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Interesting Article on ISO at DPR

Discussion in 'Open Discussion' started by drd1135, Aug 10, 2018.

  1. drd1135

    drd1135 Zen Snapshooter

    Mar 17, 2011
    Southwest Virginia
    Steve
    • Informative Informative x 2
  2. exakta

    exakta Mu-43 Veteran Subscribing Member

    412
    Jun 2, 2015
    Hmm, only 766 comments so far. Guess all the DPR folks are still asleep ;) 
     
    • Funny Funny x 3
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  3. gryphon1911

    gryphon1911 Mu-43 Hall of Famer

    Mar 13, 2014
    Central Ohio, USA
    Andrew
    I'm not a fan of that article at all...i think it just will cause more confusion and arguing...and it really didn't say much other than "I don't like the way that ISO is used in digital".

    I like to learn about how things work...but in the grand scheme of things in the picture making process having some kind of standard to base your exposure against is a good thing. If someone along the way can come up with some other way of dealing with that part of the exposure triangle, I'm all for considering it.

    This most likely will be a moot point within the next 20 years anyway for newer build imaging devices as they will inevitably be using AI algorithms to determine images and exposures as clean as clean can be.
     
  4. agentlossing

    agentlossing Mu-43 Hall of Famer Subscribing Member

    Jun 26, 2013
    Andrew Lossing
    It's a very frustrating article because it picks nits but offers nothing for a solution. Very like DPR in general.
     
    • Agree Agree x 6
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  5. ralf-11

    ralf-11 Mu-43 Top Veteran

    516
    Jan 16, 2017
    not well written either
     
    • Agree Agree x 1
  6. tkbslc

    tkbslc Super Moderator

    They timed it along with rumors about the new Nikon mirrorless, so perhaps Nikon has all the answers. :flypig:
     
    • Agree Agree x 1
  7. Well they agree that a RAW histogram and clipping warnings would help a lot.
     
    • Agree Agree x 1
    • Winner Winner x 1
  8. bassman

    bassman Mu-43 Top Veteran

    997
    Apr 22, 2013
    New Jersey
    The Bassman
    ISO, as we use it with digital cameras, is a significantly different thing than the older concept we used with film. With film, it was a measure of how sensitive the recording medium was to light. With digital, it has nothing to do with the recording medium's sensitivity - rather, it's a measure of how bright the jpeg produced will be. This brightness (for a given quantity of light) is achieved through some combination of analog amplication of the signal captured by the sensor and digital processing. The exact nature of the manipulation is unknown to us, and presumably differs between manufacturers and perhaps camera models. Contrast this with film, where the "manipulation" (i.e. developing the film) of the "raw data" (i.e., exposed but undeveloped film) was publicly defined by the developing instructions.

    Importantly, there is no definition of ISO for raw data - it's defined solely for the jpeg output.

    It's this opaque processing, which hides the true nature of the sensor’s light capture, that prevent us from having really useful tools when using digital sensors.

    So while I might disagree with some of Butler's suggestion, I agree with his main point: ISO for digital cameras misses the point. We need a new set of tools that are designed for the new technology we use. ISO was a nice bridge from the old days, but should be retired.
     
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  9. ToxicTabasco

    ToxicTabasco Mu-43 Top Veteran

    520
    Jul 2, 2018
    South West USA
    Interesting, and not explaining anything that I already know. Not that I'm a expert, but if you like to push cameras and software to the limits with dark night exposures, you learn a lot as you go. That experience teaches you what you can get away with, and where the limitations of a camera are. In the end, all the science behind it means nothing. And if you go by what the science indicates, you'll never really know what your camera can do unless you get out in the dark sky nights, or any other condition where you need high ISO and longer exposures, and push your gear to the limits. That's the best way to learn about ISO and what it does.
     
    • Agree Agree x 2
  10. exakta

    exakta Mu-43 Veteran Subscribing Member

    412
    Jun 2, 2015
    But what do we replace it with? All I care about is knowing how to set the exposure and ISO works fine for that.
     
    • Agree Agree x 2
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  11. drd1135

    drd1135 Zen Snapshooter

    Mar 17, 2011
    Southwest Virginia
    Steve
    Why do we need to know ISO? Set Speed and aperture and auto ISO does the rest. Most of us only think to keep iso as low as we can for noise reasons.
     
    • Agree Agree x 1
  12. Drdave944

    Drdave944 Mu-43 All-Pro Subscribing Member

    Feb 2, 2012
    Now that we know that ISO has limited importance,we can move on to optimization of the important parts of the picture,dealing instead with blown and noisy parts on the picture and spend more time worrying about range of the sensor,which is the only real ares improvement which will deal with the problem. The thought process of the author is not always clear. For example,saying you get less light in a hi ISO picture,while it may be true,obscures the fact that increasing the exposure may be exactly what you don't want to do,or you get camera shake. Avoiding this was exactly why you increased the ISO.
     
  13. coffeecat

    coffeecat Mu-43 All-Pro Subscribing Member

    Aug 4, 2012
    SW England
    Rob
    @bassman@bassman - you just summarised the whole DPR article, in a lot less words, but, for me at least, your version was much easier to understand! Thanks
     
    • Agree Agree x 1
  14. bassman

    bassman Mu-43 Top Veteran

    997
    Apr 22, 2013
    New Jersey
    The Bassman
    Thanks!
     
    • Like Like x 1
  15. bassman

    bassman Mu-43 Top Veteran

    997
    Apr 22, 2013
    New Jersey
    The Bassman
    So many things would be more useful, many related to raw data. First off, having something which told us how saturated the raw pixels are - the so-called raw histogram. Then settings that directly let us manage the raw pixels: why can't we directly set ETTR, for instance? In other words, let the pixels fill until the first one (or thousand, etc) fill to overflow? Perhaps we could take advantage of e-shutters at the pixel level, and shut off lightcapture at highlights while continuing for shadows, effectively increasing DR?

    Knowing the "brightness" of the camera produced jpg is useful if you shoot jpgs, which I only do while traveling and posting on my iPad.
     
    Last edited: Aug 16, 2018
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  16. Lcrunyon

    Lcrunyon Mu-43 All-Pro Subscribing Member

    Jun 4, 2014
    Maryland
    Loren
    I have a couple of questions/comments about the points made in this article (most of it is probably because of the wording the author used):

    It states that raising ISO may cause a reduction in the exposure value gained from aperture and shutter speed, but I would think this is only true when unnecessarily using ISO in lieu of aperture or shutter speed; i.e., I may have a smaller aperture or quicker shutter speed than the image really needed, and I raise ISO to compensate. But let's instead assume I am shooting wide open, or limiting aperture because I need more DoF. Perhaps I am shooting at the shortest shutter speed I can use without inducing motion blur. Whatever the reason, if I have achieved the closest exposure I can with aperture and shutter speed, but it still is not enough, then raising ISO is the only thing left to do. In that scenario, raising ISO does not reduce the amount of light I am collecting. Or am I missing something?

    He says that ISO is not always amplification of the light signal that was captured by the sensor -- which is what I thought it was, like turning the volume up on a radio (not sensor sensitivity). If it isn't always that, what else is it?

    He claims that exposing to the right can "sometimes result in noisier mid-tones than you want." Is what he is really trying to say that ETTR may not be enough to eliminate noise? Or is he claiming that somehow ETTR can induce more noise in the mid-tones? If it's the latter, why?

    The author says the reason we don't have a RAW histogram is because ISO is reportedly focused on JPEGs. It seems an insufficient reason to me. ISO is applied (perhaps there are differences, I don't know) to RAW files as well. Am I correct in understanding that there is no real technical limitation preventing histograms and blinkies from being based on a RAW file's dynamic range as opposed to a JPEG's? Considering how prevalent RAW shooting is -- particularly among photographers who would bother looking at a histogram to begin with -- what motivation has been keeping all camera companies from introducing a RAW-based histogram?​

    The author dislikes the way all digital cameras meter by honing in on mid-tones. But I'm not sure that there is a more elegant solution. It's a way to average out the scene's brightness so that the result is easy on our eyes; and the stops of light concept (increments of x2) is easy to grasp and apply for photography purposes. I suppose going to a completely different method would require a specific measurement for light (would that be candela?), which I imagine would be a lot more complicated and time consuming. Perhaps it could all be implemented behind the scenes (internal to the camera but with the same interface we are familiar with), but I am not sure it is necessary to go that far to fix the problems we have with ISO and histograms.
     
  17. Hypilein

    Hypilein Mu-43 All-Pro

    Mar 18, 2015
    If all this article does is create some big hype on Raw-Histograms (I've never seen a new camera thread where this was demanded) I would gladly welcome this development. It may be poorly written, but I agree with the general point, that Highlight warnings/Histograms etc based on Jpegs are less useful than what we really want. This has been annoying me for some time.
     
  18. Aristophanes

    Aristophanes Mu-43 Top Veteran

    https://www.iso.org/obp/ui/#iso:std:iso:18383:ed-1:v1:en

    Bizarre article.

    ISO in digital is sensitivity, visibly measured in noise, electrically by current, with the SNR variable while photosite are of fixed ring dimension.

    ISO in film is also sensitivity, visibly measured in grain, photosites determined at the emulsion lay-down phase of manufacture, fixed thereafter.

    The principle is the same, though going from chemical to electrical. Noise versus grain. It’s 2001 all over again.

    I agree that the JPEG engines get in the way, but I suspect that may have more to do with rear LCD capabilities.

    Also, JPEG is an industrial and journalistic standard. Many institutions cannot use RAW. They must use JPEG to preserve the chain of evidence against manipulation.

    Of course the digital standard is to expose for mid-tones. That’s the bell curve at work and a necessary baseline. If you don’t like it, move the focus point and take a reading from there. The built in spot meter of digital cameras solves his problem. Only a few very high-end, late era film cameras had that capacity.
     
    • Agree Agree x 2
  19. JanW

    JanW Mu-43 Regular

    Would all the different films have had exactly the same characteristics?
    Or did we have to know what film we used and how it responded to the exposure. I was always told to underexpose a positive film but I don't think I ever did. But that is what I heard from several people.
    I was not an experienced photographer when I switched to digital but it seems to me nothing has changed.
    One has to know his gear to get the best out of it...
     
  20. Machi

    Machi Mu-43 Veteran

    474
    May 23, 2015


    You're right in your scenario but he is too. If in-camera metering is set to zero then increasing ISO will lead to closing aperture or shortening exposure time => less light for sensor.

    As I understand he is (at least partially) wrong here. He is right that digital ISO isn't the same as film ISO.
    Also ISO doesn't change quantum efficiency of sensor.
    But with exception of so called ISO-less cameras, ISO changes sensitivity of sensor.
    That's because in most cameras ISO settings affects amplification of signal and it leads to different base noise level for the output from the sensor (it lowers read-out noise).
    That's why lots of M43 cameras have similar maximum achievable SNR at ISO 200 as at ISO 400.

    As I understand his point, sometimes camera on it's own produces images with clipped highlights because it can overexpose some parts of scene. For midtones it means more light and less noise. Because for ETTR "best results are achieved by giving as much exposure as possible without clipping the brightest tones you care about" you can end with lower exposure for the same scene and that means less light and more noise.

    You're correct and I want to see camera in which there would be possibility of choosing between standard histogram and RAW histogram.

    I thing that he wants metering based on the preservation of highlights and I agree with him that it would be nice to have it for RAW shooters as one of the possible settings in the camera.
     
    • Appreciate Appreciate x 1
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