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Thread: Apature

  1. #121
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    Quote Originally Posted by Razr View Post
    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.
    The diaphragm's diameter may not change, but the aperture value changes proportionally to the focal length - regardless of exposure mode.

    All that happens in M or Av mode is that the diaphragm's diameter may remain constant (or close to it for simplicity), the aperture value meanwhile must change as defined by mathematics.

    Oh, did I mention you are an idiot?
    Last edited by cwphoto; 10-25-2007 at 07:55 PM.
    Christian Wright; Dip Phot
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  2. #122
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    Okay I'm going to have to back up Razr on this. I tried that test with the aperture thing and the lens thing. I put the 35mm 1.4 on my camera and turned the ring on the lens and the aperture stayed at 1.4 no matter how much I turned the ring!!!!! all that happened was the image got fuzzy, but I think that's because my lens is crap. I'm thinking of getting something sharper. Any suggestions Razr? Oh and I think my zoom is broke too. The only way I can get bigger images is by walking closer? Have you ever had that problem? What a waste of money that lens was!
    5D MK III, 50D, ELAN 7E, 17-40mm 4, Sigma 10mm 2.8 fisheye, 18-55mm 3.5-5.6 IS, 30mm 1.4, 85mm 1.8, 580 EX, 430 EX speedlight, Pocket wizard flex and mini.
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  3. #123
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    Maybe Razr is Ken Rockwell. I've never seen them both in the same room.
    Adam
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  4. #124
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    Quote Originally Posted by D Thompson View Post
    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
    "It" what? F/2.8 in Av mode? In Av mode, only the selected aperture (in this demonstration-f/2.8) setting is “available” to use and that throughout the zoom range.
    How many more times do you have to be shown?
    You're all reading it wrong.
    I cannot believe people out there use Av mode and do not know what the aperture is doing (and not doing as in "not changing") in Av mode.

  5. #125
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    Quote Originally Posted by Razr View Post
    No test needed: and here's why:
    Any person with the slightest bit of knowledge about the brute mechanical end of photogrpahy knew/knows what Wikipeida says (above) is 100% true.
    The operative phrase being: "allows the photographer to force the camera to operate the lens at its optimum aperure":
    which means from wide open or anywhere in-between.

    If you have any differences about what I said about aperture priority, take it up with Wikipedia, which literally pimp slapped all your uninformed arguments.
    Yeah... Because wikipedia isn't just some site that gathers knowledge from its users without any credentials... Oh wait... That's exactly what wikipedia is.

    And aside from that:

    Quote Originally Posted by Razr
    "allows the photographer to force the camera to operate the lens at its optimum aperure":
    which means from wide open or anywhere in-between.
    I seriously suggest you learn to read. "Optimum aperture" (or aperure as you quoted it) does not mean wide open at the arbitrary number of your choosing, it means wide open at the mathematical ability of the lens at the given focal length. Optimum and imaginary aren't the same word. Sorry.

    There are two possibilities here. 1. You're mentally retarded and you need a great deal of help because of your learning disability, or 2. You have never owned an SLR or SLR lens. Either way, I feel sorry for you.


    Finally, why would every lens manufacturer list their lenses as "f/3.5-5.6" or "f/2.8-4" if they could be used at f/3.5 or f/2.8 throughout the entire focal length? What possible reason could there be aside from the fact that you're wrong for them to inform people that at the telephoto length, they'll only be getting f/5.6? Why wouldn't they just list their lens at the maximum aperture that you have found a magical way to invoke despite the fact that physics deem it impossible?
    Last edited by griptape; 10-25-2007 at 09:03 PM.

  6. #126
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    Quote Originally Posted by tim11 View Post
    RAZR,
    Can a photographer use F2.8 at 70 mm on a Sigma 17-70 F/2.8-4.5?
    In Av mode and full manal mode he can: In Av mode, the photographer selects f/2.8 and the camera body is forced to use the selected aperture.
    In full manual mode, the photographer selects f/2.8 as their shooting aperture, adjusting the shutter speed and ISO (if neccessary) to balance the exposure.
    _________________
    Question for you: in full manual, the photographer (above) selects f/2.8 @ 1/320th sec. to start a shoot.
    When he zooms, he is two stops over on his match needle reading.
    Since the photographer will not change the aperture setting, what does the photographer have to do to balance the exposure?

  7. #127
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    Quote Originally Posted by Razr View Post
    "It" what? F/2.8 in Av mode? In Av mode, only the selected aperture (in this demonstration-f/2.8) setting is “available” to use and that throughout the zoom range. You're all reading it wrong.
    I cannot believe people out there use Av mode and do not know what the aperture is doing (and not doing as in "not changing") in Av mode.
    NO. YOU ARE WRONG. At full zoom of the lens in question (ie. sigma 17-70 f/2.8-4.5) only F/4.5 is available.

    You are a bigger idiot than I previously thought you were since you keep denying you are wrong.
    Nikon D90, D80
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  8. #128
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    Quote Originally Posted by Razr View Post
    "It" what? F/2.8 in Av mode? In Av mode, only the selected aperture (in this demonstration-f/2.8) setting is “available” to use and that throughout the zoom range.
    OK, real easy, just a yes or no answer will do. On a f2.8-4.5 (using your example on this thread, page#1, post#8) I can use the aperture of f2.8 at any focal length the lens has? Mode is set to AV or M of course.

    You're all reading it wrong.
    I cannot believe people out there use Av mode and do not know what the aperture is doing (and not doing as in "not changing") in Av mode.
    I think all of us here but you have an ideal how to use AV and what it does.
    Dennis

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    Georgetown, KY Photographer
    Retouching

  9. #129
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    Quote Originally Posted by Razr View Post
    In Av mode and full manal mode he can: In Av mode, the photographer selects f/2.8 and the camera body is forced to use the selected aperture.
    In full manual mode, the photographer selects f/2.8 as their shooting aperture, adjusting the shutter speed and ISO (if neccessary) to balance the exposure.
    _________________
    Question for you: in full manual, the photographer (above) selects f/2.8 @ 1/320th sec. to start a shoot.
    When he zooms, he is two stops over on his match needle reading.
    Since the photographer will not change the aperture setting, what does the photographer have to do to balance the exposure?
    Alright, that's it. This guy has never owned a DSLR. Leave him to his delusions. Any moron that has ever put their DSLR in manual mode (hell, it's the only mode I shoot in) knows that lenses state their aperture range for a reason, and that Razr is delusional. Let's just let this poor fellow fade away into his delusions of owning an actual SLR camera.

  10. #130
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    Holy cow this is getting just plain rediculous

    First of all Razr needs to be educated not ridiculed and maybe we all need a lesson in Semantics. Of course he did come on like we all needed to be educated. He's arguing aperture (opening), and maybe that doesn't change (but I think it does) but rather appears to change. I really don't know the inner workings of a lens. I do know however a variable aperture lens cannot attain a lens opening larger than the f-stop ratio advertised for a given focal length. It's a simple ratio and it's physically impossible to change it.


    I will explain as best I can the way I understand aperture, focal length, and f-stop.

    First, my out of context quote from Wikipedia's article on aperture:

    "Zoom lenses typically have a maximum aperture (minimum f-number) of f/2.8 to f/6.3 through their range. A very fast zoom lens will be constant f/2.8 or f/2, which means the relative aperture will stay the same throughout the zoom range. A more typical consumer zoom will have a variable relative aperture, since it is harder and more expensive to keep the effective aperture proportional to focal length at long focal lengths; f/3.5 to f/5.6 is an example of a common variable aperture range in a consumer zoom lens."

    The key words are relative aperture. An f-stop is very simply a ratio of the diameter of the aperture of a lens to the focal length. The tube a lens is built in is only so big, and this determines the maximum opening (aperture) the lens has. As focal length (the center of the lens to focal plane) increases the opening (aperture) required to transmit a given amount of light to the focal plane must increase. This ratio is constant, your aperture has to be a certain size for a given focal length to maintain a given f-stop.

    Think of being in a railroad tunnel standing 10 feet from the exit(short focal length) looking out. You can see a huge opening (aperture) with lots of light coming in, there is plenty of light hitting you, enough to read a newspaper. Now back up into the tunnel a hundred feet(zoom in)the exit will appear like a much smaller opening (relative aperture) with much less light entering. Has the size of the aperture changed? No of course not, but your position to the opening has given it the appearance of being smaller...and, there is much less light reaching you now, and you"ll probably have some trouble reading the news now. The aperture is the same size but your position relative to the aperture has made it appear much smaller, with much less light reaching you.

    Let's make a hypothetical lens, a 50-200 f/2-f/8. A lens is built in a tube much like the aforementioned railroad tunnel: lets say this tube is 25mm in diameter, that's as big as the opening can get, it physically can't get any bigger. I need all of this opening of 25mm to get an f stop of 2 at 50mm.

    Now, I'll zoom my lens in to 200mm, my focal length has increased therefore my distance from the center of the lens to the focal plane has increased, just like moving back into the tunnel. I need more opening now to maintain f/2 but my lens is only 25mm in diameter: it can't physically get any larger. I can't make the opening any larger, and the opening now appears smaller because of the increased focal length. So my ratio has changed, I still have a 25mm tube but my ratio has changed 200mm divided by 25mm (the size of my tube) equals f/8. That's the best f-stop I can get with my hypothetical lens, the size of the opening (aperture) didn't change, but my ratio to focal length sure did.
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