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Thread: What is the Zone VI modified pentax spotmeter?

  1. #11

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    Re: What is the Zone VI modified pentax spotmeter?

    Quote Originally Posted by Ole Tjugen View Post
    Which film? And would it be equally well matched to other films?
    I believe it was designed to match Tri-X 4 x 5. (Fred Picker's favorite) I have been using it with T-Max 100 4 x 5 with great success for many years. When the T-Max films came out, I remember that they would render a blue sky darker (more natural-looking) than any other film I'd used. So that may be the biggest difference between these two films. In general, I would have thought that the differences in spectral response between films would be negligible when using this meter.

    The best thing about the Zone VI Modified in my opinion, is that its response to green (at least in nature) is much more correct than an unmodified meter. Before I got this meter, I was using an umodified one, and grass and foliage would often come out about 1 zone darker than expected. The modified meter would provide a correct reading of these subjects, and I could adjust exposure and/or development to get what I wanted.
    Another advantage is that this meter will give a correct reading through strongly colored filters.

  2. #12

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    Re: What is the Zone VI modified pentax spotmeter?

    Fergeddabout modifying a meter yourself. It's not an easy job, nor can you acquire a filter pack (yes, it's multiple filters) from any source for a price less than the cost of a modification (if, in fact, you can still get meters modified).

    Richard Ritter just investgated the cost of getting a supply of filter packs, in case Calumet would grant him permission to do modifications (looks like they're going to stop doing it). He couldn't afford them. Neither could I, based on what he said the optical company was asking.

    Plus, after the modification, the meter has to be calibrated, requiring a known reference light source and the skill to know what to do.

    By the way, any Pentax Digital will "drift" over time, needing recalibration. Richard Ritter does that. He keeps mine in trim, and I know Hollywood guys send him multiples to calibrate and align so thay all read the same.

    Life would be much harder without my modified meter and my Compensating Developing Timer. I don't know if Butzi's position is accurate. I do know that I have total peace of mind in the field, and I never have to worry that it MIGHT be inaccurate.
    Bruce Barlow
    author of "Finely Focused" and "Exercises in Photographic Composition"
    www.brucewbarlow.com

  3. #13

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    Re: What is the Zone VI modified pentax spotmeter?

    Quote Originally Posted by Ole Tjugen View Post
    Which film? And would it be equally well matched to other films?

    All BW films have slightly different spectral response. IMO it makes more sense to learn the characteristics of the film you are using than to buy a meter perfectly matched to one specific film.
    Yes, it appears to be possible to get well exposed pictures with unmodified meters.

    The differences in the spectral responses of B&W films are most marked at the red end of the spectrum, which is probably the most critical end for metering through filters. Making the blue end of the meter's response more like that of film, and removing the green peak could be worthwhile though. (Side note: when you look at the spectral sensitivity of B&W film you need to bear in mind that Kodak publish equal energy curves, and almost everyone else publishes wedge spectrograms made in tungsten light. This leads to a very different shape, and comparing the two can be very misleading.)

    My musings on a DIY kit were just musings. Is there a demand? I wasn't asking from a commercial viewpoint, but because it would be an interesting side project. I have modified a Pentax Digital Spotmeter to mimick HIE. Even expensive filter material is cheap for the amount needed to modify a meter - you just need to share out bits of the 50 mm squares among your friends. Deciding on the filter pack isn't rocket science. I wrote some software a while ago for designing optimum filter packs for another purpose, but it could be adapted for mimicking film spectral response using commercially available filters. Finding time is a different matter, of course, and if nobody wanted it, not even me, I wouldn't take this any further. I don't wish to tread on anyone's toes either.

    Best,
    Helen

  4. #14
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    Re: What is the Zone VI modified pentax spotmeter?

    I have used my Zone VI modified Soligor Digispot II since 1987? very successfully with transparency film.

    Rich
    Richard A. Nelridge

    http://www.nelridge.com

  5. #15

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    Re: What is the Zone VI modified pentax spotmeter?

    "I believe it was designed to match Tri-X 4 x 5."
    IN another thread by Richard Ritter he debunks this claim. It is true that Fred said to do it to Tri-x but they knew better and did an average of all the primary films available at that time.

  6. #16

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    Re: What is the Zone VI modified pentax spotmeter?

    As far as the "calibrated for which film" question goes, it's worth noting that the respsonse of the standard CdS cell is off by a mile compared with any film; so the "inches" difference between various (panchromatic) b&w films is functionally irrelevant. To quote Paul Caponigro; "if you're measuring to that level, you're living inside a test tube".

  7. #17

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    Re: What is the Zone VI modified pentax spotmeter?

    Quote Originally Posted by Ole Tjugen View Post
    Which film? And would it be equally well matched to other films?

    All BW films have slightly different spectral response. IMO it makes more sense to learn the characteristics of the film you are using than to buy a meter perfectly matched to one specific film.

    Supposedly it's matched to Tri X. I've never done any testing with the meter so I don't know for sure whether it would be equally well matched to other films. However, I don't use Tri X, I use TMax 100 and HP5+, and it seems to work fine with both of them. The original question was "what's the modification" and nobody had actually answered that question. So I listed the things that Zone VI Studios said they did in making the modifications. I deliberately avoided commenting on the merits of the modifications since I don't really know, never having tested a modified vs an unmodified meter (I did skim Paul Butzi's article some time ago but wasn't sufficiently interested to really study it). But if it makes more sense to you to learn the characteristics of the film you're using rather than using a modified meter then that's certainly fine for you.
    Brian Ellis
    Before you criticize someone, walk a mile in their shoes. That way when you do criticize them you'll be
    a mile away and you'll have their shoes.

  8. #18

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    Re: What is the Zone VI modified pentax spotmeter?

    Quote Originally Posted by Helen Bach View Post
    I wrote some software a while ago for designing optimum filter packs for another purpose, but it could be adapted for mimicking film spectral response using commercially available filters.
    Helen - can I get a copy of your software?

    I would love a DIY kit for this. I've done some spectral scans of a few different meters and there as differences between different models especially response to IR. (my scans went from 320 to 900 nm.) I've yet to scan a modified Pentax meter though to compare.

    I've looked into the Zone VI mods and they say there are 4 filters. I can't remember what 3 of them do, but one is an IR blocking filter. I suspect that a magenta filter is used to level out the high green response that many meters have.

    Kirk

  9. #19

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    Re: What is the Zone VI modified pentax spotmeter?

    Quote Originally Posted by Bruce Barlow View Post
    Plus, after the modification, the meter has to be calibrated, requiring a known reference light source and the skill to know what to do.
    It doesn't really have to be calibrated to a known light source.

    As long as you don't care for "absolute" accuracy, you could just slap a correctoing filter pack on the meter, and then do a film test with that meter making the expsoure determination, and that would give you an EI that would work for that meter and film. Just don't expect it to be very close to box speeds depending on how much filtration you've added.

  10. #20

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    Re: What is the Zone VI modified pentax spotmeter?

    Quote Originally Posted by Kirk Keyes View Post
    Helen - can I get a copy of your software?
    Kirk,

    Yes. I'll have to remove some information that isn't mine to give away but otherwise there should be no problem.

    Best,
    Helen

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