Leica Circle of Confusion

[USLatin]

What value should I enter for the circle of confusion for the stock leica on an HVX when using pCINE on a palm to use the DoF calculator?

[Barry_Green]

How large do you intend to view the footage? Circle of Confusion size is related to the size of your final viewing system.

[USLatin]

??? I thought it was but I still don't fully understand how it works...
Tanks for responding!
Well I am not sure... I guess till I get the on-camera monitor I will be using the built in LCD? right? or does it mean a 1080p screen?



EDIT: just to clarify my confusing post... does that relate to the actual dimensions of the screen?? or the resolution?

[shiny4]

assuming the barry's book info the lens of the hvx at 7.8 is equivalent to 60mm in the 35mm still photography.
now enter this number in this calculator http://www.dofmaster.com/digital_coc.html#coccalculator
and you will find that the CoC of the hvx200 is 0,003 if you assume the CoC of the still photography 35mm as 0,025
or hvx200 CoC is 0,004 if you assume the CoC of the 35mm as 0,030.
then read this:
http://en.wikipedia.org/wiki/Circle_of_confusion
:thumbsup:

[USLatin]

does the CoC stay the same (0.003) through the different focal lengths?

[shiny4]

sure.!!!
you can try by yourself.
insert this numbers and you will see that the CoC never change.
from barry book:
hvx200 4.2= 32,5mm(in 35mm format)
5.1=39,3
5.5=42,4
18,7=144
25,2=194

[USLatin]

ok so that's all I need for the application, thanks shiny4 and Barry

but it is still not working right... I have all the numbers in but I still don't get the proper results... ???

anyone use pCAM and pCINE before?

[Barry_Green]

Ah, the appropriately-named Circle of CONFUSION. I doubt there's any aspect of DOF that's more confusing than this is.

To understand it, you have to understand the thought process that brought about the Circle of Confusion in the first place. The CoC was developed, as you no doubt know, to allow cinematographers to calculate what range will be in focus and what will be out of focus. But somewhere along the way a vital component was left out of the understanding, so now today we have people thinking that there's some magical absolute number that just "applies" and that's not true.

The issue facing the cinematographer was to know what's in focus WHEN IT'S PROJECTED. That was the common denominator -- all footage was projected on a cinema screen. There were no 13" televisions, there was only the projector and the movie screen. So the question was: what will be in focus after I've magnified this image so much that it's filling an entire movie screen?

See, that's the other thing -- the larger you magnify something, the less sharp it appears. The smaller you resize something, the sharper it appears. Something might look very crisp and sharp on a 13" TV but when you blow it up to a movie theater size it'll be soft and blurry and out of focus, right? Well, that's what cinematographers were dealing with. They had a 1" wide piece of film that was going to be blown up to 30 feet wide. In cases like that you can't trust your eyes, you had to trust the math -- how sharply must something be in focus when you shoot it, so that it'll STILL be in focus when you project it?

So they came up with the Circle of Confusion, which is the diameter of a point of light that, when projected on the standard movie screen, will still look sharp. If an item was recorded on the film that was larger than the circle of confusion, you could be sure that it would look fuzzy when projected.

Now, there are different sizes of circles of confusion for each different format, because whether you shot 35mm or 65mm or 16mm, the movie screen didn't change. Your format changed, yes, but you were still projecting to the same movie theater screen. So, if you shot 16mm, it would need to be optically magnified much more than 35mm would be. And 35mm would need to be optically magnified a lot more than 65mm would be. This means that what was "in focus" on 65mm, may not be "in focus" on 16mm, once they were projected -- the greater level of magnification may result in an overall fuzzier image that crosses the threshold from "sharp" to "out of focus", whereas the identically-focused image on 35mm film wouldn't cross that threshold.

So they came up with the circle of confusion, to standardize this process. But something has changed since then -- we no longer view our footage exclusively (or even primarily!) on a big movie screen. We view it on 150" plasma TVs or 37" LCD TVs or 7" PSPs or in a 176x144 window on a computer. So the old rule of "well, the DOF calculator says that this part is in focus and that part's out of focus" may not have *any bearing* on your footage -- it all depends on how large you're going to project it! Something that is comfortably out of focus in the background (when projected on a movie screen) may be razor sharp when downrezzed for internet streaming.

There is no one, fixed, absolute size for a circle of confusion for any format -- the circle of confusion's diameter must necessarily change based on the size you're magnifying the footage to display at.

[USLatin]

Barry... you make me feel I owe DVXuser a monthly fee when you go off like that nailing the subject and explaining it JUST the way I most of the time only hopelessly pray someone will do for me. :)

The pleasure of knowing why things became... ahhh...

Thanks... now THAT is logical and makes heaps of sense... this is something I noticed myself when rendering streaming versions of projects... it also happens to be mentioned countless times in millions of SD-HD conversations, follow focus discussions, lens discussions... it was there in my head and it was connected to all of these pertinent areas. But there is no substitute to having someone that obviously seeks this mastering of the craft AND is obviously a smart bastard :) AND has heaps of experience...

Thank you, sincerely, as always!


I completely forgot about the application... lol...
So there is no way for me to effectively use this DoF calculator without a list of the CoC's for each focal length of the Zoom lens, right?
If so too bad, because I love zooms... and I could really use a little PDA calculator that gave me exact depths on a snap.