Re: Need Guidance on Getting a Densitometer
Hi, being new to this, I was thinking a sensitometer would simplify the exposure process of the step wedge by not having to expose a test wedge and then either use a lux meter or convert EV values to lux of the exposure light source to ultimately create the characteristic curves, etc.
I did find this interesting thread about various sensitometers used on B&W films:
Color of Light in Sensitometer Tests by IC-Racer
https://www.photrio.com/forum/thread...hootout.95837/
I was originally thinking about making an in camera 4x5 sheet film 21 step Stouffer step wedge exposure by placing the Stouffer wedge in front of a sheet of test film in the film holder and then setting the lens to infinity and exposing the film against at white board at +5 stops (Zone 10) in open shade at various EI ratings. I think I read about this on Paul Wainwright's website first. I have used this method for finding the true film speed of my film and developer combinations and for establishing N, N+ and N- development times, but never for plotting the 21 densities for the purpose of creating characteristic curves. Maybe that approach is valid, or there is a better approach using an enlarger maybe? Anyone here shed some light on this with your experience?
Quote:
Originally Posted by
Oren Grad
Larry, the error was mine, not yours. I've reset the thread title accordingly, and I apologize for the grief it caused you.
FWIW, I can't recall reading about any still photographer using a sensitometer to expose film for these tests - it's always been a step tablet and/or carefully timed direct exposures to light. The methods Phil Davis describes in the various editions of "Beyond the Zone System" are par for the course. The only references I can find to sensitometers relate to use for X-ray and cine film process control in a commercial setting. I'm happy to be corrected if someone can point to documentation. But if you can lay your hands on one inexpensively enough, and can figure out how to check its calibration...
Re: Need Guidance on Getting a Densitometer
That seems to be the path that is most likely I think.
The one question I have is how would you know where to start with an exposure time using the enlarger light source for the step wedge contact exposure?
Would you do some trial and error exposure and development tests to find a test strip that has good tonal separation across the 21 steps or is there a better approach?
Also, this would have to be done in total darkroom since I would be exposing B&W panchromatic film.
Quote:
Originally Posted by
Oren Grad
And a follow-up: I've now read page 5 of that Kodak workbook and I see where this is coming from. Everyone I know who has done this procedure for themselves has made the required exposures simply by contact printing a step tablet under an enlarger.
Re: Need Guidance on Getting a Densitometer
Quote:
Originally Posted by
LFLarry
Thanks for that link!
As you're figuring out what will work best for you, do take a look at "Beyond the Zone System" if you haven't already - the current edition is pricey but earlier editions are available inexpensively on AbeBooks. Phil described his procedures in detail.
Re: Need Guidance on Getting a Sensitometer
https://live.staticflickr.com/65535/...13d405dd_z.jpgArt of Pyro Zone Board by Nokton48, on Flickr
Here is my homemade "Zone Board" as described and discussed in the back of "The Art of Pyro" by Gordon Hutchings.
From the top, Zone VIII, Zone VII, Zone VI, Zone V, Zone IV, and Zone III. As I recall that was really all the info you needed to plot.
Nice big references when you go to measure the negs.
I will be firing this back up soon, as I have time.
Re: Need Guidance on Getting a Sensitometer
Oren, et al, here's another reference to using a sensitometer for film testing:
https://www.youtube.com/watch?v=VNbyShwYi6c
Re: Need Guidance on Getting a Sensitometer
Quote:
Originally Posted by
Keith Pitman
Oren, et al, here's another reference to using a sensitometer for film testing...
Excellent, thank you!
Re: Need Guidance on Getting a Densitometer
Thanks. I just purchased the kindle edition of BTZS and will check it out for more details that will likely help fill in the cracks.
Quote:
Originally Posted by
Oren Grad
Thanks for that link!
As you're figuring out what will work best for you, do take a look at "Beyond the Zone System" if you haven't already - the current edition is pricey but earlier editions are available inexpensively on AbeBooks. Phil described his procedures in detail.
Re: Need Guidance on Getting a Sensitometer
Thanks Keith. I will watch it and see if it will help fill in some missing info for me. Have a good weekend.
Larry
Quote:
Originally Posted by
Keith Pitman
Re: Need Guidance on Getting a Sensitometer
Re: Need Guidance on Getting a Sensitometer
Hi Greg, really fantastic that you are producing these videos. I watched all 3 videos you have published so far and they are very well done. Great job!! Looking forward to watching the rest in this series.
Larry
Quote:
Originally Posted by
Greg Davis
That video is mine. I also have two videos following along with the Kodak Basic Sensitometry Workbook. Part 1 ( Exposing the step tablet and drawing the curves) is here:
https://youtu.be/eILVzTNWnq8, Part 2 (Calculating Gamma) is here:
https://youtu.be/OnhcX3x2YvU. I will get Part 3 (Contrast Index) up this weekend.