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03-07-2011, 05:07 PM   #31
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Don't confuse quantization noise with banding. As long as the last bit is noisy there won't be any banding. And if you look at my figures above, you'll see that the 14th bit is noisy for the K-5 in even the most favourable situation. So, there will be dithered rather than posterized surfaces.

03-07-2011, 08:55 PM   #32
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QuoteOriginally posted by dosdan Quote
Consider a full implementation of this:

1. All shots are taken at base ISO. In "ISOless" AE mode, you adjust aperture & shutter manually.

2. Camera metering decides on a "correct" EV boost parameter from base ISO. It could show this in the viewfinder as a guide or show equiv ISO instead for users who have trouble comprehending the new exposure paradigm.

3. This EV Boost is used to show the LCD preview & embedded JPEG in the raw file at the "correct" EV level.

4. The raw file stores this parameter and the converter is aware of it. Like embedded WB. The raw converter uses it by default.

5. In PP, you can adjust away from the stored EV boost value (no need for EV comp in-camera), so you can compensate in PP for very bright objects in frame. You can also play with the TRC to your hearts content in PP.

6. As long as you are not reaching FS quantization (equivalent to switching to an ISO higher than the base ISO) and the signal is sufficiently dithered, you are getting extra clipping headroom that you can work with in PP. This would be a highly effective raw highlight "recovery" - not like the marginal results you get currently.


Dan.
I'll try again .....

What is stopping you shooting in manual mode, ignoring metering, setting base ISO, adjusting shutter apertures as desired, and then adjusting your EV in PP, with the current camera models?

I hardly ever run into any problems with blown highlights. Frankly if I wanted to capture the details of a solar flare I would expose accordingly. Other than those kind of conditions I would rather load the RAW into PP and not ahve to look at a dark frame and then boost the EV to what I originally wanted. if I'm going to boost the EV in PP, I'd rather it was done already.

So, given that those ( presumably yourself ) who want to ignore metering and ISO can already do so, where is the benefit in removing the ISO parameter?
03-07-2011, 09:20 PM   #33
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QuoteOriginally posted by Smeggypants Quote
would rather load the RAW into PP and not ahve to look at a dark frame and then boost the EV to what I originally wanted.
If the system was implemented fully, you wouldn't see a darkish frame on either the camera's LCD screen or in the raw converter. So, if you shot -2 stops underexposed, i.e. at base ISO100, instead of ISO400, the raw converter would know to apply +2EV exposure boost when the raw file was loaded.

Dan.
03-07-2011, 09:48 PM   #34
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QuoteOriginally posted by Smeggypants Quote
.... but surely a sensor is ISOless anyway? After all isn't the ISO setting an applied amplification ( either before or after the AD convertor?
When I wrote "sensor" I meant to include the analogue amplification and A/D stages.

What I see the "ISOless" proponents saying is that analogue amplification will soon be a thing of the past.

They might also be saying that an "ISO setting" is not needed as way to control a camera. They could do your "base ISO" and push in PP approach right now but would have dark previews and would have to apply initially unknown amounts of exposure push in PP.

Given a way to tag an image with the intended exposure push, previews will be as intended and PP would start from the intended exposure as well. In contrast to the current "ISO"-approach, the full dynamic range would be kept intact as the RAW data would not be scaled by the camera.

I'm fine with the above concept but am not sure whether ISO control will disappear from cameras as it is an intuitive way of communicating an exposure push to the camera that is independent from aperture and shutter speed settings. If one only had a single "exposure compensation" control then one would have to tell the camera what do do with it, i.e., change the shutter speed when in Av mode or just the change the exposure push, or both. In a way the "ISO setting" seems to be a good way to provide intent for some forms of exposure compensation.

03-08-2011, 01:28 AM   #35
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QuoteOriginally posted by Smeggypants Quote
In practise I do lot of low light shooting in TAv mode with my K-5. The ISO can auto range between anything from 1600 to 51200.

So, unless i've got you wrong your saying that I could set manual mode and choose shutter and aperture and leave the camera set on ISO1600 ... and then boost the exposure of the picture in post pro once I get home?

This means of course that previewing pics in camera will mean most of them are really dark.

So the question is: is post pro exposure boosting a set of pictures all taken at ISO1600 going to yield better results than using TAv during the shoot and have the exposure roughly correct before you start the Post pro process?

I'm sort of beginning to understand that ISOless is no worse than using ISO, but I'm still failing to see the advantages.

Cheers for your patience.
The last ISO that is not simply a firmware boost is ISO 1600. If you shoot in RAW, shooting at a higher ISO will not give any benefits (other than the preview image in the camera). There are however at least two drawbacks in using a higher ISO in the camera:

  1. K-5 forces noise reduction to images shot at over ISO 1600 - this can not be disabled, thus there is some loss of image quality.
  2. One loses highlights - one stop per level of ISO - as the camera pushes the signal in software.
03-08-2011, 08:11 AM   #36
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Class A, we're not quite there yet as even the K-5 has one electron less read-out noise when using ISO 1600 or higher. Moreover, the JPG engine adjusts its black level according to ISO.

Other than that though, I don't see why the JPG engine wouldn't search for the brightest pixel and THEN do the JPG/preview, i.e. it would always use perfect exposure (maybe not artistically, but technically). There could be an image parameter (like natural, bright, ... add a dark scene setting) to make images appear dark.

So, the EV compensation becomes the new ISO dial (they have been one dial in some analog cameras anyway). And to add an Auto-EV mode is straightforward. I cannot see any lost functionality. But highlights aren't thrown away anymore. I would prefer Auto EV over Auto ISO. otherwise, there is little difference in practice though.
03-08-2011, 02:36 PM   #37
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QuoteOriginally posted by Aku Ankka Quote
The last ISO that is not simply a firmware boost is ISO 1600. If you shoot in RAW, shooting at a higher ISO will not give any benefits (other than the preview image in the camera). There are however at least two drawbacks in using a higher ISO in the camera:

  1. K-5 forces noise reduction to images shot at over ISO 1600 - this can not be disabled, thus there is some loss of image quality.
Are you sure? I've disabled noise reduction for ALL ISO settings on my K-5 . Or is there some hidden NR I dont' know about

QuoteQuote:
  1. One loses highlights - one stop per level of ISO - as the camera pushes the signal in software.
It would only lose those highlights if they were there in the first place. And this is my point. ... why digitise the signal with less bits when you can boost it before hand and optimised the conversion process. for example if you've got a 14bit convertor and your brightest highlight is, say, 30db down ( 5 stops I think ) then you are only digitising the pic with a 9 bit dynamic range
03-08-2011, 03:30 PM   #38
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An interesting trick for faster shutter speeds might be:

Set sensor to base ISO.
Take a reading
Determine maximum sensor reading
Reset analog gain (ISO) so that the maximum sensor reading is just below full scale. (maybe 95%?)

03-08-2011, 09:53 PM   #39
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So, was all this impying that a camera such as the D700 reacts better to being shot at higer ISO's and the K5 reacts better to being shot at low ISO's and having EV bumped up in PP?

This stuff is like rocket science, but I seriously am trying to understand it!
03-09-2011, 02:12 AM   #40
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QuoteOriginally posted by Smeggypants Quote
[/LIST]Are you sure? I've disabled noise reduction for ALL ISO settings on my K-5 . Or is there some hidden NR I dont' know about
Yes, there is hidden NR at ISO 3200 and beyond which can not be removed.

QuoteQuote:
It would only lose those highlights if they were there in the first place. And this is my point. ... why digitise the signal with less bits when you can boost it before hand and optimised the conversion process. for example if you've got a 14bit convertor and your brightest highlight is, say, 30db down ( 5 stops I think ) then you are only digitising the pic with a 9 bit dynamic range
I am not sure I understand what you mean. Naturally if there is nothing bright in the image, nothing will be lost, but if there is, it will be lost.

The sensor has programmable gain amplifier which allows the signal to be boosted from ISO 100 up to ISO 1600. This signal goes through the AD converters thus is now a 14 bit number. Now the question is, does one want to let the camera push the ISO to, say, 12800, or does one want to do it in a computer. If one does it in the camera, one loses three stops worth of highllight data permanently without any advantages in the data quality.
03-09-2011, 02:45 AM   #41
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QuoteOriginally posted by Smeggypants Quote
Are you sure? I've disabled noise reduction for ALL ISO settings on my K-5 . Or is there some hidden NR I dont' know about
The NR is on-sensor and can't be switched off. I think it can be switched off in the D7000 & A580 versions. This amount of NR in the K-5 is not strong and, since the NR is applied before demosaicing, rather than after demosaicing, as it is in software NR, it will barely affect perceived detail resolution compared to the normal loss of theoretical resolution due to the demosiacing of the Bayer Colour Filter Array.

See (remove space in URL) http://forums.dp review.com/forums/read.asp?forum=1036&message=36670777

Dan

Last edited by dosdan; 03-09-2011 at 03:08 AM.
03-09-2011, 02:58 AM   #42
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QuoteOriginally posted by C-Factor Quote
So, was all this impying that a camera such as the D700 reacts better to being shot at higer ISO's and the K5 reacts better to being shot at low ISO's and having EV bumped up in PP?
The reason for the existence of an ISO sensitivity control in a DSLR, which is really an analogue variable-gain pre-amp before the ADC, since the sensor itself is a fixed-gain device, is to raise the sensor signal in a low light situation higher above the electronic read noise floor. It does this at the expense of reducing DR as the ISO increases.

As sensor read noise reduces, the need for the presence of variable analogue gain/ISO control, is reduced. I'd expect the D700 replacement to have much lower read noise too if Sony uses this sensor topology in other sensors.

Eventually there'll be no technical reason for a ISO sensitivity control at all, but traditionalists may still want it.

Dan.

Last edited by dosdan; 03-09-2011 at 03:27 AM.
03-09-2011, 07:25 AM   #43
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Ei tarvitse kauheasti ihmetellä ison kennon etuja. Ne jotka on kuvanneet aikanaan 35mm kinolla ja 6x9 nekakoolla tietävät eron joka on kun yö ja päivä. 6x9 käsittely oli helppoa ja kuvat oli, kun eri mailmasta. Ja sama on täysin pikku kenno ja täydenkoon kenno. Kunhan ei ole enään sony, useammat muut kelpaavat.
03-09-2011, 07:39 AM   #44
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QuoteOriginally posted by dosdan Quote
The NR is on-sensor and can't be switched off. I think it can be switched off in the D7000 & A580 versions. This amount of NR in the K-5 is not strong and, since the NR is applied before demosaicing, rather than after demosaicing, as it is in software NR, it will barely affect perceived detail resolution compared to the normal loss of theoretical resolution due to the demosiacing of the Bayer Colour Filter Array.

See (remove space in URL) http://forums.dp review.com/forums/read.asp?forum=1036&message=36670777

Dan
Ahh I see, there are two levels of NR in the K-5. Gotcha - thanks
03-09-2011, 08:05 AM   #45
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QuoteOriginally posted by dosdan Quote
The NR is on-sensor and can't be switched off. I think it can be switched off in the D7000 & A580 versions.
Actually it is not on-sensor, but the PRIME II processor which does the NR.
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