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  1. #21
    Photo Engineer's Avatar
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    Guys;

    We had this problem at EK. We had standards committees for all work so that all things were as equal as possible!

    PE

  2. #22

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    I use the same standard ole Kodak plotting paper that I've used for decades. No fancy programs. Just
    a densitometer and a sharp pencil. It's translucent, so one can directly compare curves over a lightbox.

  3. #23

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    Quote Originally Posted by albada View Post
    Do the edge-markings look thin? If so, your exposure is probably fine. Anyway, it would be interesting to re-try the process with an added pre-soak and/or longer time.

    Mark Overton
    Mark, what I'd like to do is run some TMY-2 in both XTOL and D-76. Perhaps my "batch" of XTOL packets is bad. I don't know why that would be but who knows. But I won't have time for this until the weekend so if you want to go ahead, don't wait for my tests.

    While it has been a while since I used TMY-2, in sheets I always got pretty long, straight curves with short toes and a gradual shouldering (slightly more gradual than say Delta 100). Actually I found the curves very similar to TMX, which made TMY-2 an almost ideal large format film for my work (except for the slightly glossy emulsion which can be a serious pain in the ass as far as Newton rings go). So this thread is somewhat troubling.

    PE - how likely is it there is really something wrong with the film? Realistically, can this happen? I mean obviously it can happen, but ?

  4. #24
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    I just double checked some of my results. All from the same batch. Basically all TMY curves in my results do tend to be upswept.
    Except with FX-39.

  5. #25

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    Quote Originally Posted by StoneNYC View Post
    So, how do you guys measure this stuff? Like can you explain the process if messing a curve? Do you scan it with a special program or how do you plot it?
    The normal method is to start by exposing a piece of film through a commercial step wedge. The wedge is typically a piece of B&W film, with each step getting successively darker, by a specified amount. So you essentially have made a single exposure, but it contains a very wide range of light intensities. A common style of wedge covers a 10 f-stop range in 21 steps.

    After developing, you measure each step on your film with a transmission densitometer, which is essentially a light meter for the darkness of film. It reports this as "optical density," thus the name densitometer.

    Finally, you plot each step on a graph. For the scales, the exposure is normally done in log units; typically the amateur doesn't know the exact power of the light source, so they just use the relative values. The other scale is the film density. This is basically the same thing as the published "characteristic curves" for film.

    Since about the mid-1980s, nearly all densitometers have a computer interface, at least as an option, so if you have a proper program, you can collect the numbers automatically. It's easy enough to make graphs using a computer spreadsheet. Or just bypass the graph and calculate what you want directly.

  6. #26
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    T-Max 400 has boomerang curve

    Quote Originally Posted by Mr Bill View Post
    The normal method is to start by exposing a piece of film through a commercial step wedge. The wedge is typically a piece of B&W film, with each step getting successively darker, by a specified amount. So you essentially have made a single exposure, but it contains a very wide range of light intensities. A common style of wedge covers a 10 f-stop range in 21 steps.

    After developing, you measure each step on your film with a transmission densitometer, which is essentially a light meter for the darkness of film. It reports this as "optical density," thus the name densitometer.

    Finally, you plot each step on a graph. For the scales, the exposure is normally done in log units; typically the amateur doesn't know the exact power of the light source, so they just use the relative values. The other scale is the film density. This is basically the same thing as the published "characteristic curves" for film.

    Since about the mid-1980s, nearly all densitometers have a computer interface, at least as an option, so if you have a proper program, you can collect the numbers automatically. It's easy enough to make graphs using a computer spreadsheet. Or just bypass the graph and calculate what you want directly.
    Oh that description was perfect for my kind of brain, now I understand what the heck everyone is talking about (sort of) so the tow and tail are the highlight and blacks? So why does the upswept whatever mean, I didn't see a boomerang shape at all when I looked at the first OP's graph so I was totally confused (still am) so anyway this at least gets me a little more understanding.

    I was thinking this was done on any normal picture (I was going to ask if I could use my most recent uploaded image haha).

    Thanks.


    ~Stone

    Mamiya: 7 II, RZ67 Pro II / Canon: 1V, AE-1, 5DmkII / Kodak: No 1 Pocket Autographic, No 1A Pocket Autographic | Sent w/ iPhone using Tapatalk
    ~Stone | "...of course, that's just my opinion. I could be wrong." ~Dennis Miller

  7. #27

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    Quote Originally Posted by StoneNYC View Post
    Oh that description was perfect for my kind of brain, now I understand what the heck everyone is talking about (sort of) so the tow and tail are the highlight and blacks? So why does the upswept whatever mean, I didn't see a boomerang shape at all when I looked at the first OP's graph so I was totally confused (still am) so anyway this at least gets me a little more understanding.
    Cool, that's what I aim for, is to make it understandable.

    With film, the traditional layout is that the clear part of the film starts at the lower left. The "toe" (like on your foot) of the curve is where the film goes from clear to some moderate amount of density. Then there is a mid-range zone (a lot of people like to call this the "straight-line part," even if it isn't). Eventually, the line will stop climbing, and roll off in a "shoulder". Sometimes you don't see a shoulder, because it is so far off that it doesn't make it onto the graph - in these cases, the printing time would be so exorbitantly long that no one wants to go there. So there's no real need to graph it

    Regarding the "boomerang shape," everybody gets their own descriptive words for things. I think he means the point where, halfway up, the line takes an upward bend; it's very slight. (I wouldn't personally say boomerang, 'cuz I'd get tired of explaining what I mean).

    When they say the curve is "upswept," they mean it keeps getting steeper and steeper, at least in the "useable" part that is graphed. To me, in a "typical scene," (whatever that is), an upswept curve means that the highlight areas may be getting out of control. But if your subject doesn't have real highlights, this sort of film curve might build some in for you; closeups of fern leaves under soft light might be an example?

    Hope this helps.

  8. #28
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    T-Max 400 has boomerang curve

    Quote Originally Posted by Mr Bill View Post
    Cool, that's what I aim for, is to make it understandable.

    With film, the traditional layout is that the clear part of the film starts at the lower left. The "toe" (like on your foot) of the curve is where the film goes from clear to some moderate amount of density. Then there is a mid-range zone (a lot of people like to call this the "straight-line part," even if it isn't). Eventually, the line will stop climbing, and roll off in a "shoulder". Sometimes you don't see a shoulder, because it is so far off that it doesn't make it onto the graph - in these cases, the printing time would be so exorbitantly long that no one wants to go there. So there's no real need to graph it

    Regarding the "boomerang shape," everybody gets their own descriptive words for things. I think he means the point where, halfway up, the line takes an upward bend; it's very slight. (I wouldn't personally say boomerang, 'cuz I'd get tired of explaining what I mean).

    When they say the curve is "upswept," they mean it keeps getting steeper and steeper, at least in the "useable" part that is graphed. To me, in a "typical scene," (whatever that is), an upswept curve means that the highlight areas may be getting out of control. But if your subject doesn't have real highlights, this sort of film curve might build some in for you; closeups of fern leaves under soft light might be an example?

    Hope this helps.
    It does a lot, I've been here for a year and no one has explained these graphs to me at all, now I get it (at least a lot more) thanks!


    ~Stone

    Mamiya: 7 II, RZ67 Pro II / Canon: 1V, AE-1, 5DmkII / Kodak: No 1 Pocket Autographic, No 1A Pocket Autographic | Sent w/ iPhone using Tapatalk
    ~Stone | "...of course, that's just my opinion. I could be wrong." ~Dennis Miller

  9. #29

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    Quote Originally Posted by StoneNYC View Post
    It does a lot, I've been here for a year and no one has explained these graphs to me at all, now I get it (at least a lot more) thanks!
    Once you know what to look for in a curve, it tells you a lot. For example, you'll know...
    If shadows will look dark and mushy (long toe) versus snappy (linear or downswept).
    If highlights will lack gradation (downswept) or be snappy (linear or upswept).
    How much overexposure you can get away with (linear on right end).
    Likewise with underexposure (short toe).

    You can use curves to your advantage. For example, Bill Burk mentioned that an upswept curve can improve gradation in faces. A downswept curve will let you cram a large luminance-range onto the print by compressing highlights (example: snow/sand/clouds, where you also have something dark or shadows). Downswept also will give you strong shadow-gradation which can help in low-key shots. An S-shaped curve will have snappy midtones at the expense of reduced gradation in both shadows and highlights, which might be just what's needed to strengthen a midtone-heavy scene.

    Developers and agitation change the shape of curves, so you can alter curves to suit your needs. I haven't seen curves produced by Diafine, but I'd guess they're downswept.
    For general usage, a straight-line curve is best because it gives equal gradation in shadows, midtones and highlights.
    Anyway, it's a good idea to be familiar with the curve for your film+dev combo so you'll know what you're going to get.

    Mark Overton

  10. #30
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    T-Max 400 has boomerang curve

    Quote Originally Posted by albada View Post
    Once you know what to look for in a curve, it tells you a lot. For example, you'll know...
    If shadows will look dark and mushy (long toe) versus snappy (linear or downswept).
    If highlights will lack gradation (downswept) or be snappy (linear or upswept).
    How much overexposure you can get away with (linear on right end).
    Likewise with underexposure (short toe).

    You can use curves to your advantage. For example, Bill Burk mentioned that an upswept curve can improve gradation in faces. A downswept curve will let you cram a large luminance-range onto the print by compressing highlights (example: snow/sand/clouds, where you also have something dark or shadows). Downswept also will give you strong shadow-gradation which can help in low-key shots. An S-shaped curve will have snappy midtones at the expense of reduced gradation in both shadows and highlights, which might be just what's needed to strengthen a midtone-heavy scene.

    Developers and agitation change the shape of curves, so you can alter curves to suit your needs. I haven't seen curves produced by Diafine, but I'd guess they're downswept.
    For general usage, a straight-line curve is best because it gives equal gradation in shadows, midtones and highlights.
    Anyway, it's a good idea to be familiar with the curve for your film+dev combo so you'll know what you're going to get.

    Mark Overton
    Hmm I've been just testing agitation styles and developers and seeing what I get, though fun it can be costly, this makes sense, I'll certainly re-read this when I'm at a computer and try and log it all to commit it to understanding and give reading curves a try.

    Thanks again.


    ~Stone

    Mamiya: 7 II, RZ67 Pro II / Canon: 1V, AE-1, 5DmkII / Kodak: No 1 Pocket Autographic, No 1A Pocket Autographic | Sent w/ iPhone using Tapatalk
    ~Stone | "...of course, that's just my opinion. I could be wrong." ~Dennis Miller

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