I would say exactly the same about you! I think we should end this dialogue as it is going nowhere.
Dec. 8, 2023
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Question to you: what is the focal length of a pinhole camera?
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Focal length = (pinhole diameter in mm / 0.03679)^2. The focal length is the distance that the pinhole should be from the film.
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All this would seem to involve a theodolite or a Disto laser to measure distances and a calculator to do the mathematics.
Just take your camera with some lenses of differing focal lengths (maybe a good zoom) and find the picture you want by trail end error, It will be much quicker.
Just yesterday I came across this on TOP, the best photo blog on the web.
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Check out his CV
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This is ideal distance for real pinhole camera to minimise diffraction effects and getting enough sharp image.
I actually asked about ideal pinhole camera (infinitely small pinhole, no diffraction) (but well, I forgot to say that explicitly).What I wanted to say that purely geometrically pinhole cameras focal length is always pinhole distance from film/sensor plane. This means that in discussions about perspective you don't need to use neither real lens formulas nor trigonometry - you can just use model of simple pinhole camera. Using real lens changes real distance from lens to image plane, but this is usually negligible compared to object distance from lens.
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That's really not a strong argument. It's essentially the ad-hominem fallacy. Stick to dealing with what he says, not who he is, or isn't.
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This was another case of the ad-hominem fallacy, on Nigel's part this time. It doesn't matter what is his CV, what he says is still wrong. A few examples from that text:
"Focal Lengths Have Equivalents, Apertures Don't." - and then he goes on to talk about f-number.
"The f-number, along with the shutter speed, controls exposure. If your light meter is telling you that the exposure should be, oh, say, 1/100th of a second at ƒ/4, it's going to be 1/100th of a second at ƒ/4 no matter what format or focal length lens you are using. Assuming all the cameras have the same sensitivity/ISO setting, of course." It doesn't matter what is the ISO, since ISO is not a component of exposure. So long as the scene luminance is the same, then if the EV is the same the exposure will be the same, regardless of exposure.
And this is the root of the issue with most equivalence deniers, they both fetishise exposure and are ignorant of what it actually is. So for them, when they say that at equivalent settings the exposure is different that's the end of the argument, since exposure is all important. But what they think exposure is, is how light or dark the image looks, and they know that it's set by shutter and 'aperture' - but hey that doesn't work so let's throw in ISO as well. -
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I suspected that Adams was well aware of the fact that the perspective seen by the viewer of a photograph also depends on the viewer's position (relative to the image). So ... why didn't he say that in the passage above? I assume he skipped it there only because it's in the book titled The Camera.
In his book titled The Print, I found this passage:
If readers don't look in that book to see what Adams wrote about perspective when viewing an image, it's not his fault. IMO, it's unfair to characterize the passage in The Camera as a fallacy simply because people didn't read further.
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Thank you very much for that. I was unaware of that passage in "The Print".
I am pleased that this is clear evidence that Adams understood the importance of the viewer's perspective as well as the camera's perspective. However, it is a pity he did not mention it in the passage I quoted from "The Camera" because many people since have read that passage and assumed that he had included everything that mattered. I suspect that his book "The Print" is much less frequently read today, so most people (like me) have only seen what he said in "The Camera".
If you look at modern online tutorials on the perspective effects of focal length on the image, there are remarkably few that even mention the viewer's perspective and many of them explicitly make statements to the effect that perspective depends only on the camera position. They often make quite a big thing about saying it depends on nothing else. They frequently make a point of saying that the perspective produced by a telephoto lens can be be proved to be the same as the perspective produced by a wide-angle lens because one is just a small crop from the other.
The fact that so many people have taken the passage from "The Camera" so literally justifies calling it a fallacy in my opinion. It was most likely a completely unintentional omission on Adams' part; I am sure he wasn't trying to deliberately mislead his readers. Nevertheless, many readers have been misled by his failure to mention the relevance of the viewer's perspective.
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OK, that was also not a great line of argument.
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Lest we lose the point here... There is an obvious answer to the silence that greeted the question. Namely that nobody on the thread actually disagreed with the concept that as telephoto compression, being something we experience when we view a 2D image is in itself a consequence of how it is taken combined with how it is viewed.
As I have oft said, it also involves a perceptual element. And the nature of human vision being scientifically demonstrated to be the one place where we do not see pure geometric perspective correctly it obviously follows that there are problems when you try to define what we observe with a human eye directly to the mathematics of image geometry.
I would also caution against the idiocy of standing of a highway trying to take close-up shots of cars. But hey, I'm not a mathematician so I will certainly be proved wrong here... :-)
@bobn2 Yep, slightly different username but same PITA. I'm offski, I was before but came back when this thread was resurrected coz there was something I was thinking of saying but didn't. You know, we were talking about colour, and colour science and you commented later on in the thread that we really need to use a common language with absolute terms so we can understand each other. Or words like that. Which translates into, roughly, for the subject of colour which you define as something that only happens in the human brain we only talk about it in terms of the mathematical model, or how the camera or the computer handles it. For something defined by perception we only discuss how it is handled outside that perception. Then the gem:
Talk about photography... It might be nice. How are most people supposed to respond to that? What on earth has it got to do with general photography , colour, or the differences between... Talk about alienating a large section of your target audience. You cant think of a more simple answer to the OP's question?
I am no mathematician by choice. I am also no fool. There are a lot of people who may wish to come here who are equally not fools but also not mathematicians. But they can't compete if you don't learn to talk in a language they understand instead of insisting we all talk in the language you understand. I also get the point of equivalence, but a favorite topic on a photo forum (about photography) deliberately cancels out the photo from the equation. But maybe I am a fool and have missed the profound significance of this.
Just sayin'
Also just sayin' that some of the theories here indicate strongly that where scientific method is concerned someone can't tell his AFHE. (Elbow-his).
My last post. BTW DPR has dropped off considerably, it's mostly nonsense and garbage. But that may be the current nature of internet forums these days. It's a musky place and smells like someone trumped.
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But referring to it as the Ansel Adams Fallacy impugns him rather than the people who failed to read far enough.
It's just the Premature Conclusion By People Who Didn't Read It All Fallacy.
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Even though it was completely unintentional, I think he deserves to be impugned far more than the people who failed to read far enough. You seriously think they should have read right through into his next book before they tried to understand what he was saying?
