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XP2: ISO L

Discussion in 'X-Pro2 and X-Pro1' started by (c)ow, May 18, 2017.

  1. (c)ow

    (c)ow Premium Member

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    Hi all,

    I read somewhere that ISO L has some disadvantages but can't find it anymore. The Fuji manual is no help.
    Setting ISO to 125 you can use a wider aperture by almost one step. I know ISO L works only with mech. shutter. Any idea?

    Thanks,
    Oli
     
    Last edited: May 18, 2017
  2. J J

    J J Premium Member

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    Don't have xp2 but Jpeg only?
     
  3. Richard_R

    Richard_R Eclectic eccentric

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    When you use an iso outside the sensors native range (i.e. iso "hi" or iso "lo") the camera is amplifying all the signal noise (usually) to an unacceptable level at the high end and compressing all the data from the sensor at the low end which also introduces noise and colour issues. There is nothing wrong with you using hi or lo if you want from the cameras point of view but many people find the images unacceptable so they don't. I suspect camera manufacturers use the hi and lo settings as a cop out. Essentially what they are saying is "hey if you want top use this go ahead but don't say we suggested it" type of thing.
     
  4. (c)ow

    (c)ow Premium Member

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    Richard,
    Thanks for your explanation. So I need to test...
    Oli
     
  5. Richard_R

    Richard_R Eclectic eccentric

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    You are not going to damage the camera and if the results are acceptable to you that is all that matters.
     
  6. (c)ow

    (c)ow Premium Member

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    Correct!
     
  7. Dirk Offringa

    Dirk Offringa Premium Member

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    You won't be able to shoot raw (at least on the X-T1 generation). It's done in in-camera jpeg conversion.
     
  8. David Anderson

    David Anderson Premium Member

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    I found the low ISO on the XT1 easily cooked the highlights and being JEG only, it was harder to shoot with correction in mind.
    The rest of the image was quite acceptable.
    On the X-T2 the low ISO is much better in raw and don't hesitate to use it.
     
  9. (c)ow

    (c)ow Premium Member

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    @ Dirk: XP2 shoots RAW with ISO L
    @ David: Thanks , will try
     
  10. dko22

    dko22 Premium Member

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    according to Rico's X-Pro2 manual, ISO 100 gives you one stop less DR. This is quite simply because ISO 100 overexposes by 1 stop and then the camera pulls back the exposure. My own experience shows it is much easier to blow highlights with this setting. On the other hand, in dull lighting, it can be used creatively to boost contrast.

    David
     
  11. dko22

    dko22 Premium Member

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    strictly speaking, every ISO above ISO 200 is simply amplifying the signal. ISO 51200 does an extra amplification at the internal RAW processing stage which is why there is a significant decrease in quality at this stage. ISO, as stated previously as just ISo200 with an extra stop exposure which is then pulled back.
     
  12. Mahasamatman

    Mahasamatman Well-Known Member

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    I may be wrong as I've not read as widely as I could about this but aren't Fuji sensors, and some others, described as Isoless? If I read correctly, the difference is that where the Canon processing effectively doubles the photon count to go from ISO 200 to 400, the Fuji model is to say the shot at ISO 400 was shot at ISO 200 but has a +1 exposure compensation which is then applied automatically in post-processing.
     
  13. dko22

    dko22 Premium Member

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    Let me just quote from Rico Pfirstinger's book "115 X-Pert tips for the X-Pro2". I don't know anyone who has a sounder overall grip of the technicalities of FujiX cameras.
    So what exactly is ISO doing? ISO determines the amount
    of signal amplification that’s applied to the image. ISO 200,
    the sensor’s native setting, is equivalent to the camera’s
    basic calibration. At ISO 400, the signal (or sensor data) is
    amplified by one aperture stop to brighten the image and
    increase its exposure. At ISO 800, the amplification amounts
    to two stops, and so on.

    So I would say you are right as well :)

    ISO invariance, which I assume is the same meaning as ISOless means that if you, say, push a 4 stop underexposed ISO 200 by 4 stops, it should give the same result as a shot at ISO 3200. If it doesn't -- and thus the camera is adding extra noise -- then it is not ISO invariant. Although I haven't spent much time testing it, Fuji is regarded as ISO invariant.
     
    Last edited: May 18, 2017
  14. tbear

    tbear New Member

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    Richard, I'm brand new to this forum, My X-T2 is just a few weeks old and I'm still in a steep learning curve. A few days ago, I took my X-T2 to a shoot rather than my D800, recording the behind-the-scenes happenings at a local semi-pro theater. My primary experience is nature photography, so not only was I learning to use the Fuji, but also shoot under very unique-to-me conditions. The first night, I accidentally moved the dial from auto ISO to "L" and didn't realize it for a few frames. I was very pleasantly surprised with this JPEG of one of the directors. X-T2, 1/45 sec at f / 4.0, ISO 25,600, 55MM (XF18-55F2.8-4 R LM OIS). Processed in Lightroom: Cropped, Highlights -43, Vibrance +3 and that's it. I believe at that time all the IQ settings in camera were set to "0". I shoot RAW + JPEG, but liked what I saw on this shot from the JPEG.
    I will add that I needed to use my RAW files when shooting the on-stage actors as the lighting color temperatures varied, with multiple light sources constantly changing and each with its own color temp and tint (sometimes extreme variation). In that case the JPEG couldn't handle the color and tint shift I needed to make.

    Temp Titanic selected night one-0770.jpg

    View attachment 105376
     
  15. (c)ow

    (c)ow Premium Member

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    I never use the DRxxx setting (mean leave it on DR100) because I understand they don't apply to the RAW files. Maybe I need to look into that with the plan of shooting more JPG. But that's a different story...
     
  16. dko22

    dko22 Premium Member

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    trouble is that's not quite right -- the DR settings on Fuji definitely can affect the RAW files as well. If you shoot high ISO, for instance, you need to manually select DR 400 for maximum dynamic range, otherwise you can lose the highlights --as I found when first testing the X-Pro2. Unlike with my X-E1 (now passed on to my brother), the Pro2 doesn't select 400 if you're on auto for reasons which are beyond me.
     
  17. ysarex

    ysarex Premium Member

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    No, that's not correct. ISO 200 is not the sensor's native setting. Fuji does not assign ISO values to the sensors in their cameras. This is a common error so seeing Pfirstinger repeat it isn't surprising. Otherwise the language used there is confusing and misleading. The ISO values used and assigned by digital camera manufacturers including Fuji are assigned to the standard output of the camera's JPEG processing software, not to the sensor. It's a distinction of some consequence.

    Saying that the signal (sensor data) is amplified is touchy but it's common terminology and all the various terms used (amplify, gain, boost, etc.) carry connotation problems so I think we have to accept that. Problems arise with the implication that recorded data is somehow expanded or increased. What absolutely does not happen is an increase of exposure. The term "exposure" has explicit photographic meaning and it's very confusing to mix it up with any form of electronic post processing which is what's going on here. ISO on a digital camera does two things: 1) The ISO value is used by the camera's meter to bias the result returned. 2) ISO's second function is entirely a post processing function used to brighten the raw file generated by the ADC through either/or, or a combination of both a boost to the analog signal from the sensor (amplify) and digital scaling during ADC.


    That's a fair definition of ISO invariant. In most cameras amplification of the analog sensor signal prior to ADC is beneficial and yields less overall data loss -- basically an engineering issue. Cameras that are ISO invariant are engineered such that there is no additional data loss if the analog signal amplification is skipped. The X-Trans II sensor was for all practical purposes ISO invariant. The X-Trans III sensor is most certainly not.
     
  18. ysarex

    ysarex Premium Member

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    Yes, the DR function does effect the raw files in all Fuji cameras. DR200/400 respectively withhold one and two stops of analog signal brightening that would otherwise be applied to the raw file. Sensor dynamic range is normally decreased by any increase of ISO -- see this chart: Photographic Dynamic Range versus ISO Setting The ISO post process function is chopping off DR with every incremental increase. In the case of the DR200/400 functions the normal one and/or two stop signal boost isn't applied.
     
  19. (c)ow

    (c)ow Premium Member

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    OK, different discussion but nevertheless interesting. What's the benefit of DR200 or 400 then? Have to admit I never paid much attention to this function. I was always very happy with the DR of the Fuji RAW files. Is there even more to recover from RAWs when using this function?
     
  20. ysarex

    ysarex Premium Member

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    It makes a JPEG that you couldn't otherwise get from the camera. In other words if you want the specially processed JPEG use the DR200/400 function. If you don't want that JPEG it offers no advantage.

    There is NOT more data in the raw files using this function. Maximum data in a raw file occurs when the sensor is fully exposed. Any reduction from that exposure level reduces recorded data. To use the DR200/400 functions you must raise the ISO on the camera. Fuji's intention in the design of the function is that you will expose for the raised ISO and reduce exposure = less recorded data. You do have the option to use the camera in full manual and ignore the meter in which case you could circumvent the intent of the function's design, but that really begs the question what are you doing and why. If you're interested in the raw file then expose the sensor to get a best raw file -- straight and simple.
     
    Last edited: May 19, 2017

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