Understanding HDR from a photographer's perspective.

[Moglex]

I'll second this.

Moglex you are certainly using some very impressive terminology,

I'd actually tried to keep the technicalities to a minimum, They only intruded when I quoted what Helen had said.

and I have to admit that when we start getting into the technical aspects of how sensors actually 'sense' I start to get out of my depth. I'd like to see some supporting references for your statements.

I'm afraid that really, if you want to know whom to believe, there is no substitute for going to texts and actually understanding what is going on.

There is absolutely no way you can possibly gain any knowledge about sensor function from examining my photographs. Or Helens.

Frankly, Helen's mentioning them is nothing more than a cheap diversionary tactic designed to shift attention away from the fact that she has got out of her depth on the technicalities.

Not saying I don't believe you, but I have seen Helen's work and I know from other posts she's made that she is extremely knoweldgable, and I'm more than a little reticent to doubt her.

What Helen tends to do is to regurgitate large chunks of photographic and optics texts in what appears to be an attempt to impress people with her knowledge (which I dare say is impressive, though not inexhaustible).

Answering questions on fora such as these should be about looking at what the OP has asked, understanding why they are having difficulty with their problem and explaining it in the simplest terms that will get the message across (perhaps with pointers to extra reading).

It should not be taken as an opportunity to show off the fact that you can read an optics or photographic text and paraphase it. If the person asking the question had the time and/or capability to do that they would have done so.

If you wish to determine the truth or otherwise of what I have written on the basis that Helen has typed a great deal of theory (which you admit you do not always understand) in the past, then I can't really stop you. (Although all you are really saying is that she's typed a load of technical stuff, I've typed a load of technical stuff and because she's been doing it longer you're inclined to believe her).

I would point out, however, that after I last pointed out the flaw in her understanding of range and resolution as it relates to a sensor in a camera system she failed to come up with any counter argument and limited herself to a denial of disagreeing with Arch.

I'd also like to comment on a statement made earlier in the post refering to the distinctive appearance of HDRs. A properly executed HDR should NOT have a distinctive appearance. Discussions of bit-depth, dynamic range and so forth aside, just because you can produce an image with a mind-boggling dynamic range doesn't mean it's a good image.

It is true that if you use HDR sparingly you can achieve a perfectly natural result that just looks as if you have been lucky/careful with your lighting.

I was really refering more to those shots where HDR is used in such a way that is has a sort of signature look.

In both cases, however, there is actually much more going on than simple tone mapping which is what Helen/Bufurcator seem to be implying.

 

[Moglex]

come on guys.. im sure we are all smart enough to know that disagreeing with someone only makes you learn more about looking at the subject from another perspective, even if you think the other person is dead wrong.... after all disagreeing is where real progress is made... however it doesn't need to get personal... im sure we can all agree that.

So please show a little self restraint and bite your toungs

Sorry, I started my last post before I read this (I had lunch between starting and finishing it).

I entirely agree with you but I really feel that trying to get ahead in a technical argument by introducing irrelevancies such as looking at someone's photographs is going a bit far.

I'd like to keep this discussion going in a steady, non confrontational way as I think there is much of interest to be brought out.

Even though I haven't changed my opinion I've certainly learned by being forced to think about it in ever greater detail to try and get my point across as clearly and concisely as possible.

 

[Bifurcator]

bite your toungs

Ouch! <bleeds excessively on the floor> Thanks allot!

 

[tirediron]

I'm afraid that really, if you want to know whom to believe, there is no substitute for going to texts and actually understanding what is going on.

That's one way of doing it, however generally in a debate persons making statements also cite references; to what page(s) of which publications shall I look to find corroborating evidence for your statements?

There is absolutely no way you can possibly gain any knowledge about sensor function from examining my photographs. Or Helens.

Granted, and to be quite honest, nor do I care. As a film photographer, I knew that the my film was comprised of silver halide in a gelatin base and that's about all. What I can get from your images is a sense your abilities as a photographer and from that make an assessment on the likely accuracy of your posts. If for instance I look at a gallery of your work and say, My god, this man is the next Ansel Adams or O. Winston Link, then it's much more likely you do know what you're talking about and not simply regurgitating paragraphs out of textbooks, whereas if I go to your gallery and see a half-dozen poorly exposed holiday snaps with fingers and toes cut off, I'm going to [reasonably I think] have some doubt about your level of expertise. I have seen Helen's work, readily available by the links in her signature, and while it's by no means all to my taste, it is definitely the work of a skilled photographer.

What Helen tends to do is to regurgitate large chunks of photographic and optics texts in what appears to be an attempt to impress people...

Unless you can substantiate these allegations, please refrain from personal attacks; it's hardly the mark of a gentleman!

 

[Helen B]

...

I would point out, however, that after I last pointed out the flaw in her understanding of range and resolution as it relates to a sensor in a camera system she failed to come up with any counter argument and limited herself to a denial of disagreeing with Arch.

That's because I have suggested dropping the topic. Although you can't let it go, you can't come up with a reasoned, technical argument that can be discussed to show that you are correct. You simply say that I am wrong, and make a personal attack on my motives and knowledge, and make false claims about me that you cannot know the truth about.

Best,
Helen

 

[Bifurcator]

Quote:

What Helen tends to do is to regurgitate large chunks of photographic and optics texts in what appears to be an attempt to impress people...

Unless you can substantiate these allegations, please refrain from personal attacks; it's hardly the mark of a gentleman!

Hey, no picking on Helen! Helen has got to be one of the most helpful and knowledgeable people here!

 

[Moglex]

That's because I have suggested dropping the topic.

And then started up again.

Although you can't let it go, you can't come up with a reasoned, technical argument that can be discussed to show that you are correct.

No, I explained exactly where your error was and you simply ignored that.

You simply say that I am wrong,

No, I explained:

The sensor is mounted in a camera so it's raw range is irrelevant. What is important is its resolution because that is what determines the amount of shadow detail it can capture at the point that highlight detail is about to be lost.

Let's drop the personal stuff.

I'm quite prepared to admit that I could be wrong. It happens.

Just explain what is incorrect about the above, bolded, statement. It's not a complicated statement so it should not be hard to point out any error.

If you can't, admit that it was you who was confused.

Remember this 'discussion' started because you accused me of being confused in what I wrote in the OP.

 

[ksmattfish]

Back to the initial point (I think)... Yes, there is a difference between a high dynamic range photo and local contrast manipulation (such as tonemapping), and when many photographers refer to the look of HDR they are really concerned with modified local contrast. Google "dynamic range" and "local contrast" to learn a lot without the bickering.

 

[tirediron]

The sensor is mounted in a camera so it's raw range is irrelevant.

Okay, for my edification, what is the "raw range" referred to and why is it irrelevant?

What is important is its resolution because that is what determines the amount of shadow detail it can capture at the point that highlight detail is about to be lost.

Which resolution?

 

[Moglex]

That's one way of doing it, however generally in a debate persons making statements also cite references; to what page(s) of which publications shall I look to find corroborating evidence for your statements?

You cite references to back up facts.

Your audience has to use their own brains to decide if your reasoning is correct.

I'm not arguing about facts, I'm arguing about the deductions that can be made from known facts.

If someone had made the same argument already (that I was aware of) I'd simply point to it.

What I can get from your images is a sense your abilities as a photographer and from that make an assessment on the likely accuracy of your posts. If for instance I look at a gallery of your work and say, My god, this man is the next Ansel Adams or O. Winston Link, then it's much more likely you do know what you're talking about and not simply regurgitating paragraphs out of textbooks, whereas if I go to your gallery and see a half-dozen poorly exposed holiday snaps with fingers and toes cut off, I'm going to [reasonably I think] have some doubt about your level of expertise.

I'm afraid that's logically nonsensical.

I could be a superb photographer and talk complete and utter garbage about technicalites or I could never have taken a photograph in my life and yet be a scientifc geniius who knows the technicalities inside out. (Actually, I'm not that good at either :blushing.

If you think you can get any idea of someone's technical knowledge at this sort of level of abstraction by looking at their photographs you really are deluding yourself.

This is somewhat different to someone discussing the technicalities of, say, lighting placement, where you could glean some knowledge of their competance from their results.

 

[Moglex]

Okay, for my edification, what is the "raw range" referred to and why is it irrelevant?

A sensor will have a certain range of light values for which it will respond in a consistant fashion. Above that level it will saturate and be unable to produce useful information.

This is the equivelant of overexposing a film. You lose information in the highlights because once the film is completely exposed that's it and anything brighter will only result in the same density on the -ve.

It's irrelevant for the same reason that a film's range (not its speed) is irrelevant in that once it is in the camera you have various means at your disposal to shift the effective range over a vast field (exposure control).

Which resolution?

The resolution of the sensor-ADC (hereafter refered to as the sensor).

If this resolution is low, then you will not be able to expose for very bright objects and retain detail in the shadows.

As it increases you can decrease the exposure to handle brighter subjects and the extra resolution will mean that shadow detail can be kept the same.


I hope I've made that clear.

It's not an easy concept to distill into a few lines.

 

[tirediron]

I'm arguing about the deductions that can be made from known facts.

Fine; I'm an eager little beaver, I would like to learn more about this (and no, that's not sarcasm); I'm asking you as the person who is alleging expertise, where I should go.

I'm afraid that's logically nonsensical... <snipped> ...This is somewhat different to someone discussing the technicalities of, say, lighting placement, where you could glean some knowledge of their competence from their results.

Not at all; you purport to be very knowledgeable in the matter, so it doesn't seem unreasonable of me to assume that you must have produced one or two HDR images, I would submit that those would serve very well as indicators of your skill level, unless of course this is supposed to be a purely academic discussion based on theory, in which case I believe you want www.thephilosphyforum.com.

 

[Moglex]

Fine; I'm an eager little beaver, I would like to learn more about this (and no, that's not sarcasm); I'm asking you as the person who is alleging expertise, where I should go.

For starters, look at the answers I gave to the two specific questions you asked.

If anything is unclear, please say so and I'll try and explain further.

Not at all; you purport to be very knowledgeable in the matter, so it doesn't seem unreasonable of me to assume that you must have produced one or two HDR images,

I'm afraid on its own it's completely unreasonable.

Would you expect someone who was a expert scalple maker to have performed an operation?

I would submit that those would serve very well as indicators of your skill level

They would indicate photographic skill, not the underlying knowledge of the technology which is why I say you are deluding yourself if you think you can ascertain whom is correct about an aspect of sensor technology by looking at photographs.

 

[tirediron]

For starters, look at the answers I gave to the two specific questions you asked. If anything is unclear, please say so and I'll try and explain further.

You in fact only answered the former; to the latter you simply said, "The resolution of the sensor". Does term as you intend it refer to the number of pixels on the sensor? Does it refer to the sensors ability to distinguish between different wavelengths of light, or? Again, there was no sarcasm intended, but the term 'resolution' when applied to the sensor of a digital camera can be interpreted in several different ways.

They would indicate photographic skill, not the underlying knowledge of the technology which is why I say you are deluding yourself if you think you can ascertain whom [sic] is correct about an aspect of sensor technology by looking at photographs.

I would no more assume that a photograph was indicative of someone's knowledge of camera sensor theory than I would assume that taxi-driver's skill behind the wheel is indicative his knowledge of the workings of the internal combustion engine, however, since your thread title is: "Understanding HDR from a photographer's perspective." I have to take from that you are a knowledgeable photographer, and in particular well versed in the "making" of HDRs, since you couldn't apply theoretical knowledge without practical experience. Therefore, to assess the extent of said practical background, I would like to seem some of your work.

Oh, and BTW, it's "ascertain who is correct".

 

[Moglex]

You in fact only answered the former; to the latter you simply said, "The resolution of the sensor". Does term as you intend it refer to the number of pixels on the sensor? Does it refer to the sensors ability to distinguish between different wavelengths of light, or? Again, there was no sarcasm intended, but the term 'resolution' when applied to the sensor of a digital camera can be interpreted in several different ways.

Oh dear. I had hoped that your questions were genuine but it is clear from the above that you are just playing silly beggers.

You claim that your questions were genuine but you make no comment about the answering of the first - did it enlighten you?

About the second you are obviously not really interested as you are merely nit picking. When talking about the dynamic range of a sensor could any intelligent person really believe that a reference to resolution referred to the number of pixels? Even if by some stretch they could, could they really be so stupid as to omit the one resolution that actually relates to the subject in hand?

The answer, to keep playing your game, is the number of bits of luminance information per channel.

Now, do you understand why what Helen said about the dynamic range showed a fundamental lack of understanding of the subject or do you want to keep nit-picking?

I would no more assume that a photograph was indicative of someone's knowledge of camera sensor theory than I would assume that taxi-driver's skill behind the wheel is indicative his knowledge of the workings of the internal combustion engine, however, since your thread title is: "Understanding HDR from a photographer's perspective." I have to take from that you are a knowledgeable photographer, and in particular well versed in the "making" of HDRs, since you couldn't apply theoretical knowledge without practical experience. Therefore, to assess the extent of said practical background, I would like to seem some of your work.

You've still got it completely wrong, though, haven't you? The article as you quoted is: "Understanding HDR from a photographer's perspective", not: "How to actually produce an HDR image". Had it been the latter your desire to see some evidence would have made sense. As it is it makes none.

Oh, and BTW, it's "ascertain who is correct".

You are quite correct. A silly slip, but I trust you realise that by descending to contravening netiquette and picking up on spelling, typos or grammatical errors you have clearly shown that your pretence at a legitimate desire to understand is just that: a pretence?