"gain" question

Discussion in 'Nikon' started by rick_pascale, Dec 10, 2007.

  1. Hello,

    Trying to get familiarized with the D-300 and came across a term I was unaware

    I first saw it in the manual in the Multiple Exposure section. It is not
    defined in the manual and Im having trouble determining exactly what it is.

    It is mentioned in relation to Multiple Exposure shooting, however, when I look
    at "properties" of pictures I have posted to the web I see some of them have
    a "Gain" property, usually "High Gain Up" or "Low Gain up".

    The only thing I can surmise is that there is a relationship between "gain" and
    ISO because Ive noticed that when the high gain is noted the ISO setting was
    relatively high in that particular shot.

    Does gain have something to do with the sensor's sensitivity to light?

    Appreciate your help with this.

  2. I've never heard it in relation to photography, but it's used in electronics - specifically when talking about the result of amplification. For example, if perhaps the voltage at a pixel was amplified before going through the analog-to-digital converter, the degree of amplification would be the "gain".

    Not a definitive answer, so maybe somebody else has something better.
  3. Gain when it comes to digital photography would be directly linked to ISO sensitivity, for the sensor has a fixed sensitivity (usually ISO 100) and whenever you want to go above that, the sensor's sensitivity in itself doesn't change, but the signal is amplified, which is where gain comes into it. I've not heard of that signal amplification referred to as "gain" in photography terms before. For digital cameras, it's normally referred to as "ISO", even if "gain" is more correct in electro-speak. <p>With photographic film, the film's sensitivity to light is what is different between different ISO films, which is different from how digital sensors work, but since that scale is so firmly fixed in photographic terminology, it makes it a lot easier to use than an arbitrary gain scale. Strange that there should be any reference to it at all in the manual or EXIF data of the pictures from a D300...
  4. Here's the simplest way I've found to grasp the concept of "gain."

    When you hear a clean electric guitar sound on your stereo, the guitarist used a low gain setting on the amplifier. No matter how loud you turn up your stereo (well, within reason) the guitar will still sound clean.

    When you hear a dirty, distorted, raunchy electric guitar the player has cranked up the gain on the amplifier (for the sake of simplicity we'll assume a good ol' Fender, Marshall, Orange or similar tube amp). No matter how low you turn the volume on your stereo, the guitar still sounds raunchy.

    That's gain.

    In digital terms, cranking up the gain to achieve more light sensitivity usually results in "dirtier" photos - more digital noise.

    Frank Zappa once said "The disgusting stink of a too loud electric guitar; now that's my idea of a good time." I'm betting he would have appreciated being able to shoot at ISO 3200.
  5. bmm


    I have also come across the term "gain" in reading up on my newish D80. It is used to mean the same thing as "hotness" (granted, a less precise term!) and I think signifies a natural propensity towards a particular exposure bias. So, for example, "high gain" or "hotness" would indicate a tendency to overexpose given a set aperture, shutter speed and ISO configuration. That is my guess/interpretation.

    Less of a guess is my reply to Lex's guitar amp analogy. I am a long time guitarist and frequent tinkerer of my various amps. So permit me a clarification - as he is half right and half wrong.

    A guitar amp is made up of 2 stages. A pre-amp (that primarily gives tonal flexibility to the guitar's raw signal) and a master amp which does the bulk of the amplifying of the sound as it comes out of the pre-amp. The volume control on BOTH is in fact a gain control, as both vary the output voltage to the next stage of the kit (be they another amp or speakers). The only reason for the pre-amp distorting it is set up to do just that, including having a low input threshold past which it no longer cleanly reproduces sound. Though you'd blow out all your windows, turn your speaker cones into flying saucers, and render yourself deaf, the master amp will do exactly the same thing (just at far higher volume) if you overload its input or crank its dials past the level at which they are comfortable.

    Turning this metaphor back to photography, I would suggest that the pre-amp is the shutter-speed/aperture combination selected, the folters used and any lens distortions introduced. In other words whatever affects the optical image that hits the sensor. The master amp is the sensor, and yes it's gain control is the ISO setting (with noise - as Lex suggests - coming in direct proportion with the "gain" selected).
  6. Well, I was trying to keep it fairly simple, Bernard. ;>

    Some amps, like those wonderful Paul Rivera-era Fenders (I had a Rivera designed Super Champ and Princeton Reverb II - used the latter to play small clubs a couple of times), used lots of pre-amp gain. So it was possible to get that great tube amp sound at reasonable volumes.

    But my old plain Jane Twin Reverb was a somewhat different beast. Part of the sound came from gain, and part of that magic tone came from sheer power distorting the speakers and feeding back through the guitar.

    In photographic terms, the hotrodded amps might be compared to digital cameras at high ISOs, while the older style amps might be more comparable to fast film and push processing.
  7. bmm


    Lex - if you ever get down under, then bugger the airline's hand luggage limits, bring your camera gear AND guitar kit. A jam and a good old BBQ in on the cards!

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