I'm affraid it won't be long

[Nathan Potter]

I'm not saying to stop, only that it is difficult to apply data to human perception. One can come with all sorts of measurements and theories, but how relevent that is to a photograph beyond what the eye and emotions can perceive isn't exactly a deal breaker, is it? But it is certainly worth discussing, sort of like Aquinas and the number of angels that can dance on the head of a pin.
Carry on!

John, unfortunately a fine camera and lens is a sophisticated instrument as is much of the rest of the equipment used to produce a fine print. Discussion of this mumbo jumbo "stuff" like resolution, developer chemistry, film emulsion data, etc. is all critical to the mastery of the photographic craft. The more we know about such "stuff" the better is our ability to achieve the particular results we may want to seek. And I understand that accidents of perfection can happen with no knowledge of that "stuff".

Now clarity of vision is something quite different, as you point out. I would agree that it may be the most crucial part of great images and without that you may have sh.t to put it bluntly. Aquinas and pins however is in the realm of philosophy and not basic physics, chemistry or even engineering technology.

BTW there are a number of fields of scientific research which generate data on human perception. One example for instance involved measuring depth perception of a group of individuals using a vernier acuity test. The results precisely identified a large range of depth perception variation among the individuals tested.

In another famous test of perception the victims were outfitted with a special headpiece which, using a system of mirrors, converted the normal horizontal eye pair to a vertical eye pair. Thus the horizontal stereo vision was converted to a vertical stereo vision. Tests were done to determine the time of acclimization sp. for doing some standard tasks.

Just want to point out that IMHO you and others have some good and critical points that you are sharing. As Tim says we got a bit derailed into a resolution discussion by some "woolly" comments by Mr. Wiley.

Nate Potter, Austin TX.

[timparkin]

Tim, Just D = 2.44 X N X wavelength. Gives the airy disk diameter for a particular wavelength of light. D = diameter of the disk, N = f/no.

Nate Potter

Isn't that the equation you used to het the results that don't match peoples visual results on film, let alone aerial results as you mention? I.e. it doesn't match zeiss optics

Isn't D=Nw a better equation (for the Abbe limit) which at least matches visual experience?

Or were your tests specifically looking for MTF50? Sorry if I'm confused - I like to have the maths match accumulated experience in at least some fashion...

[tgtaylor]

Does anyone know the molecular radius of silver chloride? In silver photography the silver chloride molecule is comparable to the photo site or pixel in digital photography and I'm wondering if it is smaller or larger than the smallest pixel currently produced. Does anyone here know?

Thoma's

[C_Remington]

Does anyone know the molecular radius of silver chloride? In silver photography the silver chloride molecule is comparable to the photo site or pixel in digital photography and I'm wondering if it is smaller or larger than the smallest pixel currently produced. Does anyone here know?

Thoma's

8?

[tgtaylor]

8 what: Inches meters, miles? Ya gotta be more specific than "8."

Thomas

[rdenney]

What i meant to say is, do I make photographs for human enjoyment (myself and whomever else may be be visually assaulted by the picture) or do I make photographs to achieve some technical "standard" far beyond what can be observed by the senses unaided?

Only you can decide what is far beyond what can be observed. In my own experience, I want the photograph to look like one can step into it, even if they are nose-to-print. When I approach a print, I often reach a distance where believability can no longer be sustained, because it turns to fuzz. I was at the airport the other day, and United, or maybe it's Delta, has posted some very large panoramic prints of scenes from the west on the wall of one of the gate areas at Dulles. They were posted at eye level, and were about six feet wide. From across the lobby, they were interesting. But when I got withing 8 feet--nowhere near the point where the print filled my peripheral vision--the detail broke down. That's exactly what I don't want. I doubt that I make prints large enough for this to be a problem with the technologies Tim compares, but I sure understand why people want fine detail in their prints, even if other aspects of the photograph are just as important.

Ctein has reported that people sense detail far finer than the usual 5-8 lpm. Maybe so, maybe not. But I'm not willing to dismiss it altogether.

Rick "for whom sharpness is--much of the time--necessary but not sufficient" Denney

[Jac@stafford.net]

Does anyone know the molecular radius of silver chloride? In silver photography the silver chloride molecule is comparable to the photo site or pixel in digital photography and I'm wondering if it is smaller or larger than the smallest pixel currently produced. Does anyone here know?

Thoma's

Roughly 0.004064mm, however it is transformed in development. The grain we exploit are the clumped, or clustered grain, and to add to complexity is the Bayer pattern and other things that just hurt my head to think of 'em. So I don't think the size of silver chloride molecules is going to lead anywhere certain.

[tgtaylor]

Well they better clump because you're sure not going to see something that small (lol). Actually the van der Wallis (that spelling cant be right) radius is 144pm. But what is the radius of the digital "pixel?"

[Corran]

Depends on the camera and how many they put on the sensor.

[tgtaylor]

Give me a number.