Talk:Circle of confusion

Love the mm and " mixed in the same paragraphs with no relation or equivalence ... not

Yeah, see "... Viewing conditions. If the final image is viewed at approximately 25 cm, a final-image CoC of 0.2 mm often is appropriate. A comfortable viewing distance is also one at which the angle of view is approximately 60° (Ray 2000, 52); at a distance of 25 cm, this corresponds to about 30 cm, approximately the diagonal of an 8″×10″ image (A4 paper is ~8"×11″) ..."

So, who wants to link mm and inches equivalents for every dimension reference?

68.100.25.247 (talk) 04:41, 12 August 2020 (UTC)

You could use the {{convert}} template. For example {{convert|25|cm|in}} renders as: 25 centimetres (9.8 in) Vexations (talk) 11:04, 12 August 2020 (UTC)

Human vision resolution

Visual acuity. For most people, the closest comfortable viewing distance, termed the near distance for distinct vision (Ray 2000, 52), is approximately 25 cm. At this distance, a person with good vision can usually distinguish an image resolution of 5 line pairs per millimeter (lp/mm), equivalent to a CoC of 0.2 mm in the final image.

If we have 5 lp/mm this is actually 10 dots per mm (dpmm), as for each line we need 2 dots, one black and one white. So is it not the appropriate CoC of 0,1 mm rather than 0,2 mm? This is than related with the critical print resolution of 300 dpi or 12 dpmm and CoC of 0,085 mm.

Thanks for an answer

84.52.165.129 (talk) 21:47, 24 March 2012 (UTC) Rajko Bizjak 84.52.165.129 (talk) 21:47, 24 March 2012 (UTC)

The key is understanding what resolution means: it means that something is being resolved from something else, for instance two objects side by side look like two objects instead of one bigger one. Let's say the object is a white line of 0.1mm width against a black background. If two white lines were side by side without gaps they would look like a single thicker line therefore they would not be resolved. So when we speak about a resolution of 5 lp/mm we are really saying that there is a line of width 0.1mm next to a gap of the same size, which we can also consider a line, this time black. That's the line pair every 0.2mm. But there is only one object per cycle (a white 0.1mm line ). If the retina is able to 'see' the dark gap between two white lines we can say that it is able to resolve them. We could also say that in those conditions it is able to resolve objects down to 0.1mm repeating every 0.2mm. The period, hence the CoC, is 0.2mm.

This was clear in the late 1800's to Abney and Dallmeyer referenced in the historical section. The average human is said to be able to resolve objects of 1 arc minute size on the retina, repeating every 2 arc minutes. In lines, that's equivalent to about 30 lp/degree. Therefore a person with 20/20 vision has a CoC of about 1/30th of a degree on the retina, and Abney and Dallmeyer were correct after all. Jack Hogan (talk) 09:17, 28 March 2024 (UTC)

Not May not do this right: This slide deck talks about the Barten model, j-curve, JNDs and HVS. https://humanhealth.iaea.org/HHW/MedicalPhysics/TheMedicalPhysicist/Studentscorner/HandbookforTeachersandStudents/Chapter_18.pdf

May help explain the terms and why they are.Purduephotog (talk) 20:17, 1 April 2020 (UTC)

Addition to Section "Circle of confusion diameter limit in photography"

Note that this definition of CoC is base for a final image obtained from a 35mm full frame format and that all other formats are enlarged to obtain a final image of the same size. The differences in enlargement causes the difference in the required CoC of the image on the film or sensor to maintain the same CoC of e.g. 0.2mm on the final image. When making identical enlargements from different formats, so an object from the original image, captured at the same focal distance, will have the same size on the final images, the CoC is identical for all formats. Only the outer size of the final image will differ equaly to the difference in size between the formats. Furthermore, in digital photography, a comparison often starts from a 1:1 representation of the sensor pixels on a screen. In this case it will be a differences in the resolution (pixels per inch) of the sensor that will lead to different enlargements. These different approaches to obtain and compare a final image have lead to many misunderstandings and errors when discussing focus and dept of focus differences between sensors of different format and/or resolution.Johnny Swinnen (talk) 23:48, 3 March 2013 (UTC)

Switch to physics conventions?

Whoever created the formulas and diagram used nonstandard notation. The standard notation is "o" for object distance and "i" for image distance. Using nonstandard notation makes the article much less accessible. Does anybody know how the diagram could be changed? That is the most difficult thing to change, the formulas would be easy.

Joel Frederico (talk) 23:32, 26 February 2015 (UTC)