Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 71,829   Posts: 1,582,174   Online: 998
      
Page 3 of 6 FirstFirst 123456 LastLast
Results 21 to 30 of 53
  1. #21
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,528
    Images
    65
    Ian;

    Thanks.

    PE

  2. #22
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,528
    Images
    65
    I've been thinking this over and trying to come up with a better way to express things in answer to the OP which is "number of silvler halide crystals vs film speed".

    Lets look at it again.

    As grain size increases, speed goes up. In a given coating of 100 mg /square foot of silver halide then, as the grain size and speed goes up, at a fixed silver level, the actual number of grains goes DOWN. The larger grain size and decreased number of centers will decrease contrast and increase grain as described in another post.

    To fix this, the grains can be packed more tightly by decreasing gelatin, or the number of grains can be increased to equal the number present in the finer grained film. The latter approach here increases the amount of silver that is coated, but the number of halide crystals can remain the same.

    Therefore, we must distinguish between the number of crystals and the amount of silver coated per unit area. These do not necessarily correlate if the grain size and speed are changed.

    Think about 1 boulder lying on the ground. Now, crush it into many tiny pieces of gravel. The weight is the same, but the number of lumps is greater in the case of the gravel.

    So, I can describe to you a slow film and a fast film which contain the same number of crystals per unit area but where the fast film has more silver per unit area. Therefore, both Ian's answer and mine are correct and again I say that 'it depends'.

    It is entirely possible to have a slow and a fast film with the same number of crystals but with different silver levels. It is also possible to have a slow and a fast film with the same amount of silver but with the fast film having fewer crystals. In this case, the packing of the crystals would be denser (less gelatin) or the crystal habit might have to change, or the crystal content might change.

    Have I done any better this time?

    PE

  3. #23
    Mark Antony's Avatar
    Join Date
    Mar 2007
    Location
    East Anglia,UK
    Shooter
    Multi Format
    Posts
    772
    Images
    38
    Thanks for your explanation PE, it was this 'article' that confused me.
    http://www.luminous-landscape.com/essays/clumps.shtml
    I didn't think film grain was binary
    Mark

  4. #24
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,528
    Images
    65
    This statement here:
    ---------------------------------------------------------------------
    "Not so fast! Here's the catch that many testers trip over. Grain particles are binary. An individual film grain can only be either black or not-black, on or off, exposed or not exposed. Sort of a binary device. A photo site (pixel), on the other hand, has a range of thousands of brightness levels, because it's an analog device. (Curious isn't it, that at this level film is binary and digital is analog?)"
    --------------------------------------------------------
    is totally incorrect! A grain has many sensitivity sites and can form from 3 - billions of atoms of Silver metal, but a digital sensor is either on or off. The number of levels (the number of bits - 8, 16, 32 etc determine the number of brightness levels and they are not analog, they are either on or off). The digital effect therefore leads to jagged edges and a stepped look whereas the analog image has smooth curves and a smooth curve of density vs exposure.

    Sharpness is enhanced in digital pictures via software and this can be demonstrated by making a huge enlargement of a knife edge in both digital and analog and then comparing the edges. The edge effects in digital are 'huge' to say the least. To me, they add to the artificial nature of the digital picture.

    This error, from the article quoted above, can show how bad the internet can be for passing along information.

    PE

  5. #25
    Mark Antony's Avatar
    Join Date
    Mar 2007
    Location
    East Anglia,UK
    Shooter
    Multi Format
    Posts
    772
    Images
    38
    Thanks for confirming my suspicions. Can I use some of your info in my blog, I'm going to re-dress the balance with a re-buff.
    Mark

  6. #26
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,528
    Images
    65
    Mark;

    Be my guest. Also, if you can, run the sharpness comparisons. I have and they are eye opening.

    PE

  7. #27
    Mark Antony's Avatar
    Join Date
    Mar 2007
    Location
    East Anglia,UK
    Shooter
    Multi Format
    Posts
    772
    Images
    38
    Here is my Blog,
    http://photo-utopia.blogspot.com/
    anything you'd like to add?
    Mark

  8. #28
    CBG
    CBG is offline

    Join Date
    Nov 2004
    Shooter
    Multi Format
    Posts
    894
    Quote Originally Posted by Mark Antony View Post
    Thanks for your explanation PE, it was this 'article' that confused me.
    http://www.luminous-landscape.com/essays/clumps.shtml
    I didn't think film grain was binary
    Mark
    That link encourages a simplistic way or looking at film and digital.

    Without rehashing the endless boring debate on what's better etc ... Here's a way of looking at the comparison that gets too little attention:

    First, it's always dangerous to treat very different media as if they were the same, i.e. just two differnt ways of doing the exact same thing. They are different ways of doing different but related things. The link and it's ilk encourage the false perception of a binary argument who's only possible answers are: a is better than b, or b is better than a.. In truth, each media imposes it's own character upon the results and much like PE's thoughts, the real answer is, "it depends".

    A film based image breaks the image down into random grain based clumps with varying edge softness or sharpness, varying size and distribution of sizes. Beyond a very modest enlargement, the grain becomes a very important part of the image. It is a part of the aesthetic. Silver grain imaging is so different from digital that comparison is pointless. Like comparing apples and anvils.

    Digital on the other hand offers up a "Chuck Close" grid based world. Utterly different from film. Again, why try to compare? Who's Close? Look at: http://www.artsconnected.org/artsnet...ity/close.html and http://en.wikipedia.org/wiki/Chuck_Close

    The grain itself is an integral part of the film image, and to reproduce the grain with great fidelity demands huge amounts of information. If you want a result that looks like film, choose film. If you want a digital look, go digital. If you want images at an undemandingly low enlargement then it may just be mundane practicalities that make the decision.

    Digital does one thing well and film another.

    Best,

    C

  9. #29
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,528
    Images
    65
    Well, here are some other facts.

    For every ~108 grams of silver there are 6.023 x 10^23 atoms that divided by 3 can form any level of density you wish. That is a HUGE range. It is 2 followed by 23 zeros!

    Now, in addition, silver grains can be stacked while sensors are side by side, so you have the additional enhancement of stacking or the detraction in digital caused by aliasing of the image by the nature of the pixel arrangement.

    These additional facts should be of some use to explain the incredible detail in film images.

    Digital is convenient and very portable. Good for snapshots and proofing professional LF shots in the studio. Analog is good for perfect professional pictures and is economical. It is slower to yield up the pictures.

    Analog pictures are permanent. Digital pictures are fugitive.

    PE

  10. #30
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,528
    Images
    65
    For those who don't know what aliasing is, here is a description.

    Lets say there is a red thread on a white dress. In analog it is recorded as-is.

    In digital, the thread may cross over 3 pixels R/G/B and therefore may not be recorded as-is, but may appear and vanish many times as it crosses the various pixels.

    This is not related to the jagged lines caused by digital images.

    I hope that this simple explanation helps.

    Until digital sensors have stacked R/G/B sensors, aliasing will remain a problem. Some such sensors are being tested. Kodak has just invented a new type of sensor that supposedly eliminates this problem.

    PE

Page 3 of 6 FirstFirst 123456 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin