# Hitting ASA Triangle Does Not Mean You Got Full Film Speed

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• 07-22-2012, 05:02 PM
ic-racer
• 07-22-2012, 05:54 PM
Bill Burk
Quote:

Originally Posted by ic-racer
With the revised numbers it still looks pretty odd at the toe. But this is not the dataset you fit to the ASA triangle, I suspect you used on of the others (which one?).

Dataset error again. Sorry. The numbers are scrawled on unlined paper and I averaged them in my head when I graphed the first time. I did it right the first time, the graphs are good, but yesterday and today it wasn't easy lining up the columns...

The test wedge is just "taped" to top of glass, but I just am leery of tampering with it. The higher densities are "calibrated by me". I read the 2 stop ND filter on the densitometer, and added the result to the calibrated step it overlaid to get the simulated steps above 21. Next time I am getting a 31 step wedge.

The 13 minute fits the ASA triangle.
• 07-22-2012, 06:25 PM
ic-racer
Quote:

Originally Posted by Bill Burk

The 13 minute fits the ASA triangle.

I took the opportunity of adding some functionality to my spreadsheet. Now it also calculates the "0.1" point and automatically shows the correct placement of the ASA triangle on the grid. The user can easily determine if the data passes through the red circle or not. In this case you can see that it does pass through the red circle (1.2 log out from the speed point and 0.8 log up from the speed point).
So the spreadsheet automatically calculated the 0.1 point as 3.11. How does that compare with what you got by hand?

http://img.photobucket.com/albums/v6...2/13minASA.jpg
http://img.photobucket.com/albums/v6...cer/Detail.jpg
The 0.1 point is the GREEN CIRCLE and the ASA/ISO speed point is the GREEN TRIANGLE. To save weeks of programming I did NOT use a spline. I used linear interpolation. As you can see it is as good as one could eyeball it on graph paper. I'm happy with it.
The WHITE TRIANGLE is the W-speed point with the safety factor added (surrogate for 0.3G point with one stop safety factor). Delta-X plus safety factor would likely be similar. For educational purposes, I guess the next step is to program the Delta-X into the spread sheet....
• 07-22-2012, 06:42 PM
ic-racer
At this point I'm reluctant to pass out the spreadsheet as the calculations are hidden all over the place and the spreadsheet is essentially held together with bailing wire and duct tape. One click in the wrong place and it could start giving bogus numbers or stop working all together.

For example there are over eighty cells with the following equations to systematically search for the W point and the 0.1 point:

=IF(H23=0, 0,(C23+(H23*(\$E\$35-B23))))
=IF(AND(B23>=\$E\$35,B22<\$E\$35),(((C22-C23)/(B22-B23))),0)
=IF(AND(C25>=0.1,C26<0.1),(((C25-C26)/(B25-B26))),0)
=IF(K25=0,0,(B25-(C25-0.1)/(K25)))
• 07-22-2012, 06:48 PM
Bill Burk
3.11 is what I got by linear interpolation as well. And right through the circle too.
• 07-28-2012, 03:26 AM
Bill Burk
Not Hitting Full Film Speed In Tests Does Not Mean You Didn't Get Full Film Speed
I did quite a few development tests the past few days, where I developed one sheet at a time versus my usual six sheets at a time.

The only thing that seemed to change was decreased time to develop to similar contrast.

I didn't see any speed increase.

The EG&G results remain around 200 to 250. I am used to that.

I may make other attempts to increase speed. But I am beginning to think maybe I "really" get full speed. Maybe the tests just aren't confirming. There could be a good reason. Maybe the "discontinuous spectrum" of the xenon flash doesn't match daylight... Maybe excessive "blue" absorbtion by the No. 96 ND filter makes it a poor choice to include in sensitometry tests...

I believe now that stacks of six in tray provides "pretty good" agitation. Earlier I posted a significant difference but that was a mistake because I accidentally developed in Dektol 1:1 instead of D-76 1:1 as I planned.
• 07-28-2012, 04:29 AM
ic-racer
Quote:

Originally Posted by Bill Burk
But I am beginning to think maybe I "really" get full speed. .

I'd re-do the estimated EG&G light output based on your tests. With all the estimated densities in your calculation of ISO 200/250 it could easily be 1/2 stop off. That is, work backwards, saying the film is ISO 400 by definition and your light out put is 2 millilux-seconds at the 0.1 point after you subtract all the density you have between the lamp and the film. That is the way I calibrated mine.
• 07-28-2012, 11:53 AM
Bill Burk
Quote:

Originally Posted by ic-racer
I'd re-do the estimated EG&G light output based on your tests. With all the estimated densities in your calculation of ISO 200/250 it could easily be 1/2 stop off. That is, work backwards, saying the film is ISO 400 by definition and your light out put is 2 millilux-seconds at the 0.1 point after you subtract all the density you have between the lamp and the film. That is the way I calibrated mine.

Big issue is the contradiction that I got from Panatomic-X. I am using that placement as the position for the film speed scale.

Differences I think play into it are:

-> Panatomic-X is a traditional emulsion, TMY-2 is T-grain.
-Different spectral sensitivities, Panatomic-X vs TMY-2... Maybe the EG&G is "bang on" for traditional emulsions so it was deemed a good sensitometric light source on that basis... But maybe it is not as great a match for TMY-2.

-> No. 96 ND 0.6 has its limitations in sensitometry.
-I do not use it at all to catch the toe of Panatomic-X.
• 07-28-2012, 03:13 PM
Stephen Benskin
Bill, why not do a TMY test with the ND 0.6 on top of the flash housing? Forget about trying to extend the range of the step tablet and limit the variable.
• 06-22-2013, 04:29 PM
Bill Burk
Just to record a thought, I had not been consistently applying "hold time", as Stephen pointed out in a similar thread the temptation is there, the lab is setup and ready, to expose and process immediately.

And so. It is quite possible the Panatomic-X reads higher speed than its rated ASA 32 in my testing - because I developed immediately after exposing.

http://www.apug.org/forums/forum37/9...stability.html
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