At 10/10/2019 02:57 PM, Moose wrote:
>On 10/10/2019 10:42 AM, Wayne Shumaker wrote:
>>rambling on iso-invariance...
>>
>>Moose linked to a dpreview article on iso-invariance. I was reviewing what it
>>says and was questioning....
>>
>>https://www.dpreview.com/reviews/panasonic-lumix-dmc-zs200-tz200/5
>
>I also linked to a sample.
><http://www.moosemystic.net/Gallery/tech/GX85/GX85Shadows.htm>
>
>>. . .
>>
>>To me this means I can under expose at lower ISO, but if over exposed at
>>higher ISO, it could blow out highlights - sensor saturation or clipping.
>
>Exactly so.
>
>> From a user point of view, I don't see the advantage of cranking the
>> exposure knob to -3 versus cranking the ISO knob +3 stops.
>
>For the reason above, to avoid clipping. Upping the ISO, with no EV
>compensation change will just change aperture and/or shutter speed to give the
>same exposure. Unless shooting manual.
>
>>Other than the exposure knob is more accessible than the ISO knob? and the
>>need to then post process the exposure setting. Am I missing the point?
>>Perhaps this changes the way auto-ISO selects ISO when the exposure is at -3?
>>Or changes the way the camera captures highlights.
>>
>>In conclusion, iso-invariance has nothing to do with sensor performance or
>>improvements.
>
>Here, you have missed the point. Some newer sensor systems have vastly
>improved noise and color accuracy in the shadows. If I were home, and so
>inclined, I could do the same thing to a shot of the same subject as above
>with an older sensor. With the shadows pulled up that far, they would be very
>noisy, and the colors would be way off.
That is true, not arguing that you can push a better sensor further. What I was
implying is that the "ISO invariance", as defined in DPR, does not depend on
sensor performance.
Of course the better SNR a sensor has, the more dynamic range it has, the more
latitude one has to push it. But that is not the "ISO invariance" that was
defined in the article. Utilizing the higher dynamic range of a better sensor
is a different type of "ISO invariance".
>If you go back and re-read the comments to my originals posts of this sample,
>you will find comments on exactly this major improvement.
>
>DPR wouldn't be talking about ISO invariance if it wasn't something new, the
>result of sensor improvements.
But they say, it is not dependent on sensor noise, but the effect of
electronics post the sensor.
"...This has the advantage that all the shots should exhibit the same shot
noise and any differences must have been contributed by the camera's circuitry."
>>One potential use of iso-invariance might be from the difference in how
>>cameras capture highlights. The sonies tend to preserver the highlights, say,
>>compared to a nikon which preserves shadows.
>
>Are you talking about JPEGs? Any such difference from Raw files would be the
>result of the conversion software.
I shoot raw. The difference in how a camera treats ISO setting, one may need to
use the technique to preserve highlights. And "Why ISO Isn't ISO"
Use lower ISO and -EV if you need to overcome a camera's bias toward blowing
out the highlights. Note this article:
https://theslantedlens.com/2019/camera-comparison-z6-vs-a73/
The Nikon blows out the highlights quite early compare to a73, while the a73
blocks up in the shadows sooner. If the sensor dynamic range is the same, the
use of the ISO invariance(DPR defined), lower ISO with -EV compensation, is
merely overcoming the way the camera decides what ISO is.
Being able to pull out detail in an underexposed image is improved by better
sensors, no doubt, but is a different definition of ISO invariance.
I may be biased using my Sonnies, which tend to preserve the highlights in the
first place, whereas using a Z6 one might want to employ the technique to
preserve highlights.
WayneS
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