New darkroom calibration software.

[Pere Casals]

I'd request opinions and suggestions for a new software I'm developing (to be relesed as open source/freeware), intended to speed up darkroom technical procedures.

Motivation: a) To plot curves is boring, for DIY emulsion, BW slide reversal calibration, carbon calibration, paper calibration, paper contrast calibration for a RGB LED illumination of the enlarger, SCIM/CRM and calibrations for contrast color mask with Alan Ross method. b) Practicing a bit GDI+ I'll have to use, this was also a motivation.

Features:

1) Densitometer:

A pictorial Negative is scanned alongside the stouffer wedge, the red cells are dragged (mouse) on the stouffer, densities of the steps are in a configuration so the software can compare what gray levels are what densities, by moving the mouse to any spot on the negative we see what density is.

2) Curve families for Film calibration:

We place (wyswyg) the green cells on the contact copies osf the stouffer, we enter the exposure in LUX.S, then from densities in the stouffer we know exposure in each green cell, so the software knows the exposure in Lux·S and density for each step of each curve, a text file is generated with a data column for each wedge (All have same exoisure but each has a different development, see BTZS)

This file is imported in Exel so we can plot all curves instantly. So a film calibration requires scanning the contact copies of the stouffer alongside the stouffer itself, adjusting position of the step areas by dragging with mouse, and a click in the calibration button, and then data rows are in Excel, no densitometer, no manual data handling to make a calibration, just making an scan.

Until here it works nice yet, next is planned:

3) Paper calibrations.

4) Proofing silver gelatin paper result by selecting a paper calibration, a negative scanned alognside with a stouffer, and LUX.s exposure reading with lux meter on the easel without the negative. We can determine aproximate paper grade and exposure, this development step is necessari to to to the 5).

5) Generating a 3D LUT to be used in Ps, that will allow proofing the printing of a negative sandwiched with contrast color mask. In one Ps layer we have the image, with calibrated densities thanks to the stouffer that has been scanned with the negative. In the next layer we have the color mask for VC papers that we draw on the BW image. Nex is a applied the calibrated 3D LUT generated by this software that is to make the proofing, so wswyg the effect of the contrast mask.

The target is to make easy crafting a good contrast mask, sure some adjustments would be required in the darkroom when we see the real result on paper, but 90% of the work would be made without wasting paper.


Welcomed:

Any kind of critique, constructive or destructive. Ideas. Opinions about what components would be useful, possible additions. Volunteers to test the software while is developed to see how the thing goes.

I don't ask help for coding the software but that it would also be welcomed, PM for that.

IMHO a tool that boosts control in the darkroom would make optical printing more competitive, being easier to obtain sound results that now are only possible with hybrid system.

Well, perhaps this is also kind of hybrid process, because be make the contrast mask from digital, but at least we have an authentic optic projection crafting the image, helping with complex prints, but at same time allowing for adding any ammount of manual crafting, burning/dodging and the like.

[Larry Gebhardt]

Sounds interesting. A few suggestions:

- make work on mac, linux and windows
- put the code on github to enable collaboration
- support multiple step wedges
- support multiple step wedge layouts and density ranges

[Pere Casals]

- support multiple step wedges
- support multiple step wedge layouts and density ranges

It suports any wedge, you load a text configuration file of any wedge, just two rows, step number and calibrated density. When loading a Wedge the step count is updated, but it can we modified if we want:



It also supports any pattern, with mouse we place the first and last position, and we can also change the rectangle XY area size where we average the reading:

make work on mac, linux and windows
- put the code on github to enable collaboration

I'm a native windows programmer, perhaps in on github someone may help porting to mac/linux or making a cross platform app, I'm encapsulating in classes so it would be easier, perhaps dependence to gdi+ should be removed.

[Tin Can]

I would need a youtube tutorial.

Thanks!

[neil poulsen]

This is really interesting. Here are some of the calibrations in which I'd be interested. (Plus, recommended methodology to execute the calibration.)

A proper way for testing to use aperture adjustments to compensate for black and white film reciprocity failure, so that one need not rely on mfg graphs. (These are often not very complete.)

Testing for contrast grades on paper using a reflection densitometer.

If it helps, I use a particular routine in SYSTAT statistical software to plot my film curves; it works perfectly and doesn't assume any particular model. It's called "double-weighted least squares" analysis. All one needs to do to use it is enter two columns of numbers (zone number as the horizontal axis and densities measured using a transmission densitometer on the vertical axis) and say go. It does the rest. I've not taken the time to determine how this method relates to regular least squares analysis, but as I indicated, it works really well for these and many other types of curves.

[Jac@stafford.net]

This is really interesting. Here are some of the calibrations in which I'd be interested. (Plus, recommended methodology to execute the calibration.)

A proper way for testing to use aperture adjustments to compensate for black and white film reciprocity failure, so that one need not rely on mfg graphs. (These are often not very complete.)

Testing for contrast grades on paper using a reflection densitometer.

What ever happened to test strips or personal experience?

While not perfect what about Ilford's variable contrast heads and controllers for the dimwits?

[interneg]

What ever happened to test strips or personal experience?

It's the same old belief/ delusion that has persisted for many, many decades that art in photography can be reductively turned into a form of applied maths that will hence produce a 'perfect' print. Which while it is fine (great, even) for industrial printmaking, it just doesn't understand the way that making a great print is about far more than sensitometric calculations.

Fundamentally, it's a worldview that denies the acquisition of aesthetic skill (art) & knowledge (science) & the practice thereof in favour of a techno-fetishistic belief that with all this software, gubbins etc you too can become a great printmaker...

[Pere Casals]

Which while it is fine (great, even) for industrial printmaking, it just doesn't understand the way that making a great print is about far more than sensitometric calculations.

Interneg, this is not the aim of this software. Since several years ago I'm addicted to Sally Mann and Denise Ross ways.

I'm thinking in this tool as a way to assist those (me the first) wanting learn advanced techniques and to also be useful to speed up boring technical tasks.

The last thing I want is being intrusive in the optical path. I'm a radical beliver in the purity of the optical crafting.

There is something that I don't like: positive discrimination for the optical process. To me it's wrong to give a higher value to an optical work because "it's more difficult". What need a positive discrimination are digital works, IMHO.

...but optical crafting of a print can be exhausting when a situation is complex.

I don't plan making great prints from great sensitometric calculations, at all. What I plan is making sensitometry easy, to reach the good point easier, faster and by wasting 1/4 of the paper.

What the print has to be it's in the photographer's mind. This tool it's not about the photographer's mind. This tool will be about making easier to craft in a print what's in the photograper's mind.

I hope that if you follow the evolution of the development then you may find that this is the intention.

[faberryman]

I am not sure what you plan to do with all this sensitometric data to help you print a negative. Is it to select paper grade?

[Pere Casals]

I am not sure what you plan to do with all this sensitometric data to help you print a negative. Is it to select paper grade?

Yes, we can load:

> a negative, calibrated with the stouffer, we know densities
> a film calibration, with several curves
> a mask (crm/scim) that is obtained from the negative + particular curve of the film calibration + exposure setting
> we also have the negative + mask sandwich like if it was a new negative
> a paper calibration, with different grades, a particular calibration is for grades from a color contrast masking of the Alan Ross process
> a color contrast mask, Alan Ross type
> a preflash layer

This is to make a proofing of how the print of a negative will be with a particular BW masking + Color masking + paper curve.

I don't plan that the result has to be exact, just it will show the path we should follow, allowing for example to know how to expose an scim mask to have more or less the effect we want, delegating in the manual crafting the refined adjustments.

BTW it plots fim/paper calibrations, and tells how to expose/process BW slides.

Most of the structural work is done, user interface development is slow and boring. In some two months it may be ready for testing, if someone wants.

For the moment you scan a calibration alongside the stouffer and it delivers data to Excel to plot the film curves, and works like a densitometer if scanning a negative with the stoffer. This weekend paper calibrations will be up. A paper calibration has 2 wedges, one is the trasmission one to say the exposure each step on paper received, and an additional reflective wedge scanned alongside the paper strips calibrates the resulting densities in the steps.