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Re: How much post processing?

DailyShooter wrote:
gdanmitchell wrote:
DailyShooter wrote:
I agree with what you wrote, but I just want to add that if 1 or 2 of the 3 channels are blown (x'255'), recover is not possible...one tries and then gets a strange color cast.

Perhaps you missed "this part...?" ;-)

gdanmitchell wrote:
Since we're getting into nuance now, I'd differ with the point made earlier that all three color channels must hit the maximum luminosity level before we have a "blowing out" problem. That is, indeed, a bad thing and it results in the camera essentially recording pure white where there should be something else. But it can actually happen when we hit the maximum and can't accurately record the value for a single channel.

Accurate color (with the exception of pure red, blue, or green) comes from recording an accurate balance among the three channels. (It is even a bit more complicated than that, but I digress...) Imagine that some very slightly poking gray color comes from R:255, G: 250, B: 250. The ration between those three values is what produces that subtly pink almost-white gray color.

Now let's overexpose that a bit so that an accurate version of that color would require (and, again, I'm simplifying) R:260, G: 255, B: 255. See the problem yet? In this case we'll blow out the R channel since it now requires a value higher than 255. Now all three channels would be 255... and the pink tone is gone and we just get pure white.

There are plenty of obvious real-world examples of this in photography that we see all the time on the internet and, unfortunately, even in prints from people who should know better. Let's consider the ubiquitous sunset or sunrise photographs, in which the red channel can be extremely hot. In this case you camera may not even show that the image is blown out — no blinkies, and no "past the right" tip of the luminosity curve. You might be tempted to push to almost the right, just below where the camera indicates that you are going too far.

But don't. The camera is (unless you use the three-color histogram and look very carefully) basing its indication on as sort of average of the three color channels... and if you push all the way to the right you can easily blow out just the red channel even thought the R and G channels are well below that level.

Here's the problem. In your photograph there are things like sunset-lit clouds that are both very bright and very hot in the red channel. And you'll lose important details in those clouds. I regularly see such photograph with brilliant and overly-intense clouds... that have lost their details.

And, in addition, let's not forget that color balance issue that I described above. Not only do we lose detail in that single hot channel, but any balance among the three color channels is now thrown off and the color of that brilliant sunset doesn't look right either. (Another place where this problem shows up a lot is with fall color photographs, where letting the red channel get too hot results in leaves that lose all detail.).

Yes, a lot of words. But perhaps the main point of that post, too!

Getting past some of the (often repeated) naive misconceptions about digital imagery sometimes requires more than a few words. As you may have figured out, we can reply to nonsense about things like what it means to "blow out" an image or how to address this by typing something quick and pithy like, "You are wrong!," or fire off another ad hominem distraction (see elsewhere in this thread), or point out that "blowing out only one or two color channels can create problems, too."

But I like to imagine that at least some FM posters are interested enough in understanding this stuff that they might take the time to read a more thorough explanation.

I also do understand that others won't. I can't make them.

They are free to ignore the posts. We are free to ignore them, too. Which in some cases (examples in this thread) is the best approach. In that regard, another favorite quote comes to mind:

“To argue with a person who has renounced the use of reason is like administering medicine to the dead.” -Thomas Paine


Often, my curt "you are wrong" responses are less for the one I am responding to (their minds will rarely change...we see this in the MAGA crowd), and more for the potentially thousands of readers that read bogus and ignorant claims about highlights, and such.

I think your explanations are correct and most who are in the know would agree with you. But it's sad that there are some with decades of experience that still harbor bogus opinions, and on such basic things.

We often cannot change such minds...but the readers of these exchanges...I believe that their minds often can be...and it is those I respond to...

Once while out photographing I had a long and pleasant conversation with someone who was more comfortable sticking with his older perspective and not trying to understand more accurately how things work with newer tools. The reason it was pleasant is because he didn't take the "you young-ins are idiots and my way is the only way" approach. Instead he said — and I agreed with him — that her had shot and processed using film-based photography for years, he had tried to make the transition to newer photographic technologies, they didn't make sense to him, and he was just more comfortable continuing to work with film.

I thought that was a great perspective — that he was comfortable doing what he was familiar with and that he didn't need to attack everyone else who was moving on. Note also that I felt no need to challenge his preference. We share a pleasant 10-15 minutes chatting at a turnout overlooking a beautiful Sierra Nevada viewpoint that we were both photographing.

That conversation coalesced a thought that I had based on interactions with another photography I know who has a long and honored career as a well-known (mostly — he is also known for a highly regarded project photographing NASA stuff) landscape photographer and former Ansel assistant who works (almost) entirely with optical/chemical photography. This person is among those who has inspired me, and I eventually realized that continuing to rely on the traditional processes made complete sense for him — he had mastered those tools in the service of his vision, and there was little reason to go in a different direction. (To be fair, he does know about digital techniques and they are part of his workshops — for example, some time ago he was scanning negatives, printing large versions of them on digital printers and making very large contact prints. But, again, I digress...)

In fact, none of the photographers I know in the real world — as opposed to this virtual, semi-anonymous online world — gets into these heated, insulting, attack-trading screaming matches that too many threads turn into. We all use different equipment, different techniques, and photograph different things... but rather than railing against what our acquaintances do we (mostly) are just interested in how they operate or (if it is too much) we just subtly roll our eyes and move on.


May 29, 2023 at 12:48 PM

  Previous versions of gdanmitchell's message #16257100 « How much post processing? »


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