How far away is infinity? (optically speaking, of course)

Sparrow said:
... and he often gets accused of burning many of JWM Turners less salubrious work while working as the old man's executor ... which I like to think the little ****e was capable of
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He may have been capable of it, but I am less convinced that he actually did it; possibly because he wasn't capable of much, except nasty attacks on far greater artists than himself. As far as I recall, at least some of the 'destroyed' pictures have been rediscovered, despite Ruskin's saying he had destroyed them. "All mouth and no trousers" might have been coined for Ruskin.

Cheers,

R.
 
mdarnton said:
...If you are relying on or asking about "depth of field". . . there really is no such thing--the specific distance you focus on will always be noticibly better focused than closer or beyond. "Depth of focus" really means "how low are your standards, and what will you tolerate?"
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sorry, but that's wrong.
Ideally, you would be right, but, only in case of infinitely good resolution of your sensor, (sub)atomically thin emulsion/sensor and picometer flatness of film/sensor.
Which is obviously not the case.
In practice, it is like drawing two lines: An exponential and a straight line asymptotic to it. In principle, ideally, they only touch in the infinity. In practice, they touch where your pencil thickness is more than the distance between them.
Or where your pixel size is bigger than the distance, in our digital world.

I am surprised that noone gave a **** on my previous reply/replies.
I see three tendencies here in replies:

1. The one who goes very practical and says "2000x focal length is enough". This is a bit-just a bit- too vague and too simplified since it does depend ultimately on magnification of final image, on sensor resolution, flatness, etc. Of course if you pick a number large enough, it will fit all. But that's not 2000xfocal length i am afraid.

2. The completely theoretical answers like the ones with absolute sharpness only at focus distance. This is impractical, plus, it is also not what you see in nature since we live in a 3D world, plus, optics are not perfect, plus, sensors are not perfect, etc.
3. The ones who say 42 :)

If i disregard my own replies, which are the best so far;) , i agree most with the 3rd types:)
 
Pherdinand said:
. . . If i disregard my own replies, which are the best so far;) , i agree most with the 3rd types:)
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Assuming perfect competition, should we hang economists with light inextensible string?

Note for those who have studied neither economics nor physics: certain assumptions are often made in order to simplify calculations, or as one might say philosophically, to render the conclusions at best partially valid.

Cheers,

R.
 
This question isn't as puzzling as it appears - potential is, by definition, measured as the work done in bringing a charge from infinity up to a particular point .. so a 'normal' calculation for the mid-point potential is with respect to infinity.a5 envelope
 
Who knew RFF was red hot center of Ruskin antipathy? Not I, surely. I should not have said anything, having hardly read him. I like the idea of massively influential critics but they do so often prove unpleasant personally. Roger speaks as if from extensive and repugnant experience -- and puts his distaste so forcefully it is difficult not to be influenced by it. Me, I have only read him on how to sketch. Rather thick going too. And, of course he was hyper bourgeois: he was a Victorian.
 
Now I'm thinking of the Ruskin quote in light of later developments: Benjamin's art and reproduction, Greenburg's Avante Garde and Kitsch... MacDonald's Masscult and Midcult. Anytime after 1835 or so that you start to distinguish between something you deem to be fine and other lesser cruder cheaper imitations of it, or even mass scale reproductions of it, you are messing with the idea of value in some way, and you are somehow endorsing the existence of an elite of some kind. Which brings us right around to THE central topic of interest to RFFers, men (and women) : film is finer than digital. Even when digital looks better. Because it is harder, more mysterious, more intuitive, and belongs to a kind of priesthood of the darkroom. Right?
 
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