I've attached a family of curves for HP5-P developed in Xtol. I have a feeling if you want to achieve the higher CIs, you're going to have to reduce the dilution.
Shutter out of calibration
I had completed quite a few rolls of testing as per my earlier posts to this thread and I was becoming aware of a disturbing pattern. All of my shots were being over exposed ! Fortunately most of the test results were able to be shifted around to compensate for this, but it prompted me to measure the shutter speeds and compare them to the nominal values.
I was frustrated to find nearly all of them were 50-100% too slow. I made my own shutter speed tester by using an LED in reverse as a light sensor and connected it's output straight to an analog CRO. The persistence of the phosphor on the CRO screen together with my Android phone's video camera @25fps helped me to accurately measure the speeds.
Anyway, the moral of this post is to never assume your old analog shutter is reliable unless you or somebody else has tested it to be so !
I nearly sent it off for a Clean, Lube, Adjust and Test here on the other side of the world to me, until I discovered a reputable place right in my own backyard of Sydney (Legend Camera Services). They confirmed my measurements and also discovered the control spring had lost its tension and needed replacing.
Some time after it is returned and repaired I will finish documenting my film speed test results here.
Is Ralph's effective film speed at 0.17 above B+F ?
Well, my lens/shutter has been mostly CLA'd (2 speeds are still out by 1/2 a stop), and I have now repeated the test to determine the film's ISO in my workflow.
I need help interpreting Ralph's instructions. In summary I need to know if he is suggesting to set the speed point at
- 0.17 absolute transmission density, or
- 0.17 above base+fog level.
My B+F=0.13, so if I use (1) then the ISO for my HP5+ seems unusually high at 635 , but if I use (2) then the ISO is a much more sensible 252.
Here are the instructions from Ralph's pdf above:
"A long but precise way to determine the normal EI requires one more roll of film and an additional test.....as explained in Way Beyond Monochrome, ....enter your normal EI into cell ‘L9’."
then reading from p.139 in WBM, step 9.
"9. Using a densitometer, start with the first frame and twice the advertised film speed, count down 1/3 stop for every frame until you find the frame with the transmission density closest to 0.17 (Zone 1.5). The film speed used to expose this frame is your customized 'normal EI'"(I only reproduced step 9. to ensure Ralph still sells his book for those interested in the full test procedure )
Anyway to put the 0.17 into perspective, have a look at the following Figure 4 from the pdf Ralph attached above.
So far so good, as it appears to refer to using 0.17 above B+F (so in my case this equates to an abs density of 0.13+0.17=0.40 which is pretty high but gives an ISO of 252 by my testing).
There are however two points which conflict with 0.17 being a relative measurement above B+F.
- In the Figure 4 above, the RHS column shows Zone II beginning at 0.17 rather than Zone 1.5
- All the density measurements done thus far for the spreadsheet and entered into the "Input Data" tab (fig 3 in Ralph's pdf) are absolute values, but in point 9. above, there is no mention that 0.17 is a relative value in the instructions.
Can anybody explain why Zone II is beginning at 0.17 and reassure me that 0.17 is actually a relative density measurement ?
The diagram clearly illustrates with two arrows (bottom arrow pointing up to B+F), the point selected is 0.17 above B+F.
With seven zones fitting in 1.2, each zone is 0.17 of density on film. Ralph positions Zone I so it is in the density range from B+F to 0.17.
Ralph may explain better but I think Zone I is "at" 0.09 and ranges from 0.00 to 0.17 thus Zone I 1/2 is conceptually the border between Zone I and II.
Last edited by Bill Burk; 12-13-2011 at 11:44 AM. Click to view previous post history.
Reason: First answer not so helpful
Originally Posted by PeterB
This is Ralph's method of determining the speed point, the film speed rating that produces .17 negative density above fb+f and there's nothing wrong with that.
In the ZS as it is taught in The Negative , the speed point is determined by the film speed rating that produces a Zone I negative density of between .09 and .11. In past discussions, I know that Ralph does not consider a Zone I neg density value and thus a Zone I print value (i.e., the first suggestion of tonality, but containing no textural quality) to be of any "pictoral" value at all. Therefore, he dismisses it in his interpretation of the useful log exposure range. Again, nothing wrong with that------it's the same ZS principle, but IMO, with a different interpretation on establishing the speed point. I'm sure when Ralph sees this thread he will quickly set it straight if I have mispoke.
Last edited by CPorter; 12-13-2011 at 10:13 PM. Click to view previous post history.
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Thank you Bill for reinforcing for me that 0.17 is indeed a relative measurement. I'll re-read WBM to see if Ralph's half zone nomenclature refers to the boundaries between zones while an integral zone number would refer to the mid point of a zone range. It does get confusing as I have always thought of each zone as a range rather than a discrete point, but the latter makes more sense.
Originally Posted by Bill Burk
I'm sorry but, Angels...head of pin...dancing.
By attempting to understand either the location of a zonal mid point or the meaning of 0.17 we are actually talking about half a stop difference in exposure. That is far from "wasting time debating topics of no practical value"
Exposure placement is of importance. There's no question. Credit to anyone who wants to understand it better. My remark wasn't meant to disparage the questioning. My contention is that the question needs to be approached from a different conceptual direction in order to satisfactorily answer it or else things could remain in an endless round robin. Sorry, I don't have the time to go into details at the moment. Hopefully, later today.
If you want something in the mean time, there's a rather lengthy series of posts on the subject of expsoure in the thread "Is the K factor relevant to me or should I cancel it out?"
Last edited by Stephen Benskin; 12-14-2011 at 10:13 AM. Click to view previous post history.