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Thread: CFL's and Daylight balanced film making me blue

  1. #21

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    Apr 2006
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    135

    Re: CFL's and Daylight D50 making me bluer with D65

    One more thing (I'm agnostic about film and digital, both having strong and
    weak points), I've seen a transparency that had no grain (way above 3200dpi)
    and a digital image that exceeded the nyquist frequency[1] limit by a factor of 2.

    These are extremely rare occurrences but do exist. Almost all claims to be able
    to achieve these results on a regular basis should be dismissed out of hand (sigh).

    That aside, we need to be aware of is the weakness of dslr's and digital backs
    since we are using these for calibration tools and are a part of our (or at least
    my) daily work flow.

    Because of the well known RGBG arrangement slight differences in colors are
    the Achilles Heal of the 40Mega-pixel chip.

    The full color pixel value is 40mp/RGBG (four photo sites) == 10 megapixel color camera

    I've been using and selling Charles Sleicher targets (RGB and Black on White)
    for awhile. To see the 10 mega pixel effect make red line pair targets
    on a red background with a sinusoidally decreasingly small difference in color.
    At some point the scanned film image will show up to 2-3 times the resolution
    (lp/mm) as compared to the dslr or digital back image (given 2G photosites and
    perfect point algorithm mentioned in Note 1 on the bottom of a highly intelligent
    and no doubt expensive, stack of software).

    This is only being pointed out to show that the digital image will lose some
    of its color acutance as it approaches the megapixel/RGBG limit.

    Given what I've seen (both good and bad) from film and digital sensors I
    would be comfortable estimating that a well exposed color balanced piece of
    6x6 or greater mirror like flat piece on film (using the fine focusing loupe lp/mm
    kit I sell) behind a good Schneider, Nikon, Zeiss etc. APO lens will out capture
    the finest color detail of the large format 40 Mega pixel back (based on a
    2800dpi 16bit nikon fluid scanning limit for color film).

    I did not account for the less than 16bit per channel color depth of the kodak
    KAF-39000-AAA chip (has anj internal 12bit dynamic range but outputs 16) so
    just think of that as my four bit margin of safety.

    A lot of 4x5 film verses digit test reviews have been popping up which I'm having
    trouble with.

    My Engineering Test Requirements
    The first is I want to see a picture of the reflection of an unexposed
    piece of film in the film holder to check for flatness. The reflected image
    should be perfectly mirror like, demonstrating no out of the box film curl.
    (As far as I know flatness can only be obtained by a specific unexposed
    film taping technique in the black bag or dark room).

    The second is I want to know is the reviewer used my fine focusing loupe kit (for
    precision plenum photography) that will bring the lens image and emulsion plane
    into perfect focus simultaneously (across the entire frame inspected on the
    side and corner stand). Once observed (validates most of the camera system
    and) it guarantees the best possible image resides within the approximately
    .001 to .002" emulsion plane.

    The reviewers will only need to pay actual postage to them AND back to me
    (unless they want to buy it or craft their own from almost 70 pages of
    documentation, photographs and drawings that comes with every kit).

    I don't like to name names but some of great renown have done that and more
    for me, so its time to give back to those who share one of my life's great
    passions.

    Note [1]
    40Mega-pixel the monochromatic value. There also is a airy-disc (perfect-point)
    algorithm being used that can make digital pictures "scary". But I digress, I do not
    even know if its published (a tightly held trade secret no doubt). Simply put it is
    possible (with high speed sampling deterministic algorithms) to achieve reliable sub
    pixel accuracy (yes, exceeding the monochromatic 2d nyquist frequency limit in
    something resembling a virtual 3d working space).

    There was also a very fine diffusion filter used in an attempt to emulate the
    Super-Angulon 8/65mm (magic glass)

  2. #22

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    Apr 2006
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    Re: CFL's and Daylight D50 making me bluer with D65

    You probably already know this already but be sure to scan the film in
    16bits (preferably wet, 3200 dpi and tiff).

    I'm not sure about the latest photoshop (or scanner) software but picture
    window pro is (IMHO) the preferred tool for fine tuning color drift.

    Sorry about the previous long winded post (but it is a passion) .,.

    All the Best,

    Richard

  3. #23

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    Oct 2008
    Location
    Scottsdale Arizona
    Posts
    4

    Re: CFL's and Daylight balanced film making me blue

    As the original poster, I wanted to follow up. I appreciate every ones comments and thoughts. I did a digital shoot under my new CFL kit and it was great. I also did some black and white 35MM and they were great as well. So... I decided to keep the CFL's for certain digital work and went back to 3200k photofloods with blue filters and my 5500K strobes.(No i Don't use both at the same time) Guess what? Both look fantastic. My color problem was one of my own making. Thanks again to every ones comments.

  4. #24

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    Feb 2001
    Location
    Nara, Japan
    Posts
    1,296

    Re: CFL's and Daylight balanced film making me blue

    Which CFL kit did you buy?

    Kumar

  5. #25

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    Re: CFL's and Daylight D50 making me bluer with D65

    Quote Originally Posted by rvhalejr View Post
    One more thing (I'm agnostic about film and digital, both having strong and
    weak points), I've seen a transparency that had no grain (way above 3200dpi)
    and a digital image that exceeded the nyquist frequency[1] limit by a factor of 2.
    I saw a troupe of six fingered gnomes playing dodge-ball with a Fabergé egg in my garden this morning. They said something about being the point spread function of a moonbeam.

  6. #26

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    Re: CFL's and Daylight balancing DIY

    Quote Originally Posted by Brian Drake View Post
    Should I ditch and go back to strobes? I like hot lamps for composition
    and I love the CFL's, for placing in and around delicate art work, as well
    as portraits.
    Assuming you did not find a solution already, I always opt for a DIY solution
    first before recommending the really wonderful several thousand dollar solution.

    Working to a setup thats known to be good (perfect white on your film - see
    notes below on film types) is a good way to sanity check your colorimeter
    and/or dslr white balance.

    If you do not use the CFL with a Softbox diffuser or white umbrella without
    the black backing then go no further since light transmitted through
    such a white medium tends to attenuates spikes by re-transmitting photons
    that are statistically more likely to be equal parts of RGB (white light).

    I consider it a calibration exercise, science project that re-affirms
    theory on verifies re-reproducibility.

    Photographers generally agree that its less time consuming to shoot
    something right than muck around photoshop, picture window pro and/or
    other types of software.

    You use a STROBE (like most tend to) using daylight balance film
    (D50 or D65) and when you shoot a white target paint, cloth,
    paper, etc. you get a perfect white (RGB balance in 16 bits).

    Balanced film (and strobe) around ambient daylight is exactly the same
    temperature (otherwise blue tint would be seen since > 8500K
    natural daylight tends to swamp out skylight filters).


    Now we have all variables under control, except for the CFL.


    Do you have a Roscolux Swatch Book (they used to be free)? For blue
    balance look at straw, bastard amber, etc. and get an few test sheets
    (only a few dollars).

    Cut test sheets in 1/4" strips of a sheet and start taping them on the
    CFL (with 1/4" gaps) and shooting test shots (keep the CFL on and let
    it warm up for at least 15 minutes). I prefer to calibrated a single bulb
    at a time. As strips are added to the light the blue tint will disappear.
    If two many strips are added you will notice a yellow or amber tint
    creeping into the white target.

    I've used the same technique on my nikon stobes, the strips are more
    like 1/8 - 1/16" wide over the bulb , it dials in so well that the white
    diffuser is not need.

    DIY is crude and time consuming. But without filters and diffusers even
    the best CFL Full Spectrum Lighting system calibrated with the Minolta
    color meter III (or similar device) will have some peaks and valleys
    throughout the spectrum.

    If there are several out-of-gamut artist colors to die for adjustment
    of your lighting will be needed (unless the technology is much further
    along now and they actually test for those paints, white wedding dresses,
    material, black tux seams, and every swatch on your color target).

    The only way to escape DIY is to have it serviced periodically to keep
    it in calibration, as well as your strobe(s), or just replace everything
    periodically.


    Other Issues

    Our worst enemy is winter daylight as it can tend towards 10,000K
    (really, really bluer).

    Velvia (and 100Vs) are almost impossible to balance because of the
    intentional over-saturated look.

    In the case of fuji any other E6 would be better, likewise Kodak 100G
    and maybe 100GS should be an improvement.

    C41 is usually the choice for ultra-fine color accuracy (at the cost of
    more grain), I'm a portra addict .,.

    Another variable (out of scope here is scanner calibration,) using targets
    periodically or rescanning film known to be perfect is a good check to
    make sure nothing has changed .,.

    Out-of-gamut that kill me are all those colors out printers and monitors
    cannot recreate.

    Film and Digital Out-of-gamut colors seem to be less of an issue. I'm going
    to try to ignore RGB, CYMK, CIE details for now. But if today's compressed
    capture color space contains a 16bit true color image is accurate relative
    colormetricly then it should be possible to map to a future expanded color
    space (if need be) to drive color display devices that can accurately render
    todays Out-of-gamut colors.

    This last paragraph of verbosity is from an old film scanner soul getting up
    the nerve to ask a poster in this thread if (someday) it will be possible (if
    standards exist) to take out-of-gamut artist paints (maybe six
    rgb, cym cie vectors) and add them into the tanks of a really big awesome
    (sixteen reservoir ?) continuous ink system.

    Then out-of-gamut would be gone (sort of in the case of hardcopy) .,.

  7. #27

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    Re: CFL's and Daylight D50 making me bluer with D65

    > Originally Posted by rvhalejr View Post
    > One more thing (I'm agnostic about film and digital, both having strong and
    > weak points), I've seen a transparency that had no grain (way above 3200dpi)
    > and a digital image that exceeded the nyquist frequency[1] limit by a factor of 2.


    Quote Originally Posted by Edwin Beckenbach View Post
    I saw a troupe of six fingered gnomes playing dodge-ball with a Fabergé egg in my garden this morning. They said something about being the point spread function of a moonbeam.
    So they were qualified radiometry experts discussing moon beam scatter and spectral emission line shift

    One out of 10,000 slides, its the holidays ok?

    I've never seen a transparency (before or since) that would benefit from a
    greater than 5000 ppi fluid scan, except for that one. It was old ISO 25
    E6 Kodak film (legendary noise floor 1/2 that of ISO 50).

    Maybe Nyquist sampling of sequential data got those gnomes (they might
    have been department chairs at prestigious institutions).

    If the data context is from an image, (not just a simple string of
    bits) the matrix will have a huge amount of information that (in theory) can
    be exploited to build a 3d model, effectively appearing to be subpixel (or emulsion
    cloud) sampling, as an admittedly overly simplistic analogy, hence the
    "factor of 2" comment.

    Those gnomes do need to allow for the possibility (how ever remote) that
    1 out of 10,000 sub N frequency sampled photos will not exhibit aliasing due
    to some factor not often encountered or observed.

    Is this worthy of publication and peer review ? No. Will there never be a
    generally accepted dissertation on MTF and how it might be cracked,
    like an egg ?

    That thesis was originally outlined by 10,000 monkeys in a room jumping
    up and down on keyboards.
    ------------------
    I wanted to edit that post but then ran into the 120 minute time out (after the
    wife started screaming in one ear "GO GET MORE RIBBIONS AND BOWS !!!").

  8. #28

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    Jul 2006
    Location
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    Re: CFL's and Daylight D50 making me bluer with D65

    Quote Originally Posted by rvhalejr View Post
    > Originally Posted by rvhalejr View Post
    > One more thing (I'm agnostic about film and digital, both having strong and
    > weak points), I've seen a transparency that had no grain (way above 3200dpi)
    > and a digital image that exceeded the nyquist frequency[1] limit by a factor of 2.




    So they were qualified radiometry experts discussing moon beam scatter and spectral emission line shift

    One out of 10,000 slides, its the holidays ok?

    I've never seen a transparency (before or since) that would benefit from a
    greater than 5000 ppi fluid scan, except for that one. It was old ISO 25
    E6 Kodak film (legendary noise floor 1/2 that of ISO 50).

    Maybe Nyquist sampling of sequential data got those gnomes (they might
    have been department chairs at prestigious institutions).

    If the data context is from an image, (not just a simple string of
    bits) the matrix will have a huge amount of information that (in theory) can
    be exploited to build a 3d model, effectively appearing to be subpixel (or emulsion
    cloud) sampling, as an admittedly overly simplistic analogy, hence the
    "factor of 2" comment.

    Those gnomes do need to allow for the possibility (how ever remote) that
    1 out of 10,000 sub N frequency sampled photos will not exhibit aliasing due
    to some factor not often encountered or observed.

    Is this worthy of publication and peer review ? No. Will there never be a
    generally accepted dissertation on MTF and how it might be cracked,
    like an egg ?

    That thesis was originally outlined by 10,000 monkeys in a room jumping
    up and down on keyboards.
    ------------------
    I wanted to edit that post but then ran into the 120 minute time out (after the
    wife started screaming in one ear "GO GET MORE RIBBIONS AND BOWS !!!").
    High five on the very entertaining reply!

    RAP100F holds a bit of detail above 2500cpi and so could benefit slightly from sampling a bit beyond 5000ppi but of course this would be with contrast that is far less than inspiring and of probably of marginal utility (not to mention beyond my ability to pull off in the real world). If there was truly a film in the distant past that exceeded this I would enjoy hearing more about it.

    There is no unfiltered sub N frequency image that will be immune to aliasing in the real world. You can theoretically model what would be required but it won't look like anything we commonly think of as a photograph. However, this is the irony of the situation, if there is no aliasing there is also no contribution of higher frequencies in the sample to the frequency content which is resolved and if there is aliasing the contributed information is absolutely ambiguous. Also, if a given sample doesn't have sufficient information to represent subpixel frequencies in 2D how on earth do you presume it has enough to build a 3D model with perhaps orders of magnitude more degrees of freedom?

    If you can do this it would be more than worthy of peer reviewed publication because it would be absolutely astounding to see a method that allows resolution beyond the folding frequency of the sampling system without some variation of oversampling (and statistical oversampling can be ruled out because we're only talking about one image) in which case the 'assumed' Nyquist frequency really isn't.

  9. #29

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    Re: CFL's and Daylight D50 making me bluer with D65

    Quote Originally Posted by Edwin Beckenbach View Post
    High five on the very entertaining reply!
    ...
    There is no unfiltered sub N frequency image that will be immune to aliasing in the real world.
    ...
    I humbly submit that you are correct.

    Spectral Transmission and CIE Chromaticity (from rosco.com/us/filters/roscolux.asp)
    suggest two gels worthy of consideration in this threads context:

    #06 No Color Straw (ideal suppression curve for blue tint in white)
    #3317 Tough 1/8 Plusgreen (partial green to balance with fluorescents)

    When beloved photographers become concerned about the ghastly glow
    of wide spectrum filtered and diffused florescent lighting one can say
    "Its Moonlight" and perhaps let out a little wolf howl at an imaginary full moon.

    During the pursuit of a disciplines advancement conventional wisdom,
    canonical facts and empirical truths might be considered temporary final
    approximations in the moment.

  10. #30

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    Re: CFL's and Daylight balancing DIY

    Quote Originally Posted by rvhalejr View Post
    ...
    Other Issues

    Our worst enemy is winter daylight as it can tend towards 10,000K
    (really, really bluer).
    See Attached Image, You can imagine what the 10K curve looks like.

    Ref ...xritephoto.com/html/ECM%20Tech%20Brief-en.pdf

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