Noob questions- ISO and mm equivalent

Discussion in 'Photography Beginners' Forum' started by Hermie, Jun 11, 2009.

  1. Hermie

    Hermie TPF Noob!

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    Hello, I'm fairly new to photography, and I'm trying to figure out what ISO is and what it does.

    As it is right now, I know how to point the camera at something good and take a picture of it, but I don't know all the advanced tricks that professionals use.

    Also, I was thinking about getting a Canon SX10 because it has a 20X zoom lens.. What would be the equivalent in a DSLR lens in mm?
     
  2. Samanax

    Samanax TPF Noob!

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  3. ANDS!

    ANDS! No longer a newbie, moving up!

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    The 20X zoom refers to the magnification from the widest end, to the longest end. So if I had a zoom lens that went from 18-200 that would be a magnification of 11X. A 20X lens would be something like 20-400.

    ISO is merely the sensitivity of the sensor to light. The higher the ISO, the higher its sensitivity is to light (and thus the faster your shutter speed, and larger your aperture). Useful for lowlight shooting when your lighting conditions aren't ideal and you need a higher light sensitivity to register the image.
     
  4. Hermie

    Hermie TPF Noob!

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    Thanks for the link!

    So that's what "noise" referrs to as well.. I thought the camera itself was loud or something.

    Much appreciated!
     
  5. seward93

    seward93 TPF Noob!

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    Ya, noise is when the image looks grainy.

    Generally, with a higher ISO (800 and up on entry level DSLR's I believe, but it depends) you will get a little bit of noise.
     
  6. Dwig

    Dwig TPF Noob!

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    ... or a 30-600mm or a 45-900mm lens. There is absolutely no way to say what the mm equivalent would be to the 20x lens in the SX10 knowing only that it was 20x.

    The typical "super-zoom" digicam has little or no true wide angle. The widest is usually only a true "normal" or slightly wider Commonly, their wide end is roughly equivalent of a 35-40mm lens on a 35mm film body or 24-28mm on the common "cropped sensor" (APS-c, DX, ...) DSLR.

    This link

    PowerShot SX10 IS Digital Camera

    indicates that the SX10's lens is roughly equivalent of a 28-560mm lens on a 35mm camera, so it does have more wide angle than most of its class. That would equate to very roughly 18-370mm on a APS-c/DX format DSLR.

    These are very, very rough equivalences. The aspect ratio of the SX10's sensor is quite different, more square, that that of a 35mm film image or the common DSLR (4/3rds' format being the exception). The equivalences are calculated on the diagonal field of view, not the horizontal or the vertical. If you calculate using either of those two, you will get two different answers that each differ from the diagonal.
     
  7. KmH

    KmH Helping photographers learn to fish Supporting Member

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  8. djacobox372

    djacobox372 No longer a newbie, moving up!

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    Correct, but not all cameras are created equal: some cameras have much less noise at high-iso's then others, typically these are cameras with physically larger image sensors (slrs).

    In fact, the most important difference between a $3000 camera and a $300 camera is the high-iso peformance.
     

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