I'm saying that ISO documents exclude raw but camera manufacturers ignore it when it suits them, making a mess.
May 18, 2023
305
-
-
Jim, @SrMi,
I mostly shoot with a Sigma SD9 in Manual mode.
Twiddling the ISO does not change "the exposure" one little bit. The resulting raw histograms are all the same.
Changing the ISO does alter the metering "needle" and one is prompted thereby to change the exposure EV appropriately.
Jim, I got the trap ;-)
@SrMi - Posting statements without qualification, as if everybody here owns "the latest Sony, Canon, Nikon, and Leica cameras" can be very misleading, I reckon.
-
I believe we have a communication issue.
Changing ISO alone does not change the exposure but it changes raw histogram in many cameras. On the other hand SD9, upper ISO range of GFX50, do not change the raw histogram but have a tag that simulates ISO brightness. That is very cool. It allows keeping the ISO high without worry of clipping highlights. I wish other cameras would do that for ISOs above the dual conversion gain point, if that range is invariant. -
My comment about raw histogram being unimportant for higher ISOs is also valid for SD9, if I understand it correctly (raw histogram does not change with higher ISO).
The point is to keep the histogram away from the right side by lowering ISO, not by lowering exposure. Always maximize the exposure, regardless of ISO used. -
And those are also not very useful at high ISO settings.
-
If the statement is true for "the latest Sony, Canon, Nikon, and Leica cameras", I will not argue with that.
-
Has ISO 12232 changed in that regard? My 2006 copy doesn't specify an amount of headroom per se, but following their math for both the saturation-based and the standard output sensitivity methods gives 1/2-stop and none, respectively.
-
ISO doesn't have a meaning of 'sensor exposure'.
-
They define different exposure indices which may or may not provide different results. The saturation based ISO speed provides a definition based on the maximum signal level. The Standard Output Sensitivity exposure index provides for an exposure producing 18% in the output file. You can put the two together and come to the conclusion that they were supposed to produce the same numerical value with a given headroom (as I used to do) but the 2019 edition tells us that was wrong. They say 'Note 1 to entry: The ISO speed is usually the highest exposure index value that still provides peak image quality for normal scenes. However, a DSC does not necessarily use the ISO speed value as the exposure index value when capturing images.' For SOS they say 'Note 1 to entry: SOS provides a practical exposure index value based on the signal level of images captured with a DSC, but images taken using this exposure index value do not necessarily provide the best image quality.'
The truth is that ISO 12232 is a mess top to bottom, and 2019 is chock full of political compromises. -
As you should know, "EI" is their term for what most people call "the ISO" and, [comment withdrawn] ...... here in America, it is quite correct to write "sensor exposure" in place of "the exposure provided to an image sensor" , therefore, I.S.O.b has a meaning of "sensor exposure" which is clearly stated above.
-
Not quite right. 'EI' is what they call any exposure index. It's defined in the standard:exposure index
EI
numerical value that is inversely proportional to the exposure provided to an image sensor to obtain an image
Note 1 to entry: Images obtained from a DSC using a range of exposure index values will normally provide a range of image quality levels.
People who think it's 'the ISO' are under the misapprehension that all the defined exposure indices would give the same result. As they say explicitly above, they won't. The ISO EI used can be found in the EXIF. -
i will make that test for you you and post the reasults to see if it matches the general concensus.
-
Before you do it, please describe what are you going to do.
-
shooting max ettr shifts the WB. i prefer just to shoot correct and lift shadows.theres very little dofference in shadow noise.
-
My main point edited out of the quote and my side-ref seized upon as a Straw Man, so ...
... 'bye
-
Cheers thanks Bob. i had read about per square meter for lumens, but couldnt get my head around per unit area. eg: sensor area 36x24mm 0.00091m2
-
Im going to shoot my doll in the studio with a black background. im going to fix exposure and raise iso and adjust ambient light (colour corrected LED)and compare what the live histograms and taken image histograms look like. i will also fix the iso and lighting and float the exposure to see if there is any difference in WB as well as the raw histograms in FRV.
-
forget about iso being acurate across cameras, whats worst is F vers T stops 🤨
