Extended ISO?

Discussion in 'Photography Equipment & Products' started by battletone, Oct 31, 2009.

  1. battletone

    battletone TPF Noob!

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    I googled it, but it looks like you loose dynamic range with all of these extended ISOs? But for something like ISO100, why does Nikon not offer it as a normal mode? Is their 200 just that good?
     
  2. Garbz

    Garbz No longer a newbie, moving up!

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    Lowest sensitivity of the sensor. Making a sensor with a very wide range of possible settings is hard. By raising the native ISO of their recording system to 200 they raise the maximum ISO of the system as well with less loss in quality.

    These extended ISOs like Lo1 and Hi1 are just software hacks, so you do lose the dynamic range in your RAW data but in the case of Lo1 the final JPEG still looks very good making it very usable.

    Here's another question, why do you need ISO100? There's one stop difference. The concern would be more valid if we start talking about ISO400 or ISO800 being the native, but as ISO200 you can still use a very very wide range of settings in the sun without hitting the limits of the shutter / aperture, and if you want to go darker there's always ND filters.

    Film used to be very very slow, whereas these days you pay a premium to go below ISO100, and ISO400 film they practically give away.
     
  3. battletone

    battletone TPF Noob!

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    Does it raise it that much?

    I don't know. It just seems that whenever possible we are supposed to use the lowest possible ISO to achieve the cleanest (least noise) image possible (100 seeming to be the norm, at least on Canons). Maybe that is a false theory. But what about long exposures? Isn't one stop a big deal here? Would portraiture photographers have any objection to using ISO200 over a system with a lower native?

    The whole reason I ask is that I have a Canon, my first digital SLR, and now that I am learning more and more about what I want/need, somethings I take for granted are not the same on others platforms. Which I have to figure out why, so that if I switch systems I am not doing so blindly, and if I stay with Canon, I am not doing so blindly.
     
    Last edited: Nov 1, 2009
  4. musicaleCA

    musicaleCA TPF Noob!

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    The rule of thumb should be the lowest possible native ISO of the sensor. That gives the cleanest possible image. On Nikon that's 200, on Canon that's 100.

    My only objection to the one stop difference is that in the sun when using flash, a single stop of less sensitivity on the sensor can make all the difference. It's great to have one stop more latitude in which you don't need to push your flash into HSS. It's splitting hairs, I know, but in some situations the difference can be important.

    And, in some situations, one stop less on the shutter with no change in the aperture can make a difference too, if you want motion blur, say. But again, splitting hairs.
     
  5. battletone

    battletone TPF Noob!

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    Okay, so then the actual number is more or less irrelevant for digital? (which wouldn't make sense given the rest of your post suggesting an extra stop down) Would this mean Canon is capable of a cleaner image at the native ISO?

    This interests me. I have been reading up on wildlife photography. Is there any situation that high-speed sync would be a real negative outside of hummingbirds?
     
  6. musicaleCA

    musicaleCA TPF Noob!

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    Nope. Not AFAIK.

    Ooof. Wildlife is even worse, because you have to throw the flash a long way too usually. Better Beamer is a must at really long focal lengths, but with HSS the drop off will be even more noticeable. I was thinking more along the lines of any time where you need to fight to sun to get fill light from a speedlite; it's good in such cases to be able to get an extra stop less from the sensor, but as I said it's splitting hairs. Less sensitivity on the sensor means less sensitivity to the flash too, but it keeps you out of HSS land for a little bit longer, which can be a plus.

    HSS is a neat trick, and it lets you do lots of cool stuff with your flashes, but it's something best avoided if you can. (Avoidance to the point of slapping an ND filter on your lens is silly.)
     
  7. Garbz

    Garbz No longer a newbie, moving up!

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    You raise the entire system ISO by one stop. So if you go from ISO100 to ISO200, you effectively go from ISO6400 to ISO12800. The key here is that you're raising something that isn't variable. Maybe you have a slightly more powerful low noise signal amplifier that operates more ideally in the range that is slightly higher. Analogue electronics is an art form with a lot of intricacies, and there are many cases such as in high end audio where for instance raising the amplifier gain can result in a better signal. ISO200 being the lowest point may even be a design limitation rather than a choice. Many precision amplifiers can be set below a minimum gain before becoming unstable.

    It is the range of ISO that is not relevant. The number itself is still quite relevant as it is a standard sensitivity. The sensor is set so that ISO200 on digital is ISO200 on film. However the actual base ISO has no effect at all on the quality of the image. One can't say that ISO100 on a Canon system is more or less noisier than ISO200 on the Nikons because that is generalising a very large multitude of noise sources combined in a very complicated amplification and digital conversion system. (god that sounds like marketing speak). The only thing one can conclude is that Canon's go to ISO100 natively.

    The only thing you need to remember is that for best quality you shoot at the native ISO of the sensor which is usually it's lowest setting (bar those Lo1 type settings). Would a portraiture photographer feel any different about it? He might. If all things such as picture quality stay the same between two systems, I imagine one would welcome the greater light capturing ability of ISO200 as it would reduce the need for expensive higher powered flashes.

    Ultimately even the issue musicaleCA raised isn't anything to worry about. If you need a less sensitive system you can always throw an ND filter on the lens with no ill effect. Do not base any comparison of Nikon vs Canon vs anyone else on the base ISO of the system (unless it's actually relevant like a base ISO800 not that I have seen something like that). Ultimately the real comparison should be the usability or any features that you desperately need (like a 5:1 macro, or the ludicrous megapixel count of the 1DsMkIII), everything else changes faster than the weather. For instance only 2 years ago Nikon were a laughing stock to all high ISO shooters, and no one thought they'd ever release a full frame camera. Competition in the digital age means that there is little to nothing that separates the camera systems of various companies.
     

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