Gast
I’m having a problem with the Classic Arts Polywarmton baryta paper. I have to print my negatives with a gradient of 3.5–4, otherwise the prints turn out too flat. I measure the density of the negatives using a Kunze FEM; these are between 0.9 and 1.2, which is in the range of gradation 2–3. Could it be that the paper has a significantly lower gradient than 2 under white light? My darkroom light is red.
MirkoBoeddecker
Hi Tammo,
That may well be the case. The paper’s spectral sensitivity has been modified so that, when used with multigrade filters, there should be no increase in exposure time between gradients 1–4 (though, of course, this doesn’t work perfectly).
As a result, the green and blue sensitivities have been altered. No other manufacturer does this.
Depending on which ‘white light’ you use, it may therefore be the case that Polywarmton produces a different gradient to other multi-contrast papers.
Best regards,
Mirko
Gast
Will the gradients be correct if I use multigrade filters or a colour mixing head (Kaiser)? Where can I find out which filter values (for the colour mixing head) produce which gradient on the paper? I do have a table that I usually work with, but it tells me that I have a gradient of 2 under white light, and that doesn’t quite add up anymore. :angry:
Gast
Will the gradients be correct if I use multigrade filters or a colour mixing head (Kaiser)? Where can I find out which filter values (for the colour mixing head) produce which gradient on the paper? I do have a table that I usually work with, but it tells me that I have a gradient of 2 under white light, and that doesn’t quite add up anymore. :angry:
You’ll have to test it out. Get yourself a grey scale and expose different filter settings on test strips (the exposure time doesn’t matter at this stage). By counting the steps between almost completely black and almost pure white, you can determine the ISO-R value. You can set which gradient corresponds to which ISO-R value as you see fit (manufacturers do the same); a popular sequence is 160-130-110-90-70-50 for grades 0 to 5.
Gast
By counting the steps between almost completely black and almost pure white, you can determine the ISO-R value
OK, I suppose I can work out the black and white areas, but how on earth do I work out the ISO-R values from that? :angry:
Gast
By counting the steps between almost completely black and almost pure white, you can determine the ISO-R value
OK, I suppose I can work out the black and white areas, but how on earth do I then work out the ISO-R values? :angry:
The ISO-R value is the decimal logarithm of the exposure difference between the exposure that produces a density of 0.04 (which is a very faint, delicate light grey) and the exposure that produces 90% of the paper’s maximum density, multiplied by 100.
Got it?
No?
A grey scale has uniform steps, usually 0.10d (31-step grey scales from 0-3.00d) or 0.15d (21 steps from 0-3.00d). One f-stop is equivalent to a 0.3d difference (i.e. 3 or 2 steps on the grey scale). If you now (in contact printing, never in projection!!!) expose a grey scale onto the paper, there will be some pure white steps, some grey ones and some completely black ones. If you now count the steps between the first step that is not quite white (that is roughly 0.04) and including the last step that is not yet completely black (that should be 90%), you will know the exposure difference that caused them. Then simply multiply the number of steps by the density per step (i.e. 10 or 15), and you have the ISO-R of this paper for this filtration with this enlarger.
Example: a 21-step wedge is used; step 7 is minimally greyed, step 16 is not yet pitch black: 16 minus 7 is 9; multiplied by 15, this gives 135 ISO-R. This is then approximately grade 1 (normally 130).
You must never do this in the projection, because effects such as diffuse or directional light, stray light in the lens and stray light in the Duka would come into play.
Martin
Gast
Oh man, that sounds like a lot of work in the lab. I’ll give it a go next time I’m mixing drinks. Thanks!
MirkoBoeddecker
Otherwise, you can of course click on ‘Photographic Paper’ at the top at any time and then select ‘Polywarmton’.
If there are no values listed for PE, use Baryt – the emulsion is the same.
However, it’s always best to test it first, as, as I said, not every light bulb is the same shade of white.
Under normal circumstances, it shouldn’t be much softer than 2.
Best regards,
Mirko
Gast
Hi Mirko,
Have I got that right? With the Polywarm tone, I don’t need to worry about the exposure time increasing as the filter density increases?
So, just use yellow for a softer look and magenta for a hardener? No counter-filtering to keep the exposure times the same, no extension factor between grades 1–4?
I’m just checking to be sure. I’ve always used your film filter set before, but I’m now starting to use my DeVere with a colour head.
Regards, Sven.
Roman
Hi Mirko,
Have I got that right? With the Polywarm filter, I don’t need to worry about the exposure time increasing as the filter density goes up?
So, just use yellow for a softer look and magenta for a hardener? No counter-filtering to keep the exposure times the same, no extension factor between grades 1–4?
I’m just checking to be sure. I’ve always used your sheet filter set before, but I’m now starting to use my DeVere with a colour head.
Regards, Sven.
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Sven,
I’m not Mirko – but I think you’ve misunderstood – that was about multigrade filter sheets, where theoretically there shouldn’t be any change in exposure time between grades 1–4.
If you’re working with Y and M filters on a colour head (and not using a combination of Y and M simultaneously according to a table, but only the respective individual colour filters), the exposure times definitely change, as the amount of light also changes.
Roman
Urnes
Hi Roman,
Thanks for that. I suppose I’ll have to dig out the old Ilford chart with the C and M values to test it out.
I was just surprised that Mirko specifically pointed out that no other manufacturer does it this way. With Ilford’s Multigrade, there’s no change in exposure time between 0 and 4 either. At least according to the instructions. I usually stick to between 2 and 3, and then maybe add a bit of 5 on the shadows.
By any chance, does anyone here have any reference values for filtering with Polywarmton?
Regards, Sven.
cfb_de
Guys,
apparently this can’t be shouted loud enough: ‘Consistent’ times only apply to *one* and *the same* grey scale!
Any statements to the contrary lie outside the realm of physical chemistry and remain purely within the realm of marketing.
This is precisely why there is this conflict between RH-Analyzer, Splitgrade and Fineprintern. Some are willing to spend money to buy tolerance, whilst others know what it’s all about :-)
The filter combinations of yellow and magenta also apply to only one grey level. This is reflected, amongst other things, in the fact that every (already semi-spectrally blind) measuring probe must be recalibrated via filtering. So, in each case, ‘one paper index per gradient’.
Much of our hobby has to do with faith, love and hope. But absolutely nothing can bypass the exact natural sciences. Absolutely nothing! It’s all about the effect of light on silver halides. Consequently, it’s genuine applied physical chemistry. Including everything that can happen with green and blue light during exposure. Or the corresponding subtractive colours.
Best regards,
Franz
Roman
Franz,
Why do you think I specifically wrote 'theoretically' in my thread...?
Roman
Kiste
Hello,
Sven’s question wasn’t half bad, because I think Mirco
explained it a bit wrongly.
The exposure time mainly affects the highlights.
With the ‘Hauch’ print on ‘Papierweiß’ paper (especially when viewed from above), you can
compare exposure times for different gradients.
The more light the negative lets through (i.e. in areas with shadows), the greater
the influence of the filters.
However, there are at least five common methods for adjusting the gradient without knowing the exact values.
Ilford filters are the same up to #3.5; after that, the times are supposed to double.
MG heads mix Y and M and attempt to balance the density.
Colour-mixing heads can be set using tables either
a) with one filter at a time (with exposure correction) or
:D as with the MG head, both filters simultaneously, with a small exposure correction
Finally, there is split-grade (manual or digital (Heiland) – it doesn’t matter).
All methods have advantages and disadvantages.
I would recommend exercising control over the negatives and creating them
as ideally as possible; and with the paper, because it has several
variables
(age of the lamp, halogen or opal, age of the filters, different gradation curves, etc.),
simply print a few images to get an impression rather than searching for specific filter values, etc. If something isn’t working properly, look for the cause specifically,
as with the grey scale.
Then there’s the method of measuring a negative!
Why not try the following test? Make a test strip on the edge strip of the negative in the contact sheet.
The time at which the test strip first stops getting darker is the
correct exposure time for the base fog.
Use the filter you would use for neutral exposure
(e.g. #2 or even #2.5?!)
Then make another contact print using these settings.
If the shadows are too dark, you have underexposed; if the highlights
are ‘mushy’, you have developed for too short a time. The reverse is also possible,
e.g. blown-out highlights = overdeveloped.
The gradient number is just as relative as the sensitivity rating on a film; it exists, and you use it as a guide, ....
Regards, Stephan
Gast
Hello Franz,
"The filter combinations of yellow and magenta also apply to a single grey scale. One consequence of this is that every (already semi-spectrally blind) measurement probe must be recalibrated using filters. ....
I’m not sure if I’ve understood you correctly, but as a rule, measurements are taken without a filter in the beam path (at least that’s how I do it). The spectral sensitivity of the measuring probe therefore plays no role in this.
Best regards
Ralph
Gast
Hello,
I’m still using fixed gradation, so I haven’t tested it yet, but in theory you should be able to achieve the same exposure times if you use three filters instead of two and always set them to the same density sum.
Roland
Roman
Roland,
The cyan filter has absolutely no effect on VC paper, and consistent light levels can already be achieved by carefully combining Y and M (that is precisely what the tables are for) – the problem is simply that highlights, mid-tones and shadows change to varying degrees due to the change in contrast; so if you want a constant exposure time across multiple contrast levels or filter settings, this can only ever apply to a single grey value within the spectrum from highlights to shadows.
