Help me understand ISO

Discussion in 'Photography' started by Steve B, Jan 5, 2013.

  1. Steve B

    Steve B Guest

    Yesterday, I went and looked at the D7000. The counter guy, who is very
    experienced, said that the camera was very good in low light conditions, and
    that is what distinguishes it in the Nikon line.

    I read Floyd's statement that he uses ISO 5000 for inside shooting of events
    and NO FLASH.

    Am I to understand that ISO is a function of the camera to balance light,
    aperture, and speed to the scene? And that outdoors uses a lower ISO
    number, and indoors without flash, a higher one? I line natural photos,
    soft lines and borders, and soft faces, not blown out by the whiteness of
    everything in range caused by flash, nor warts subdued instead of
    highlighted DEPENDING ON THE PHOTO.

    And when is it "best" to use AUTO on the ISO setting? Sunny/cloudy day when
    the conditions are changing? Maybe when shooting very general outdoor
    building photography like I do where quality is "acceptable" on AUTO?

    Thanks fer putting up with a newbie.

    Steve
     
    Steve B, Jan 5, 2013
    #1
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  2. If you are taking pictures of negroes, you will need to use a higher ISO
    or your picture will be underexposed.

    If the negro has teeth and smiles, you can lower that by one stop.
    And depending on the negro.
    It is best to use low ISO settings for higher quality pictures. However
    you will need more light to take pictures of negroes and have acceptable
    skin tones. That's how NatGeo does it when they take pictures of topless
    negro women in African Booganyie tribes-the ones with the large brown
    nipples and purple clitorises.
     
    Kwincay Ercolinowitz, Jan 5, 2013
    #2
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  3. Steve B

    Peter Guest

    It depends. Here is my non-scientific understanding. But then I have
    only been into photography for well over sixty years.
    ISO is a function of sensitivity. Thus at a higher ISO you may shoot
    with a smaller aperture and a higher speed. However, there is a price,
    which in this case is background noise. Sometimes called grainy looks.
    In theory a lower ISO will give you a cleaner image and better contrast.
    Noise reduction software, is nothing more than color blurring, so the
    image may not be a crisp.
    Google the term and you will learn more than can be discussed here.
    BTW, for reasons of control, I never use auto ISO. The only auto setting
    I use is for white balance.
     
    Peter, Jan 5, 2013
    #3
  4. Steve B

    DanP Guest

    Go back and ask him if the ISO performance for the D7000 is better than theD3s.
    The salesman is full of shit, no surprise. Have a look at this http://goo.gl/QkQNc and see the score for ISO. It is decent but not very good. But compared to your old small camera it is fantastic. For better results use a fast lens (wide aperture, small f number).

    Think of the ISO as a signal amplifier. The sensor collects a signal over aperiod of time and it needs to boost it. Amplifying it means the noise is amplified as well.

    At ISO 100 there is no amplifying. This happens when you shot in sunlight or when expose for a long time with less light or keep the aperture opened wide on a fast lens.

    Indoors without flash or at night the signal needs more amplifying and a higher ISO will be used by the camera.

    If you have used film cameras you would know the film had an ISO number on it. 100 for sunlight and 400 for indoors. ISO 100 film gave best picture quality and ISO 400 gave grainy pictures. The same goes for digital, only nowISO goes up to ridiculous numbers.

    With digital some cameras have less noise at high ISO. Saying a camera can use a high ISO does not mean anything. To see how good it is compare controlled test shots against other cameras. See this http://www.dpreview.com/reviews/nikond7000/20 and change ISO for all 4 shots. Pan on the test image.

    Keep the ISO to AUTO, the camera will decide what to do. If you use the highest ISO that is acceptable to you your shots in sunlight will be blown andyou will get the maximum noise you can put with on all shots. If you use alow ISO you will get good pictures in sunlight but indoors the exposure time will increase and get shaky images. I was told Nikon can cap the ISO to a value you want. I use Canon.


    DanP
     
    DanP, Jan 5, 2013
    #4
  5. Steve B

    Steve B Guest

    Go back and ask him if the ISO performance for the D7000 is better than the
    D3s.
    The salesman is full of shit, no surprise.

    * * * *

    There is, of course, the differences in price, too.

    Steve
     
    Steve B, Jan 5, 2013
    #5
  6. Danp nailed that one... :)

    Incidentally, both Peter and Dan had pretty good
    discussions, though Peter simply doesn't understand the
    value of Auto ISO, while Dan does. Not all cameras can
    make good use of Auto ISO, so unless a person has one
    that is it is useful it might not ring a bell yet.
    First understand a couple things. One is that I use a
    Nikon D4 and lenses like the 70-200mm f/2.8 VRII to
    shoot "events", commonly in poorly lit gymnasiums and/or
    auditoriums. It's a job where it helps to throw money
    at it, and then it still takes some experience and skill
    to get good results even with the best equipment.
    First, any given scene might have a "Light Value", which
    is a measure (using a light meter) of how much light
    there is, from say 0 to maybe 16 EV. Each number is
    twice as much as one smaller. So EV 6 is twice as much
    light as EV 5. EV 1 is moonlight, EV 2-3 is candle light,
    EV 4 to 5 is enough to easily read, EV 6 or 7 is a very
    well illuminated basketball court. EV 8 to 10 is a
    relatively dark overcast day. EV 11 to 12 is a normal
    overcast day. EV 13 to 14 is a sunny day. EV 15-16 is
    high noon at mid summer on a beach with white sand. (I
    may be off by one or two in the middle there, but you
    get the idea.)

    The aperture determines how much of that light hits the
    sensor. The shutter speed determines the interval over
    which photons (light particles) are captured. So if you
    are shooting in a gym with EV 4.5, you need a big wide
    aperture and a long shutter speed to capture any photons
    at all. But if you go to the beach on the 4th of July
    it takes a very short shutter speed and a very small
    aperture to prevent the light from overwhelming the poor
    collection wells in the sensor.

    So aperture and shutter speed are what determines how
    many photons are collected, and technically that (and
    that alone) is referred to as "exposure".

    In practice though almost everyone who is not being
    pedantically technical thinks "exposure" is how bright
    the picture is... and that includes this thing called
    ISO.

    It is, as Dan said, how much the signal from the sensor
    is amplified.

    That means we can have only a few photons collected on a
    very dim day with a wide open aperture and a very long
    shutter speed produce a picture that is just as bright
    as the one taken on a very bright day where a small
    aperture and short shutter were all we could do to keep
    from overloading the sensor. (But the first picture is
    full of noise caused by the amplification... which is
    okay because the second picture is also full of a
    different kind of noise just because the short shutter
    speed snips just an instance of photons landing on the
    sensor, and these photons arrive at random speeds so
    some pixels get more and some get less for the same
    shutter speed! Photon noise... ignore it though, cause
    you don't want to know.)

    But the ISO does allow the same brightness from either a
    lot of light or just a little light, because it is the
    "sensitivity to light" of the system.
    Well, outdoors in the bright sun as opposed indoors in
    dimmer light, yes. Of course if you shoot outdoors at
    night in the moonlight, then things are worse there than
    indoors with just the kitchen light on.

    The deal with or without flash is important, because
    flash does several things besides just provide a lot of
    light. It can annoy people too, so you can't use it in
    some circumstances, and you can in others. It is harsh
    (deep shadows) unless you do something to change that.

    And another odd thing is that it just isn't the sun! I
    shot a few pictures the other day here in Barrow of a
    lady on the beach at 2 PM. Well, in January here there
    is just barely a bit of twilight at that time of day, so
    I had to use a flash. It was -20F with a 20MPH wind and
    the flash got very cold very fast, and the recycle times
    were very slow. It ended up firing one out of four
    shots. The shots where the flash goes off have a very
    bright person standing in white snow... and the
    background is pitch black. The shots where the flash
    did not go off have very low contrast, but the Arctic
    Ocean that is covered with ice can clearly be seen in
    the background too. Both sets of images turned out to
    be very useful.
    I pretty much agree with that, and rarely ever use a
    flash because of it. But I don't do posed portraits
    very often either. Someone who does studio work lives
    by their strobes (and reflectors and diffusers and so
    on).
    There are times when fully manual is best, because even
    if the amount of reflected light changes the actual
    desired exposure does not. Shooting in a gym is a
    typical example. Point the camera at a group of people
    with dark clothing and the light meter thinks you need 2
    stops more exposure than if you point it at a group of
    people with light clothing. Set it where it needs to be,
    and use manual exposure.

    On the other hand if you are walking down the street in
    the big city, you might point the camera inside at a
    shaded area, down a dark alley, or at something in the
    sunlight. Set the aperture and shutter speed for
    artistic effects (DOF for the aperture and freeze-action
    with the shutter speed), and then put it on Auto ISO and
    let 'er rip.

    These are all things that experience will eventually
    teach you well enough that they seem simple. (And then
    some really complex stuff will keep you occupied... for
    the next several decades.)
    Like everyone else, you and I were both born knowing
    absolutely nothing about this stuff...
     
    Floyd L. Davidson, Jan 6, 2013
    #6
  7. Steve B

    Peter Guest

    Sounds good, but Peter finds that auto ISO does not work for what he
    wants to do. Indeed I was careful to state what I do, and more
    importantly, why. YMMV
     
    Peter, Jan 6, 2013
    #7
  8. All you said was "for reasons of control, I never use auto ISO."

    You took care to avoid anything explicit? I'll stand by the
    obvious: you don't understand how to use it, or why.

    If you had so much as said "don't often use it" I'd be inclined
    to give you the benefit of the doubt, by when someone says it
    the way you did... it's pretty clear. The same thing applies
    to folks who say they *always* use aperture priority, or shutter
    priority, or for that matter manual exposure mode. If they use
    only one of those, ever, they clearly don't understand any of them.
     
    Floyd L. Davidson, Jan 6, 2013
    #8
  9. Steve B

    Robert Coe Guest

    : On Saturday, 5 January 2013 19:24:39 UTC, Steve B wrote:
    : > Yesterday, I went and looked at the D7000. The counter guy, who is very
    : > experienced, said that the camera was very good in low light conditions, and
    : > that is what distinguishes it in the Nikon line.
    :
    : Go back and ask him if the ISO performance for the D7000 is better than the D3s.
    : The salesman is full of shit, no surprise. Have a look at this http://goo.gl/QkQNc and see the score for ISO. It is decent but not very good. But compared to your old small camera it is fantastic. For better results use a fast lens (wide aperture, small f number).
    :
    : Think of the ISO as a signal amplifier. The sensor collects a signal over a period of time and it needs to boost it. Amplifying it means the noise is amplified as well.
    :
    : At ISO 100 there is no amplifying. This happens when you shot in sunlight or when expose for a long time with less light or keep the aperture opened wide on a fast lens.
    :
    : Indoors without flash or at night the signal needs more amplifying and a higher ISO will be used by the camera.
    :
    : If you have used film cameras you would know the film had an ISO number on it. 100 for sunlight and 400 for indoors. ISO 100 film gave best picture quality and ISO 400 gave grainy pictures. The same goes for digital, only now ISO goes up to ridiculous numbers.

    Addressing the OP, since I know that Dan already understands the concept ...

    Keep in mind, however, that the ISO scale, like almost every measure
    describing the behavior of light falling on a two-dimensionsl surface, is
    logarithmic. A one-stop increase in the sensitivity of the sensor represents a
    doubling of the ISO number. So, for example, a sensor operating at ISO 200 is
    one stop faster rhan a sensor operating at ISO 100; a sensor operating at ISO
    400 is one stop faster than a sensor operating at ISO 200; etc. So as better
    engineering improves the sensitivity of modern sensors, their maximum ISO
    numbers go up pretty fast. That's why the numbers look so ridiculous.

    Bob
     
    Robert Coe, Jan 6, 2013
    #9
  10. It has one EV advantage at the bottom and 1-2 at the top compared to the
    Canon G1X and EOS 600D, and Olympus Pen E-P3. Wow. One cheap lens is going
    to take away that advantage. What, you're not going to buy the best lens
    they have going for three times the price of the cheapie? But, but, but it's
    buh-buh-better... Yes but who for and how much?

    I know some men like to go in for all the willy waving and sales people love
    their fat commission's but what's important for you? Eeeeeeh... That's a
    different question with a different answer.
     
    Charles E. Hardwidge, Jan 6, 2013
    #10
  11. Steve B

    dadiOH Guest

    If your flash is blowing out stuff, you are not using it properly.

    Relative to your subject line, "ISO" is an acronym for "International
    Standards Organization". That supplanted "ASA" , meaning "American
    Standards Association".

    In relation to photography, both describe the reactivity of a medium to
    light. The lower the ISO/ASA the lower the reaction.

    With film, any particular film had a fixed ASA/ISO. High numbers were
    achieved by making the grains of silver salts larger; that increased
    sensitivity but also increased the granularity of the image and its
    contrast. The same is true - but differently - with digital; instead of
    increased granularity, you get increased noise.

    The purpose of varying the ISO in digital is not to directly balance the
    relationship between it and shutter/aperture but to allow you to use the
    shutter/aperture combination that you want. For example, if the light is so
    low that the shutter speed is too low at maximum aperture to record the
    scene, you can increase the ISO, thereby increasing the sensitivity, so that
    you can use a higher shutter speed. With film, the "sweet spot" (in later
    years at least) was ISO 100-200 for normal use.

    Back to the flash. It is blowing out stuff because it is over exposing
    them. It is over exposing them because they are a relatively small portion
    and/or much closer than the remainder of the image within the frame but the
    flash exposure is trying to be for the *entire* image. You need to modify
    your technique so that the flash is only emitting enough light for the
    objects you want lighted by it (anything closer will still be over exposed).

    The same sort of thing is true without flash...you need to determine the
    amount of light falling on the object you are photographing. Your camera's
    internal meter is viewing the *reflectivity* of objects - not, directly, the
    amount of light falling on them - and reducing it to an "average". In most
    cases, that average will be adequate but it will fail miserably in special
    cases...a white plate on a white table cloth...the proverbial black cat in a
    coal bin...a single spotlighted performer on a dark stage...anywhere that is
    not "average" in reflectivity.


    --

    dadiOH
    ____________________________

    Winters getting colder? Tired of the rat race?
    Taxes out of hand? Maybe just ready for a change?
    Check it out... http://www.floridaloghouse.net
     
    dadiOH, Jan 6, 2013
    #11
  12. Steve B

    Steve B Guest

    During the holidays, my SIL, who was born knowing everything, was fudutzing
    with his sb400, and taking multiple shots, and looking at them in the
    preview window, and adjusting the flash until he would get the shots he
    liked.

    He also shoots 99.999% in AUTO mode. I asked him why didn't he bounce the
    flash. He was totally against bending the flexible head back, like I was
    trying to decapitate his Yorkie. And when I suggested he might want to try
    bending it as far back as it would go, facing slightly rearward, I think the
    thought of it was more than he could bear, as he pulled his camera to his
    chest and he walked off.

    I asked him if it was a thyristor. He said, "A what?"

    Is bounce flashing a viable acceptable alternative for a newbie, pro, or
    know-it-all, or does it too have its specific niche in flash photography?

    Steve
     
    Steve B, Jan 6, 2013
    #12
  13. Steve B

    dadiOH Guest


    Both. Bounce is great when you want an overall light...something other
    than flat on light...soft(er) light..light from another direction...etc. It
    is something I used with great frequency from 1955 on.


    --

    dadiOH
    ____________________________

    Winters getting colder? Tired of the rat race?
    Taxes out of hand? Maybe just ready for a change?
    Check it out... http://www.floridaloghouse.net
     
    dadiOH, Jan 6, 2013
    #13
  14. Bounce flashing is quite acceptable in getting good light to reflect off
    a negro's curly hair. Unless of course the negro is bald then you will
    need to use a different technique that the police use when taking mug
    shots of negroes.
     
    Kwincay Ercolinowitz, Jan 6, 2013
    #14
  15. Steve B

    Robert Coe Guest

    :
    :
    : > Back to the flash. It is blowing out stuff because it is over exposing
    : > them. It is over exposing them because they are a relatively small
    : > portion and/or much closer than the remainder of the image within the
    : > frame but the flash exposure is trying to be for the *entire* image. You
    : > need to modify your technique so that the flash is only emitting enough
    : > light for the objects you want lighted by it (anything closer will still
    : > be over exposed).

    And even if you succeed in getting the subject properly exposed, you're likely
    to be left with an unacceptably dark background. In recognition of this, most
    modern flash units have a mode which prevents the subject from being
    overexposed, even if you expose for the background. In effect, the flash
    provides "fill" light only. (In fact, many flash units have two modes, one
    designed to work with the metering system of the camera one one that makes
    exposure decisions on its own. And, of course, a manual mode.)

    But then it can be difficult to get enough light on the scene. The flash
    thinks it's done its job, but you find that you need a very slow shutter speed
    (or a very wide aperture) to capture the background. If you're indoors, that's
    when bounce flash comes to your rescue.

    : During the holidays, my SIL, who was born knowing everything, was fudutzing
    : with his sb400, and taking multiple shots, and looking at them in the
    : preview window, and adjusting the flash until he would get the shots he
    : liked.
    :
    : He also shoots 99.999% in AUTO mode. I asked him why didn't he bounce the
    : flash. He was totally against bending the flexible head back, like I was
    : trying to decapitate his Yorkie. And when I suggested he might want to try
    : bending it as far back as it would go, facing slightly rearward, I think the
    : thought of it was more than he could bear, as he pulled his camera to his
    : chest and he walked off.
    :
    : I asked him if it was a thyristor. He said, "A what?"
    :
    : Is bounce flashing a viable acceptable alternative for a newbie, pro, or
    : know-it-all, or does it too have its specific niche in flash photography?

    If you're relying on manual calculations (light output, lamp-to-subject
    distance, etc.), bounce flash can be tricky, because it's hard to know exactly
    where the light will be coming from and how intense it will be. But in the
    sutomatic mode that works with the camera's metering, it gets much easier,
    because the camera doesn't have to know how the light got there; it just
    reacts to what it sees. The flash will still shut down when the brightest part
    of the scene has received enough light, but the bounced light will have
    illuminated the rest of the scene as well. Often the result is that the scene
    will be more brightly lit, and lit much more evenly, with bounce flash than if
    the flash were pointed at the subject. The trickiest part of using bounce
    flash is estimating the angle at which to bounce the flash off of the
    reflecting surface (usually the ceiling), but it's a skill that improves with
    practice. If you get to be reasonably proficient at using bounce flash, you'll
    wonder how you ever got along without it.

    I've encountered a fair number of photographers who eschew flash indoors and
    wax eloquent on the virtues of available light. And I'll readily concede that
    there are times when available light is the right, or even the only, solution.
    But I think most indoor photographers will do a better job most of the time if
    they use bounce flash.

    Bob
     
    Robert Coe, Jan 7, 2013
    #15
  16. Steve B

    Steve B Guest

    TY

    I'll try to convince SIL to bend that little thing that's built to bend
    ........ even bend over backwards.

    And comments noted for my own use.

    Steve
     
    Steve B, Jan 7, 2013
    #16
  17. Steve B

    Savageduck Guest

    There are a few places to explore for information regarding use of
    flash or speedlights:

    < http://neilvn.com/tangents/flash-photography-techniques/ >
    < http://neilvn.com/tangents/flash-photography-techniques/4-bouncing-flash/ >

    < http://photographylife.com/flash-photography-tips >

    < http://www.nikonusa.com/en/Learn-And-Explore/Query/h4l7gjfh/flash.html >

    < http://www.kenrockwell.com/nikon/flash.htm >
     
    Savageduck, Jan 7, 2013
    #17
  18. Steve B

    Whiskers Guest

    When you aren't using a flash-gun, almost all your photos are taken using
    bounced light; it's "natural". Flash lighting is not natural, and
    flash-on-camera is the cause of "red-eye" and "deer in the headlights"
    images; unless you /want/ that sort of effect, you have to bounce the flash
    off something, and/or put the flash gun(s) where you want the light to be
    coming from in your image.

    Improvised surfaces for bouncing off can be created by using newspapers or
    a pale coat or cloth, held by a by-stander, if you don't happen to have
    purpose-made reflectors with you.

    Beware of bouncing your flash off something that will give your pictures a
    colour you don't want - a white or grey ceiling might by OK, but green
    might not be, and dark colours don't bounce much at all. That's why press
    photographers often have 'diffuser reflectors' attached to their on-camera
    flash guns and tilt them around to get slightly softer and more flattering
    lighting.
     
    Whiskers, Jan 7, 2013
    #18
  19. Steve B

    DanP Guest

    Unless this is exactly what you wanted. Have a look at this http://photo.net/photodb/photo?photo_id=10161232
    Flash killed the daylight.


    DanP
     
    DanP, Jan 7, 2013
    #19
  20. Steve B

    DanP Guest

    DanP, Jan 7, 2013
    #20
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