Calibrating 4x5; gray card Zones don't match still life Zones

Getting accurate spot readings of a real subject is quite a skill, requiring years of practice to achieve with consistency.

The reflectance characteristics of real materials and surfaces can vary all over the map.

You need to build a still-life subject with fixed lighting, not flash.

Take an incident reading with the dome facing the camera lens.
Then work with a spot meter until you get exactly the same reading from an 18% gray card.

That's the way the system is calibrated by definition.
If your results vary, your technique is wrong.

- Leigh

Keep in mind that all gray cards are not created equal. I was teaching a class on the Zone System many years back...during which I supplied each student with his/her own gray card, then shared out my Zone-VI modified Pentax spot meter - and results were inconsistent. The problem? The gray cards were basically "el-cheapos," manufactured using a rather shiny card stock - thus exhibiting a high degree of specularity, even in relatively flat light. I then purchased a much better gray card - made of a plastic material and finished with a good matte surface. Ideally, a gray card would exhibit no specularity at all. This is why I often trust an incident reading over a gray card reading. Not saying to ignore specularity...just that the specularity exhibited by a cheap gray card would likely not relate to that of a given subject.

From what I can tell, you overexposed and overdeveloped your film. For a film test, why not start using the rated film ISO (400) and Normal development?

Secondly, why are you surprised that a gray card exposure was different from an exposure based on a real life object? It is quite possible that your zone placement of the still life object was an artificial or inappropriate setting (i.e. such as deciding to place a deep shadow tone higher up the zone scale than it should be naturally). For your still life, if the lighting and everything else was the same, you could/should have used the gray card indicated exposure for the still life. Or at least, compared the zone settings you were getting from the still life with your gray card zone settings to see how the placement of tones would compare.

Lastly, your film test with the gray card should really just be to determine your effective film speed and optimum development combination, and that's all.

Here is a graph

I show what your teacher had you aiming for in dotted line and you can see the exposure and aim are for ASA 125 normal (I think it is pretty cool your teacher had you aim at ASA target. Anyway you can call that N+1).

Your line is the solid line above that.

Since you used 400 speed film, your film is more sensitive to light and you got higher densities for each test point. You can see the two graphed lines parallel each other.

That means you got the development time right.

Then when you did your still-life, you used appropriate exposure, and got appropriate results for 400 speed film.

Attachment 157295

If your teacher told you to expose an ASA 400 film at ASA 125 on a normal subject, he screwed up.

Modification of film speed is used to accommodate extreme variations in the subject or lighting conditions.

We usually consider the "detail" range of a subject to be 7 zones, being II through VIII on the negative.

So the first step is to assess the detailed areas of the subject and determine its "natural" range.

If it differs significantly from the expected 7 zones, you modify exposure and/or development to compensate.
Exposure changes affect the shadow detail and highlights. Development changes affect the highlights.

- Leigh

thank you all so much. I don't understand most of the feedback. Perhaps because I am a newbie.
I chose an EI of 125 because previous tests of a gray card Zone I where I found appropriate densities with ISO 125 and one of my teachers after looking at many of my tests of gray card said he thought it was 125. However, yesterday after getting the feedback that ISO 125 with HP5+400 was unlikely. I did more tests of varying ISOs. I have been getting more consistent densities using a still life scene with flood lights than with the gray card so I have switched to using still-life scenes to calibrate. Here are the results of yesterday's test of N+1. All densities except Zone 0 are net densities. DT HC-110, 1:47, 11’30”, 68 degrees Fahrenheit. I am using a Saunders Enlarger. My target densities for Zone III and Zone VI (pushed to VII) are 0.45 and 1.20

ISO, Zone, Camera Settings, Density
NA 0 NA 0.10
250 III, VI 1/15, f/20 0.32, 0.97
200 III, VI 1/15, f/18 0.37, 0.97
160 III, VI 1/15, f/16 0.42, 1.04
125 III, VI 1/15, f/14 0.49, 1.09
100 III, VI 1/15, f/13 0.57, 1.10

As you can see, at least from this test, ISO 125 doesn't seem so far off, although 160 is a little closer to the target. (I know Bruce Barnbaum thinks measuring densities is useless, but from what he says about shadow detail a little farther out of the toe towards Zone IV might be even better.) My plan today, unless one of you says something that might change my mind, is to stick with an EI of 125 and increase my development time by 30" to 12' in order to pull Zone VI up to 1.20.

I just re-read this. The way I wrote it may lead to a misunderstanding. These densities are from negatives, not prints. I mentioned the Saunders Enlarger in order to explain why my target Zone VI target density was 1.20.

I have been making prints using 35mm, 120 and large format film for thirty years and never felt the need for a density reading. Instead I follow the film maker's instructions for film speed and development. I make sure I follow the instructions carefully. I make prints using variable contrast paper. I get high quality results. I am able to make a print of a gray scale that matches the original when placed next to it.

While you are learning I urge you to step back and adjust your choices of materials and methods to be exactly "by the book". Once you have established the normal performance of your chosen materials and processes there will be opportunity for experimentation when the necessity arises, however it seems to be inviting trouble to begin by deviating from normal exposure and development of film material. Relying upon density readings seems to add fuel to the fire.

Why not make a nominal exposure, give nominal development and print the result on a selection of paper contrasts and inspect the results. Calibrating a camera lens film and developer is a fine tuning process for the advanced user who has established competence with normal materials.

Thanks Ted for your thoughtful and kind response. I appreciate you taking the time to write, particularly from your thirty years of experience. My response may not be adequate but it is simple: I am taking a Photography Class, Introduction to Zone. I am completing the assignments for the course. In this moment, I am trusting the wisdom of my teachers. I posted here to see if someone could help me understand the results I have been getting. Something that my teachers and I haven't been able to figure out.

Quote:

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Originally Posted by Richie

I posted here to see if someone could help me understand the results I have been getting. Something that my teachers and I haven't been able to figure out.

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It may not be too much of a mystery. Given that HP5+ is basically ISO 250 for N development *, if you're getting 125 you are off by 1 f/stop. If your lens is focused closer than infinity, that can cost you a fraction of an f/stop. If your shutter speed is off - or your thermometer - or your water - or your agitation...etc. those can cost a few more fractions. Those fractions can easily add up to 1 f/stop.

* You might find it helpful to search this forum for discussions about film speed and why manufacturers provide the ISO numbers as they do.

One of the principal benefits of working with the Zone system is to get you to see in B&W. It's a bit like learning scales and intervals in western music, or ragas in Indian music. In the end it's inspiration which matters, but it manifests through a command of the grammar.

Quote:

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Originally Posted by Richie

thank you all so much. I don't understand most of the feedback. Perhaps because I am a newbie.
I chose an EI of 125 because previous tests of a gray card Zone I where I found appropriate densities with ISO 125 and one of my teachers after looking at many of my tests of gray card said he thought it was 125. However, yesterday after getting the feedback that ISO 125 with HP5+400 was unlikely. I did more tests of varying ISOs. I have been getting more consistent densities using a still life scene with flood lights than with the gray card so I have switched to using still-life scenes to calibrate. Here are the results of yesterday's test of N+1. All densities except Zone 0 are net densities. DT HC-110, 1:47, 11’30”, 68 degrees Fahrenheit. I am using a Saunders Enlarger. My target densities for Zone III and Zone VI (pushed to VII) are 0.45 and 1.20

ISO, Zone, Camera Settings, Density
NA 0 NA 0.10
250 III, VI 1/15, f/20 0.32, 0.97
200 III, VI 1/15, f/18 0.37, 0.97
160 III, VI 1/15, f/16 0.42, 1.04
125 III, VI 1/15, f/14 0.49, 1.09
100 III, VI 1/15, f/13 0.57, 1.10

As you can see, at least from this test, ISO 125 doesn't seem so far off, although 160 is a little closer to the target. (I know Bruce Barnbaum thinks measuring densities is useless, but from what he says about shadow detail a little farther out of the toe towards Zone IV might be even better.) My plan today, unless one of you says something that might change my mind, is to stick with an EI of 125 and increase my development time by 30" to 12' in order to pull Zone VI up to 1.20.

I just re-read this. The way I wrote it may lead to a misunderstanding. These densities are from negatives, not prints. I mentioned the Saunders Enlarger in order to explain why my target Zone VI target density was 1.20.

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If you are following Barnbaum's boook, throw it away. His methods work for him but not many others. Step 1 - determine your EI Step 2 determine your normal development time Step 3 use this info on rea subjects, still life or other, and make the minor adjustment needed.