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05-17-2017, 06:55 AM   #1
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Zone VI Spot Meter off?

Hi, Team,

I visited my local camera store yesterday and inquired about any used spot meters they had for sale. The clerk showed me a Zone IV modified spot meter that appears to have originally been a Soligor. The price was great - he knocked $40 bucks off for a final price of $80. I asked the clerk if it was tested, and he said he used it around the store and it seemed accurate. This gent is a straight shooter, so I trusted him. Knowing what they go for on Ebay I snatched it up.

I took it for a spin last night with my K1000. But it seems to be reading quite brightly. Either that or my new-to-me k1000 is reading very dimly. That being said, the K1000 light meter seems to read accurately based on my exposure intuition. I need to test them both against my Canon 70D to figure out what is going on.

I have two questions:

1) What is the best way to test the accuracy or a spot meter?
2) If it is badly inaccurate, do I take it back, try to get it repaired, or just compensate in my head for its inaccuracy (if it is systematically inaccurate)?

I need a spot meter for my trip to Seattle next month. I'll be using my Pentax 67 for landscapes and such. So I need to figure out a solution within the next month, even if its getting a loaner.

Thanks for your input!

05-17-2017, 07:04 AM   #2
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QuoteOriginally posted by Femto1969 Quote
1) What is the best way to test the accuracy or a spot meter?
Test against a known good meter (does not need to be a spot meter) using a gray card or uniformly lit white or gray surface. Alternatively, have a repair shop calibrate your meter against a standardized light source.

BTW...the Zone VI is a modified Pentax unit. If yours says Soligor on it, you may not have the genuine article. I was wrong on this.

Edit:
There may be quirks to doing a calibration and/or using the meter for other than the B&W films it was optimized for (the Zone VI modification). This thread at Luminious Landscape's forum may be helpful:

Calibrating a Zone VI Pentax Digital Spotmeter

@tuco Do you have any experience with or information about the Fred Picker modification?


Steve

Last edited by stevebrot; 05-17-2017 at 07:46 PM.
05-17-2017, 07:41 AM   #3
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Meter a clear blue sky--midday/not near sun. It should give a reading of 1/iso sec at f/16. E.g., set iso 100 and should read 1/100 sec at f/16. This should be accurate to about +/- 1/3 stop.
05-17-2017, 07:49 AM   #4
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Thank you for the quick responses.

Let me clarify: this looks like the original meter was a soligor, but it has been modified by Zone VI and has the stickers and such. It looks exactly like this:

Zone VI 6 Studios Modified Spotmeter W/Holster Vtg Soligor Exposure Camera Meter | eBay

I plan on using the meter for BW photography primarily.

I'll try to get a grey card from my camera store so I can test its accuracy. Maybe it seems high compared to my k1000 metering because it is designed for BW? Or maybe because I wasn't expecting such high results at ISO 200. I'll do some more testing tonight and compare it to my Canon 70D TTL meter.

05-17-2017, 08:02 AM   #5
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Perhaps a bit more about light meter and calibration. There is some disagreement about proper exposure/meter calibration.
--Often it is said that a midtone is 18% reflectance (e.g., Adams and the zone V), while the more proper standard (as far as I can find out) is 10%--and various manufacturers could likely use a value in the range 10% to 18%. This (10% vs 18%) is almost a full stop difference.
-- In the end one should adjust the meter (e.g., bias iso value) to give what you find good. But of course it should read consistently with changes in light level.
-- BTW the metering of the blue sky is the most accurate way of reflected light metering in high sunny conditions--which are otherwise tough to meter (except with incident meter). And then adjust (+ 1/2 ~ 1 stop) for snow/highly reflecting ground. But of course recognizing that as a midtone meant it wasn't necessary to meter at all.

About your saying maybe it is high for B&W. A meter should yield a value that indicates the light level it is receiving (and presumably the zone you are placing the reading on--if it is modified for the zone system). It may have an indication to set the zone you are placing the reading on--in which case reading from an average midtone (blue sky, etc.) is zone V. The user adjusts for what was metered: highest level [~VIII] for color slide, lowest level [~I] for typical B&W, etc.

Last edited by dms; 05-17-2017 at 08:19 AM.
05-17-2017, 08:08 AM   #6
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QuoteOriginally posted by dms Quote
-- In the end one should adjust the meter (e.g., bias iso value) to give what you find good. But of course it should read consistently with changes in light level.
So if my meter is off, it will be off systematically, so biasing with ISO value will provide accurate results across the EV spectrum?
05-17-2017, 08:29 AM   #7
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QuoteOriginally posted by Femto1969 Quote
So if my meter is off, it will be off systematically, so biasing with ISO value will provide accurate results across the EV spectrum?
Yes it should if the meter is working properly. Although you may want to compare against another meter (e.g., in camera)--at significantly lower illumination--to verify it is OK.

BTW instead of a gray card a white paper (typing paper) can be used. It is about 90% reflectance, or about 2-1/3 (e.v.) stops brighter than Kodak (18%) gray card.

05-17-2017, 08:42 AM - 1 Like   #8
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QuoteOriginally posted by dms Quote
BTW instead of a gray card a white paper (typing paper) can be used. It is about 90% reflectance, or about 2-1/3 (e.v.) stops brighter than Kodak (18%) gray card.
I confirm that.
Bright hazy sun here in Michigan today at 11:30 am
Using a vintage Honeywell Pentax 3/21 spot meter modified with my own electronics:
Boise Polaris Premium white paper : EV 15.0
digitalimageflow.com Kolor Kard Gray Lab 50,0,0 RGB 89,89,89 : EV 12.8
05-17-2017, 09:07 AM   #9
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QuoteOriginally posted by stevebrot Quote
...
@tuco Do you have any experience with or information about the Fred Picker modification?
Steve
No I don't.

My outdoor BW work is the Sunny 16 now and exposures are pretty much all rounded to the nearest whole stop. So having my spot meter within 1/3rd stop of some standard doesn't mean much to me anymore.
05-17-2017, 10:31 AM   #10
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I quite often use M exposure mode, even with fancy lenses. After 66 years of using Pentaxes, I find that Sunny 16 and variations are about as accurate as you can get. I grew up using the handy little piece of paper that came with the roll of film. My brother used my Minolta 16 for trips because of the light weight, and it simply had a dial with a sun, partial cloud, etc in icons. Perfectly adequate for negative film.

With modern lenses on a K-3 or K10, Sunny 16 is so close to the correct exposure that shooting RAW+ will allow you to fix the odd JPG that doesn't quite work. I gave up using light meters years before my original Pentax from 1956/7 died.

One old grump's opinion. Use at your own discretion.
05-17-2017, 01:53 PM - 1 Like   #11
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TBH, this is a tricky one to answer as it is not really clear on how you conduct your tests i.e.test object lighting conditions, that lead you to believe that the K1000 light meter 'seems to read accurately'
I would suggest that as you are going to be using a Pentax 67 for landscape work that you actually conduct a series of tests using your Soligor.

Some thoughts and information that I hope may be of some help:

1. There is a huge difference in both meters and this must be taken into account when testing.

The Pentax K1000 meter uses Cadmium Sulphide CDS which measures the average brightness of the ground glass using I believe the whole area to take an average reading (and integrates to grey?).
The Soligor meter uses a Silicon Photo Diode (SPD) which should be more accurate or at least able to measure in very low light conditions in comparison to CDS. In addition it reads a very small area that being as you know 1 degree.

Due to the difference at least in angle of measure you should take trouble to check the metering by from both is exactly the same. One way take a card white, grey or black (does not matter) and set the K1000 up on a tripod with the card absolutely filling the viewfinder with ISO set for 100 and note meter reading then with your spot meter to eye and on the same axis as the camera lens (as near as possible) make your reading. Ideally do this on an overcast day where light conditions not likely to vary over a minute or so

By how much do the readings differ?

2. Your comparing two different types of meters as well, relating to in camera or hand held and there are international standards for each. Additionally manufacturers are given some +/- tolerances by the standards so really you can expect some change between meters and systems. Exposure meters have an exposure equation including a constant 'K' (reflected) and 'C' (incident). The K being the famous or infamous and by some mysterious 'K factor'

The net result would seem to be exposure meters can use a percentage value for a mid tone grey equating to and varying between 10.5 - 14% (with possible a little more leeway). Leading to a possible difference of around 2/3rds of 1 EV.

Any more than this then you may perhaps want to get one or both checked out and perhaps the Spot meter may be the one to go for as it may prove quite useful for landscape work.

Richard Ritter, I understand worked with Fred Picker on the Pentax and Soligor meters and may be able to help (assuming still in business) with a service.
RTRITTER Large Format Camera Repair Services

3. If you are feeling adventurous/brave or are technically inclined you may consider having a play with calibrating the meter yourself if it is truly out and you can prove so with practical tests against a known source.
Underneath the label Soligor or Zone VI are 3 potentiometers which can be used to calibrate the meter each does a different job to bring the meter into line. I do have some information from someone who tackled this but do not have any method to prove the technique works. I will send you the information if you think it of some use with the caveat that any work you undertake will be solely your responsibility.

This is what you should find under the label
Soligor Digital Spot Sensor Meter Disassembly & Notes

In case you need the manual
Soligor Ditital spot meter, soligor CDs Exposure Meter instruction manual, user manual, free PDF manual, camera manual

I have a the same Soligor meter, somewhere, modified only with my own Zone scale and not with the Zone VI modifications. Although I understand that modifications to the meter was made which included IR, and a filter pack, to match the sensitivity to Tri-X film and some colour materials of the day the articles I have seen indicate that these applied to Pentax Spot meter with no mention of the Soligor.

Perhaps too much information here But IF you are needing the accuracy and intending to follow the Zone system principles then a sound methodical testing procedure needs to be undertaken with the film/s of and developers of your choice to maximise IQ
05-17-2017, 02:34 PM   #12
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Right now I just need the basics. I have extremely limited experience in film photography. It is all brand new to me.

I know that if I am going to get high quality landscape photographs with my Pentax 67 in Seattle, I need to have a working spot meter to ensure that my exposures are right. I plan on using the most basic methods for exposing with the zone system. Either expose for the mid tones or average the highlights and shadows.

I bought ten rolls of budget BW film: Ultrafine 400. Maybe I should buy some Tri-X film to maximize the chances that the Soligor will be useful. I'm content sticking to whatever method I need to in order to make my current outfit work well.

I will try the spot meter measurement process you outline above. However I am wondering if I could use my Canon 70D on spot metering mode to make the process easier.

Are you saying that the Soligor Modified Zone 6 may not actually have any true modification beyond the zone sticker on the barrel? This copy may not have any additional filters or a replaced sensor?

Thank you for that manual. I really do need to look through it to make sure I'm even using it right. Right now I'm treating the number that it reads as the EV, and using the wheel to calculate camera settings based off that. Its possible I don't even have the basic premise down, which may explain the wonky readings! Ha ha.

I'll check it out when I go home this evening. Thanks for all of your help!
05-17-2017, 03:59 PM - 1 Like   #13
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Before you embark on your Seattle journey it is a strong recommendation that you actually try your film and I am assuming home development to make sure that you are in the ball park for both exposure and development. It is my view that you should stick to one film to begin with and as you have settled on Ultrafine use that to get a feel for the system.

Your Canon throws another variable into the pot and while it may be a work around to use the spot reading just be aware that the spot area is much larger than 1 degree on the Soligor and the area you select to measure is very important as this is going to be your mid tone and will be recorded as such regardless of shooting a black cat in a coal cellar or a white horse in the snow i.e. a potential muddy grey. Frankly I think you will find it a pain juggling two cameras for the sake of exposure readings

I could not say that the Soligor has not been modified with filters or replaced sensor- just that I have not seen any statement to this being fact. In the Zone VI Workshop book printed in 1979 Fred Picker had this to say at the new at the time Soligor (prototype even before the digital readout version?)

"The new Soligor 1 degree blue cell spot meter was not in production at press time...the meter shown a hand made prototype...It proved so sensitive and accurate that, if production models are as good and pass our field test, we will carry them"

This may suggest the possibility that this meter not modified internally but I am sure Mr Ritter would know. Why not fire off an email using link in last post and see if he can suggest if modifications likely on your model.

Sounds like you are using the meter correctly. Set the ISO first then use the spot to centre on an area of known tonal value e.g. grey card, palm of hand then set the EV number on the lens wheel to calculate - remembering that if the meter calibration not changed then the figures refer to producing a mid grey tone. You will need to increase/decrease exposure accordingly for lighter/darker tonalities e.g. Kodak grey card needs to be angled to the light and the exposure indicated increased by approx 1/2 stop. You could meter off the palm of your hand in the same light as your main subject and increase indicated exposure by +1 EV, which should get you somewhere in the ballpark for 'correct exposure'
05-17-2017, 05:36 PM   #14
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https://app.box.com/s/yxzg6ak5axfbi4m0mfwtpll3ygviki3z

RB67 with C41, as I recall with the 90mm fairly wide open in the late afternoon, based on eyeball.
Under or over exposed ?
05-17-2017, 07:17 PM   #15
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QuoteOriginally posted by wombat2go Quote
https://app.box.com/s/yxzg6ak5axfbi4m0mfwtpll3ygviki3z

RB67 with C41, as I recall with the 90mm fairly wide open in the late afternoon, based on eyeball.
Under or over exposed ?
Neither. It supports the lighting at the time, as far as I can see.
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