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Author Topic: Techniques for getting lower noise, more usable High ISO images?  (Read 24139 times)

Jack Hogan

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Re: Techniques for getting lower noise, more usable High ISO images?
« Reply #40 on: April 23, 2015, 04:39:57 am »

That's right -1 2/3 stops under.  Was still afraid to go lower.  Will try this weekend.

D810 w/ AF-S Nikkor 70-200mm f/2.8
Auto ISO 64-600
Manual Mode
-1 2/3 stops Exposure Compensation
Center Weighted Metering
Shutter Speed 1/640th (manually set)
Aperture f/3.5 (manually set)
ISO 4500 (Auto, combination of the shutter/aperture and exposure compensation)
Image Area set to 1.2x (25MP)

Nice picture.  May I ask why EC was set to -1 2/3 with Exposure fixed manually?  That forces a brightness correction on every image in post.  It would seem more efficient to leave EC at 0EV and simply set Max Auto ISO so that the brightest desirable highlights are safely below clipping (-1 2/3 stops?).  And following what Jim and -h have said, in any case no higher than ISO3200 for the D810.

Jack
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EricV

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Re: Techniques for getting lower noise, more usable High ISO images?
« Reply #41 on: April 23, 2015, 01:24:13 pm »

The exposure system of most cameras does not guarantee against highlight clipping afaik. The in-camera histograms and "blinkies" are not robust indicators of raw file clipping. Thus there is some risk of clipping highlights if you increase ISO ...
  This concern is independent of ISO setting.  Even at low ISO, with plenty of light, you have to expose to avoid clipping.  Just keep doing that at high ISO.
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hjulenissen

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Re: Techniques for getting lower noise, more usable High ISO images?
« Reply #42 on: April 23, 2015, 02:23:46 pm »

  This concern is independent of ISO setting.  Even at low ISO, with plenty of light, you have to expose to avoid clipping.  Just keep doing that at high ISO.
Well, but by reducing ISO you can (practically) remove the clipping concern altogether. Choose aperture and exposure time for aesthetical reasons and fire away (some caution is needed of course to avoid too much underexposure).

-k
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dwswager

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Re: Techniques for getting lower noise, more usable High ISO images?
« Reply #43 on: April 23, 2015, 04:13:26 pm »

Nice picture.  May I ask why EC was set to -1 2/3 with Exposure fixed manually?  That forces a brightness correction on every image in post.  It would seem more efficient to leave EC at 0EV and simply set Max Auto ISO so that the brightest desirable highlights are safely below clipping (-1 2/3 stops?).  And following what Jim and -h have said, in any case no higher than ISO3200 for the D810.

Jack

Setting EC in Manual Mode on the D810 means the camera will adjust exposure computations solely with ISO.  Hence, I set negative EC to keep ISO down.  Typically I won't let it get higher than 6400 and usually is in the range of 1250-4000.  So if I set -2 stops EC and the shutter is fixed at 1/640 and aperture at f/2.8 and ISO reads 3200, then without the EC, the camera would set the ISO to 128,000.  BTW, not many cameras worked this way in Auto ISO mode in the past and was a Rant by Michael.
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Jim Kasson

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Re: Techniques for getting lower noise, more usable High ISO images?
« Reply #44 on: April 23, 2015, 04:23:51 pm »

  This concern is independent of ISO setting.  Even at low ISO, with plenty of light, you have to expose to avoid clipping.  Just keep doing that at high ISO.

What you say is true, but the risk/reward calculus is different if you're at base ISO and if you're not. At base ISO, ETTR actually buys you something: increased photon noise SNR, and read noise SNR, too, although at base ISO that is usually not the problem. Since there's a reward, it's worthwhile to take a few risks with the highlights. Now, say, for some good reasons you can't put that much light on the sensor, so you'll have to stop down from that ideal exposure, or go for a shorter shutter-open time. In an ISO-less camera, there's little reward for artificially pushing the in-camera histogram to the right, and the risk of highlight clipping is still the same if you do.

Jim

Jack Hogan

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Re: Techniques for getting lower noise, more usable High ISO images?
« Reply #45 on: April 24, 2015, 02:28:12 am »

So if I set -2 stops EC and the shutter is fixed at 1/640 and aperture at f/2.8 and ISO reads 3200, then without the EC, the camera would set the ISO to 12,800.

Right, nothing wrong with that.  I am merely suggesting that if desirable highlights are appropriately away from clipping with those settings and scene, you could achieve the same objective by leaving EC=0 and setting Maximum ISO at 3200.  This would for instance save someone like me innumerable underexposed shots the next day out, when the camera gets quickly pulled out , switched to A mode and a few shots fired for a 'moment'... only to discover later that they were all captured with EC = -1 2/3 :)

Cheers,
Jack
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dwswager

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Re: Techniques for getting lower noise, more usable High ISO images?
« Reply #46 on: April 24, 2015, 09:25:47 am »

Right, nothing wrong with that.  I am merely suggesting that if desirable highlights are appropriately away from clipping with those settings and scene, you could achieve the same objective by leaving EC=0 and setting Maximum ISO at 3200.  This would for instance save someone like me innumerable underexposed shots the next day out, when the camera gets quickly pulled out , switched to A mode and a few shots fired for a 'moment'... only to discover later that they were all captured with EC = -1 2/3 :)

Cheers,
Jack

1. Yes, it is almost criminal that modern cameras, where everything is set electronically, do not have a system to save and recall the entire state of the camera.  The shooting banks on Nikon pro cameras are almost worse than nothing because it is easy to change something and forget that it was changed during shooting and then go back to that bank thinking you are back to the base state you want.

2. I'm actually trying to figure out what is best.  Do I want 0EV compensation and ISO 3200 or -2EV compensation and ISO 800, for example?  I seem to be hearing from Jim Kasson that it is worth staying under ISO 1000 which is where the D810 starts applying digital gain when possible. 

Most games I shoot start in late afternoon where assuming 1/640 and f/2.8, for example, the ISO would normally range between 320-1250.  By the end of the game, it is normally ranging between about 1600-6400.  That is due to loss of the ambient light filling in the stadium lights.  Of course, the light color shift is the other issue.
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Jack Hogan

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Re: Techniques for getting lower noise, more usable High ISO images?
« Reply #47 on: April 25, 2015, 03:25:45 am »

I seem to be hearing from Jim Kasson that it is worth staying under ISO 1000 which is where the D810 starts applying digital gain when possible. 

That's a good point.  I guess it comes down to whether one believes that the D810's input referred read noise drop at ISO 3200 is real or subliminal NR.  I tend to think it's real mainly because it would be unusual for Nikon to be doing NR in the green channel at ISO 3200 (never seen it, at least under my watch) - but I don't have a D810 and I don't know of anyone who tested for NR there.

Jack
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Iluvmycam

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Re: Techniques for getting lower noise, more usable High ISO images?
« Reply #48 on: April 25, 2015, 12:02:21 pm »

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BJL

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I seem to be hearing from Jim Kasson that it is worth staying under ISO 1000 which is where the D810 starts applying digital gain when possible.
It seems to me that all this agonizing would be avoided if a camera were to
(a) only ever apply as much analog gain as is beneficial to improving shadow noise (maybe only to about ISO 800 with many modern sensors?), and
(b) applying digital gain only during raw-JPEG conversion, indicating this in raw files only with a flag rather than actually increasing the numerical levels recorded in the raw file.

That would seem to offer the best of both worlds for low light high exposure index photography:
- minimizing the effects of read noise through adequate analog gain,
- live view and in-camera reviews displaying at the intended level placement, rather than appearing too dark, and
- avoiding any highlight damage due to excessive amplification, either analog or digital.

A question: when cameras use digital rather than analog gain beyond a certain ISO speed setting, which ones apply this to the raw levels (dumb!), and which do it as I propose above, only in conversion (the safer approach, used even by my ancient CCD-powered Olympus E-1 for its highest ISO speed settings.)
« Last Edit: April 25, 2015, 02:56:43 pm by BJL »
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Guillermo Luijk

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Re: Techniques for getting lower noise, more usable High ISO images?
« Reply #50 on: April 26, 2015, 07:48:20 pm »

A question: when cameras use digital rather than analog gain beyond a certain ISO speed setting, which ones apply this to the raw levels (dumb!), and which do it as I propose above, only in conversion

As far as I know, only the Fujifilm X-100 uses your (and mine) preferred approach:

spidermike

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Re: Techniques for getting lower noise, more usable High ISO images?
« Reply #51 on: April 27, 2015, 03:42:36 am »

1. Yes, it is almost criminal that modern cameras, where everything is set electronically, do not have a system to save and recall the entire state of the camera.  The shooting banks on Nikon pro cameras are almost worse than nothing because it is easy to change something and forget that it was changed during shooting and then go back to that bank thinking you are back to the base state you want.



On my Canon camera, if you are using one of the Custom Settings, it reverts to the predefined setting if it goes into sleep mode or you turn the camera off. I can sort of understand why Nikon have taken the approach they did but I prefer the Canon approach.
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hjulenissen

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Re: Techniques for getting lower noise, more usable High ISO images?
« Reply #52 on: April 27, 2015, 03:59:26 am »

As far as I know, only the Fujifilm X-100 uses your (and mine) preferred approach:
I was under the impression that some MFDB also used this approach:
http://www.dxomark.com/Cameras/Hasselblad/H3DII-50---Measurements

I find it really strange that manufacturers does not follow simple engineering best-practice. Especially since raw formats are proprietary and they get to define both the encoding and decoding behaviour (3rd party will have to reverse-engineer anyways). What are their assumptions about their customers?

Perhaps an ETTR "preprocessor" for Lightroom is in order? Parse the raw file. Apply the specified EC to the raw values directly (taking care of bias) and round the result. If overflow occurs, split into 2 files (mimic exposure bracketing). Import into Lightroom.

For my 7D, this is not such a big problem. I should (if possible) bump ISO to 1600/3200 anyways to reduce noise (Canon are not "ISO-less"). I don't care much for under-exposing a lot beyond that point now matter if the gain is applied in-camera or in raw editor. Further, I generate my own camera profiles, and I believe that they are without twisting.

-h
« Last Edit: April 27, 2015, 04:06:15 am by hjulenissen »
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BJL

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Re: Techniques for getting lower noise, more usable High ISO images?
« Reply #53 on: April 27, 2015, 02:44:04 pm »

I was under the impression that some MFDB also used this approach:
http://www.dxomark.com/Cameras/Hasselblad/H3DII-50---Measurements
That approach of fixed gain (a fixed ratio of numerical raw levels per photo-electron) makes particular sense for MF backs with CCD's, where (a) any gain must be applied relatively late (after transport to the corner of the sensor at least) so that increased gain is of little help is reducing dark noise, and (b) the ADCs are usually good enough ("16-bit"?) that the sensor output can be reliably handled with a fixed gain regardless of the exposure index in use. (That is, a single amplification level can simultaneously handle full wells without clipping while having ADC discretization noise well below the noise floor in the signal coming from the sensor.)

And yet AFAIK, not all MFD backs do it that way: maybe engineering bet practice clashes with the expectations of some users and hence leads to push-back from the marketing division.  Remember all the talk that any such failure to amplify the raw levels up to the point of leaving bare minimum acceptable headroom makes higher ISO settings "fake", as still propagated by DXO's ill-informed declaration that the H3D50-II actually has the same "ISO" of 50 at all its ISO exposure index settings.  That is, adopting engineering best practice can get you accused of dishonesty and/or technical inferiority.
« Last Edit: April 27, 2015, 05:39:02 pm by BJL »
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Guillermo Luijk

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Re: Techniques for getting lower noise, more usable High ISO images?
« Reply #54 on: April 27, 2015, 03:08:36 pm »

Remember all the talk that any such failure to amplify the raw levels up to the point of leaving bare minimum acceptable headroom makes higher ISO settings "fake", as still propagated by DXO's ill-informed declaration that the H3D50-II actually has the same "ISO" of 50 at all its ISO exposure index settings.  That is, adopting engineering best practice can get you accused of dishonesty and/or technical inferiority.

The same happens when a particular camera has specially low real ISO values vs declared ISO (which should be the trend while sensors improve their dynamic range), like most of the Olympus for instance: ISO200 meters for ISO200 but amplifies the RAW data by an equivalent ISO100. People say: hey! ISO100?!? that is cheating to get lower noise!!! funily a deeper understanding of what's going on will show that low effective ISO's usually mean the opposite, a challenge to keep SNR at good ratios because they basically produce RAW underexposure. The good news is helping to prevent disgusting blown highlights by compressing the right end of the camera JPEG histogram in a more pleasant and filmic way.

Regards
« Last Edit: April 27, 2015, 03:16:30 pm by Guillermo Luijk »
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Jim Kasson

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Re: Techniques for getting lower noise, more usable High ISO images?
« Reply #55 on: April 27, 2015, 05:02:02 pm »

The good news is helping to prevent disgusting blown highlights by compressing the right end of the camera JPEG histogram in a more pleasant and filmic way.

And, for raw shooters, aided and abetted by the PV 2012 Exposure slider in Lr, which introduces a "shoulder" like film.

Jim

dwswager

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Re: Techniques for getting lower noise, more usable High ISO images?
« Reply #56 on: April 27, 2015, 05:24:44 pm »

On my Canon camera, if you are using one of the Custom Settings, it reverts to the predefined setting if it goes into sleep mode or you turn the camera off. I can sort of understand why Nikon have taken the approach they did but I prefer the Canon approach.

I like Nikon's approach to that situation in that the camera holds the set values.  There is a big difference between the camera going to sleep or being turned off and having the ability to select a set of predetermined settings.  

How every camera should work:

1. Set the way you want say for Night Sports
2. Save the settings, preferably giving it a unique menu name.
3. You select the menu item Night Sports and the camera returns to the state when you saved the settings.
4. During shooting you decide to back Auto ISO down 2 stops and lower the minimum shutter speed.
5. The camera is now in a new state and when it goes to sleep or is turned off it should come back on in the same state as sleep or off.
6. But, when you select Night Sports again, the camera goes back to the original Night Sports settings you actually saved, not changed during shooting.
7. Of course, you are always able to change the settings of Night Sports to whatever you prefer.


I don't want a saved mode where changes to the settings while in that mode become the new settings for the mode,  I want a set of home base states[/b] that I can quickly get back to.  But the camera should only change back to the home base state when I tell it, not on it's own because that was the last state I set.  If the camera allowed you to set 10 states and give them menu names, then it would require 11 states to be saved.  The 10 you set, and the current state of the camera at the time it is turned off or goes to sleep.  It would always power on in the last current state, but you could always choose a different state.

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fdisilvestro

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Re: Techniques for getting lower noise, more usable High ISO images?
« Reply #57 on: April 27, 2015, 06:50:49 pm »

I don't want a saved mode where changes to the settings while in that mode become the new settings for the mode,  I want a set of home base states that I can quickly get back to.  

Agreed 100%. Unfortunately, Nikon's approach with the custom banks does not work that way. In the mean time, I follow Joe McNally's suggestion of "resetting" the camera to your default settings before every session / day.
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