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xpatUSA
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The Ansel Adams Fallacy: "True perspective depends only on the camera-to-subject distance" Technical Discussions Feb. 14, 2024, 1:34 a.m.

@TomAxford has written:

@xpatUSA has written:

No need to "shout", Tom.

I made no mention of the absolute size of the image. My comment referred only to the relative angular size of the two persons.

I'm very sorry, I was not intending to shout, simply trying to be unambiguous and to the point.

I agree that you referred only to the relative size, but you then deduced that there was no difference between the two cases (I assume that is what you meant by "ergo, no difference").

Yep, I should have said "no difference between the relative angular size of the two persons in the image in case (1) and case (2) irrespective of the absolute physical size of the viewed image" ... thereby trying to avoid misunderstanding by your good self. Pardon my lack of clarity , folks.

Quoted message:

That deduction implied to me that you had assumed that the absolute size was unimportant. Why did you not mention the absolute angular size when it is the main thing that varies when the viewing distance changes?

I did not feel that it was a factor in the context of my post.
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xpatUSA
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Share your Color IR shots Infra Red/UV Photography Feb. 14, 2024, midnight

Some over-the-top methods when I first got the G1 done:
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xpatUSA
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"The Basics" category - please clarify header text Requests, help and bugs found Feb. 13, 2024, 9:34 p.m.

@AlanSh has written:

There you go - any better now?
Alan

Thanks Alan - makes much mo' sense now.
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xpatUSA
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The Ansel Adams Fallacy: "True perspective depends only on the camera-to-subject distance" Technical Discussions Feb. 13, 2024, 6:06 p.m.

@TomAxford has written:

@xpatUSA has written:

@TomAxford has written:

@Andrew564 has written:

You're wrong about the effect viewing distance has on perspective, your conclusions are not supported by observation.

So, please explain what you think observation would show in the following situation.

You take a photograph of two people, both of height 1.8m. One is standing 10m from the camera and the other is standing 20m from the camera.

The photo is viewed from (1) the centre of perspective, and (2) the point halfway between the centre of perspective and the centre of the image.

How would you describe what is seen in each of those two cases? What is the difference between the two?

Although the question is not addressed to me, I would say:

Case (1) the person at 10m subtends twice the angle of the person at 20m.

Case (2) the person at 10m subtends twice the angle of the person at 20m.

Ergo, no difference, 😉

If you assume that the absolute size of the image makes no difference then it is easy to prove that the viewing distance makes no difference.

But why do you assume that the absolute size is unimportant? I think this is probably the key to the whole of this discussion. I think Ansel Adams assumed that an image always looks exactly the same whether you look at it as a 4" x 5" print or as a 4' x 5' print.

No need to "shout", Tom.

I made no mention of the absolute size of the image. My comment referred only to the relative angular size of the two persons.
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xpatUSA
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The Ansel Adams Fallacy: "True perspective depends only on the camera-to-subject distance" Technical Discussions Feb. 12, 2024, 10:13 p.m.

@TomAxford has written:

@Andrew564 has written:

You're wrong about the effect viewing distance has on perspective, your conclusions are not supported by observation.

So, please explain what you think observation would show in the following situation.

You take a photograph of two people, both of height 1.8m. One is standing 10m from the camera and the other is standing 20m from the camera.

The photo is viewed from (1) the centre of perspective, and (2) the point halfway between the centre of perspective and the centre of the image.

How would you describe what is seen in each of those two cases? What is the difference between the two?

Although the question is not addressed to me, I would say:

Case (1) the person at 10m subtends twice the angle of the person at 20m.

Case (2) the person at 10m subtends twice the angle of the person at 20m.

Ergo, no difference, 😉
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xpatUSA
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"The Basics" category - please clarify header text Requests, help and bugs found Feb. 12, 2024, 6:56 p.m.

It says "Questions and their answers may be moved to the Beginners Question Discussion forum (below this one)"

I can not find a "Beginners Question Discussion forum" and I am not sure what is meant by "below this one".

In any case, the category seems to have died with no recent posts; perhaps re-titling to mention "beginners" might fix that.
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xpatUSA
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DNG versus proprietary raw Technical Discussions Feb. 12, 2024, 6:30 p.m.

@TimoK has written:

@xpatUSA has written:

@DonaldB has written:

I dont think any camera brand uses raw raw anymore. I think they are all manipulated by every manufacturer.

Agreed ... which is why I said "what a camera writes to the card" and which is why I examined raw histograms with RawDigger.

Has it ever been that "raw raw" ? I think the "raw" has always been "what a camera writes".

RawDigger does not confirm your thought, unfortunately.

A lot can happen between the ADC output and the writing to the card.

Examples for 12-bit ADC (0-4095):

Nikon D50: 683 loss-less compressed

Sigma SD9: around 6000

Sigma DP2: around 3000

Quoted message:

And what is the camera today? A computer with a lens and a sensor.

Sorry, not sure what that means in context.
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xpatUSA
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DNG versus proprietary raw Technical Discussions Feb. 12, 2024, 1:30 p.m.

@DonaldB has written:

I dont think any camera brand uses raw raw anymore. I think they are all manipulated by every manufacturer.

Agreed ... which is why I said "what a camera writes to the card" and which is why I examined raw histograms with RawDigger.
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xpatUSA
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DNG versus proprietary raw Technical Discussions Feb. 12, 2024, 5:20 a.m.

I'm no fan of Adobe. However their effort to provide an alternative to proprietary raw converters was at first seemingly laudable.

But then along came RawDigger which allows one to examine raw data. To one's surprise and in spite of early Adobe-speak, DNG "raw" is not the same as what a camera writes to the card.
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xpatUSA
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The Ansel Adams Fallacy: "True perspective depends only on the camera-to-subject distance" Technical Discussions Feb. 12, 2024, 4:54 a.m.

@JACS has written:

@TomAxford has written:

It seems that we agree on all the key points. Telephoto compression is something that we see when we view an image from closer than the centre of perspective.

I do not. I'd always put "telephoto compression" in quotation marks because I find it a fuzzy concept.

Anyway, whatever that is, I can see it from arbitrarily far distances as long as I can still distinguish different object in the photo. Take this page from example:

m.facebook.com/AliciaCliffordPhotoArt/photos/this-is-a-lesson-on-lens-compression-i-took-these-so-that-i-could-demonstrate-a-/471677232901516/

Sorry, not all of us use facebook.
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xpatUSA
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The Ansel Adams Fallacy: "True perspective depends only on the camera-to-subject distance" Technical Discussions Feb. 8, 2024, 11:13 p.m.

@Andrew564 has written:

The front and back of our table here are exactly the same size, and so the two side are exactly parallel, and so the opposite angels are also exactly the same. This is the geometrical truth of the image and the truth of the photo and how it is mapped to the back of the retina.

Looks similar to an Isometric projection whereby the edges of the table are the same size as their opposites, i.e. no perspective involved.

en.wikipedia.org/wiki/Isometric_projection

upload.wikimedia.org/wikipedia/commons/9/93/Comparison_of_graphical_projections.svg
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xpatUSA
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"all subcategories" does not list ALL Requests, help and bugs found Feb. 5, 2024, 2:08 p.m.

@AlanSh has written:

I don't recognise 'all sub-categories'. Can you tell me the steps you took?

Alan

Here's what I get, for what it's worth:

Dell 4-core, Win 7 Pro, FireFox
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xpatUSA
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This, to me, is street photography Documentary and Street Feb. 1, 2024, 4:41 p.m.

Here in America, anywhere vehicles go can be called a "street", unlike in photography where an urban location is implied.

I don't get out or shoot much, after an accident over a year ago - so here's my street:
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xpatUSA
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Ho Ho ... Photoshop did it! Photography News & Rumours Feb. 1, 2024, 1:16 a.m.

petapixel.com/2024/01/31/news-director-blames-photoshop-for-sexist-edit-of-female-politician/
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xpatUSA
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Gotta love ChatGPT ... Technical Discussions Feb. 1, 2024, 12:26 a.m.

@PHz has written:

iT IS WORTH NOTING (and entering once capslock is off) that there is a chabot "user", justifying itself on the "MFlenses" site

Where is that "MFlenses" site?
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xpatUSA
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A conspiracy theorists view Technical Discussions Jan. 31, 2024, 9:33 p.m.

@JACS has written:

@xpatUSA has written:

@TomAxford has written:

The absolute size of an object affects our perception of how far away it is. The absolute sizes are just as important as relative sizes. We know by experience the correlation between the absolute size (we are talking about angular size, of course) and distance away, although most of us are very bad at expressing such distances in yards or metres.

However, in other respects our judgement is remarkably good. If you regularly drive a vehicle you are probably very good at judging the point at which you need to start braking in order to pull up at a red light. You can judge the distance pretty accurately even if you cannot say what it is in feet or in metres. You do that mainly by the absolute size of familiar objects, i.e. the angle they subtend at your eye.

Good to see angular measure mentioned - anathema to some.

It does not explain it all.

Never said that it did.

Quoted message:

Theoretically, that car could be tiny but very close to us, giving us the same angular view as a normal car at a safe distance. We do not just judge the distance by the angle though. We compare it to the surroundings; and we know that it is a car of a certain size, etc. And then, of course, we have two eyes.

Obviously.
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xpatUSA
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A conspiracy theorists view Technical Discussions Jan. 31, 2024, 6:11 p.m.

@Andrew564 has written:

Not really sure what you are talking about here (not a trick question, just not sure what you're talking about or how it relates). I'm talking about "Telephoto Compression", or how you can look at a picture of a distant barn, from the centre of perspective, which has the absolute and mathemtically correct perspective A burned in the image and actually see B, or why you don't see "Telephoto Compression" when you look at a photo from the centre of perspective.

Is A simply B with a bit cropped off at right?

If so, each one has the same single viewpoint - for what that's worth.
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xpatUSA
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A conspiracy theorists view Technical Discussions Jan. 31, 2024, 3:10 p.m.

@TomAxford has written:

The absolute size of an object affects our perception of how far away it is. The absolute sizes are just as important as relative sizes. We know by experience the correlation between the absolute size (we are talking about angular size, of course) and distance away, although most of us are very bad at expressing such distances in yards or metres.

However, in other respects our judgement is remarkably good. If you regularly drive a vehicle you are probably very good at judging the point at which you need to start braking in order to pull up at a red light. You can judge the distance pretty accurately even if you cannot say what it is in feet or in metres. You do that mainly by the absolute size of familiar objects, i.e. the angle they subtend at your eye.

Good to see angular measure mentioned - anathema to some.