This site is supported by the advertisements on it, please disable your AdBlocker so we can continue to provide you with the quality content you expect.

Fujifilm X series 100 iso less perceived Noise

Discussion in 'General X Camera Forum' started by Benjamin Kanarek, Sep 13, 2018.

  1. Benjamin Kanarek

    Benjamin Kanarek Premium Member

    Joined:
    Oct 8, 2017
    Messages:
    169
    Likes Received:
    230
    Location:
    Born in Toronto, Canada based in Paris, France

    -Return to Top-

    Hi All,

    Just been testing out my X-H1, X-T2 and X-T20 and I was quite startled (in a good way) to notice that at 100 iso, I am getting less perceived noise and cleaner grain. Anyone else notice this or the contrary?

    Best Wishes

    Ben
     
    Last edited: Sep 14, 2018
    JimFenner and Tilphot like this.
  2. ysarex

    ysarex Premium Member

    Joined:
    Mar 21, 2014
    Messages:
    1,094
    Likes Received:
    750
    Location:
    St. Louis

    -Return to Top-

    Why would that startle you? At ISO 100 you're going to expose the sensor more and more exposure = less noise.
     
  3. Benjamin Kanarek

    Benjamin Kanarek Premium Member

    Joined:
    Oct 8, 2017
    Messages:
    169
    Likes Received:
    230
    Location:
    Born in Toronto, Canada based in Paris, France

    -Return to Top-

    But I was startled in a good way! :)
     
  4. Tilphot

    Tilphot Premium Member

    Joined:
    Mar 22, 2015
    Messages:
    1,101
    Likes Received:
    611
    Location:
    Germany

    -Return to Top-

    I guess the surprise lies in the fact that the Fuji‘s base ISO is 200 and the “L-ISO 100” setting is basically an in-camera processed JPEG from an underexposed ISO 200 picture. (At least that’s how I always understood it.) Actually I have never used the “L-ISO 100” because I thought there wasn’t a benefit to it. So this is in fact very interesting news (to me) and I’ll definitely see if I can benefit from it with my X-T1!

    Interesting discussion about it to be found here: Please login or register to view links
     
    JimFenner likes this.
  5. Benjamin Kanarek

    Benjamin Kanarek Premium Member

    Joined:
    Oct 8, 2017
    Messages:
    169
    Likes Received:
    230
    Location:
    Born in Toronto, Canada based in Paris, France

    -Return to Top-

    I am referring to shooting it in RAW at 100iso. I only shoot RAW.
     
  6. Tilphot

    Tilphot Premium Member

    Joined:
    Mar 22, 2015
    Messages:
    1,101
    Likes Received:
    611
    Location:
    Germany

    -Return to Top-

    Ah, so this must have changed. With the X-T1 it‘s only JPEGs at ISO 100.
     
  7. Benjamin Kanarek

    Benjamin Kanarek Premium Member

    Joined:
    Oct 8, 2017
    Messages:
    169
    Likes Received:
    230
    Location:
    Born in Toronto, Canada based in Paris, France

    -Return to Top-

    Here is a screen capture of my Adobe RAW file before importing into Photoshop. Check the iso...It is 100 iso in RAW. Taken with the X-H1

    Screen Shot 2018-09-14 at 14.49.40.png
     
    Last edited: Sep 14, 2018
  8. Benjamin Kanarek

    Benjamin Kanarek Premium Member

    Joined:
    Oct 8, 2017
    Messages:
    169
    Likes Received:
    230
    Location:
    Born in Toronto, Canada based in Paris, France

    -Return to Top-

    ...here is a photo taken with the X-T20 at 100 iso in RAW.

    Screen Shot 2018-09-14 at 14.56.25.png

    Screen Shot 2018-09-14 at 14.56.49.png
     
  9. ysarex

    ysarex Premium Member

    Joined:
    Mar 21, 2014
    Messages:
    1,094
    Likes Received:
    750
    Location:
    St. Louis

    -Return to Top-

    You mean the L-ISO is basically a JPEG from and OVERexposed ISO 200 picture -- not really.

    I think what tends to confuse folks about this is the assumption that base ISO is a hard value that applies to the camera sensor. It's not. The base ISO value is assigned in reference to the output of the camera EXR processor and the sensor has no assigned ISO value. At both ISO 200 and ISO -L Fuji X cameras do not gain the signal from the sensor prior to ADC. The EXR processor does adjust it's JPEG processing accordingly and so the ISO-L setting is in fact no different than setting the camera to ISO 100. That change adds a stop of exposure to the sensor. Image quality improves with increased exposure up to the physical limits of the sensor.

    Fuji has taken a very conservative position in engineering the X series cameras and designed the EXR processor to generate good JPEG output (the basis for ISO values) from a sensor exposure that stays very clear of the hard physical limits of the sensor.
     
    Brian Kimball and Tilphot like this.
  10. lawsofphysics

    lawsofphysics Premium Member

    Joined:
    Apr 17, 2013
    Messages:
    2,647
    Likes Received:
    1,050
    Location:
    usa

    -Return to Top-

    Here's some Please login or register to view links for noise at the sensor (the signals are DC analog voltages). The X100F, X-H1and X-Pro 2 are identical. The X-T2 only differs by about 1/3 stop.

    Hers's similar Please login or register to view links from raw files.

    The ISO 100 and 200 performance is identical within measurement error. Oddly the X-H1 noise levels are higher at ISO 160 compared to 100 and 200. These results are consistent with the notion that ISO alone can not increase photo-diode full-well capacity (i.e. the maximum possible signal level can not be higher, so the S/N can not be higher). (1)

    These results are from unrendered data, so potential differences due to subjective renderings do not come into play.

    I never use ISO 100, so I'm unable to share personal observations.

    1/ For XTrans 3 cameras this is only true for ISO 100-640. These cameras use dual conversion-gain photo-diode circuity. From ISO 100 to 640 the conversion gain is optimized to maximize full-well capacity. Above ISO 640 the conversion gain changes in order maximize sensitivity.
     
  11. Tilphot

    Tilphot Premium Member

    Joined:
    Mar 22, 2015
    Messages:
    1,101
    Likes Received:
    611
    Location:
    Germany

    -Return to Top-

    Yes, of course! OVERexposed, then pulled by the camera processor is what I meant - obviously incorrectly again! Sorry, still having problems with the concept of sub—base-ISO ...
     
    Last edited: Sep 14, 2018
  12. ysarex

    ysarex Premium Member

    Joined:
    Mar 21, 2014
    Messages:
    1,094
    Likes Received:
    750
    Location:
    St. Louis

    -Return to Top-

    Don't think of base ISO as applying to the sensor. It's not a hard value, it's a soft value. The sensor's physical behavior is hard but what Fuji implements in software is soft. Because it's a soft value base ISO is arbitrary. Fuji could just as easily have set base ISO on the X-Trans III sensor at 160 or 125 or 100 or even 80.

    Lawsofphysics posted above a couple graphs from Bill Claff's site that indicate no change in read noise between ISO 200 and ISO-L. There's no change because nothing hard in the camera changes. ISO is doing two things in a digital camera: a) it causes the metering system to calculate an exposure change. b) it brightens (gains, amplifies, boosts, scales -- word choice here can be tricky) the sensor signal prior/during ADC (analog digital conversion) to compensate for the exposure change just applied from a). What ISO does in b) can be and most commonly is a hard change and is baked into the raw file.

    When considering noise in a photo we look to two primary sources: shot noise and read noise. Shot noise is related to exposure and read noise to ISO brightening. In the graphs Lawsofphysics posted there is no read noise difference between ISO 200 and ISO-L because no physical (hard) change takes place. There is however an improvement in IQ with a decrease in shot noise because of the exposure change since shot noise is a function of exposure.

    The risk with ISO-L is sensor highlight clipping. The exposure increase takes us closer to the sensor's clipping threshold and that's very very hard -- reaching the sensor saturation limit is like smashing into a concrete wall; hurts bad (clipped highlights in the raw file)! So Fuji has engineered the X cameras with a software-implemented base ISO that keeps us on average at least a stop clear of a hard smash into that wall. Using ISO-L is living dangerously hoping you'll still avoid the concrete wall and then benefit from less shot noise. Although I think most people who use ISO-L want it so they can get specific shutter/aperture values.
     
    Last edited: Sep 15, 2018
    lawsofphysics, Tilphot and JimFenner like this.
  13. Benjamin Kanarek

    Benjamin Kanarek Premium Member

    Joined:
    Oct 8, 2017
    Messages:
    169
    Likes Received:
    230
    Location:
    Born in Toronto, Canada based in Paris, France

    -Return to Top-

    Appreciate all of the feedback regarding my observations.
     

Share This Page

  1. fujix-forum.com uses cookies to help personalize content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice