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Thread: Precision and Accuracy in LF Photography: How much is enough?

  1. #91

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    Re: Precision and Accuracy in LF Photography: How much is enough?

    Quote Originally Posted by Bernice Loui View Post
    What brand of light meter, checked for accuracy?
    How is the lighting metered for film exposure?
    It is a Seconik L-758D and it agrees with any digital camera I have (Canon 5DII and Mamiya ZD) and it agrees with all MF slides (Provia 400X and 100F and Velvia 100) I have taken the last 10 years. 90% of these is incident measuring, spot is only used if not in the same light or when photographing stained glass. I do know from experience that if the build in meter of a camera says something very different than the Sekonic, it is the Sekonic that can be trusted. Slides developed by a pro lab that has its own machines and does daily development of chromes.

    Do the film test with gray scale step tablet and 18% gray card as previously mentioned.
    I have not done that test. But I suppose that if I expose at box speed and develop according to manufacturers recommendation I should get something acceptable. It might not be acceptable to "zone system users" but it should be better that those 4 examples I posted.

    After this comes shutter speed, lens aperture scale correct for the lens cell set.
    If this meter can produce the correct exposure for slides I suppose it is "good enough" for b&w. The same lens can produce with the same film, development and procedure fine results. (obviously with the same shutter) But the result is not consistent. And the non consistency can be in the final image (as in being too light, too dark, no greys) or just not being sharp.

    I can accept that exposure might not be always perfect if the shutter is a bit off. But focusing on the GG with a Gaoursi 8x loupe and then having some negatives sharp and other like those above (flou artistique is an understatement) is not something due to exposure or development issues.

    Source of this problem can be figured out by breaking down the film image making process one item and step at a time.
    You should think so. But when you do everything exactly the same each time and get different results every time, this doesn't work.

    But Ok, I give up because you lot obviously don't think this is happening. Discussion is meaningless if you cannot accept me writing down my experiences as dry as possible. Doing that grey scale step test is just useless as each time it will give different results.

    As long as taking textbook photos, meaning exposing to box speed with incident metering, on a tripod with a cable release and then developing with the same developer at the same temperature for the same time with the same agitation (in a Jobo CPE) according to manufacturer recommendations for that film, exposure and developerAND not getting consistent results then there is something fundamentally flawed.

    Using the same film in a MF system with the same workflow and getting consistent results makes it even more of a problem.

    When you get better results from a film that has stayed 40 years in a drawer after being shot with an Agfa Clack (no metering at all) compared to all this... You need a miracle.
    Expert in non-working solutions.

  2. #92

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    Re: Precision and Accuracy in LF Photography: How much is enough?

    “ But focusing on the GG with a Gaoursi 8x loupe and then having some negatives sharp and other like those above (flou artistique is an understatement) is not something due to exposure or development issues.”

    In a situation like that I generally assume that I inadvertently kicked the tripod or didn’t lock down the focus. Another thing to check ( and you can see this on the negative) is if the film was properly inserted in the holders by examining the edge pattern. It’s not unheard of that one side or both are not in the film Raul, but in front of it. That would put at least part of the film slightly out of register and there might not be enough DOF to cover it.

  3. #93
    Drew Wiley
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    Re: Precision and Accuracy in LF Photography: How much is enough?

    It's amazing how simple things become after habit and intuition take over, versus all the hubub theory in advance.

  4. #94
    Resident Heretic Bruce Watson's Avatar
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    Re: Precision and Accuracy in LF Photography: How much is enough?

    Quote Originally Posted by Drew Bedo View Post
    How much precision and accuracy is enough?
    Accuracy and precision are two different concepts -- they are not synonyms for each other. First thing you have to do in any discussion is to agree how to define your terms. Otherwise, your discussion can be pretty meaningless. So, here's how most engineers and scientists define these terms:

    Accuracy speaks to whether or not something is correct. Precision speaks to whether or not something is repeatable.

    For example, a darkroom thermometer might give you a different temperature reading each time you use it. If you take 20 readings and average them and you get the actual correct temperature (compared to, say, a NIST calibrated reference thermometer), this thermometer is considered accurate. But since you get a different result every time you use it, it is not precise.

    A different thermometer might always give you the same result, and that result might be low by a couple of degrees compared to that same reference. So it is considered not accurate, but it is precise.

    Now that you understand the difference... which would you rather work with? I don't know about the rest of you, but I'll take the precision one over the accurate one every time. Why? I can adjust for the precision one's readings, so I only have to make a single reading. If I need my developer to be at 20C, and the thermometer reads 2C low every time, I can heat my developer to an indicated 22C and be spot on, and because of the precision of the instrument, I can do it every time. This is what I want.

    Bruce Watson

  5. #95

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    Re: Precision and Accuracy in LF Photography: How much is enough?

    Repeatability can be useless without accuracy, depending on which action is being evaluated.

  6. #96
    Drew Wiley
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    Re: Precision and Accuracy in LF Photography: How much is enough?

    A rubber band is repeatable, but hardly accurate. We used to speak of "Fisherman's weight scales" that way; good for tall tales and little else.

  7. #97
    Alan Klein's Avatar
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    Re: Precision and Accuracy in LF Photography: How much is enough?

    Quote Originally Posted by Havoc View Post
    It is a Seconik L-758D and it agrees with any digital camera I have (Canon 5DII and Mamiya ZD) and it agrees with all MF slides (Provia 400X and 100F and Velvia 100) I have taken the last 10 years. 90% of these is incident measuring, spot is only used if not in the same light or when photographing stained glass. I do know from experience that if the build in meter of a camera says something very different than the Sekonic, it is the Sekonic that can be trusted. Slides developed by a pro lab that has its own machines and does daily development of chromes.



    I have not done that test. But I suppose that if I expose at box speed and develop according to manufacturers recommendation I should get something acceptable. It might not be acceptable to "zone system users" but it should be better that those 4 examples I posted.



    If this meter can produce the correct exposure for slides I suppose it is "good enough" for b&w. The same lens can produce with the same film, development and procedure fine results. (obviously with the same shutter) But the result is not consistent. And the non consistency can be in the final image (as in being too light, too dark, no greys) or just not being sharp.

    I can accept that exposure might not be always perfect if the shutter is a bit off. But focusing on the GG with a Gaoursi 8x loupe and then having some negatives sharp and other like those above (flou artistique is an understatement) is not something due to exposure or development issues.



    You should think so. But when you do everything exactly the same each time and get different results every time, this doesn't work.

    But Ok, I give up because you lot obviously don't think this is happening. Discussion is meaningless if you cannot accept me writing down my experiences as dry as possible. Doing that grey scale step test is just useless as each time it will give different results.

    As long as taking textbook photos, meaning exposing to box speed with incident metering, on a tripod with a cable release and then developing with the same developer at the same temperature for the same time with the same agitation (in a Jobo CPE) according to manufacturer recommendations for that film, exposure and developerAND not getting consistent results then there is something fundamentally flawed.

    Using the same film in a MF system with the same workflow and getting consistent results makes it even more of a problem.

    When you get better results from a film that has stayed 40 years in a drawer after being shot with an Agfa Clack (no metering at all) compared to all this... You need a miracle.
    Have you thought of joining a local photo club where you have local advice and meet with friends who are doing the same kind of shooting? When I started LF photography about a year ago, I found someone who lived an hour away from me who was graceful enough to spend an afternoon with me shooting our cameras. I learned a lot. A photo club is also a great placed to review your pictures with others and get advice and do photo shoots together. Working and learning from other is a faster way of getting to your objectives. Good luck.

  8. #98

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    Re: Precision and Accuracy in LF Photography: How much is enough?

    I did have the luck that someone showed me how to develop and yes, this is still the best way to learn. But there are very few clubs around and none of them have film users afaik.
    Expert in non-working solutions.

  9. #99

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    Re: Precision and Accuracy in LF Photography: How much is enough?

    Black & White film image-print making is nothing like color transparency or color negative image-print making. They are essentially different critters in their own way. Film exposure techniques that is effective for color often does not work in the same way for B&W.

    Color transparency aka "positive" film must be exposed at box ISO "speed" rating, often within +/- 1/2" f-stop (if lucky) AND at the box rated color temperature (typical 5000K to 5500K for daylight, typical 3200K for tungsten) as a starting point.

    Much the same applies to color negative film, ISO speed rating at box "speed" often within +/- 1 f-stop at most.

    B&W films are essentially light intensity mixed with color response to film density converters, with significant ability to bend light intensity and color response as negative density. Making the print is essentially inversion of these negative densities to "positive". Know the densities on the negative cannot fit the density scale of the print material. To get this system to work at all, it is mandatory to compress or expand the light intensity range in the scene to be photographed into what can be printed.. The negative is essentially an intermediate step in this process. This is one of the many reasons why exposure techniques that are SO effective for color film may not be effective at all for B&W. Know B&W films can have a LOT more density range than color films both positive and negative.

    This is why ISO "speed" rating of the film to be used IS so important (and why the box ISO film speed rating is often of limited value)
    to get the print image as intended and assure consistency of results.

    Give up the incident metering for outdoor B&W images, never got that to work at all.

    The only images where an incident light meter works IMO, is for in-studio work using strobes or constant light and figuring out lighting ratios or outdoors with controlled conditions. Incident light meters indicate the intensity of light to produce essentially what would be 18% gray density on film. Meter f-stop reading of the light hitting a white sheet will produce what should be about white on film.

    Light meter readings using a Minolta spot F on the white sheet -vs- Minolta incident light flash meter IV reading of the light arriving at this same white sheet.
    Both light meters set to 1/8 sec, ISO 100. ~Note the (2) f-stop difference.~
    Click image for larger version. 

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    ~If the taking lens aperture is set to the spot meter reading of f16.7, that white sheet will render a film density equal to 18% gray, or no longer "white".

    ~If the taking lens aperture is set to the incident meter reading of f8.9, that white sheet will render a film density equal to white..

    One example of how metering light works, and how light meter reading render density on film.

    Since you've got that combo spot-incident light meter, point the spot meter direct into the blue sky, what is the meter reading for a set ISO and shutter speed?
    Repeat the same using the incident light meter, what is the meter reading for a set ISO and shutter speed? On a sunny day, this is likely going to produce the "sunny 16" rule.

    Once that experiment has been run, using ONE type of film do the gray step tablet and 18% gray card test using the spot meter reading on the 18% gray card. Repeat the same using an incident light meter reading. Process/develop film as routine. Examine the resulting film densities.

    Post the results to discuss.

    Bernice







    Quote Originally Posted by Havoc View Post
    It is a Seconik L-758D and it agrees with any digital camera I have (Canon 5DII and Mamiya ZD) and it agrees with all MF slides (Provia 400X and 100F and Velvia 100) I have taken the last 10 years. 90% of these is incident measuring, spot is only used if not in the same light or when photographing stained glass. I do know from experience that if the build in meter of a camera says something very different than the Sekonic, it is the Sekonic that can be trusted. Slides developed by a pro lab that has its own machines and does daily development of chromes.

    I have not done that test. But I suppose that if I expose at box speed and develop according to manufacturers recommendation I should get something acceptable. It might not be acceptable to "zone system users" but it should be better that those 4 examples I posted.

    If this meter can produce the correct exposure for slides I suppose it is "good enough" for b&w. The same lens can produce with the same film, development and procedure fine results. (obviously with the same shutter) But the result is not consistent. And the non consistency can be in the final image (as in being too light, too dark, no greys) or just not being sharp.

    I can accept that exposure might not be always perfect if the shutter is a bit off. But focusing on the GG with a Gaoursi 8x loupe and then having some negatives sharp and other like those above (flou artistique is an understatement) is not something due to exposure or development issues.

    You should think so. But when you do everything exactly the same each time and get different results every time, this doesn't work.

    But Ok, I give up because you lot obviously don't think this is happening. Discussion is meaningless if you cannot accept me writing down my experiences as dry as possible. Doing that grey scale step test is just useless as each time it will give different results.

    As long as taking textbook photos, meaning exposing to box speed with incident metering, on a tripod with a cable release and then developing with the same developer at the same temperature for the same time with the same agitation (in a Jobo CPE) according to manufacturer recommendations for that film, exposure and developerAND not getting consistent results then there is something fundamentally flawed.

    Using the same film in a MF system with the same workflow and getting consistent results makes it even more of a problem.

    When you get better results from a film that has stayed 40 years in a drawer after being shot with an Agfa Clack (no metering at all) compared to all this... You need a miracle.

  10. #100

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    Re: Precision and Accuracy in LF Photography: How much is enough?

    Hmmmm… with black&white I’ve had success with incident metering and box speed. What am I doing wrong, or right? It’s not the perfect option in all situations but certainly good enough in many and cannot be totally discounted. IMO, of course.

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