what do you do? I'd say, adjust filtration by half a grade and live happily ever after. At least, that's what I'd do and try not to lose any sleep over it.

 

[Nicholas Lindan]

You will never hit D-Max with only a green light exposure. VC paper is made from two emulsions - one sensitive to blue & green (orthochromatic) and one sensitive to only blue. With a green-light only exposure you will only get to an OD of 1.0 - each of the two emulsions contributes 1.0 OD of density and only when both are fully exposed can you get to an OD of 2.0.

If you are using the old MGIV VC papers then you might get better results standardizing on a #3 filter contrast grade as the HD curve becomes more linear as the contrast increases. This problem has been corrected in the MGV papers.

See http://www.darkroomautomation.com/support/appnotevcworkings.pdf

The contrast/HD curve of VC papers is unique to each emulsion. If you switch from one brand to another, or even from RC to fiber with the 'same' emulsion, you will have to play around with the contrast filtration to find what works on the new paper. The best contrast grade will also change with paper surface - the same print made on glossy and pearl surface papers will look different. And you have to optimize the contrast grade for the lighting the print will be displayed under.

 

[distributed]

You are right, I was oversimplifying things about being able to reach Dmax in every case.

@Nicholas Lindan:
I am surprised by the magnitude of the difference between the achievable Dmaxes in the blue only and green only cases. I have measured the response of Ilford MGRC with 11 different mixes of blue and green light as produced by two LEDs, no filtering involved. You can find the HD curves in the diagram below. The DMax is pretty low as I was unfortunately using oldish developer. The leftmost curve is blue only exposure while the rightmost curve is green only exposure. The curve for green only exposure is obviously very flat and takes 2.0 exposure to get to not quite DMax. However, it goes clearly above a density of 1.

Do you have a suspicion why using only green light density goes well beyond 1.0? Is there a sufficient amount of blue in my nominally green LED light to cause this?

 

[jeffreyg]

My approach is that there are so many variables in equipment, film, chemistry, paper, subjects, lighting, etc. I have found that using film box speed and mfg's time/temperature unless a contrast change is desired is the best way (for me) to go. i have an Aristo VC light source and print on Ilford multigrade fiber paper and adjust contrast(s) by eyeball from test prints. I doubt you can standardize technique unless you control every condition. Then there is also personal preference such as liking more contrasty prints, softer images and so forth. The work comes making platinum/palladium contact prints at least now you can make enlarged negatives with digital controls if need be.

http://www.jeffreyglasser.com/

http://www.sculptureandphotography.com/

 

[ic-racer]

Cheap and easy way is to count the number of gray bands a contact-printed 21 step wedge produces, discounting the very darkest and lightest grays. Multiply that number by 15 to get the ISO(R). Grade 2 is 100 to 110. So you are looking for about 7 bands.

 

[koraks]

so in general you should be able to get to d-max or pretty close with green light.

Yes, but there's a bit of a snag. At the exposure levels you need with pure green light to reach dmax, halation tends to become a problem, resulting in very fuzzy prints with lots of bleeding. Some papers may do better than others, but it seems to me that VC papers aren't really engineered to work well with monochromatic green light.

 

[Pieter12]

Split-grade printing. Grade doesn't matter.

 

[koraks]

Split-grade printing. Grade doesn't matter.

Recently I had a negative that required split grade printing. The first in about 2 years. All other negatives in that period did fine on a single grade.

 

[RalphLambrecht]

I just started shooting a new film and developer combo, and have been doing testing to determine film speed and developing times. The method I have used for years is a pretty standard visual test, no densitometer, very similar to lots of other peoples published tests.
Here is my question, and i dont know why I have never really thought about this before, but this testing system is based on using one particular paper, and one particular contrast grade. I have always just used a number 2 filter if im using variable contrast paper. My negatives will now be tailored to that. But how do I know that that filter grade is getting the full range of what the paper can give me? Is a grade 2 really a grade two?
Should I be figuring that out before I even start, and if so, how? Or does it really matter?

here is what I can contribute:

 

[koraks]

Many thanks for posting that Ralph! Very useful write up.

 

[Craig75]

Cheap and easy way is to count the number of gray bands a contact-printed 21 step wedge produces, discounting the very darkest and lightest grays. Multiply that number by 15 to get the ISO(R). Grade 2 is 100 to 110. So you are looking for about 7 bands.

whats the rationale behind disregarding the lightest gray?

I always just count everything between max black and paper white

 

[Craig75]

For ISO purposes the density range and log exposure range of a paper isn't from paper white to max black, but rather from a very light tone to a very dark (but not d-max) black. The idea was to standardize these things based on the useful density (log exposure) range rather than absolute max reflection density range.

yes thats how I do it (I should have been clearer and said between but not including max black and paper white) but IC- Racer is saying to disregard the very lightest tone and I dont understand why one would do that.

 

[Stephen Benskin]

For ISO purposes the density range and log exposure range of a paper isn't from paper white to max black, but rather from a very light tone to a very dark (but not d-max) black. The idea was to standardize these things based on the useful density (log exposure) range rather than absolute max reflection density range.

Michael,

I know you know this, but for the others.

Specifically, LER is 90% D-Max and 0.04 above paper base plus fog. Zone System wise 90% us Zone I and 0.04 is Zone VIII. Grade 2 diffusion is considered to have a LER of 1.05.

 

[ic-racer]

but IC- Racer is saying to disregard the very lightest tone and I dont understand why one would do that.

All the magenta filters in all my dichroic heads, and the blue filter in my additive head all hit at least 4.5 grade that way
If you count too many patches one might be led down the dark slippery slope to "Faded Dichroic Filter Replacement" that frequently ends in tears when the irreplaceable (and perfectly fine) magenta filter breaks.

Seriously, even if you plot it out, it won't look smooth like this with a 21 step wedge, you will still be guessing where the 0.04 point is, so throwing out the first light gray is a pragmatic solution.

 

[Stephen Benskin]

 

[Pieter12]

Recently I had a negative that required split grade printing. The first in about 2 years. All other negatives in that period did fine on a single grade.

My point is with split grade printing it doesn't matter what grade you end up with, even if it is not an in-between grade or require split-grade burning or dodging. Why should the grade matter--except for empirical reasons--you're using VC paper after all.

 

[Stephen Benskin]

View attachment 276405

Scales and not Range? Use of E instead of H. That must have come from an older source. Or Phil Davis.

 

[weasel]

here is what I can contribute:

Thank you. This explains a lot to me.

 

[DREW WILEY]

Back when most papers actually were graded, the grade intervals varied somewhat from brand to brand anyway. There are no hard parameters. VC papers give you a full continuum from less contrast to more contrasty. You can do highly proficient work these days if you had never heard of paper grades in your whole life. Its like the holdover of "horsepower" long after people got around mainly on horses. I have two additive RGB enlargers, a CMY subtractive one, and one with a blue green cold light head on it. I can achieve the same result with any of them on VC paper; and not a single one of those machines, even the ones with fancy feedback circuitry, has paper grades programmed into it.

 

[koraks]

My point is with split grade printing it doesn't matter what grade you end up with, even if it is not an in-between grade or require split-grade burning or dodging. Why should the grade matter--except for empirical reasons--you're using VC paper after all.

Ah yes, I agree with that!

 

[Craig75]

All the magenta filters in all my dichroic heads, and the blue filter in my additive head all hit at least 4.5 grade that way
If you count too many patches one might be led down the dark slippery slope to "Faded Dichroic Filter Replacement" that frequently ends in tears when the irreplaceable (and perfectly fine) magenta filter breaks.

Seriously, even if you plot it out, it won't look smooth like this with a 21 step wedge, you will still be guessing where the 0.04 point is, so throwing out the first light gray is a pragmatic solution.

View attachment 276405

Interesting. Thanks for that very clear explanation. It's a little hard to get my head around a grade printing more tones than it is defined by but if that is what it is, then that is what it is.