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Bill Pierce - Leica M photog and author

 

“Our autobiography is written in our contact sheets,  and our opinion of the world in our selects”  

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Bill Pierce is one of the most successful Leica photographers and authors ever. I initially "met" Bill in the wonderful 1973 15th edition Leica Manual (the one with the M5 on the cover). I kept reading and re-reading his four chapters, continually amazed at his knoweldge and ability, thinking "if I only knew a small part of what this guy knows... wow."  I looked foward to his monthly columns in Camera 35 and devoured them like a starving man.  Bill has worked as a photojournalist  for 25 years, keyword: WORK.  Many photogs dream of the professional photographer's  life that Bill has earned and enjoyed.  Probably Bill's most famous pic is Nixon departing the White House for the last time, victory signs still waving. 

 

Bill  has been published in many major magazines, including  Time, Life, Newsweek, U.S. News, The New York Times Sunday Magazine, New York Magazine, Stern, L'Express and Paris Match.  :His published books include  The Leica Manual,  War Torn, Survivors and Victims in the Late 20th Century, Homeless in America,  Human Rights in China,  Children of War.  Add to that numerous exhibitions at major galleries and museums.  Magazine contributions include  Popular Photography,  Camera 35, Leica Manual,  Photo District News, the Encyclopedia of Brittanica, the Digital Journalist, and now RFF.  Major awards include Leica Medal of Excellence, Overseas Press Club's Oliver Rebbot Award for Best Photojournalism from Abroad,  and the World Press Photo's Budapest Award. Perhaps an ever bigger award is Tom Abrahamsson's comment: "If you want to know Rodinal, ask Bill."

 

I met Bill in person through our mutual friend Tom Abrahamsson.  In person his insight and comments are every bit as interesting and engaging as his writing.  He is a great guy who really KNOWS photography.  I am happy to say he has generously agreed to host this forum at RFF  From time to time Bill will bring up topics, but you are also invited to ask questions.  Sit down and enjoy the ride!

 


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Invariance
Old 01-29-2019   #1
Bill Pierce
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Invariance

I want to recommend a quick read on invariance. For people who rely on jpgs, it’s not much use. But for raw shooters taking advantage of it can actually insure more acceptable exposures and provide more room for interpretation in the digital darkroom. Using it as a tool is not for everyone; so, as always, your thoughts are more than welcome.

https://photographylife.com/iso-invariance-explained
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Old 01-29-2019   #2
Timmyjoe
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Well Bill, I had to laugh at the first line in the piece:

"ISO invariance is one of the most talked-about topics in photography today . . ."

Having never heard the term "invariance" before, and talking about topics in photography fairly regularly.

I think I know what he's referring to in the article, just never heard the term "invariance" used to describe it. Will read the article and educate myself.

Thanks for the link.

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-Tim
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Old 01-29-2019   #3
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New one on me too. I do now have two cameras that can shoot raw, so I'll try to take it in.
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Old 01-29-2019   #4
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'ISO-less' is an interesting topic and I understand that some of the newer Fuji X-series cameras are approaching that. A 12 page article with ~80 pages of comments ; )

Thanks for the link...
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Old 01-29-2019   #5
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My first thoughts when I started reading was this article was about "push processing" digital raw files as referenced in articles like these:

Best way to shoot high ISO with a Leica M9

Just crank up the ISO, not so fast

Been using this technique with my D4, figuring the highest "Real ISO" is about ISO 800, and shooting low light at ISO 800 and increasing exposure of the RAW files in Lightroom.

But after reading the Invariance article, I'm a bit confused. It seems to talk about the same thing, but when you look at the referenced charts, I get really confused.

Here's the chart for my D4:

http://photonstophotos.net/Charts/RN...#Nikon%20D4_14

It seems to indicate that the Upstream Read Noise (the read noise before the analog amplifier) goes down when you crank up the ISO on the camera. That makes no sense. Trying to find the highest "Real ISO" is more confusing after reading the article and looking at the charts.

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Old 01-29-2019   #6
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I understand (at least I think I do) the theoretical underpinnings of the article, but I have to ask whether it makes any real world difference in print quality whether you shoot at a higher ISO or lighten the RAW file in LR, at least to the extent you are careful not to clip highlights. I can't recall an occasion where I have exposed at a higher ISO than 3200, and then only rarely.
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Old 01-29-2019   #7
Bill Pierce
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Quote:
Originally Posted by Timmyjoe View Post
But after reading the Invariance article, I'm a bit confused. It seems to talk about the same thing, but when you look at the referenced charts, I get really confused.
-Tim
"These raw values are not appropriate for comparing camera models because they are not adjusted for gain or area." That's a quote from the site. I think what it means is "Don't worry; trust your results with your camera."
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Old 01-29-2019   #8
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I guess what it means, is that it's safe to crank up the ISO to a certain point. But if you go beyond the critical point, the image suffers. But didn't we already sort of know that?
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Old 01-29-2019   #9
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Originally Posted by Rob-F View Post
I guess what it means, is that it's safe to crank up the ISO to a certain point. But if you go beyond the critical point, the image suffers. But didn't we already sort of know that?
The point is to what degree would the image suffer past that point. With an ISO invariant sensor there would be none as long as you stay within the range.

Good thing is you can confidently shoot for highlight with lower ISO, knowing you can push the shadow for several stops later with zero loss.
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Old 01-30-2019   #10
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My digital cameras (Sony A7II and Ricoh GR) are both ISO invariant, and I regularly use that capability. Any time I expect that there will potentially be highlights in a scene that might blow out relative to the average metering - bright sunny days, city lights at night - I always just dial in -2EV to -3EV to cover the highlight, then lift everything in processing. Im not pixel-peeping but I've never felt there was any obvious issues in the results.

Just as an example, this was shot on the Ricoh GR with -2EV
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Old 01-30-2019   #11
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Err, haven't we been taking advantage of that ever since digital photography arrived? This article is hopelessly bloated and goes on and on and on unnecessarily. All it's saying is that sensors have a lot of latitude, and this is embedded in both camera settings (e.g. wide usable ISO range) and raw files (e.g. wide editable dynamic range). And attempting to give this a name ("invariance") that no one uses just adds pointless confusion...

Surely everyone using a digital camera knows that you have this latitude!

The photo below is from 12 years ago with a 6 MP camera that was ancient even then - to emphasise that what this article tells us is old news. It's an extreme case - very low ISO and very underexposed as I was shooting straight into the sun and didn't want to blow the highlights (including the very bright raindrops). See also my postscript under these photos.

I'd imagine every photographer would do something similar - even with film before digital was even an idea, with the aim of dodging and burning later in the darkroom.

Original


Adjusted


I saw this shot developing with the weird light and colour of the rainstorm as the woman walked up the steps, and ran and grabbed my camera. In my haste I forgot that I'd set my camera to JPG only!

So, this is what you can do with just a JPG file!

Yes, raw would have increased the technical quality. Yes, the shadows have been lifted to an extreme so technical quality has again suffered (e.g. there's unwanted noise). But it's good enough - the exposure and colours match the reality of what I saw, and I've printed it at A3 size.
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Old 01-30-2019   #12
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I have not read it properly but I presume this article refers to the characteristic which has resulted in some experienced users recommending that those who own, say, a Leica M8 should shoot these at low ISO settings and deliberately under expose the image, then correcting the image in post. (Shooting in RAW of course).

I have found this to be especially useful since beginning to use Lightroom as it has particularly good capabilities for adjusting different tonal ranges within an image separately. Thus I am readily able to pull back highlights even more without making an already under exposed image even darker then adjust those shadow areas in the opposite direction.
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Old 01-30-2019   #13
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Well I never shoot above base ISO on my Leica M9. I always rely on adjustments to the RAW files during processing and this works very well indeed. I've done it for years. Not so with the Sony A7II - I adjust ISO in camera because experience has taught me that its files are far less tolerant of being heavily adjusted afterwards and noise is significant if I do so. I'd suggest that you don't really need to read it up as much as try it. Intriguing that someone has give this a name though.
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Old 01-30-2019   #14
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I've just tried to read the article and gave up half-way...delightfully incomprehensible, at least to me.
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Old 01-30-2019   #15
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Quote:
Originally Posted by peterm1 View Post
...I presume this article refers to the characteristic which has resulted in some experienced users recommending that those who own, say, a Leica M8 should shoot these at low ISO settings and deliberately under expose the image, then correcting the image in post. (Shooting in RAW of course).
Peter,

This is how I first learned about this concept. I always thought my M9 was a good sunny day camera, but suffered in low light. I read the two article linked to above, and suddenly, shooting my M9 at ISO 640 and EV -1, then correcting in post, gave the camera a whole new life.

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Old 01-30-2019   #16
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I utilize negative exposure compensation quite often vs. raising ISO values to maximize highlight retention and raise shadow values in post processing, both in low light and during regular daylight with heavy shadows as I do not like to see beautifully exposed landscapes with large swaths of overexposed, blown clouds in the sky. 1-2 stops isn't unusual and works out very well. Depending on the raw converter you use, DXO's camera/lens profiles tend to extend one's ability to do so and produce excellent results.

Mirrorless cameras with their electronic finders and histograms makes it easy to work out the exposure maximums and minimums needed wile viewing the subject before pressing the shutter release, allowing one to stretch the files in post-processing



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ISO Invariance
Old 01-30-2019   #17
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ISO Invariance

What's invariant is the camera's read noise level

There are two main time-dependent noise sources.

One is the read noise which describes noise from electronic components (sensor, analog DC gain and the analog-to-digital controller).

The other is photon (a.k.a. shot) noise. Photon noise is inherent to the conversion of light energy to photoelectrons. Photon noise is beyond human control. It is identical for every camera (when using the same exposure). However the relative amount of photon noise depends on exposure (shutter time and aperture). The relative level of photon noise decreases as exposure increases. For ISO invariant cameras this

When a camera is ISO invariant the noise is dominated by photon noise. Except at extremely high camera ISO settings, the read noise levels are constant. This is the best you can do.

When sensor under exposure is inevitable, the only way to maximize raw-file, signal-to-noise ratio is to understand your camera's read noise vs ISO behavior.

Above base ISO settings older designs relied on DC signal gain to minimize read noise levels. For some cameras the read noise levels would decrease as the ISO parameter increased.

Here's one example.

Using ISO 400 decreases read noise levels compared to ISO 160!

For the sake of completeness, some of the newest sensors use dual-conversion gain technology. Now there are two separate ISO invariant regions.
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Old 01-30-2019   #18
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Quote:
Originally Posted by willie_901 View Post

For the sake of completeness, some of the newest sensors use dual-conversion gain technology. Now there are two separate ISO invariant regions.
William - Do you know any sources that give the two ISO's that are the two base levels for the two regions for specific cameras? I think I read the M10 was 200 & 800. It would be nice to know for those of us meshed in protective underexposure.

(Next on the topic list - the exact opposite, maximum exposure, exposure to the right, for capturing the greatest brightness range.)
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Old 01-30-2019   #19
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Is there an 'Invariance for Dummies' book? I never let my Histogram go to highlight blow. So, I'm always underexposing (in RAW a little). RAW Therapee is a great editing program to do the retrieval that the author discusses. But I've still not sure after reading this article if I doing it right.
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Old 01-30-2019   #20
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I guess I’d rather use high iso and see my exposure in my evf than be 5 stops underexposed and see nothing. With ovfs, you don’t have this issue.
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Old 01-30-2019   #21
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Quote:
Originally Posted by Gregm61 View Post
Mirrorless cameras with their electronic finders and histograms makes it easy to work out the exposure maximums and minimums needed wile viewing the subject before pressing the shutter release, allowing one to stretch the files in post-processing
The problem that relying on the histograms for exposure mins and maxs is that what it's showing you is a jpeg representation. You're actually going to have a lot more latitude in the raw file.
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Old 01-30-2019   #22
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Quote:
Originally Posted by Timmyjoe View Post
Peter,

This is how I first learned about this concept. I always thought my M9 was a good sunny day camera, but suffered in low light. I read the two article linked to above, and suddenly, shooting my M9 at ISO 640 and EV -1, then correcting in post, gave the camera a whole new life.

Best,
-Tim
Thanks Tim I will bear that in mind. For most of my time with my M8 I have tended to view it the same way as your M9 - good for bright scenes but disappointing in situations in which old Leica film M cameras excelled - available light when light was a little lacking. And of course in high contrast situations where CCD sensors do not cope well.

I was of course aware of the advice about shooting at native ISO and deliberately under exposing as my previous post indicated and have started trying it and found it can be useful. Though I have not been terribly serious about it. So for most day to day shooting I have been lazy and tend to just use auto ISO - though I keep my sensitivity limits between 160 iSO and 640 IS0 so I do not go overboard in this respect.

However I should really start to seriously use the technique of shooting at 160 ISO (base ISO), under exposing by a stop or more depending on the lighting and then try pushing the image in post, as my main every day technique. I have done it half heartedly / experimentally and while I have found it works I need to put it to serious use. I guess its habit that has prevented me from doing so, and the fact that the M8 does not have an EV dial. This means if I need to vary this parameter due to an ambient lighting change I need to delve into menus. Which is a pain. I suppose the alternative is just to set aperture and shutter speed wholly manually and deliberately under expose if necessary in that manner.

May I ask, have you tried under exposing by larger amounts than 1 EV? If so how well does this work as a technique with your sensor? (If the ambient lighting is very poor I do not necessarily want to have unduly blurry shots due to low shutter speed so more than 1 EV may be needed in some situations).
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Old 01-30-2019   #23
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I took advantage this often when I shot digital. But while it worked great for b&w, I noticed that the colors tended to go off. Maybe that was just my software, Darktable?
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Old 01-30-2019   #24
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Quote:
Originally Posted by peterm1 View Post
May I ask, have you tried under exposing by larger amounts than 1 EV? If so how well does this work as a technique with your sensor? (If the ambient lighting is very poor I do not necessarily want to have unduly blurry shots due to low shutter speed so more than 1 EV may be needed in some situations).
Hi Peter,

For some reason I can't find the original files for the image below, but from recollection, this was shot on my M9, ISO 640 (the max ISO I used on the M9), and EV -1, then corrected in Lightroom, (as per the instructions in the links I posted above.)


I've gone as far as EV -2 with the M9 but for most uses, EV -1 works better. It's a trial and error thing, but you could easily test it by shooting a low light image as EV -1 then EV -2, and see which one looks better to you when you correct exposure in Lightroom.

Best,
-Tim
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Old 01-30-2019   #25
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How does underexposure with correction in Lightroom comport with the admonition to expose to the right. They seem at odds.
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Old 01-30-2019   #26
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Quote:
Originally Posted by craygc View Post
The problem that relying on the histograms for exposure mins and maxs is that what it's showing you is a jpeg representation. You're actually going to have a lot more latitude in the raw file.
Yep, you figure out pretty quick how far "off the scale" on the right-hand side you can go with the preview and wind up with a file that holds all of the highlight detail. It gets you way closer than taking a shot or two and often having to re-shoot because you couldn't see the exposure preview in the optical finder beforehand.
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Old 01-30-2019   #27
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Originally Posted by Archlich View Post
The point is to what degree would the image suffer past that point. With an ISO invariant sensor there would be none as long as you stay within the range.

Good thing is you can confidently shoot for highlight with lower ISO, knowing you can push the shadow for several stops later with zero loss.
+1 what he said

And dr is maximized as well

It would be interesting to see how all of this applies to a Fuji S5 Pro
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Old 01-31-2019   #28
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Quote:
Originally Posted by Peter Wijninga View Post
I've just tried to read the article and gave up half-way...delightfully incomprehensible, at least to me.
I didn't even get to the halfway point.

I'm a muddler. Still I manage somehow.
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Old 01-31-2019   #29
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Quote:
Originally Posted by Bill Pierce View Post
William - Do you know any sources that give the two ISO's that are the two base levels for the two regions for specific cameras? I think I read the M10 was 200 & 800. It would be nice to know for those of us meshed in protective underexposure.
...
Here's a some data. These data show read-noise levels vs ISO setting normalized for ISO gain. They estimate read-noise levels at the photo-diode level.

FUJIFILM

Nikon

Olympus

SONY

The single large change in sensor read-noise levels is due an increase in photodiode conversion gain. More conversion gain reduces read noise at the expense of maximum photo-diode full-well capacity (dynamic range). In bright light always use the low ISO setting range. In low light use the high ISO range.

These data depict the two pseudo ISO-invariant ranges for some of these cameras. Read noise is most obvious in shadow regions. Increasing DC signal gain (i.e. increasing ISO setting) does not affect the noise level within ~ +/- 1/3 stop.

Note: These data are from statistical analyses of un-rendered, raw-file data.

Here's some data for Leica M bodies.

Input-referred Read Noise VS ISO

Shadow-Region Improvement vs ISO
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Old 01-31-2019   #30
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Originally Posted by ptpdprinter View Post
How does underexposure with correction in Lightroom comport with the admonition to expose to the right. They seem at odds.
They aren't.

Underexposure always reduces the analog signal signal-to noise ratio. Exposure only depends directly on shutter time and, or aperture. This means using practical shutter times and, or apertures often results in unavoidable sensor underexposure. There are two very different ways to compensate for sensor underexposure.

At the camera's native (base) ISO maximizing exposure (shutter time and aperture) maximizes the signal-to-noise ratio for the data. By coincidence maximizing exposure produces an expose-to-the-right histogram. Using a tripod with static subjects means the sensor exposure can be maximized. But subjects in motion require shorter shutter times. Then practicality demands sensor underexposure.

When practically requires underexposure, at the native ISO setting the rendered image will appear too dark. There are two ways to increase the final image's brightness. One is to increase the brightness digitally in post-production. The other is to increase the gain of the analog signals before they are digitized in-camera. This is accomplished by the setting the camera's ISO setting above the native value.

In the first case, the in-camera histogram will not be biased to the right due to sensor underexposure. In the second case the histogram may appear to be biased to the right. But it is identical to the first histogram. Increasing ISO also changes the exposure index calibration which simply shifts the histogram scale.

In the first case the histogram is a guide to avoid exceeding photo-diode full-well capacity. But in the second case the histogram becomes a guide to avoid exceeding the analog-to-digital converter's maximum signal threshold (clipping). These are very different situations.

In low light underexposure is often unavoidable. For some camera designs, increasing analog signal gain after the shutter closes increases the read noise levels. Underexposing at a lower ISO and increasing the brightness in post-production will result in cleaner shadow regions. However, now the best possible post-production rendering requires using raw files. In-camera JPEGs lossy compression destroys some of information needed to properly brighten the image.

With ISO-invariant designs the read-noise is essentially constant with respect to ISO setting. Shadow region SNR is not affected by read noise as ISO increases. One can use base ISO, raw files and just set the shutter time and aperture as needed. The only concern is exceeding sensor full-well capacity in bright light. Otherwise the histogram and, or meter can be ignored. When underexposure becomes unavoidable it will be impossible to clip the ADC. Image brightness is optimized in post-production.

Underexposure always increases the relative photon noise level. Camera ISO settings (electronic gain) have no impact on photon noise levels. Since read noise is essentially constant, the noise levels for ISO-invariant cameras are dominated by changes in photon noise. Otherwise, both read noise and photon noise degrade IQ as underexposure increases and the ISO setting is increased to brighten the rendered image.
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Old 01-31-2019   #31
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Originally Posted by ptpdprinter View Post
How does underexposure with correction in Lightroom comport with the admonition to expose to the right. They seem at odds.
On a practical level, for me, expose to the right has always been the way to capture the greatest brightness range in the file. With today’s sensors that can be pretty impressive, and many photographs are not going to need it. But when they do, I set my camera to its base ISO and bracket my exposures, selecting the most generously exposed one that still holds highlight detail. I think with early digital you looked to “exposure to the right” not only to maximize brightness range but to minimize noise in the darker values of your final print. Today I just use it to go for that tonal range, and it’s not something I do a lot. Truth is, I’m sort of an “expose to the left” person having spent a lot of years shooting transparency film, worrying about highlight detail and learning to live with the shadow detail it provided. The same phobia seemed to produce decent digital files.

I think willie 901 is the expert here. If he says this is wrong, I’ll have to consider changing my ways. I hope “exposing to the left” is pretty good standard practice and “exposing to the right” is good specialty practice.
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Old 01-31-2019   #32
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Bill, you've nailed the 2 most important points for the actual photographer:
1. ETTRight was desirable, and even necessary, for the early limited-range sensors.
2. ETTLeft is desrable nowadays for extreme wide range scenes, especially ones with super bright spots and/or specular highlights in which the photographer wishes to preserve detail.
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Old 02-01-2019   #33
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Whilst I can see logic and reasoning in the posts here, am I not correct in thinking that this would all be easy to put into practice IF the RAW file had not bee subjected to the manufacturer's adjustment prior to being written to the memory card? My experience with ETTR almost always leads to some discrepancy in tonality which I assume to be because the manufacturer has tweaked the RAW file for reasons which they anticipate will optimise it. So RAW files are not truly RAW and are subjected to some form of adjustment.
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Old 02-01-2019   #34
willie_901
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Quote:
Originally Posted by Bill Pierce View Post
On a practical level, for me, expose to the right has always been the way to capture the greatest brightness range in the file. With today’s sensors that can be pretty impressive, and many photographs are not going to need it. But when they do, I set my camera to its base ISO and bracket my exposures, selecting the most generously exposed one that still holds highlight detail.
That's what I do. I assume you're using raw files.

Quote:
Originally Posted by Bill Pierce View Post
I think with early digital you looked to “exposure to the right” not only to maximize brightness range but to minimize noise in the darker values of your final print.
Exactly.

Regardless of what camera we use the goal is to achieve the highest level of useful exposure without exceeding the full-well capacity of the sensor. This maximizes the signal and minimizes the photon noise levels. This is all we can do.

The difference between early and contemporary digital involves relative read noise levels. Contemporary designs have very low read noise levels over a wide range of ISO values (at least 4 stops above base ISO). Even so, deep shadow regions (more than 5 stops underexposed compared to highlight regions) can be affected by read noise even at base ISO. Relative read noises levels are much higher for early designs. Different early designs have different read noise vs ISO profiles. So some ISO values should avoided in low light.

The first place I heard about this was in a long thread about ETTR in another Forum where Emil Martinec wrote this about ETTR:

"What is the appropriate mantra?* I would prefer "Maximize Exposure"; maximize subject to three constraints:

(1) maintaining needed DoF, which limits how much you can open up the aperture;
(2) freezing motion, which limits the exposure time;
(3) retaining highlight detail, by not clipping wanted highlight areas in any channel.*(emphasis mine)

Note that ISO is not part of exposure. Exposure has only to do with aperture and shutter speed. Maximizing exposure guarantees that one captures as many photons as possible subject to photographic constraints, and therefore optimizes S/N.
"

Step 3 implies one should intentionally overexpose highlights that are not aesthetically relevant. Examples are specular highlights during daytime and bright point source lights at night. This is why I auto-bracket aperture by +/- 1/3 stops. I can keep the raw file that retains the important highlight regions.

There are three disadvantages to this method.
  • You have to use raw files
  • Chimping is compromised since the in-camera JPEG will often be too dark
  • There is some uncertainty about judging deep shadow region IQ
  • Camera profiles used in some post-production rendering software generates hue twist with large increases in rendering brightness (the Exposure slider). This means increasing brightness may require selective changes in hue rendering parameters. Sometimes this is most obvious for skin-tone rendering.

The advantage is the raw data will contain the maximum possible amount of information. In other words, SNR will be optimized.

A minor advantage is you can ignore thinking about choosing a camera ISO setting – or wondering if auto-ISO is letting you use the optimum shutter time and, or aperture.
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