Jerry, thanks for that, this looks extremely interesting to me. Out of interest, did you have to use many formulas for excel to draw that cure and plot the points
Jerry, thanks for that, this looks extremely interesting to me. Out of interest, did you have to use many formulas for excel to draw that cure and plot the points
Not really. Excel offers a host of curve types to try and get a good fit to the data points. I find the polynomial curves most useful; one can select 2nd order through 6th order to visually see which works best. As you can see in the attachments, I've opted to have the equation for the curve placed on the plot and in both cases the 2nd order (e.g., first term in the equation indicates the x-value has an exponent of 2) was adequate. It takes a while to learn how to work with Excel but I think it's time well spent. I use it for many things. My engineering experience allows me to read curves of plotted data easily and I'm often able to spot errors in the data points when the curves have strange hiccups.Originally Posted by IanBarber
Jerry,
The Kodak data sheet for TMY shows exactly what Ian posted. The info from The Negative is likely for older, conventional Kodak films; it seems to agree with the current published reciprocity characteristics for Tri-X.
The reciprocity characteristics of many Kodak films changed considerably when they were reformulated for the newer coating facility (sometime around 2002-3 if I'm not mistaken). Kodak, however, didn't change their recommended compensation, however, The point of Howard Bond's article was to test the new films and arrive at more reliable data. Kodak still hasn't revised their recommendations...
Charts like you posted above based on Howard Bond's data points for the films he tested would be really interesting. I'm pretty good at Excel, but don't know how to get the graphs going. Care to give me (us) a quick tutorial?
Best,
Doremus
What I'd like to know is what Fuji do with Across to remove the failure...
I've been reading recently about hypersensitization, used in astronomy (lumicon etc), perhaps it's related to that, or by using the sensitizing dyes developed for color films...
Make a scatter plot (be sure to pick the scatter plot type, not a regular line graph) of the desired data points
Right-click one of the points in the plot and pick the option 'add trendline'
Then right-click the trendline and choose options/properties/format trendline or whatever it's called (I don't have Excel running on this machine)
Expriment with the different types of trendlines to see what makes for the best match. You can even add an R-square value to the plot so you can see which line fits the data points the best.
The risk, of course, is that you'll find yourself picking a type of trendline that fits the data points perfectly, while in reality, you don't know what the exact relation between exposure time and reciprocity failure is. Could be logarithmic, polynomal, etc. It all remains guesswork, but obviously, the more data points you have, the more certainty regarding the shape of the curve.
Pere;
I've wondered about this as well. Speculating a bit: the issue with LIRF seems to be that a grain of silver needs 2-4 photons in order to become activated (IIRC). However, the more time passes between the arrival of these photos, the larger the chance that the effect of the previous photon has already disappeared, eliminating the compounding effect of consecutive photons. Improving the situation would require that the effect of a single photon hitting the grain lasts as long as possible. No doubt this can be achieved through the controlled addition of certain doping agents to the emulsion and/or controlled grain growth during the emulsification process. Which of the two is the key factor and which dopants are particularly effective in this, I'm not sure. I've done some limited literature crawling, but haven't come up with anything conclusive.What I'd like to know is what Fuji do with Across to remove the failure...
Ian,
Here are some times from a reciprocity table I have. Don't know if this helps as I do not use this film.
1 - 1.25
2 - 2.5
3 - 3.75
4 - 5
5 - 6
6 - 7
8 - 10
10 - 14
12 - 16
15 - 21
20 - 28
25 - 35
30 - 42
40 - 56
50 - 1'10"
1m - 1'24"
1'20" - 1'53"
1'40" - 4'42"
2' - 5'39"
2'40" - 7'32"
3'20" - 9'25"
4' - 11'18"
6' - 16'58"
8' - 22'37"
10' - 28'17"
Glad to oblige, Doremus. It so happens that Ian pm'd me this a.m., asking if I'd send him my Excel files from the screenshots. I sent him a tutorial as well to help him out, using my own gmail acct, since I'm not certain emailing him through the forum's system would allow attaching the files. So here's an edited copy/paste of the tutorial I sent him. Coupled with the screenshots I think you can follow it OK:
...Putting the curves’ equations on the plots allows one to calculate precisely any point on the curve. Here’s a step-by-step tutorial for plotting the curve for your chart:
1. Open the file. You’re on the “Home” tab at the top of the page. Also notice the CCW arrow on top row; it can be used at any time to undo any change you just made if you’re not happy with the resulting change.
2. x-y data pairs from the chart are entered in columns A & B (column headings are optional but useful).
3. Select cells A1 to B4.
4. Select “Insert” tab at top of page. Hover pointer over the various chart types to see helpful tips on which type to choose. I usually choose “Scatter (X,Y)” type, so hover over that one, then click the arrow and select “More Scatter Charts” and select “XY (Scatter)” in the drop down window. It‘ll show an example of your plot points on a chart.
5. Beside the chart notice icons [+] [brush] and [funnel]. Click on [+] to see a list of “Chart Elements” you wish to include. I usually pick Axes, Axis Titles, Chart Title, Gridlines, Legend (sometimes), Trendline (this is the one that lets you choose which type of data-fitting curve you want - I frequently pick “Polynomial”). All choices can be edited at any time.
6. Click on the chart presented and see how it’s put in a box with o’s at each corner and mid-sides. These can be clicked and dragged to change the chart’s size as desired. Also seen is what I call a weathervane with N-E-S-W arrows. Click-drag that to relocate the chart on the worksheet as desired.
7. Right click on the Trendline shown to open window to see your curve-fitting options. Clicking on Polynomial (start with Order=2 and progress up to Order=6 and it’ll show you which best fits the data points). At the bottom of this window, click the box “Display Equation on chart”. Right-click the trendline and select “Format Trendline” to change as desired.
8. To edit any title, just click on it and it’ll be shown in a box. The contents of the box can be highlighted and edited (should be self-explanatory). Use the weathervane to move the box to where you want it on the chart.
9. The x or y scale can be adjusted by clicking on it; a window opens that you can play with to figure out. Same goes for editing grid lines (both major and minor).
10. Finally, the worksheet title/color (tab at bottom) can be changed by clicking it, then select “Rename.”
End of tutorial.
It seems to me that it'd be simple to know at which points on the curve a development reduction is called for. E.g., when the reciprocity correction FACTOR (adjusted time / indicated time) reaches 2, that would mean N-1 is needed; when it reaches 4, that would mean N-2, etc.
Hope this helps,
Jerry
Last edited by Jerry Bodine; 8-Apr-2017 at 16:44.
IMHO this wikipedia article https://en.wikipedia.org/wiki/Photog...rsensitization , section "Gas-phase hypersensitization" may give a clue of what kind of processing may lower LIRF.
So a possibility is removing oxygen and water from the gelatin matrix (degassing) and inserting hydrogen.
An ammonia bath (before exposure) also lowers LIRF, but if soon adds base fog.
It is clear that astrophotography was the field where there was great efforts to fight LIRF...
Jeff and koraks,
Thanks very much for the help with Excel! I'll be making some graphs for my data soon.
Best,
Doremus
Thanks to Jerry for helping out with this, I have now created my first chart for Fomapan 100 based on his tutorial
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