Not a bird

Discussion in 'Digital Photography' started by PeterN, Jan 1, 2014.

  1. PeterN

    me Guest

    Actually, no. You are still running under the constraints imposed by
    the exposure program. In this case it is manual. If this were not the
    case then iso wouldn't float up until it's max allowable setting as
    the available light changes.
     
    me, Jan 4, 2014
    #61
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  2. PeterN

    PeterN Guest

    Yup!
     
    PeterN, Jan 4, 2014
    #62
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  3. PeterN

    sid Guest

    Well, it does have to do with correct exposure.
    And the signal, when using auto iso, is amplified to a point the exposure
    program determines is the correct exposure
    But the value of one leads directly to the value of the other, for all
    values of correct exposure. Incorrect exposure, neither make a blind bit of
    difference to the other.
     
    sid, Jan 4, 2014
    #63
  4. PeterN

    PeterN Guest

    I am thanking both of you for you helpful advice.
     
    PeterN, Jan 4, 2014
    #64
  5. PeterN

    me Guest

    I didn't say exposure. I said the exposure program within the camera.
     
    me, Jan 4, 2014
    #65
  6. PeterN

    Whiskers Guest

    Seldom anywhere else.
    ,----<http://www.hcc.commnet.edu/artmuseum/anseladams/details/moonrise.html>
    | F. Technical Aspects
    |
    | Camera: 8 X 10 view camera
    | Lens: Cooke triple convertible lens.
    | Light meter: lost!
    | Film: Speed: ASA 64
    | Filter: Wratten No. 15 (G) filter
    | Exposure: 1 second at f/32.
    | Development: dilute D-23 and ten developer to water sequences.
    | Years later - refixed, washed the negative, and treated the lower
    | section with a dilute solution of Kodak IN-5 intensifier.
    `----

    A Wratten No. 15 filter is 'deep yellow' and would normally call for
    an extra 1.5 or 2 'stops' exposure to take advantage of its 'darken the
    sky' effect while leaving landscape relatively normally exposed (all
    other things being equal).

    An exposure of 1 second at f/32 ('EV 10') on ASA 64 emulsion should put
    the face of the moon into Adam's 'zone 8' or 'zone 9' (not quite
    'maximum density' in the negative); the deep yellow filter might make
    the moon slightly darker - as Mr Adams later said, he thought the moon
    would be in 'zone 7' (see below).

    The landscape will of course be a darker, and not very different from
    the sky.

    I don't think that would be "underexposed" for a dark scene which he
    wanted to show as a dark image. The difficulty in printing is down to
    the tricky subject, not to faulty camera technique. Mr Adams had enough
    experience to be confident that he'd get a usable negative even though
    he estimated the exposure (based on his knowledge of the brightness of
    the moon, which is of course in full sunlight) without using his
    exposure meter. He even described his choice of exposure in terms of
    his usual "Weston" exposure meter's dial, in at least one description of
    the occasion.

    ,----<https://en.wikipedia.org/w/index.php?title=Moonrise,_Hernandez,_New_Mexico&oldid=585518771>
    |
    | The making of Moonrise has attracted unusually strong interest. In 1941,
    | Secretary of the Interior Harold Ickes hired Adams for six months to
    | create photographs of lands under the jurisdiction of the Department of
    | the Interior. Adams was accompanied by his young son Michael and his
    | best friend Cedric Wright on a long road trip around the west. They came
    | upon the scene while traveling through the Chama River valley toward
    | Española in late afternoon on November 1; accounts of what transpired
    | differ considerably.
    |
    | The image appeared in U.S. Camera Annual 1943, and Adams gave this
    | account:[7]
    | It was made after sundown, there was a twilight glow on the distant
    | peaks and clouds. The average light values of the foreground were placed
    | on the "U" of the Weston Master meter; apparently the values of the moon
    | and distant peaks did not lie higher than the "A" of the meter. . . .
    | Some may consider this photograph a "tour de force" but I think of it as
    | a rather normal photograph of a typical New Mexican landscape. Twilight
    | photography is unfortunately neglected; what may be drab and
    | uninteresting by daylight may assume a magnificent quality in the
    | halflight between sunset and dark.
    |
    | Later accounts were considerably more dramatic. According to Mary
    | Alinder, they encountered a "fantastic scene", a church and cemetery
    | near Hernandez, New Mexico, and pulled to the side of the road. Adams
    | recalled that he yelled at his son Michael and at Wright to "Get this!
    | Get that, for God's sake! We don't have much time!"[8] Desperate to
    | capture the image in the fading light, they scrambled to set up the
    | tripod and camera, knowing that only moments remained before the light
    | was gone.
    |
    | Adams gave a similar account in Examples[9]
    | I could not find my Weston exposure meter! The situation was desperate:
    | the low sun was trailing the edge of clouds in the west, and shadow
    | would soon dim the white crosses. . . . I suddenly realized that I knew
    | the luminance of the moon—250 cd/ft2. Using the Exposure Formula, I
    | placed this value on Zone VII. . . . Realizing as I released the shutter
    | that I had an unusual photograph which deserved a duplicate negative, I
    | quickly reversed the film holder, but as I pulled the darkslide, the
    | sunlight passed from the white crosses; I was a few seconds too late!
    | The lone negative suddenly became precious.
    `----

    ,----<http://www.hcc.commnet.edu/artmuseum/anseladams/details/moonrise.html>
    | E. Once the photograph is taken, is the development and printing a
    | mechanical process?
    | No, it is not mechanical. Although there is a procedure, there is much
    | judgment involved on the part of the artist. Ansel said that the
    | negative for Moonrise was difficult to print. He tried many methods
    | using different chemicals and times and papers. With the negative in the
    | enlarger, he increased the light hitting certain areas (burning-in)
    | which made the sky blacker and the clouds less bright so the moon would
    | stand out more. With all these artistic adjustments, Adams said "it is
    | safe to say that no two prints are precisely the same."
    `----

    Not unusual to try different enlarging and printing techniques for a
    "difficult" negative, particularly one so lucrative.

    He had a track record of getting great images at short notice as
    unplanned opportunities arose. He was very good at choosing exposure
    values and processing techniques.
    Well it added to the lustre of the fame that had been growing for 20
    years, and probably brought his work to the attention of more people.
    You'll notice that Mr Adams had time to stop the car, set up his tripod
    and 8"x10" field camera and lens, and frame and focus the shot manually,
    before inserting the dark-slide with the film. PeterN is sitting or
    standing in a boat or on land, with a digital SLR in his hands ready to
    shoot. That gives him a huge time advantage over Mr Adams with /his/
    kit. His camera even has an exposure meter built in (albeit not
    conveniently for taking manual incident-light readings).

    ,----<http://www.hcc.commnet.edu/artmuseum/anseladams/details/moonrise.html>
    | B. How did chance lead him to take this photograph?
    | Ansel Adams was returning to Santa Fe, New Mexico after a discouraging
    | day of photography. From the highway he glanced left and "saw an
    | extraordinary situation - an inevitable photograph! I almost ditched the
    | car and rushed to set up my 8 X 10" camera. I was yelling to my
    | companions to bring me things from the car…I had a clear visualization
    | of the image I wanted but…I could not find my exposure meter! The
    | situation was desperate: the low sun was trailing the edge of clouds in
    | the west, and shadow would soon dim the white crosses." He felt at a
    | loss to guess the correct exposure, but suddenly realized he knew the
    | luminance of the moon and quickly took the shot.
    `----
    Sometimes. For certain values of "high end".
    If the exposure is set manually, the camera knows nothing about
    'exposure compensation'; the only purpose for an 'exposure compensation'
    is to over-ride an automatic exposure system.
    Did I say that? I said that for a subject an automatic system can't
    handle, manual is the best approach. PeterN is clearly relying on
    automation, and getting into difficulties as a result.

    Yes, I'm biased; I learnt to take photographs before anything was
    automated. I still believe that knowing how to do things manually is
    going to help you to understand what an automatic system is trying to
    do, and what it can't do. I also like to think that *I* am taking the
    photograph, not the camera. You are of course free to disagree.
     
    Whiskers, Jan 4, 2014
    #66
  7. PeterN

    PeterN Guest

    Not completely true. When there is time, I meter and chimp. In my film
    days I eyeballed the exposure, and wa fairly accurate.
    I use autofocus only for critters in motion.
     
    PeterN, Jan 5, 2014
    #67
  8. PeterN

    J. Clarke Guest

    So if you use the same settings for Panatomic X and Tri-X both will be
    properly exposed?

    Try again.
     
    J. Clarke, Jan 5, 2014
    #68
  9. PeterN

    J. Clarke Guest

    But the exposure is only correct for the film being used. I don't know
    why you've got this need to argue over minutiae of nomenclature.
     
    J. Clarke, Jan 5, 2014
    #69
  10. PeterN

    Tony Cooper Guest

    I wonder if you don't notice light changing quicker than we do
    considering where you live.
     
    Tony Cooper, Jan 5, 2014
    #70
  11. PeterN

    sid Guest

    You are correct that iso does not effect the amount of light hitting the
    light gathering medium, but it does have a direct effect on the results
    obtained by that light gathering medium.
    Most people, when talking about exposure, would be referencing what they
    considered to be correct exposure, in which case iso has to be part of the
    equation.
    The point is that unless you put your camera into fully manual mode, no auto
    anything, you are relying on the cameras interpretation of what is correct
    exposure to set one or more parameters.
    So how does the camera decide which iso to set when using manual mode with
    auto iso? Judging by how my camera works, I do use it set that way often, I
    have to assume that the camera reads the exposure meter and sets the iso to
    what it considers to be correct exposure based on the aperture and shutter
    speed set.
     
    sid, Jan 5, 2014
    #71
  12. PeterN

    PeterN Guest

    Unless I had too much coffee, it seems to me that the magic hour light
    in FL changes faster that the light in NY.
    There are reasons for it that are not relevant. The fact is that light
    can, and does change rapidly.
     
    PeterN, Jan 5, 2014
    #72
  13. PeterN

    sid Guest

    But it does change the results one obtains at any given exposure
    Of course you are. That's what auto means. The camera is setting something
    by it's own determination.
    No it doesn't, it affects how the data captured during that exposure is
    recorded by the sensor. Got it?
    Yes quite, just as I have been saying.
     
    sid, Jan 5, 2014
    #73
  14. PeterN

    Whiskers Guest

    [...]

    It certainly can. But it can never know what the photographer intended,
    and it can never set the exposure and focus in advance of the
    photographer framing the shot and squeezing the button. Manual metering
    _in_advance_ and having known focus settings _in_advance_ can do that,
    resulting in no time at all between squeezing the button and the photo
    actually being taken - because the human involved has already set the
    exposure and got the focus close to what's needed before even framing
    the shot. If zone focussing is used, exploiting depth of field or
    hyperfocal distance, the first shot is in the bag before precise
    focussing is even tried.

    Don't just react to things you want to photograph, predict them. When
    you react without planning, you get snapshots. Fine if that's what you
    want, and better than nothing if an unexpected opportunity arises (such
    as moonrise over Hernandez) but if you've planned to be there and
    planned to take photos of [whatever it is] then why haven't you planned
    _how_ those photos will be taken?
     
    Whiskers, Jan 5, 2014
    #74
  15. PeterN

    Whiskers Guest

    This might help clarify what a digital camera does:
    <http://photo.net/learn/raw/> "Learn about RAW, JPEG, and TIFF with the
    digital photography experts at Photo.net."
     
    Whiskers, Jan 5, 2014
    #75
  16. PeterN

    Whiskers Guest

    There are several automatic exposure modes possible, eg:

    - camera sets everything
    - camera sets everything except shutter speed
    - camera sets everything except aperture
    - camera sets everything except ISO 'speed'
    - camera sets only ISO 'speed'
    - camera sets only aperture
    - camera sets only shutter speed

    and so on. If the camera sets /anything/ for itself, then you are using
    'automatic exposure'. There is only one setting that isn't automatic
    exposure, namely:

    - camera sets nothing, photographer makes all decisions.
     
    Whiskers, Jan 5, 2014
    #76
  17. PeterN

    Whiskers Guest

    Which generations of photographers have referred to as "film speed".
    Notice my use of scare quotes. If we're /really/ quibbling, in a
    digital camera the "ISO setting" doesn't change the sensitivity of
    anything, instead it changes the amount of electronic &/or digital
    "amplification" applied to the signal from the sensor.
     
    Whiskers, Jan 5, 2014
    #77
  18. PeterN

    Whiskers Guest

    .... and then the camera automatically decides what 'film speed' to use
    to get as near as it can to whatever its programming dictates the
    correct image characteristics are. This is *not* a manual exposure
    setting, it's just one particular mode of automation.

    If you want to dictate the properties of the image recorded by the
    camera, do not allow the camera to do anything automatically.
     
    Whiskers, Jan 5, 2014
    #78
  19. PeterN

    Whiskers Guest

    Apart from describing what the "ISO setting" on a digital camera
    actually does, which seems to me to be something very much to do with
    this thread.
     
    Whiskers, Jan 5, 2014
    #79
  20. PeterN

    Whiskers Guest

    In that case, whoever wrote the program used by your camera "in 'Scene'
    mode" planned how the photos will be taken. You choose what and when,
    but not how.
     
    Whiskers, Jan 5, 2014
    #80
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