Abnormal TMX Filmbase+Fog Density?

[Hwanik]

Hi,
Recently I've received my x-rite 810 densitometer(which have been bought at the used market) after repairing & calibrations service.
After shooting and development TMX sheets according to the well-known E.I test procedure described by Ansel Adams, I measured the TMX filmbase+fog density. The dev time was 8:30 with D76(1:1) at 68 degree with Jobo Tank.

The result was as follows:
(the denstiy value is the average of four times measurement)
(I measured by transmission mode & Vis mode)
------------------------------
Fb+F : 0.04
iso 50 : 0.12
iso 64 : 0.095
iso 80 : 0.08
iso 100 : 0.07
iso 125 : 0.065
iso 160 : 0.06
iso 200: 0.055
-------------------------------

According to AA and other documentations, the Fb+f should be around 0.3 but my newly calibrated x-rite reported 0.04 ( about 8 times lower ! ).
So I did recheck the x-rite calibration plasque to test the proper operation of densitomenter and it was OK.

Is x-rite's scale different from others? Should I multiply ten to get the right densty of film??

What's wrong with my result??

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Answers
Hwanik Choi , mar 19, 2006; 05:19 a.m.
Sorry, some typo in data. Fb+F : 0.04
iso 50: 0.12
iso 64: 0.095
iso 80: 0.08
iso 100: 0.07
iso 125: 0.065
iso 160: 0.06
iso 200: 0.055

[robc]

fb+f can vary greatly between different film and developer combinations. I typically get between 0.07 and 0.13 for the film developer combinations I use. 0.3 is high. Can you give a reference to where you have seen this written.

AA's numbers are from data some 30 years + old. Films and materials change. Characteristics change. Ignore old densitometry numbers since they have very little relevance to todays materials, especially developers which have all sorts of added chemicals some of which are fog inhibitors.

I am not familiar with the film dev combination you are using but if it has a naturally clear base then your figures are not unreasonable.

[Hwanik]

Rob,
The value 0.3 is from "The Negative" by AA as you mentioned and from the TMX characteristic graph (http://www.kodak.com/global/en/professional/support/techPubs/f4016/f4016.jhtml) provided by Kodak.
From this graph, the Fb+f seems to be located somewhere between 0.2~0.3 ( yes, it is not D-76(1:1) but D-76 ).

If the Fb+F 0.04 is reasonable, I'd better to rate tmx as iso 50.

[robc]

you need to take characteristic curves in manufacturers web sites with a pinch of salt. Ilfords are really bad. I have previously alerted them to obvious errors which were fixed with equally obvious errors. Kodak are better but my suspicion is that the 0.3 figure is what they consider as an acceptable fb+f which will print through without a noticeable degradation in print quality. It doesn't mean that 0.3 is what you should expect to get. This is of course a subjective criterion.

I wouldn't start to worry about fb+f until its gets over approx 0.15 since up to that level print quality should not be visibly affected although some may differ on that opinion.

[Hwanik]

Thanks Rob~