Anomaly in exposure testing

[Ulophot]

Just when I thought I had exposure and development nicely set, a conundrum arose which I hope someone may be able to help me resolve. Since there are a number of variables, I am attaching a zip file of a Word document with a full explanation, since it will otherwise make a very long post.

In brief, it pertains to exposing a set-up twice, placing two materials of different reflectance on the same zone and getting results about a stop and a half apart.

I'd be grateful if someone can explain it or suggest a new test to isolate the issue.

[ic-racer]

Expose for the lower values and set the higher values when developing and printing. So, if there is a dark shirt that needs a certain minimal value to retain texture, set that object and the others fall. Don't base a scene's exposure on a highlight value (unless exposing reversal materials). Some Zone Systems are 'black box' devices to help photographic artists. A photographic scientist will have a full understanding of the way paper and negatives behave when exposed to light and developer can complete the picture.

Here is a good start: https://www.kodak.com/uploadedfiles/motion/US_plugins_acrobat_en_motion_education_sensitometry_workbook.pdf

[Ulophot]

Thank you the link, though I have no access to sensitometric equipment. As I wrote in the attachment, I had already tested successfully for Zone I, and ran the last test placing the black shirt on III in one exposure and the tan towel on III in the next.

[Jac@stafford.net]

Test to your heart's content, but to be happy you might consider a far simpler modified Zone System. Never, ever has a properly made exposure trumped a compelling image.

When explaining one's process requires more than a page of text, it is likely your effort is a distraction from making images. Maybe scientific imaging would suit such a person. Only academics appreciate verbosity more than substance.

[Ulophot]

I regret, Jac, that you choose not to share some your photographic expertise with me. I am sure I could benefit.

[Jac@stafford.net]

I regret, Jac, that you choose not to share some your photographic expertise with me. I am sure I could benefit.

I'm sure I cannot help except to repeat my approach which is to understand the fundamentals and make photographs, then if you find compositions, photographs you like but are unsatisfied with tonalities, then look to technical exposure/filtering/development improvement. Making a compelling photo is the hardest part. Working from pure chemistry outward has not worked for anyone I've known in fifty years of photography.

Very best,
Jac

[Ulophot]

Thank you; I understand you better now. At the risk of being less than concise, I will elaborate this way: I agree entirely on compelling imagery; as in great music, a musician may give a performance of stunning technique devoid of art. My circumstances do not allow me to dedicate my life to art as I would like. My intensive studying of great art, and attempts to produce some echo of their wonder for decades, is what drives me. Having been obliged to put down my cameras about 13 years ago for financial reasons, I am now in the process of returning to serious personal work. Because of the challenges new aspirations are taking me, I think it obligatory to regain, and supersede my previous level of command of the craft as I pursue greater artistic aims as well. My technical question arose in this context.
I attach one portrait to at least indicate my genuine intent.

[stawastawa]

two guesses, but only guesses.

I) The beige towel has a greater capacity to throw light, as such it throws light in many directions and causes flare in the lens/camera/film. thus a brighter zone III in the print.

II) You may be on to something when thinking about infrared 'pollution'. The reflectivity of the two objects is probably very different, reflecting different parts of the spectrum. the Bright towel may be baised towards, say red light, while the black t-shirt may be baised towards blue. The films sensitivity to those two colors is different and so what the meter says should be Zone III is different for the two objects.


I wonder, if you place both items at zone VII what happens?
I also wonder if reciprocity failure is doing something here, eg. not enough exposure of the low values. ( I assume the exposure to place the black T shirt on Zone III is longer than the exposure for the towel on Zone III).

[Ulophot]

Thank you for your detective work, stawastawa. In response:

I think it unlikely that flare would lead to the 1.5-stop difference in these circumstances. The lens is, I believe, multicoated, and has not shown significant flare in situations with brightly lit light surfaces.

Reciprocity departure was not at issue here, neither exposure being greater than 1/2-second.

Your idea of placing both materials on a higher zone is interesting and probably worth a try, to see if the same issue persists. I'll have to wait for a brighter day to avoid reciprocity.

As mentioned, the meter is supposed to have extra infrared filtration built in, but it's hardly a new meter and this may be a variable. Whether it could account for the wide discrepancy, I don't know.

Again, thanks for taking time with this.

[stawastawa]

to test the metering see if you can locate some different meters to compare.

[Bill Burk]

When you exposed properly for Zone VII and tried to print it to be Zone VII, you found the Zone IV was too thin, printed too dark.

I think you underdeveloped. You have a flat negative. You may have chosen the time for D23 stock instead of for D23 at 1:1.

Recommend re-doing the test, keep it same - the tan towel at Zone VII wasn't a bad idea and the black t-shirt falling around Zone IV should give you a good range to work with.

But develop for 13 minutes or more.

[Ulophot]

to test the metering see if you can locate some different meters to compare.

My Luna-Pro F matches my Pentax extremely well. Both could be wrong, but as noted, I created a good Zone I with the tan towel placed on I using the same meter; it was the discrepancy between that and placing the black shirt on the same value that raised my question mark.

[Ulophot]

When you exposed properly for Zone VII and tried to print it to be Zone VII, you found the Zone IV was too thin, printed too dark.

I think you underdeveloped. You have a flat negative. You may have chosen the time for D23 stock instead of for D23 at 1:1.

Recommend re-doing the test, keep it same - the tan towel at Zone VII wasn't a bad idea and the black t-shirt falling around Zone IV should give you a good range to work with.

But develop for 13 minutes or more.

Thanks for your response. Perhaps my writing is unclear. By "meter 7," I mean the Pentax's number, not Zone VII. I placed the tan towel on Zone VI as stated, which read as 7 on the meter scale, which I believe is in the EV (exposure value) scale. In any case, having read, placed, developed and proper-proof printed (Fred Picker, ZoneVI Workshop, etc.) both a Zone I and Zone III from the tan towel, with other values falling appropriately (the Zone III was, if anything, a teence high), I remain curious about the anomaly. If time allows, I will retest this weekend, in various ways, to see what transpires.

I would only add, that this test came after a couple of months of available-time testing with HP5 and D-23 to establish basic exposure and an array of development times and procedures for N+2 through N-2, including tray and rotary processing, stock, 1:1, 1:3, and two-bath (with Borax). This test used Normal rotary processing and was meant as a concluding check of previous testing results. I will post back one I have more results.

Thanks again to one and all!