The Great Sensitometer Shootout....

[ic-racer]

This is a modern example of the gamma lambda effect, I measured today with a SensiX blue-green sensitometer. Film used was Fp4+. It shows the contrast change of the material between green and blue exposure.

Nice. How are you calculating gamma and contrast index?

 

[reneboehmer]

Nice. How are you calculating gamma and contrast index?

gamma

ci

 

[ic-racer]

Thanks for the detailed description. so, for the gamma, you are including the toe, or 'filtering' out the toe? (OK I see it now, in Gamma Start and Gamma End)

Is that C? What is bestFit? is that your own subroutine?

 

[reneboehmer]

Thanks for the detailed description. so, for the gamma, you are including the toe, or 'filtering' out the toe?

Filtering out the toe, but in my program the start logH and end logH of the gamma can be user defined. The gamma in this case is only a measurement of the slope of the straight line portion of the curve.

 

[reneboehmer]

Is that C? What is bestFit? is that your own subroutine?

The tool is written in HTML and JavaScript. I made this together with the use of AI. I make small portions at once with an environment called "Cursor" it allows me to code alongside prompting and is a very quick and efficient way to build stuff like this.

 

[reneboehmer]

Thanks for the detailed description. so, for the gamma, you are including the toe, or 'filtering' out the toe? (OK I see it now, in Gamma Start and Gamma End)

Is that C? What is bestFit? is that your own subroutine?

Best Fit refers to the "concentric arc method" The tool needs to test many values in order to find the one best complying with Ci specification. It's like using the Ci ruler but not actually using the ruler. The value found that best fits is taken to work with.

 

[ic-racer]

Best Fit refers to the "concentric arc method" The tool needs to test many values in order to find the one best complying with Ci specification. It's like using the Ci ruler but not actually using the ruler. The value found that best fits is taken to work with.

Are you using a graphing software package or are you writing all the subroutines yourself?

 

[reneboehmer]

Are you using a graphing software package or are you writing all the subroutines yourself?

Im using chart.js and for pdf creation i use jsPDF
https://www.chartjs.org/

 

[ic-racer]

Im using chart.js and for pdf creation i use jsPDF
https://www.chartjs.org/

Thank you for the link!

 

[spookyphoto]

I can't believe I found posts on this subject. I feel like I am in a time warp I'm a retired photo-analyst who used to design film analysis systems and programs for the govt. and the micrographics industry some 40 years ago. Worked with $ 250K sensitometers and auto scanning densitometers. I wrote software for sensitometric analysis of every kind of film and paper on the planet. Ran many processing and developer studies. If I can be of any help let me know.

 

[MattKing]

Welcome to Photrio @spookyphoto !

 

[reneboehmer]

I can't believe I found posts on this subject. I feel like I am in a time warp I'm a retired photo-analyst who used to design film analysis systems and programs for the govt. and the micrographics industry some 40 years ago. Worked with $ 250K sensitometers and auto scanning densitometers. I wrote software for sensitometric analysis of every kind of film and paper on the planet. Ran many processing and developer studies. If I can be of any help let me know.

Spooky that sounds amazing!

 

[spookyphoto]

Spooky that sounds amazing!

It was pretty interesting work. Got to see some pretty interesting things along the way. Opened a small photo engineering company in San Diego specializing in subminiature cameras and film technology.

Picture of $ 250K MTL Star sensitometer. Best on the planet. When kodak wanted to calibrate their sensitometers they called us. Same with the Air Force and other agencies.

 

[ic-racer]

Looks like a fantastic machine.

 

[spookyphoto]

Looks like a fantastic machine.

Another version had a built in radiometer to cross check calibration.

 

[Bill Burk]

Another version had a built in radiometer to cross check calibration.

Oh right, a radioactive element that has an absolute luminance reference. I've seen some meters that have those on eBay

 

[spookyphoto]

Oh right, a radioactive element that has an absolute luminance reference. I've seen some meters that have those on eBay

A radiometer is an instrument for measuring radiometric quantities such as radiant flux (power), irradiance, or radiance. [1] Definitions typically limit radiometry to optical radiation,

 

[Gorrunyo]

Have a question that somebody might have answered before, but I couldn't find it.

Will an LED-based light source with a CRI 99, like this one, be suitable for a basic B&W sensitometer?

Thanks

 

[spookyphoto]

Great picture and diagram of a Kodak 1B model 5 sensitometer on page 125 at the link below.

https://www.nro.gov/Portals/65/documents/history/csnr/programs/docs/Bridgehead%20Eastman%20Kodak%20Company.pdf?ver=2019-03-29-103653-233

 

[ic-racer]

Great document, thanks for posting.

 

[reneboehmer]

Great picture and diagram of a Kodak 1B model 5 sensitometer on page 125 at the link below.

https://www.nro.gov/Portals/65/documents/history/csnr/programs/docs/Bridgehead%20Eastman%20Kodak%20Company.pdf?ver=2019-03-29-103653-233

This is such a great thing to read! Thanks.

 

[spookyphoto]

That was really the golden age of high end photographic processes.