ChartThrob V1.01

[sanfrancisconudes]

Works great for cyanotype. I haven't tried to figure out the mechanics of what it's doing, but basically if it has a range of density values from light to dark it doesn't really matter what color they are as long as it's monochromatic.

 

[donbga]

Is my point valid or have I got myself confused here, any help on steering me on the right track would be great!
Thanks
Jag2x

I think you are generally confused. Which ever process your are calibrating, scan the printed step palette in 16 bit greyscale.

Once in PS set the black and white points properly. Blur the scanned image slightly and then read the step values which shoud range from 0 for pure black to 255 for pure white.

Don Bryant

 

[jag2x]

I think you are generally confused. Which ever process your are calibrating, scan the printed step palette in 16 bit greyscale.

Don Bryant

Ah that makes sense. So whatever COLOURED process I use, such as cyanotype or coloured print, I should automatically convert the scaned print from COLOUR to a 16BIT GREYSCALE. Then get ChartThrob to analayse the print and create the curve from there.
Thanks Don.

 

[donbga]

Ah that makes sense. So whatever COLOURED process I use, such as cyanotype or coloured print, I should automatically convert the scaned print from COLOUR to a 16BIT GREYSCALE. Then get ChartThrob to analayse the print and create the curve from there.
Thanks Don.

There is one caveat I will mention if your are doing gum printing with colorized negatives the process adjustment curve will change depending on the color of the pigment used, at least in my experience. For example if your are printing tri-colored gums each gum layer will probably require a different process adjustment curve.

Howver you would still scan the step tablet in grayscale to determine the curve for that layer.

Don Bryant

 

[jag2x]

I'm infact going down the imagesetter route of producing a B&W negative. Unsure what densities I'd get with the actual imagesetter negatives. I'd need a densitometer for that. Infact what would be the benefit if I did get one? ChartThrob would do the same job more or less?
I wonder what the differences would be, if any between the coloured ink density desktop printer approach to the imagesetter negative. I'd probably think it would have to do with what your printing on and the emulsions spectral density sensitivity.
Jag2x

 

[roy]

Being relatively new to this forum and having only sketchily trolled through previous posts, is it correct that the system cannot be applied to either PS7 or early CS ? I do not have access to a later version of CS.

 

[donbga]

ChartThrob requires CS2 or better.

Don Bryant

 

[Katharine Thayer]

Ah that makes sense. So whatever COLOURED process I use, such as cyanotype or coloured print, I should automatically convert the scaned print from COLOUR to a 16BIT GREYSCALE. Then get ChartThrob to analayse the print and create the curve from there.
Thanks Don.

Hmm, now I'm confused. It's my understanding, reinforced by a re-reading of the preceding pages of this thread, that it doesn't matter what working space you choose to analyze the charts in, as long as you maintain the same settings consistently throughout the process. And that since the calibration is done in 8-bit, there's no particular advantage to switching into 16-bit before analyzing, although if your workflow calls for working in 16-bit greyscale, there's also no harm in staying in that mode. I hope Kevin's still watching this thread and can clarify. Did I misread the advice given earlier? Thanks,
Katharine

 

[dazedgonebye]

Chart Throb and the Epson R800/R1800

Hello all,

I just picked up an Epson R1800 and I'm wanting to create my curves for cyanotypes using Chartthrob. I've done this once before, using a borrowed R2400 and I was very pleased with the results.

I've read in other places that dialing in color is a good way to get the needed UV density in the negative.
Is this true/helpful at all, or does it even matter, as long as I'm consistant and do the same thing to my final negatives that I do to the chartthrob test pattern?

Thanks

 

[mkochsch]

Negative Colour

Hello all,

I just picked up an Epson R1800 and I'm wanting to create my curves for cyanotypes using Chartthrob. I've done this once before, using a borrowed R2400 and I was very pleased with the results.

I've read in other places that dialing in color is a good way to get the needed UV density in the negative.
Is this true/helpful at all, or does it even matter, as long as I'm consistant and do the same thing to my final negatives that I do to the chartthrob test pattern?

Thanks

You can do it without using a coloured negative, but using a colour eliminates one of your printing variables. If I told you that I had a way of eliminating say temperature as a variable when you were developing your black and white negatives you'd probably be all ears, right? Well I haven't figured out the latter yet but the colour --> density range relationship has been known since Dan Burkholder published the effect in "Making Digital Negatives for Contact Printing". (See the other threads running in this forum on the arrays too. i.e. ChartThrob, RNP Arrays.) What printing an ordered array of colours does is essentially the same thing you do in Photoshop when you use the "Levels" menu to set the white point, it trims the excess head room. You could also choose more advanced method such as using a RIP method which allows you to achieve this by setting ink limits on your printer (thus setting the density range) and creating custom curves to smooth out the tonal scale. There are several books and systems you could also buy. You basically have to see what works for you. But that said all the parts necessary to achieve great results are available here for free on hybridphoto.
~m

 

[bjorke]

Hmm, now I'm confused. It's my understanding, reinforced by a re-reading of the preceding pages of this thread, that it doesn't matter what working space you choose to analyze the charts in, as long as you maintain the same settings consistently throughout the process. And that since the calibration is done in 8-bit, there's no particular advantage to switching into 16-bit before analyzing, although if your workflow calls for working in 16-bit greyscale, there's also no harm in staying in that mode. I hope Kevin's still watching this thread and can clarify. Did I misread the advice given earlier? Thanks,
Katharine

Yes, you're correct. What you want to avoid is automatic recalibrations, but in general since ChartThrob is intended for gauging grayscale values, the color of the scan, when reduced to grayscale, should be consistent with the charting process and not a cause for alarm.

 

[amphoto]

charthrob scanner

Hey everyone. Just wondering what scanners/scanning software people are using with Charthrob and what sort of scanned results they're getting (i.e. is there any affordable flatbed scanner out there that gives anywhere near a linear response out-of-the-box). I just scanned an IT8 target with my ancient Epson and the Luminance values for the greyscale patches along the bottom of the target are waaaaaaaay off from what they should read. In fact, they were still pretty far off even after I'd profiled the thing! Looks like it's time for a new one, primarily for using in the production of digital negatives via charthrob, so any recommendations would be appreciated.

 

[mkochsch]

Colour Space Warning: sRGB vs Adobe 1998

Important Note: When using ChartThrob set your "Color Settings|Working Space|RGB" to Adobe 1998 or Adobe RGB rather than sRGB else you'll get less than optimal results. Off by one to three per cent in places.

~m

 

[Katharine Thayer]

Thanks!

Important Note: When using ChartThrob set your "Color Settings|Working Space|RGB" to Adobe 1998 or Adobe RGB rather than sRGB else you'll get less than optimal results. Off by one to three per cent in places.

~m

Ah, maybe that explains the nonlinearities I mentioned earlier. I had to go into the chart and manually change the values of the squares to what they should be, because they were off by that much in many places.
kt

 

[mkochsch]

Me too

Yes I just noticed I had the problem. I had change my working space to match my digital camera and forgot to change it back again...

~m

 

[MVNelson]

Just an update....still looking at my work flow that includes scanning MF and LF negs, ChartThrob-arrays, Canon-TCFilm, CanoniPF5000 pt/pd printing...I am finding that my initial color choice in CHartThrob (R 144, G 128, B 0) --greenish-yellow---has not needed any tweaking yet. In fact all my prints seem to be about right with either straight pd or few drops of Na2 5% . I posted a scan in the gallery of a pd print that I was doing to exam tonal range and smoothness with in ahighly textured subject....

Miles

 

[MVNelson]

Important Note: When using ChartThrob set your "Color Settings|Working Space|RGB" to Adobe 1998 or Adobe RGB rather than sRGB else you'll get less than optimal results. Off by one to three per cent in places.

~m

I seemed to be doing well until you said this and I went back and checked ...I probably have been using the sRGB from the beginning..I plan to leave it that way until I prove otherwise...I will try a dig neg for pd print with RGB1998 to see what happens...

Miles

 

[SMBooth]

I just found this tool, and pleased to see that it was received well here. So maybe this is just a little bump to let newer people to the site know it exists.

 

[nmp]

Exporting ChartThrob Data

If this thread is still active, I wanted to ask - particularly to the writer(s) of this great piece of software, is there is any way I can export the readings from the 101 squares to a text file which can then be imported in to Excel. I would like to compare/analyze various processes and it would be nice if I can plot them all together without having to manually type in all that information.

 

[RalphLambrecht]

Click "Save Link As...." here to get a new version of ChartThrob.

What it is: a Photoshop script for CS2+ -- install it in your CS2/Presets/Scripts directory and restart Photoshop. It will appear in the File->Scripts menu.

What it does: It creates (positive) grayscale charts. If you print these charts via digital contact printing (or any other process), you can scan the results, run ChartThrob a second time to analyze the scan, and it will automatically create a Photoshop "Curves" adjustment profile that you can apply to digital positives before printing to ensure that they get the full range of available grays from your wet process.

Caveats: your process must be consistent between prints, and the tones should not vary wildly depending on location on the print (that is, 50% gray should always be 50% gray whether it's in the center, corner, bottom, top, etc)

Feedback most appreciated!

I like the idea but it didn't work for me(it doesn't show up in the script menu)

 

[wilsonneal]

Sorry to resurrect an ancient thread, but I have a (possibly stupid) question.
I don't see where it tells you how to get your base exposure. I am just getting ready to get back into PtPd and instead of in-camera negs will be using digital negs. Would you take a blank piece of film and do a test strip with whatever method paper/sensitizer combo one uses looking for your best black on a test strip to find an initial time for exposure? Are people still using this method? Thanks,
Neal in NJ

 

[nmp]

Sorry to resurrect an ancient thread, but I have a (possibly stupid) question.
I don't see where it tells you how to get your base exposure. I am just getting ready to get back into PtPd and instead of in-camera negs will be using digital negs. Would you take a blank piece of film and do a test strip with whatever method paper/sensitizer combo one uses looking for your best black on a test strip to find an initial time for exposure? Are people still using this method? Thanks,
Neal in NJ

That's how I do it. Some people look at the difference between area that has film on it and the area without and where the two are the same gives the correct exposure (as described in the Step 1 here: http://www.alternativephotography.com/digital-negatives/)

If you haven't done a digital negative before, brace for a lot of fun....

:Niranjan.