digitaldog

9 hours ago, NAwlins Contrarian said:

I'm not sure I understand the question, but I'll take a crack at it. If the photographer reduces exposure, then that causes reduced signal. The photons coming through the lens and striking the sensor are the signal. 

No argument.

The photographer reduces (under exposes). The results are more or less noise? That's kind of the OP.

28 minutes ago, NAwlins Contrarian said:

reduce signal, which lowers signal-to-noise ratio

Caused by what action by the photographer? 

Getting back to the original topic (since the ISO invariance myth has been dismissed). 13 conversations with one fellow, I've distilled the following statements, and I'm trying to wrap my head around the various comments as:

1. We're just speaking in different terms (English may not be his native language, I'm not joking or being rude, that's likely true). 

2. He's all over the map in the statements. 

3. I'm missing his points.

So here's copy and paste in one place, comments welcome of course:

Underexposure does not cause noise. It only increases its magnitude in relation to the signal.

Sure underexposure increases noise in digital too but it is far less of a problem.

You let less light into the camera by exposing three stops shorter. So you should get a worse signal to noise (SNR) ratio that is approximately 2.8x worse exactly like you observe. Underexposing only increases it (noise).

You can also correctly say that an 'underexposed' image will have worse noise than a 'correctly' exposed image and an 'overexposed' image (as long as it doesn't blow out too much) will have less noise.

I would say that exposure choices are the primary controlling factor but not the cause of noise. This is a very important distinction as it goes to the heart of how image capture works. Exposing less increases the relative noise. Exposing more decreases it.

It's again simply due to the shorter exposure. You expose at 1/125 vs 1/15 seconds. Exposing less actually decreases the absolute amount of noise. It also doesn't cause the noise. The noise is caused by the photon particle nature of the light. It is not caused by something in the exposure. Exposure however influences it.

At best I would agree with saying that underexposure causes an increase in the noise to signal ratio (or alternatively said, a decrease of the signal to noise ratio).

8 hours ago, Alfred_Pennyworth said:

 In modern digital cameras, underexposure alone does not produce noise. Rather, noise is primarily caused by the number of photons (light) hitting the sensor. This means that if a photo is underexposed, it may appear darker, but it will not necessarily be noisier than a properly exposed photo taken with the same ISO and shutter speed settings.

The example above is from a modern camera released 6 months ago.

Underexposed has less photons yes.

How then is it not necessarily noisier (under-exposure does not produce noise)?

Darker not the case due of increase of brightness in raw converter orthe default rendering for JPEG (not optimal exposure for the raw).

Agreed that ALL noise is from underexpose capture indeed (read noise).

On 5/7/2023 at 8:42 AM, paddler4 said:

ISO invariance means only that the impact of amplification in camera (boosting ISO) and of amplification in post are similar, so there is no reason to bump ISO in camera. 

Here's what I'm refining text wise if you have any comments:

The term "ISO invariance" refers to a camera's ability to maintain consistent image quality while capturing images at different ISO settings. Suppose a camera is (perfectly) ISO invariant at all ISO settings. In that case, it will produce the same level of image quality whether the ISO setting value that was set at capture or image brightness is adjusted in a raw converter. This ISO setting “doesn’t matter” in that scenario.

A non-ISO invariant camera may introduce more noise or less noise depending on the exposure due to this ISO setting; there is a variant to the outcome of setting the ISO.

In both kinds of systems, ISO will affect the recommendation of exposure (Aperture + Shutter speed), which affects the degree of noise produced. In a non-ISO invariant camera, a higher ISO at optimal exposure can produce less noise than a lower ISO setting using the same exposure! This should not be the case with an ISO-invariant camera system. Hence the name and behavior. This behavior destroys the myth that “higher ISO produces more noise.” Underexposure is the cause of (increased) noise, not ISO.

Altering ISO and, thus, the exposure recommendation can come in handy in low-light situations where you may need to increase the ISO setting and this exposure recommendation to avoid camera shake or stop motion with a higher shutter speed. Or if you wish to alter DOF, that wouldn’t be recommended* at a lower ISO setting. This results in less exposure and more noise. Again, it is worth stressing: underexposure is the cause of (increased) noise, not ISO.

* Lastly, the ISO provides a ‘recommended’ exposure (Aperture + Shutter speed), but the savvy photographer does not need to accept this! Even without the inclusion of ISO, a savvy photographer will often ignore a reflective meter recommendation, for example, a black cat on coal or a white dog on snow. Such a recommendation would produce an overexposed or underexposed capture, despite the ISO setting in those examples.

Indeed: I didn't show it, it's not a myth and again, Frans is misunderstanding then posting. That is no myth!

8 hours ago, frans_waterlander said:

Seems to me you did the right thing and showed that ISO invariance is a myth. Good for you and good for all of us.

🤫

https://forum.luminous-landscape.com/index.php?topic=136134.msg1185926#msg1185926

The R6 MII is pricey! Which is why the R8 might fly. But I decided at the time I didn't want to wait for the R8 and I'd spend the money since I don't expect to do so for quite some time. 

I'm pretty pleased with the R6 MII. I have only had it for about 2 months. I was going to wait on the R8 but decided to go this route for the better viewfinder, batteries, etc. This is only my 2nd mirrorless. I decided to try this technology a few years ago with a Sony RX-10 IV and wanted better image quality and a battery that didn't die in an hour. For my uses, 24.2MP is more than enough. It is a bit heavier than the Sony, as I expected but I'm okay with that. The focusing system is amazing. The menu system is vastly superior to Sony. A huge step up, but the Sony was kind of a step down from the DSLR I had prior (5D MII).

One of my issues with Mirrorless was the viewfinder. I just wasn't used to looking at a TV screen so to speak after 50 years of DSLR. But this unit is much better, I can even crop it in a tad as I wear glasses. There are two modes to control the basic visual feedback, one that tries to make it more DSLR-like. 

38 minutes ago, frans_waterlander said:

And who is this genius?

Sorry, I'm not about to unleash you on anyone. 

One more test.

1. ISO 800 but using above-recommended exposure 15th@F8.

2. ISO 50 but 125th@F8. 

Detail settings in Lightroom Classic off. 

Low ISO produces less noise: No. 

High ISO produces more noise: No. 

The quote conflates several things, and I agree. 

My main beef is: "Underexposure DOES NOT PRODUCE NOISE".

My tests seem to dismiss this. FWIW, the formatting was his, not mine. 

ISO has nothing to do with exposure per se. My old copy and paste:

Setting ISO speed does not change the sensitivity of the sensor to light, like volume control does not change the sensitivity of a radio. In both cases the setting (ISO or volume) controls only the signal processing, while the input stage (sensor, antenna) provides the same input signal.

That's why when ISO setting is cranked up, automatic exposure results in more noise - automatic exposure in this case decreases the exposure (that is, the combination of aperture and shutter speed is set to allow less light captured by the sensor). Less exposure, less light, more noise.

As for ISO invariance (and my new Canon), I don't know (nor care) but the person who I'm quoting also stated:

"Doesn't matter what camera".

The quote:

"Underexposure DOES NOT PRODUCE NOISE. That is NOT how the physics works. On modern cameras which all these are, the signal is ISO invariant because the amplifiers have gotten so good that noise is caused only by the number of photons hitting the sensor pixel. ISO just scales the number. Doesn't matter whether the entire image is over or under exposed. Doesn't matter what camera.

The test:
http://digitaldog.net/files/ISO200Normal_minus3stops.png

Details:

Canon R6 Mark II.

ISO 200 (yes, I can set it lower with a custom setting, no need).

Meter: Minolta Flash Meter III incident reading.

IncidentMeterNormal.dng:

Normal exposure is recommended exposure of the Minolta meter: 1/15th@F8

In-camera meter tells me that would be 1 stop over exposed it recommends 1/30th@F8.

-3stops.dng

125th@F8 or three stops below incident meter recommendations: UNDER EXPOSED.

All settings in Lightroom Classic’s Detail OFF.

Any comments? 

Yup; raw clipped is clipped.

Adobe and anyone else could provide a raw Histogram but sadly so few do.

Again, there isn't anything in ACR/LR that gives you info about the raw data clipping or not. ALL the RGB values you report are rendered. Many Adobe Camera Raw settings affect this. So it tells us all about the current Adobe Camera Raw settings and nothing about the capture/exposure or channel clipping. 

You can't evaluate exposure and thus clipping in Adobe Camera Raw or any Adobe converter. You need something like RawDigger to do so. 

I can do this for you if you upload the NEF to something like Dropbox. 

Raw or JPEG capture?

Depends on the goal for the old Kodak Gray card. Exposure or gray balancing (which you'd never do with raw data). 

Finding an affordable gray(s) for exposure, white balancing, gray balancing, or making DCP profiles isn't complicated or expensive. And color space agnostic (unlike sets of RGB values). 

27 minutes ago, hjoseph7 said:

Im a using a dye sub printer so it might take some type of different color management ? 

Short answer is no.

You report the screen and print don't match. 

Why are my prints too dark?

Why doesn’t my display match my prints?

A video update to a written piece on subject from 2013

In this 24 minute video, I'll cover:

Are your prints really too dark?

Display calibration and WYSIWYG

Proper print viewing conditions 

Trouble shooting to get a match

Avoiding kludges that don't solve the problem

High resolution: http://digitaldog.net/files/Why_are_my_prints_too_dark.mp4

Low resolution: https://youtu.be/iS6sjZmxjY4

12 minutes ago, hjoseph7 said:

On the screen it does not looks that bad, but when printing it becomes overwhelming. 

Well that's a different issue (a failure of sound color management). 

Resolution confirmed: 

Resolution:

The original (and untagged)? I get collar readings (with both 5x5 and 11x11 samplings) of aStar 1 and bStar 7. 

My fix was done in Adobe Camera Raw and was pretty quick and simple. The settings used are shown to the right, along with the edit itself. Mostly just an adjustment of Tint/Temp (-19 Temp) and it looked 'down' to me, so I increased brightness using Exposure (+.40). There is no highlight clipping with the new setting, but the original shadows are clipped to black a bit (no big deal):

Edit: The Lab values are shown with the cursor over the boy's white shirt and it's pretty dead nuts neutral (-1/-1).

Good testing. I might deliberately shoot a test 3 EV under, but it seems the answer to the initial question for the OP is:

1. Don't under-expose your images as grossly as you are doing (multiple articles about teaching* him how not to were provided).
2. Don't push 'exposure' (brightness) in a raw converter in sRGB on grossly under-exposed images.
3. Understand the green overlay isn't in the data; it's a preview only.  The data is still very suboptimal from the click of his shutter. 
4. Using 16-bit data doesn't help in any of the GIGO: Garbage In Garbage Out practices above in any of this. 

* "Learning is not attained by chance. It must be sought for with ardor and attended to with diligence." -Abigail Adams

On 3/3/2023 at 12:42 PM, frans_waterlander said:

Any ideas and/or solutions? 

Yes: see above!