Zone VI modified Pentax Digital Spotmeter confusion

DREW WILEY · Aug 17, 2024

An advantage of the Pentax spotmeter over the Soligor is the multicoated front optic, making it somewhat less prone to flare issues. Regardless, I always shade it facing the sun, or in relation to any large intense sunlight reflections in water.

Brian - the alleged "exposure errors" for the unmodified meter per Picker's chart aren't just suspect, they're ludicrous!

MTGseattle · Aug 17, 2024

@Kino are you having trouble locating the official Pentax manual or the one (if there was one) that the Zone VI folks wrote/amended? The Pentax one is scattered all over the web; Butkus. org, etc.
Likely a copy on ebay from time to time as well.

Kino · Aug 17, 2024

MTGseattle said:
@Kino are you having trouble locating the official Pentax manual or the one (if there was one) that the Zone VI folks wrote/amended? The Pentax one is scattered all over the web; Butkus. org, etc.
Likely a copy on ebay from time to time as well.

@MTGseattle; I do have the standard Pentax Digital Spot Meter manual from Butkus, but was wondering if Zone VI made a modified version.

The normal one should be fine thanks!

BrianShaw · Aug 17, 2024

Zone VI would have had little incentive to publish a user manual since the functionality is the same as the basic meter(s).

MTGseattle · Aug 17, 2024

A few pieces of Zone VI gear I have had have come with a simple type-written page of "instructions." The drying screen instructions being my favorite as drying screens seem fairly self-explanatory.

GregY · Aug 17, 2024

Kino, for some weekend reading here's a thread from almost 10 yrs ago.... & Richard Ritter does chime in

Spot Meter by Zone VI

I ran across a super nice Pentax Digital Spotmeter with case and manual. What was puzzling was there was a letter shown with it from Zone VI Studios and that they had modified the meter? Apparently the original owner had purchased it from them. Any ideas if this means Zone V won't be Zone V?

www.photrio.com

Regardless.... the Pentax Digital spotmeter was introduced in 1977 !..... and has proven to be a reliable and sturdy lightmeter.

RalphLambrecht · Aug 17, 2024

JerseyDoug said:
Accuracy no. Linearity and repeatability yes. After some costly incorrectly exposed shots back in the day I have all of my meters set to ISO 100 and do the ISO, zone, filter factor, etc. conversions in my head.

I have one of Picker's modified meters. It still has the dial sticker but I ignore it, and the dial itself, and just look at the digital meter LV reading.

let's not confuse accuracy and precision. Accuracy is how close a measurement is to a target value; precision is how repeatable that measurement is.

Chan Tran · Aug 17, 2024

RalphLambrecht said:
let's not confuse accuracy and precision. Accuracy is how close a measurement is to a target value; precision is how repeatable that measurement is.

If an instrument has poor precision it also has poor accuracy. And instrument with good precision can still have poor accuracy. An instrument with high accuracy must have high precision as well. So when I pay for an instrument the accuracy is most important.

DREW WILEY · Aug 17, 2024

An interesting but idiosyncratic use of terminology, Ralph. When I sold precision tools to machinists and mechanics, "precision" implied "accuracy". A precise brand was not only considered accurate by reputation, but by actual testing per piece, often accompanied with the paperwork proof that the testing protocol had specifically transpired. And that axiom would apply to quality light meters too. Maybe the concept of quality control no longer pertains to the mass of cheap junk one encounters in big box stores, but it most certainly does with respect to professional modern camera gear.

abruzzi · Aug 17, 2024

actually, Ralph is correct. I usually hear it phrased a bit differently, but a meter is imprecise if you every time you read the same location, you get a differnt value.

Accuracy and precision are two measures of observational error:

Accuracy measures how close a given set of observations are to their true value

Precision measures how close the observations are to each other

Accuracy and precision of observations lying on a bell curve
In the language of statistics:

Accuracy is a description of systematic errors, a measure of bias

Precision is a description of random errors, a measure of variability.

Sirius Glass · Aug 17, 2024

BrianShaw said:
You don't set the film speed of the film you are using on the Pentax digital spotmeter calculator dial before you start measuring?

Or did you intend to write, "use the setting [straight reading] to set the calculator dial, using your film's box speed or personal alternative, and then read the EV setting, or equivalent shutter spped/aperture, from the calculator dial for Zone or filter corrections to set your camera."

I'm assuming that @Kino already knows how to use the meter, or can look up the operating manual.

I see the Pentax Spot Meter is ISO 400 and using the spot meter to adjust to Zone exposures and filters all of the exposures were either off or way off. Alan's assistant worked with me. He saw the problem and when I followed his directions to read the shutter speed and f/stop from the spot meter and setting the lens to those, then making EV changes on the lens, led to perfect exposures.

DREW WILEY · Aug 17, 2024

Double talk. An inconsistent device, reading to reading, is not accurate either. And what do you mean by "true value"? There are certain quantifiable industry standards. But then you've got someone like Fred Picker who standardized on what he interpreted to be Zone V according to his personal development of Tri-X. I've got an old incident Weston meter which apparently only someone like Yoda or Merlin can explain the convention for. CDS receptors skew the curve differently than SPD ones, and so forth. But the model of meter needs to match every other meter of the same model.

I don't care about statistical variability. That's something for automated exposure programs. The whole idea is to minimize any kind of variability, to the effect it's a practical non-issue unless user error or poor judgment is involved. Here we're talking about handheld meters in relation to one's own f-stop and shutter speed settings. And the device sure as heck needs to read consistently every single time, or it's due for either recalibration or the trash can.

So maybe it would make sense to introduce another term: "reliability".

Chan Tran · Aug 17, 2024

DREW WILEY said:
Double talk. An inconsistent device, reading to reading, is not accurate either. And what do you mean by "true value"? There are certain quantifiable industry standards. But then you've got someone like Fred Picker who standardized on what he interpreted to be Zone V according to his personal development of Tri-X. I've got an old incident Weston meter which apparently only someone like Yoda or Merlin can explain the convention for. CDS receptors skew the curve differently than SPD ones, and so forth. But the model of meter needs to match every other meter of the same model.

I don't care about statistical variability. That's something for automated exposure programs. The whole idea is to minimize any kind of variability, to the effect it's a practical non-issue unless user error or poor judgment is involved. Here we're talking about handheld meters in relation to one's own f-stop and shutter speed settings. And the device sure as heck needs to read consistently every single time, or it's due for either recalibration or the trash can.

So maybe it would make sense to introduce another term: "reliability".

True value for a spot meter? Pentax (and Minolta) use a K value of 14 so the average luminance in the 1 degree circle is 14 Candela/m² for EV0 @ ISO 1.

DREW WILEY · Aug 17, 2024

Chan - that is a key example of an IDENTIFIABLE industry standard which filming and broadcast crews everywhere depend on. And one could count on new Pentax and Minolta meters being tightly calibrated to that same standard, as well as in relation to their own repair services. And that's why all of mine from the first, purchased nearly half a century ago, till my latest, still all read identically over their full scale.
(I do have one which has collected a little bit of mold inside the lens due to a stream dunking, which is predictably a third stop off. That being the case, it's my default choice for bad weather use).

abruzzi · Aug 18, 2024

Double talk? That is the standard scientific definition of this words. I learned the difference in 8th grade science classes 40 years ago.

chuckroast · Aug 18, 2024

Kino said:
Ok, so today I tracked down a very good condition Zone IV modified Pentax Digital Spotmeter thinking I have finally found the ultimate spot meter for large format photography.

But...

In true typical bass-ackwards fashion, I then begin researching the actual meter, searching for the "official" user's manual (which I have yet to locate) and ran across the Paul Rutzi blog posting that "debunks" the supposed gains of this modification.

http://zonevi.dk/junk/wp-content/uploads/2013/04/Paul-Butzi-Zone-VI-Meter-Modifications-Reprised.pdf

Don't get me wrong, the meter is great; everything functions fine (as far as I can tell compared to other meters), the form factor and ease of use still have me happy, but I am kind of mystified by this article.

Was it marketing hype or was there actually anything to the modifications?

Also, the darned meter doesn't have an actual Zone chart on the lens barrel below the EV dial and it doesn't appear to have ever had one!

Can I just print one out and paste it on there? What about the size/scale of this strip?

Frustrating...

The modification was claimed to do two things: Adjust for the spectral response of monochrome film, and improve the baffling to reduce internal flare. The theory was that you could meter through a filter and not have to compensate for filter factor.

This was neither completely true nor false in my experience. First of all, every film does not have the same spectral response. I believe Zone VI was compensating for Tri-X. You can do your own measurements by metering a scene directly and then through a filter to see if it properly compensates for the light loss.

NO meter is actually perfect in the first place. Even when calibrated, you still have to find your "personal EI" when metering with a given meter, your own thermometer, your own water and so on. So even with the Zone VI, you have to figure out how to translate from how it sees light to how you like to meter a scene.

I've had mine for years and it's a fine meter. But so are my other meters. The main thing I did was adjust every other meter to agree with the Zone VI. For the ones I couldn't adjust like the Nikon F Photomic FtN or the Leica M5 onboard meter, I merely noted how they varied against the Zone VI.

It doesn't matter if it is absolutely right to some lab standard. What I want is consistency. Since all my meters agree, I only have to come up with one personal EI, one development/agitation scheme, using one thermometer and distilled water and I get good consistency irrespective of the meter used. The only variability that I have to therefore contend with is the slightly different spectral responses of each meter and each film type and the different angles of view for each meter.

The one thing I've never gotten to work right is the spot attachment for the LunaPro.

Doremus Scudder · Aug 18, 2024

I have both Zone VI modified and unmodified Pentax spot meters. They are 1/3-stop different with the grey card in even lighting. I've marked them so I can adjust.

As for the modification, I don't see a disadvantage; it may well help now and then, but I don't see much of an advantage either.

In any case, the meters are workhorses, easy to use and find batteries for as well as light and portable. I keep mine on a lanyard that keeps it from hitting the ground if I drop it while kneeling. The lanyard clips to my vest or jacket.

Am I the only one who likes the Zone stickers? I find mine aids in shadow placement (no need to subtract stops, just place the LV across from the Zone (or partial Zone) you desire.

OP, just calibrate to the meter and use it as normal. The user's manual is available online. If you can't find it, let me know and I'll send it along.

Best,

Doremus

David Lindquist · Aug 18, 2024

Doremus Scudder said:
I have both Zone VI modified and unmodified Pentax spot meters. They are 1/3-stop different with the grey card in even lighting. I've marked them so I can adjust.

As for the modification, I don't see a disadvantage; it may well help now and then, but I don't see much of an advantage either.

In any case, the meters are workhorses, easy to use and find batteries for as well as light and portable. I keep mine on a lanyard that keeps it from hitting the ground if I drop it while kneeling. The lanyard clips to my vest or jacket.

Am I the only one who likes the Zone stickers? I find mine aids in shadow placement (no need to subtract stops, just place the LV across from the Zone (or partial Zone) you desire.

OP, just calibrate to the meter and use it as normal. The user's manual is available online. If you can't find it, let me know and I'll send it along.

Best,

Doremus

I also have both the Zone VI and the unmodified Pentax digital spot meters. I got the Zone VI in 1988 and the unmodified in 2008. They both have Zone stickers, personally I like them.

They differ from each other by about 1/3 stop. For T-Max 400 developed in D-23, the Zone VI is set at an E.I. of 250 and the unmodified an E.I. of 320. T

David

Bill Burk · Aug 18, 2024

DREW WILEY said:
Bill - The Macbeth chart patches are very precisely manufactured in terms of equal saturation of the primaries (R,G,B) as well as the secondaries (C,M,Y), plus a very neutral equally spaced gray scale. This is important when testing. What you term as "real" green, presumably in nature, varies tremendously, and has to be learned and accommodated through experience, exposure-wise, whether with respect to color film or black and white films, which vary in their specific green sensitivity.

Much green in nature also reflects a lot of red, orange, and yellow light due to other pigments being present, and not just the dominant green of chlorophyll, which often fades in autumn anyway. That fact make Fred's little spectrographic graph of a "red apple" versus a "leaf" rather unscientific in terms of meter response, and his other graphs are highly questionable too in terms of actual objectivity; but that's what one would expect from his county fair "snake oil" marketing approach.

I’m just saying that you would have to reconcile spotmeter readings of a scene. Readings taken with an unmodified spotmeter. Of a scene which would turn into a dramatic shot on infrared due to the effect attributed to Robert Williams Wood in 1910.

The readings would be inflated over that foliage. But they would not be inflated over a green patch on the Macbeth color checker.

It’s disingenuous to perform that test and declare the meter modifications are bunk.

DREW WILEY · Aug 18, 2024

abruzzi - statistical variation is what the photosensor supplier contends with; but the job of the meter manufacturer is to calibrate every unit to the a set standard afterwards, regardless of that variation. Hence "accuracy" and "precision" coincide. And that's what one should respect in any "reliable" meter.

My science degree was 54 years ago; but one of my first jobs was selling precision tools to not only ordinary machinists, but also to the big UC labs, including LBL. If you had a Starrett square head made in 1890, and it hadn't rusted, then a replacement blade made in 1970 was expected to fit it within 1/1000 of an inch, replete with a certificate from the Natl Bureau of Standards. Nobody went diving into a semantics debate over whether "accuracy" or "precision" was the correct description. And some of the machining was in reference to giant budget experiments resulting in Nobel prizes. A friend of mine was a staff statistician there; but the resident machinists and even scientific photographers had their own relevant trade terminology. I've worked with many manufacturing engineers, and they sure as heck didn't get worked up over common sense distinctions.

Chuck - It does matter that meters have some common denominator industry standard behind them. I've used six different meters over the past five decades (4 are still in parallel usage), and they all agree due to the fact all were initially calibrated to the same objective standard. Otherwise, you've got nothing firm to recalibrate them by if they
start to drift. Even personal E.I. is like a rubber band with no set boundaries.

In terms of those Zone labels, with each shade of gray allegedly corresponding to a single discrete interval of one stop, well, the flaw in that kind of model is that films differ in their dynamic range. Ole Triassic X Pan was kinda middle of the road, while some films have a shorter scale, and some a longer one. I shoot a lot of TMax, which allows distinctly more shadow value gradation than Tri-X. "Straight line" 200 films like Super XX and Bergger 200 allowed even more, while Pan-F has a quite restrictive range. So in theory, you'd need a different Zonie dial grayscale for each respective category, not to mention color film characteristics. Just leaving the dial alone and using it as is does it all at a glance; but to each his own.

Vaughn · Aug 18, 2024

What turned me off those stickers at the git-go was that the stickers seem to assume that a zone is the same tone throughout the whole zone...when it should be a continuous scale...not separate discreet tones. The sticker does not match reality, so it just seemed silly to me to have on there.

Which makes me wonder -- is middle gray in the middle of Zone V, or at the beginning of it?

DREW WILEY · Aug 18, 2024

What do you mean by "middle"? Are you describing that "accurately", or on the other hand, "precisely"? It's hard enough to find an "accurate" gray card. I often have to substitute quartz monzonite boulders.

Bill Burk · Aug 18, 2024

I put these patches on my exposure meters when I make Zone Stickers.

Not trying to be precise or accurate. Just checking the scene and asking myself: “If the reading I took came out like that on the print, would I like it?” How would I like it? Turn the exposure calculator to “place” the reading and walk about looking at other things. If I get a setting where everything important will be an acceptable print value, great.

Otherwise, think.

BrianShaw · Aug 18, 2024

Vaughn said:
What turned me off those stickers at the git-go was that the stickers seem to assume that a zone is the same tone throughout the whole zone...when it should be a continuous scale...not separate discreet tones. The sticker does not match reality, so it just seemed silly to me to have on there.

Which makes me wonder -- is middle gray in the middle of Zone V, or at the beginning of it?

LOL… let’s argue about whether ZS 2.0 zones should be in increments of 1/3 or 1/10 steps within each zone.

DREW WILEY · Aug 18, 2024

Let's face it; the Zone System is like a rubber band; you stretch it to fit your own needs. A few films will record texture all the way from Zone 0 through XII, if Zones are accounted as discrete stops. A few more films from 1 to X11 (not factoring minus or contraction development). And a few only III to VII. Most black and white films are somewhere in the middle.

But a different denomination of the Zone Religion teaches that the threshold of gray density is always Zone II, and the highest level always Zone IX, which means every "zone" in between has to be elastic, and not necessarily confined to discrete stop or EV intervals. Therefore you meter dial sticker would have to be elastic too.

Zone VI modified Pentax Digital Spotmeter confusion

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