big ed Loc: Dudley UK

I have come across the term "circle of confusion" in various photog blogs, could someone explain to me in simple terms what this actually means... I have googled it and much of it is way above my head, I am only a hobbyist and sometimes a bit thick!
Thanks in anticipation of your help
Regards kev :?

Scoutman Loc: Orlando, FL

Well, Kev, I've been doing photography stuff ever since my first Argus C3 and this is the first time I have heard the term. I've been to photography competitions where judging panels are occasionally confused or confusing, but it has tended to be more linear than circular.

But, now, I understand it as:

"Circle of Confusion

Vincent Bockaert, 123di.com

This term usually brings up "circles of confusion" around people's eyes. But this does not need to be the case as it is actually rather simple. Depth of field defines the distance range where things have an acceptable level of sharpness. Although sharpness is very subjective, it is in general based on an 8" x 10" print viewed from a one feet distance. You can, for instance, define that an 8" x 10" print is sharp until you can still distinguish 4 lines per mm. That would represent dots of 0.25mm each or 100 dots per inch (DPI), a fair approximation. Other areas of the image would of course be sharper. In other words, 0.25mm or 250µ (micron) is the cut-off point where we decide things are no longer sharp and is called the Maximum Permissible Circle of Confusion. An 8" x 10" print measures 203mm x 254mm and has a diagonal of 325mm, while 35mm film measures 36mm x 24mm and has a diagonal of 43.27mm or 7.5 times smaller. Since 35mm film needs to be enlarged 7.5 times to obtain an 8" x 10" print from it, the diameter of the Maximum Permissible Circle of Confusion must be 7.5 times smaller or 0.25/7.5 = 0.033mm. If you use 8" x 10" large format film, then the CoC remains at 0.25mm as the information on the negative does not need to be enlarged to create an 8" x 10" print.

This article is written by Vincent Bockaert,
author of The 123 of digital imaging Interactive Learning Suite
Click here to visit 123di.com"

And they talk of "permissible" COC (how is that pronounced?)?

Can you imagine critique of a photograph mentioning "IMpemissible" Circles of Confusion?

I'm confused. Why worry? :)

Thanks for bringing up something maybe I should start caring about.

OnDSnap Loc: NE New Jersey

Can't get any simpler than this video,

http://www.youtube.com/watch?v=Pdq65lEYFOM

mikemilton

Another simple way to think of it is that this is as large a blur you can allow before it is noticeable at a typical viewing distance for any given print or display size.

If you zoom into you image enough you will start to see things that are blurred that are not noticeable at normal viewing size and distance. They are within the permissible circle of confusion.

Further is usually does not matter if you blow it up, because you view it from further away which it typically what happens

Scoutman Loc: Orlando, FL

Good one. Even excellent: a short, <3 minute tutorial, with great examples.

Thanks a lot for posting.

big ed Loc: Dudley UK

Thank you for the info guys... Its amazing that I can still learn something new every day....
Cheers kev

robert-photos Loc: Chicago

Awesome :thumbup: :thumbup: :thumbup:

OnDSnap Loc: NE New Jersey

Quite welcome

ncshutterbug

And do you whip out some sort of measuring device and start measuring before you decide if you like it or not??

big ed Loc: Dudley UK

Do you?.....
:thumbup:

ole sarg Loc: south florida

it used to be very simple. you had a ring on the camera that controlled the aperture. you could focus at say f2 and shut down to anything between f2 and f22 and see what you had as you looked through the viewfinder on a slr. I think COC becomes important with a rangefinder.

On my canon I have a button that can be pushed to show what the image looks like when the lens is shut down.

Of course one can use DOF charts but what for? This is why you have a DSLR so that you can see what is in focus from foreground to background or infinity.

Perhaps I am wrong and if so please correct.

Jim_In_Plymouth Loc: Plymouth MN

And all this time I thought it was my stock club that meets the third Thursday of every month.

imagemeister Loc: mid east Florida

CofC is an attempt to define how far in or out of focus a portion of an image is as produced by a specific lens/aperture/distance combination. And, then of course arrises what size C of C is "acceptable" for the image application !

photoninja1 Loc: Tampa Florida

COC becomes relevant in DOF calculations and other very technical photography. The rest of us can blilthley faggetaboutit! Taint 'mportant ta us fine art types :lol: Just shoot yur stuff and ignore it. It may not go away, but it won't stalk you. :thumbup:

Radioman Loc: Ontario Canada

This YouTube video gives a good explanation (once you get past the commercial)

http://www.youtube.com/watch?NR=1&feature=endscreen&v=ev7kKzi9apw