"Sweet Spot" for ISO best sensor performance

[pgk]

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And do I dare introduce the question of ETTR/ETTL?

ETTR is an interesting concept but .....

 

The problem is that once you have a contrast range which the sensor cannot accommodate you have to decide how your exposure should best be made - i.e. at what level are you prepared to have your highlights burn out. And the reason ETTR doesn't always work is because its another metering method which you can use IF its appropriate and of course it isn't always appropriate and it has to be used intelligently too.

 

The basic problem we have is that increasing ISO is simply turning up the amplification and of course noise is boosted too. I've assumed that so far camera manufacturers have tuned their in-camera software to adjust for increased ISO so that the resulting files are optimised. But post processing software has become so good that this really isn't required anymore IMO anyway. And things will no doubt evolve further. I've come from a film background but it has always struck me that 'digital sensitivity' described in terms of ISO (and digital ISO has a technical definition) was always an odd way of doing things and rather backward looking. Backward because digital sensors do not have characteristic curves like film - and are interpreted in a different way. So using ISO as sensitivity cannot be the best solution. I would like to see RAW files 'tagged' with an optimum ISO at which they should be interpreted by software rather than embedded with it so that it cannot be undone, which appears to be the case at present. A different way of looking at things and one which won't appeal to everyone, but there you go.

 

And FWIW I DO shoot at base ISO all the time and rely of software to adjust - its not theory, its how I use my Leicas and it can work effectively, but its a slower way of operating relevant only if it suits your RAW workflow.

Edited February 29, 2016 by pgk

[hepcat]

Reminds me of those threads about the way of "composing" in PP. See what i mean, we just need a 100 MP camera, shoot and crop in PP. Seems like there are two ways of being a photographer thanks to digital: in the field and in the armchair . Just kidding folks . 

 

Well, I'm not sure that there's two ways of being a photographer, but there are certainly two different processes to understand between digital and film when it comes to how the image is recorded on the medium.  

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[ECohen]

I ask a fair question and this is what I get?.....I think your all full of crap.....but I mean it in a very nice way  

 

 

I'll keep doing what Im doing using ISO 200 as my base and 400 ~1600 as I need them....Its worked since the mid 90's and getting better all the time as tech catches up

I for one want to spend as little time in front of a computer as I can ...... but you all do what you want.

 

Funny to say this ...Im now done with  this thread ...take it where you want

[hepcat]

I ask a fair question and this is what I get?.....I think your all full of crap.....but I mean it in a very nice way  

 

 

I'll keep doing what Im doing using ISO 200 as my base and 400 ~1600 as I need them....Its worked since the mid 90's and getting better all the time as tech catches up

I for one want to spend as little time in front of a computer as I can ...... but you all do what you want.

 

Funny to say this ...Im now done with  this thread ...take it where you want

 

It IS a fair question, and honestly, we've been giving you correct and honest answers Evan.    I suspect they're just different from what you expected to hear.  You're still thinking "film."  I still think "film" too, but I've also figured out a little more about the operation of the digital sensor. 

 

But you're right... if using ISO works for you, more power to you.  

[ECohen]

Hep Your telling me that you don't use your LCD because you under expose to stay at 200 ..I think thats bunk.

 

Your also saying you have an 11 stop range so you fix everything in Post...again...more bunk.

 

I'm not looking at it as film I'm using what Leica gave me in my digital camera and spending less time in front of a computer.

 

I cant believe that this is how you work ....but I believe you to be an honest guy so ...if that really what your doing well OK

[icqcq]

OK, pgk, can I then ask how you meter? Which is to say, Yes, I understand that the CMOS has an eleven-stop range [correct value requested:    ], so then the question becomes how do I know that my lumens fall within that range? Incident metering? Multiple spot metering? Curiously, I suspect most of us have an internal meter, not unlike our internal clocks: I can typically nail an exposure within .5 stop in any situation: have you recalibrated your brain to CMOS values? Is there a meter out there that works in such a way?

 

Wouldn't that be an interesting app: the iPhone6 has something approximating a 28mm lens... and none of the apps I found in a quick survey appeared to do what we're talking about: give me a lumen/lux value for light within a reading. Perhaps that would be a starting point. Which is to say, I guess I have to learn how to program tonight, creating an artificial M240 CMOS... hold up the phone with the app running, pick a focal length, and it would simply tell you Yes, the light in this reading falls within the sensitivity range of your 'real' camera, or No, and here's where you've over-run. 

[pgk]

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OK, pgk, can I then ask how you meter?

I guestimate my settings (as I prefer them) then take a shot, check the histogram (which is apparently based on the jpeg that the camera would produce from the settings), then adjust so that the highlight areas that I want to use aren't clipping. That's how I shoot anyway. And often the inbuilt meter is useful to determine a rough setting. It only works with fairly static subjects but once you have your settings there is often little need to change them until the light changes.

 

Caveat. This is how I work but it may not suit everyone, nor may it give the results desired depending on what you want.

[hepcat]

Hep Your telling me that you don't use your LCD because you under expose to stay at 200 ..I think thats bunk.

 

Your also saying you have an 11 stop range so you fix everything in Post...again...more bunk.

 

I'm not looking at it as film I'm using what Leica gave me in my digital camera and spending less time in front of a computer.

 

I cant believe that this is how you work ....but I believe you to be an honest guy so ...if that really what your doing well OK

 

 

No, I'm not saying that at all.  I'm saying that what used to be a ruined frame with film isn't with digital because you're capturing data instead of exposing silver halides or dyes to light.  I don't get concerned about whether or not the image looks good on the LCD if it's a couple of stops over or underexposed.  I'm not shooting Kodachrome any more.  While the sensor itself may have something like 10 stops of latitude end to end, in most cases washed out highlights or muddy shadows will only be two or three stops out, and with a reasonable exposure can be recovered in PP. 

 

Basically what I'm telling you is that I shoot at ISO 160 95% of the time because the necessity of raising the ISO (like we used to NEED to switch film) just isn't the big deal it was with film.  I do the best I can to get the exposure "right on" but I don't sweat it if it's not..  especially if it's only off by a couple of stops (again which would have been fatal with K'chrome.)  And, I need to qualify that and say that I shoot RAW.  You won't get that same response if you're just shooting OOC .jpgs.

 

As far as your assertion about taking so much time in PP, if you download them to Lightroom anyway, you can either batch process them, or just do the couple of shots you want.   it doesn't take any more time than normal processing of the images.

[jpattison]

I guestimate my settings (as I prefer them) then take a shot, check the histogram (which is apparently based on the jpeg that the camera would produce from the settings),

 

Try a Monochrom; its histogram is based on the RAW image.

 

Actually, my metering technique with a Monochrom is to point the meter area at the brightest highlight (not a specular highlight ) and hold the shutter to keep that exposure whilst I re-compose. The Blacks fall where they will, and Lightroom expands the dynamic range.

You can't recover highlights like you can from an RGB file.

 

John

[pgk]

FWIW here is an example of base ISO shooting to retain highlight and post process dark areas to lighten up shadow info. Just the brightest area of sky has little detail and there is some noise in the darker shadows. Increasing the ISO would have resulted in well blown highlights. Exposing for the shadows then increasing shadow 'exposure' in post processing whilst reducing highlight exposure has resulted in a far better balanced image IMO.

 

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[lct]

Not sure to follow you Paul. You exposed for the sky here, not for the shadows. I would get the same result in auto iso. Now my cams are cleaner than your M9 so perhaps my feeling comes trom that.

[ECohen]

Not sure to follow you Paul. You exposed for the sky here, not for the shadows. I would get the same result in auto iso. Now my cams are cleaner than your M9 so perhaps my feeling comes trom that.

 

Thank You for bringing this thread back to my original question.

 

Also I don't have an an M9 I am asking about the M240.......CCD vs CMOS they are different right?  CCD deals with noise differently than CMOS

Can you really discuss these sensors as far as ISO is concerned as if they were the same ? 

 

When you use CCD there was no leeway you had to use the  ISO that sensor was designed for...or results changed fast

Edited March 7, 2016 by ECohen

[pgk]

Not sure to follow you Paul. You exposed for the sky here, not for the shadows. I would get the same result in auto iso. Now my cams are cleaner than your M9 so perhaps my feeling comes trom that.

Adjusting ISO does so globally. Shooting at base ISO allows for selective adjustment of highlight/shadows (effectively changing the 'ISO' in those areas). If the same shot was taken at higher ISO it would already have some adjustment 'taken up' so give less 'room' for adjustment later. How can auto ISO selectively shift varied areas of tonality?

 

Thank You for bringing this thread back to my original question.

 

Also I don't have an an M9 I am asking about the M240.......CCD vs CMOS they are different right?  CCD deals with noise differently than CMOS

Can you really discuss these sensors as far as ISO is concerned as if they were the same ? 

 

When you use CCD there was no leeway you had to use the  ISO that sensor was designed for...or results changed fast

 

CCD/CMOS - both operate over a limited contrast range. Using base ISO simply allows for later adjustment. Where is the problem? (I use CMOS sensors in other cameras and do the same thing except that I find the bottom level shadow noise can contain unpleasant artefacts which I've not seen on the M9. Other than that there is very little difference in how I use either as far as I am concerned.

[lct]

With respect Paul this just sounds like words to me, which does not mean that i'm right at all Just that i don't get what you say. in practice 10 years ago i would have shot the pic at 200 iso, exposed for highlights if i wanted details in the sky and adjusted shadows in PP. 

[ECohen]

+1 .....in fairness we all work differently and that way works for Paul...so OK

[pgk]

With respect Paul this just sounds like words to me, which does not mean that i'm right at all Just that i don't get what you say. in practice 10 years ago i would have shot the pic at 200 iso, exposed for highlights if i wanted details in the sky and adjusted shadows in PP. 

 

So my question is WHY would you have shot at 200ISO? What I am doing is adjusting the camera settings at base ISO to ensure that sufficient highlight detail is held, then using post processing to adjust to what I want (effectively selectively changing the gain from slightly negative in the higher highlight areas (lower ISO) to significantly positive in the shadows (higher ISO). Adjusting the ISO in camera would have given me a little more shutter speed or smaller aperture but that's all (i.e. marginally greater underexposure - which I could have just as easily used at base ISO), and would have done so at the expense of being able to adjust the shadows as much as I could from base ISO (in effect some gain would have been dialled in from the start). We all work differently though so whatever works for you is fine, but for me the 'sweet spot' is base ISO.

[lct]

So my question is WHY would you have shot at 200ISO? [...]

 

To avoid blown highlights and keep details in the sky if i wanted to. 

[pgk]

To avoid blown highlights and keep details in the sky if i wanted to. 

 

I don't see what ISO has got to do with this.

[lct]

Really? You give me the feeling that i come from another planet but never mind i can live with that 

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[icqcq]

I’ve been working to wrap my head around what’s happening technically within the camera. And here’s what I’ve come up with, as clearly as I can. What I’m writing here is specific to the M240, but certainly applicable to other cameras. Much here was gleaned from the great RED article as linked to on the first page, and the “ISOless M240” blog entry.

 

Information and Observations
The M240 CMOS sensor has a base ISO - and fixed sensitivity - of 200.
The M240 CMOS sensor has a latitude of (something like) thirteen stops [a number I’ve floated which has not yet been corrected; someone out there knows the real number].
Manually changing the ISO number does not affect the sensitivity of the sensor.
Manually changing the ISO number changes the way the software handles the light meter.
Manually changing the ISO number changes the way the software manages the data the sensor receives, sometimes in negative ways.
The light meter indicates (something like) a five stop range.
The histogram indicates that the camera has (something like) a seven stop range.

Conclusions

The M240 (and not, obviously, exclusively), through the transition to digital, limits us to an apparent seven stops of latitude, while the sensor is capable of registering thirteen stops.

Running the camera at ISO 200, and relying on the meter and histogram as programmed, effectively forces the photographer to rely only on the upper seven stop's sensitivity of the sensor; as the ISO is nudged up, the seven stops are effectively forced further down the sensitivity of the sensor.

ISO is vestigial thinking from the days of film, a static imposition of false limits; Sensor Latitude, although fixed, allows the photographer full access to the potential of the sensor.
Current camera and metering software compromises image quality because of adherence to tradition: the perpetuation of the idea that a sensor’s sensitivity can be changed, as film could (roll by roll).
A new way of thinking about light and sensitivity, and a meter that reflects the technical changes in exposure-reading and picture-taking, are required.
Utilizing the base ISO, and using the meter only to ensure that all desired data falls within the thirteen-stop range of the sensor, with proper exposure managed in post-production, is, technically, a superior method of exposure.

Proposal
I propose a light meter (fixed at base ISO) that examines a scene in its entirety (per lens in use), displays a graphic indication of the range of light - the number of stops - present in the image, and what combinations of aperture & shutter speed will allow the appropriate quantity of light to reach the sensor, so that data is registered across the range of the sensor. This light meter would indicate clearly where a scene’s range of light exceeds the capacity of the sensor (fifteen stops range in a scene, against a sensor that only manages thirteen stops).

Cameras would chimp a full-sensor-range image, along with full-sensor-range histogram. All curves/tonality would be managed in post-processing.
I would also suggest that Lux be adopted as the new standard by which we, as photographers, think about light: to learn to think and see in Lux, which can then be converted into exposure.

That committed digital photographers unlearn ISO.
I suggest that camera manufacturers eliminate ISO as a tool for exposure, and integrate Sensor Latitude into the software and processing of images.
 

Edited March 7, 2016 by icqcq