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Thread: Apature

  1. #111
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    Razr:

    I'm calling you out.

    You're still not responding DIRECTLY to this quote of yours:

    Quote Originally Posted by Razr View Post
    Only if you are in "P" (PROGRAM) or "A" (AUTOMATIC) modes.
    The aperture stays the same in "Av" and "M" (MANUAL) mode, no matter what focal length you choose, making any f/2.8-f4.5 etc. lens a "fast"-constant apeture lens throughout the zoom range.
    You like to avoid it, don't you?

    You have yet to directly respond to the fact that it is WRONG! Do you deny that it's wrong? I don't give a hoot what Wikipedia says. I am talking about what YOU wrote.

    Let's have it, Mr. "Pro".
    Last edited by JTL; 10-25-2007 at 05:27 PM.
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  2. #112
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    Ken Rockwell could do it.
    Adam
    -------------
    Canon 60D & lenses & flashes & stuff
    A bunch of cheap vintage film cameras


    My Etsy store

  3. #113
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    Sorry M8, but that's what you've ben saying all along. You have siad that a lens that has a max aperture of f/2.8-3.5 can use f/2.8 along the whole zoom range and that is using an unavailable aperture because at the long end of the zoom f/2.8 is "unavailable as its max aperture is f/3.5.
    Please, show me (in/on an unassailable website), that precise statement about ("unavailable aperture"):
    Google, Ask-you know, any URL I can search and read for myself.
    Can you please explain to all of us what a max aperture of f/2.8-3.5 really means if it doesn't mean that the max aperture is variable and changes as the lens zooms. Why would manufacturers lable their lenses this way if it is not true?
    Gladly. but first, you do know your question is mainly gobbledygook, incoherent? As for the "maximum aperture" you and others have fastened onto:
    Maximum Aperture:
    Max. Aperture F2.8
    This simply states that the maximum aperture for the lens is F2.8.
    http://www.megacameras.com/articles/...rture--53.html
    The above quote says all there is to say about "maximum aperture", which can be f/1:1.2 for my 55mm asph. CANON FD lens down to f/32 to f/45 at the smallest openings for small format to large format*.
    +"F" numbers actually go up into the hundreds, not just f/45
    *Each lens always-ALWAYS has only 1 (one) "maximum aperture" and it is ALWAYS stated somewhere on the barrel of the lens: that is, there is only one “maximum” aperture per lens.
    I'm amused how each of you, in turn, fasten onto the others misunderstandings about the brute calculus in photography. I'd venture 98% of you have no idea about things photographic. Especially since you all seemed to have followed along like sheep with your misconception about what part of the camera does what when you use any thing but "P" mode.
    __________________________________
    The operative phrase in the Wikipedia quote is this:
    allows the photographer to force the camera...
    , "Force (look it up) the camera to use an optimum aperture, "force" clearly stating the photographer can choose and shoot with any aperture within the limitations of the lens.
    Don't you think if the lens could be set to f/2.8 across the entire zoom range, the manufacturer would advertise this as to sell more of the product.
    Let's look at this little blurb:
    Coolpix 995's Way of Achieving "Constant" Aperture
    To partially overcome the problems caused by the variable aperture feature, Coolpix 995 can maintain aperture within 1/3 stop in effect before zoom operation started, if possible.
    More precisely, the camera will do its best to keep the selected aperture with 1/3 stop as you zoom.
    However, if the camera can maintain this 1/3 stop error range, aperture changes.
    Consequently, constant aperture while zooming may or may not be maintained.
    Note that this fixed aperture is only available in the Aperture-Priority mode and Manual Exposure mode when you can set aperture manually.
    You might want to point out that a dinky COOLPIX 995 P&S may not always be able to hold a set, constant aperture, though you and the rest should get the drift of my thesis by reading the COOLPIX blurb again, this time for its content.
    Better for my thesis, just because a P&P cannot, may not hold a constant aperture, I assure you any SLR (shooting with automatic lenses in Av mode)most assuredly can (and easily does).

  4. #114
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    Quote Originally Posted by Prospero View Post
    (SNIP) Of course that is a absurd posit. But it is just as absurd as opening up the diaphragm of a lens more than its maximum.
    So who is the neophyte here...
    You. All you have to do to prove I ever said such is post the exact quote, which you cannot in that I never ever said or inferred any such silliness.

  5. #115
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    Quote Originally Posted by Ray Schnoor View Post
    "In addition, aperture priority mode allows the photographer to force the camera to operate the lens at its optimum apertures within the limits of maximum/minimum aperture for a given focal length of the lens."

    OK! There we go.

    Ray.
    "Optimum": could also be the wide open position for portraiture, as with my EOS 70-200 f/2.8 "L". Or, closed down two stops from the maximum aperture.

    "within the limits" merely means the focal length; no mystery there...unless

  6. #116
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    Quote Originally Posted by dustyporch View Post
    To have this make sense, you need to remember that the aperature number is a ratio between the size of the opening in the blades, and the mm length of the lens.

    In a lens with constant aperture, the aperture blades widen as the lens zooms to keep that ratio the same. Its mechanically driven by the zoom twist. In a lens with a variable max aperture, the blades generally open too as the lens zooms, but not enough to completely compensate for the increase in length. So the max aperture number changes.

    Dusty, that's the problem --> Razr doesn't know the difference between aperture and f-stop.

    "Do you and the others now get the fact that the aperture is frozen on one f/stop in Av mode? Get it?"

    See?
    Pentax K20D/K5/15/21/40/70/10-17/12-24, Sigma 17-70 2.8-4.5/150-500, Tamron 90 Macro/70-200 2.8, Canon SX20 IS/Elph 500HS
    (formerly Pentax 50 1.4/50-200/55-300/K100D, Sigma 18-50 2.8/70-300 APO, Tamron 28-75, Viv 800, Tele-Tokina 800, Canon S3 IS, Samsung L210)
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  7. #117
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    Quote Originally Posted by Razr View Post
    Only if you are in "P" (PROGRAM) or "A" (AUTOMATIC) modes.
    The aperture stays the same in "Av" and "M" (MANUAL) mode, no matter what focal length you choose, making any f/2.8-f4.5 etc. lens a "fast"-constant apeture lens throughout the zoom range.

    Razr - you keep denying and denying and say show me proof. As you've chosen to ignore it I'm putting it up here once more. This thread, page #1, post #8.

    Tell me that we're all reading it wrong and you're not saying that on a f2.8-4.5 that you can select f2.8 in AV or M mode and it is available throughout regardless of focal length.

    How many more times do you have to be shown?
    Dennis

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    Georgetown, KY Photographer
    Retouching

  8. #118
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    Quote Originally Posted by zmikers View Post
    (SNIP)Can you please explain to all of us what a max aperture of f/2.8-3.5 really means if it doesn't mean that the max aperture is variable and changes as the lens zooms.
    I'll repeat here: only in "P" and "S" moded does the aperture setting change according to the focal setting.
    IN "M" and "Av" modes, the aperture does not change until/unless the photographer sets (selects) another aperture-got it?
    "Av" and "S" modes immobilze (lock-freeze) the aperture.

  9. #119
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    Instead of answering direct question Razr accuses people of misunderstanding, misquoting and wrongly 'inferred' what he has been saying.
    The question we ask you now is straight and simple razr... should I repeat it?


    Edit: I posted just before reading your last.
    Are you saying that on a f2.8-4.5 that you can select f2.8 in AV or M mode and and F2.8 is available throughout the zoom range?
    Last edited by tim11; 10-25-2007 at 06:34 PM.
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  10. #120
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    Oh dear.

    First of all: Razr - you're a complete idiot.

    That feels better, now the debate:

    It's easier to understand if we are concise.

    In a 'variable aperture' zoom lens (such as a 75-300/4-5.6) then the aperture itself may not change - by this I mean the actual aperture's diameter, not the aperture value.

    However what does change is the maximum aperture value, which is a function of both the diaphragm's diameter and the focal length of the lens.

    So while the actual diaphragm's diameter may not change when zooming, the aperture value most certainly will in the above example.

    This is junior maths Razr. I assume you are older than a junior so therefore you are an idiot.
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