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01-18-2014, 05:58 AM   #76
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QuoteOriginally posted by novsky Quote
Yessss I know ;-), it was a "question" about comparative High ISO results, a post-processed 6400 may/must be announced as a 6400 ?! No ?
Particularly in post like K3 vs K5, we can't say "hey, look at K3 12800 ISO" that's in fact a 6400 one...right ?
it's not a "lawsuit" about your beautiful shots John, just a question about how to present High ISO results ;-)
It's best for clarity to announce that it is ISO 6400 pushed one stop, but noise will be the same between 6400 pushed one stop, and 128000 in the camera.

01-18-2014, 08:59 AM   #77
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Underexposing to get a lower ISO and then pushing the shadows will render more noise and less detail than using the correct ISO from the beginning. The shadow part of the histogram contains fewer luminance levels than the mid and highlight part.
01-18-2014, 09:34 AM   #78
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QuoteOriginally posted by Tjompen1968 Quote
Underexposing to get a lower ISO and then pushing the shadows will render more noise and less detail than using the correct ISO from the beginning. The shadow part of the histogram contains fewer luminance levels than the mid and highlight part.
It is my understanding ISO is simply boosted amplification, no different than compensating in raw format. If the histogram is clipped at the bottom, then I would agree you will lose detail, otherwise the results should be the same.

Some manufacturers expose at a lower ISO and boost the raw so they can apply a tone curve for increased DR. Pentax does not use this technique unless you choose it manually (highlight correction).

Last edited by audiobomber; 01-18-2014 at 09:45 AM.
01-18-2014, 10:35 AM   #79
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There is a differens in hardware amplification and software tweaking. Make some test shots in dim and good light and you will see the difference. Different ISO and tweaking to same luminance...

01-27-2014, 06:20 AM   #80
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QuoteOriginally posted by audiobomber Quote
It is my understanding ISO is simply boosted amplification, no different than compensating in raw format. If the histogram is clipped at the bottom, then I would agree you will lose detail, otherwise the results should be the same.
QuoteOriginally posted by Tjompen1968 Quote
There is a differens in hardware amplification and software tweaking. Make some test shots in dim and good light and you will see the difference. Different ISO and tweaking to same luminance...
GordonBGood says no difference between shooting at high ISO and boosting base ISO in a modern camera: Re: Better to shoot at high iso or underexpose and adjust in pp?: Pentax SLR Talk Forum: Digital Photography Review

Gordon is a proven authority on sensors, that's why I'm linking to his post.
01-27-2014, 06:49 AM   #81
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QuoteOriginally posted by audiobomber Quote
GordonBGood says no difference between shooting at high ISO and boosting base ISO in a modern camera: Re: Better to shoot at high iso or underexpose and adjust in pp?: Pentax SLR Talk Forum: Digital Photography Review

Gordon is a proven authority on sensors, that's why I'm linking to his post.
I think there is a misunderstanding somewhere here. If you have a very, very dark photo at ISO100 and a "normal" photo at ISO12800, shooting at ISO100 will not give you a possibility in post to boost it up to "ISO12800" and get the same result as shooting at ISO12800. Shooting at ISO6400 and boosting to ISO12800 might not look very different.
01-27-2014, 05:52 PM   #82
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I was very pleased with the K-3 at ISO6400 at a dance competition this weekend, as the results were comparable to my K-5 at ISO3200.
The K-3 files have similar noise to the K-5 but are sharper, so after applying similar noise reduction to the pics I still have to add some sharpness back in to the K-5 files.
It is not necessary with the K-3.

K-3 at ISO6400


K-5 at ISO3200
01-27-2014, 07:14 PM   #83
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QuoteOriginally posted by Tjompen1968 Quote
Underexposing to get a lower ISO and then pushing the shadows will render more noise and less detail than using the correct ISO from the beginning.
Not once you get into the realm of digital gain, which for the K-3 is above ISO1600.

And since the K-5 & K-3 have Sony Exmor sensors, the benefit of using analogue gain to overcome the ADC noise floor, in the ISO100-ISO1600 range, is less than for other types of sensor technology.

Dan.

01-28-2014, 01:43 AM   #84
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QuoteOriginally posted by dosdan Quote
Not once you get into the realm of digital gain, which for the K-3 is above ISO1600.

And since the K-5 & K-3 have Sony Exmor sensors, the benefit of using analogue gain to overcome the ADC noise floor, in the ISO100-ISO1600 range, is less than for other types of sensor technology.

Dan.
So if I understand you correctly I could stay at ISO1600, underexpose 3EV and then correct in ACR with no difference to shooting at ISO12800?
01-28-2014, 03:29 AM   #85
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QuoteOriginally posted by Tjompen1968 Quote
I could stay at ISO1600, underexpose 3EV and then correct in ACR with no difference to shooting at ISO12800?
In theory, yes. In practice, no.
The results of doing it that way are usually pretty horrible.
01-28-2014, 03:37 AM   #86
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QuoteOriginally posted by Tjompen1968 Quote
o if I understand you correctly I could stay at ISO1600, underexpose 3EV and then correct in ACR with no difference to shooting at ISO12800?

Maybe not in ACR, as it's known to make undisclosed "optimisations" for different cameras as the gain is changed. But in a well understood open-source raw converter like RawTherapee, yes. (This is concerning a change in the digital-gain part of the ISO Sensitivity range.) There is still the possibility however that the K-3 does some sophisticated type of raw-level NR at high ISOs that DxO has not picked with their "correlated noise" approach (Noise reduction - DxOMark). If so, there would be a difference.

BTW, to show that the noise difference between shooting at say ISO1600, (with the analogue boosting of the sensor output signal from a weak exposure), vs shooting at base ISO and boosting with 16x digital gain in PP, isn't that great if you are using a camera which has an ADC stage with a low noise floor, see my example of such a test with the K-5:

https://www.pentaxforums.com/forums/61-post-processing-articles/234154-investigation-reported-colour-change-when-ev-boosting.html

Dan.

Last edited by dosdan; 01-28-2014 at 04:20 AM.
01-28-2014, 03:55 AM   #87
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Please explain what the term "base ISO" means.
01-28-2014, 04:03 AM   #88
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QuoteOriginally posted by Tjompen1968 Quote
Please explain what the term "base ISO" means.
The ISO Sensitivity setting where the minimum amount of analogue gain from the PGA (Programmable Gain Amplifier), is applied between the sensor and the ADC. Even at this level, the imaging system will probably not be operating at unity-gain since the sensor's operating output range has to be matched to the ADC's input range.

Note: this is a conceptual description since, in an Exmor "sensor", the sensor, multiple ADCs (1 for each column of sensels, so thousands of ADCs in a typical DSLR sensor) and PGAs are all on the 1 chip, perhaps best referred to as an imagining system.

Dan.

Last edited by dosdan; 01-28-2014 at 04:28 AM.
01-28-2014, 04:16 AM   #89
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QuoteOriginally posted by dosdan Quote
The ISO Sensitivity setting where the minimum amount of analogue gain from the PGA (Programmable Gain Amplifier), is applied between the sensor and the ADC. Even at this level, the imaging system will probably not be operating at unity-gain since the sensor's operating output range has to be matched to the ADC's input range.

Note: this is a conceptual description since, in an Exmor "sensor", the sensor, multiple ADCs (1 for each column of sensels, so thousands of ADCs in a typical DSLR sensor) and PGAs are all on the 1 chip, perhaps best described as an imagining system.

Dan.
Ok, thanks.
01-28-2014, 10:27 AM   #90
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I think people analyze this stuff to death. I'm not afraid of shooting at high ISO with the K3 at all.

ISO 1600


ISO 5000 and pushed 1 stop
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