true indeed that bad stuff difficult to find in the forest … and Adobe trained how ?
more so - we see that stuff goes bad not based on raw data, but based on what ? some tag in exif ? that you explain how ? may be a better way is to pay attention to the image data, not making assumption what to do just based on the tag …
in any case it is a food for thought… further testing shall be done
I would think it makes sense to process the data differently based on the recorded ISO, as having prior knowledge of noise characteristics at different ISO settings would seem, to me, to be a good input.
Imagine, for example, that your sensor is demonstrated to produce more noise in the red pixels when ISO goes above 6400. Possibly an unlikely scenario, but please bear with me.
If DxO “know” your image was taken at ISO 12800, then they can be more aggressive with (or at least more cognisant of) removal of what appear to be red noise signals.
Now that is purely a thought experiment as to why ISO level (which after all can only ever be ‘just a tag’) may affect the output. However, I am reminded of a discussion in the Pentax forums I frequent, where it was claimed (and I am inclined to believe) that the modern Pentax sensors (made by Sony, I believe) are effectively ISO-invariant.
The discussion was centred on the technique of always shooting at base ISO and pushing exposure in post, for the benefits that can bring. For the purposes of this discussion, I figure the claim that Pentax (Sony) sensors are ISO-invariant implies that some sensors are not. In which case my thought experiment above makes some sense.
of course it makes sense to pay attention to a nominal ISO in terms of what we have in deep shadows - that is what analog gain and/or dual gain affects … however it seems there is too much attention paid to a tag value to the detriment of actual data ( which seems Adobe avoids ) … and in most ( if not ALL ) modern cameras ( recent Pentax cameras with their big mandatory NR for raw data are sore exceptions ) that difference say past ISO800 seems to be non material ( of course there might be a pattern noise for example that testing sites like photonstophotos from BClaff do not test for , as it happens well above individual sensel level to see ) …
shall try more testing when time permits - say the same scene, “A” mode with fixed ISO, changing nominal ISO values across the range, then let camera meter exposure to set exposure time and dial (A) positive EC ( just barely avoiding clipping in raw ) and (B) negative EC (say to have 3-4 stops “underexposure”)… then repeat to see how DPXD works… ultimately whatever happens one needs to know if it makes sense to venture in to say past “ISO6400” nominal ISO values when shooting if the shot intended for DxO DPXD NR or stay put ( same exposure, but just not crossing “ISO6400”… 6400 is used just as an example )
It would be interesting to see an iso 400 image and an iso 12800 image of the same scene. With their original tags and reversed tags. Then you could see if that tag has any advantages or disadvantages.
It’s a neat experiment - a way of looking under the covers at how DxO’s NR works. But testing ISO invariance is where this will really get interesting, IMO. That has real value for our photography and how we use PhotoLab.
I was surprised too that ISO value in the exifdata didn’t change denoise value’s in the tool it stayed 40 when magic want was active. Which would imply “automatic”
Too long ago to remember the details. I think the original thread was even older.
I need to go to work so can’t dig deeper at this time.
Something about they remove the noisyparts before demosiacing and therefore before lighting/brighting is applied which would also be applied on the noise particles.
That’s why ISO value isn’t effecting automated deniosestrenght…
I believe that was dxo’s explaination.
From that moment i just made partial presets in my camera’s iso sections.
So when i have a lot of high iso shots i just apply that.
I don’t understand what is meant in this thread. I did create 6 copies of an image and changed the iso from 100 to 51200. No differences. And when I think about it, this is as it should.
George
but it seems it does affect how NR works ( same UI slider value )… because I only changed ISO value post factum - nothing else in raw data was different…
if I follow “exposure triangle” and give less and less actual exposure to sensor ( but increasing nominal ISO values ) then as expected DxO NR starts to meltdown at high ISO values ( because actual exposure is less and less )… so this is expected… but with the same data (as it is the same raw) just altering ISO values to have NR meltdown was not expected.
PS: and going to lower ISO value in the tag visibly reduce the amount of NR applied to the same raw file all other things equal …
So, i haven’t test it myself, with the same exposure and same imagedata except iso value in exifdata dxo’s NR algorithm is tricked by your alter and react accordingly to the iso value. That’s different then they wrote earlier.
So the strenght slider isn’t connected with the iso value in exif butunder the hood they let there “AI” known which isovalue is used so it changes approach.
Right?
DxO might have different algorithms or approaches for different kinds of raw files depending on sensor data specifications and manufacturer etc.
I just tried a picture taken at 12800 iso and compared it with the iso tag set to 100. Saved them with DeepprimeXD as jpg. There’s a difference. So the conclusion can be made that the iso tag has influence on the nr.
Now I understand what was meant.
George
so a hypo–thesis
NOTE: digital camera spot meter meters typically as 3 2/3 EV stops below clipping ( not 18% of you-know-what )
now I am a lonely sensel saturated say 5 stops below clipping in a genuine raw file shot with a nominal ISO = 6400
comes DxO and seeing this chap inhabiting 5 stops below clipping thinks - well, this single sensel is in a shadow, but not too bad as apparently ISO tag says 6400 so let us do our regular DPXD stuff w/ him ( or whatever is the pronoun )
comes a village idiot and changes the tag to ISO = 100
comes DxO and seeing 5 stops below clipping thinks - well, this lonely sensel is in a shadow - but hey ISO says 100, so there are hell lot of other stuff and stops below this stop, let us not go overboard and tune DPXD down a bit …
comes a village idiot again and changes the tag to ISO = 256000
comes DxO and seeing 5 stops below clipping thinks - well, this poor sensel is in a shadow - but whoa, Nelly ! ISO says 25600, AND at this ISO if something is 5 STOPS below clipping it is in a DEEP-DEEP-SH$T ( not just some regular shadow ) - all hands on deck , pump DPXD all the way up behind the scenes and we have a meltdown as a result
I think I make an artificial DNG and give same exposed areas different multiplication / division and see if DxO pays attention to the each area differently once I change ISO tag value
PS: comes Adobe and sees all the mess, says F… ISO, from the deepest shadow to the brightest clipping we apply NR based on where the sensel is relative to black level vs white level
I did this test again with a nightshot of stars. Original was iso250. I copied it and changed it to 25600. A lot of star where disappeared.
Original iso250
Changed to 25600
George
Would this be the same kind of difference when you shoot underexposed and correct inside DxOPL by exposure compensation vs same shuttertime “corrected” by a iso value in camera?
I did once a test by shooting fully manual on a tripod in a dark hallway and a door and wall as subject. To see when camera iso is better then postcorrection.
In the iso invariant part of a sensor should this difference of approach not be notisable.
Same noise and exposure only the oocjpeg is darker in base iso.
I recall that in the higher isovalues the difference in dxopl with 3 evc stops correction vs 3 stops iso raise was noticable. So my end conclusion was around 2000 iso the camera and DxOPL are better when it gets a raw file for a “propper exposed occjpeg by raise of iso.”
Your test seems to show this too.
When i have time i try to find those test images too see if you can replicate this.
it is not the same as invariance – if you do the same exposure ( exposure time, aperture, same scene, same illumination ) but vary a nominal ISO ( within the range where sensor operation is more or less invariant ) say from ISO800 on camera like A7R2 then there is no big difference in how DxO PL will apply DPXD … because the data in raw is as DxO PL expects it vs a nominal ISO value ( same exposure + proper gain applied after exposure to place the DN into expected position )…
the original test does break that expectation - we change the tag only, we do not adjust the data by applying any multiplication - and forces DxO to think that exposure was different from what it actually was ( see “hypo–thesis” posting above in the thread ) …
Adobe apparently pays only attention to where the data lies between black level and white level regardless of ISO - so changing ISO tag does not affect ACR / LR, DxO pays attention where data lies vs how many stops is expected based on a nominal ISO and it does not matter that your data is still in the same place between black level and white level in raw … keep in mind that in real life black level and white level can change too as we dial different nominal ISO values for camera - but in the experience we leave black level and white level intact
from DxO standpoint it is “shifting”… that same 5 stops below clipping ( below white level ) for DxO is one story when ISO tag says 100 (tune DPXD down), when ISO tag says 6400 and when ISO tag says 25600 (crank DPXD up)…
hypothesis again, needed to be further tested
the test I want to do is to repeat the same text patch several times in raw file giving it different artificial exposure (by multiplying DNs in all sensel across the patch ) and then see how DxO deals with those patches when I change ISO tag only in raw file and see if DxO will not meltdown on patches close to clipping if we change ISO tag to values like 25600
so essentially shall we see DxO PL DPXD progressively melting down on more and more “exposed” patches in raw file as we assign higher and higher values to ISO tag with exiftool
This makes complete sense to me. DxO profile equipment across their full range of parameters; in the case of sensors, that means ISO range.
It seems very reasonable to me to expect a lot more noise from ISO25600 than ISO250. Stars are small dots, just like noise.
Does Adobe ACR/LR make stars disappear ?
For Nikons .NEF there are many exif tags which are related to ISO so simply changing the ISO tag might not do it as we have no idea on which specific tags that are applicable or not in the algorithms used by PL, LR or any other raw developer.
For example the Nikon D3X uses: ISO, ISO2, ISO Setting, ISOExpansion, ISOExpansion2, High gain up.
test protocol is raw → DNG → strip maker notes → DxO PL …
we do …
