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Poser - OFFICIAL F.A.Q (Updated: 2019 Jun 20 8:35 am)
Subject: Oh python GODS! Is it possible.....
Had a crazy thought. Wondering if it is possible to use a python script to set the focus setting in the P5 render option by keying it to the location of a ball prop in your scene. By this I mean, where I place the ball prop being sort of the crosshairs to determine focus depth, etc. So, is that a pipe dream or is it doable? [bows deepy and reverently as he backs away from the altar]
Do you mean these settings? If these show up in a PZ3, it should be possible. Python would pick up the ball's location, write the corresponding focus data into a "dummy" PZ2, and quietly import the PZ2. You'll have to specify what relationship you want in numerical form, because I know nothing from focus!My python page
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Yes, that's the settings I'm referring to. That info appears to save in the pz3 as the settings stay as set whenever I reload the pz3 file. We might need help from someone who understands the focus data better, my photography skills are a bit rusty. So far I have been doing trial and render - and that ain't working out too hot! [bows worshipfully again]
Here's a trial version, with a totally
arbitrary relationship. The Ball Z
is taken as the focal length, and
Ball Y * 2 is taken as the f-stop.
See if this gives you a more empirical
sense of how the relationship should really
work..... Edit: in case it's not obvious, you move the ball, make sure the ball is still selected, then hit the script.
Message edited on: 11/21/2004 15:13My python page
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gapes You, Ockham, are a brilliant, brilliant human being. I'm not big on religion, but when you meet someone who can work miracles at will, it certainly makes you think about moving to California and starting a cult! ~To you, Ockham, LORD OF SCRIPTS, we give these blessings ~Calloo Callay, Calloo Callay, in your name we rejoice! So, um, anyway, is there somewhere we can go to bribe, er, um, donate to you? :)
Even approximate at this point is probably going to yield better results than what I have gotten thus far just playing with fstop and focal depth settings. Now, so as to not be too big an igit when I do this, let me make sure I am clear on what I am doing. I am loading two ball props - or just one? into my scene. I position these (er with one I would put it on the figure I want in focus - not sure about the other) Then I apply the python, render and do the happy snoopy Is that about it?
Just one ball. The Z-distance from center becomes the focal distance, so the idea is that you put the ball on the location where you want the focus. (As I mentioned, this won't be numerically right; it really should be dist from current camera.) The height (Y tran) becomes the F-stop, which may not feel right. Maybe more intuitive if the scale controls the F-stop?My python page
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" I think the length should really be based on crow-flies distance from current camera," Correct. Here's how to calculate the focal length to get the currently selected object in focus (in PNU):
import poser, math scene = poser.Scene() actor = scene.CurrentActor() cam = scene.CurrentCamera() p1 = actor.WorldDisplacement() p2 = cam.LocalDisplacement() p3 = actor.Origin() d = (-p3 + p2-p1, -p3 + p2-p1, -p3 + p2-p1) mag = math.sqrt (d*d + d*d + d*d)
The focal distance should be the distance between the prop and the camera. At this distance will be the maximum sharpness (point of focus). Stewer has a script to calcualte it from the position of a prop. The f-stop, together with the camera focal length, controls how deep the sharp area will be. If poser accuratly models a real lens, this area will be deeper behind the point of focus than in front of it. A bigger F-stop number gives a bigger sharp area.
Is there a numerical relationship (linear or otherwise) between the f-stop number and the area or diameter of the "sharp region"? Not one I can specify. I believe it's an inverse square. Here's the general data (re-posted from link): The smaller the aperture, the deeper the depth of field (the other two factors remaining the same). For example, if the lens focal length and the shooting distance stay the same, the depth of field is much deeper at f/16 than at f/1.4.
I don't want to miss this.
Yes. Rare opportunity to see dorks in their native habitat, eh? 8D
grins dorkily while calling to tell her parents she'll be late for dinner EDIT: Please don't think I'm calling anyone else a dork, but I relish my dork-dom. It is a badge of pride! =P Message edited on: 11/21/2004 16:32
Another quick question to Ockham... Does it matter, what I've selected in general preferences? Poser Units, centimetres, feet... ? Or will the script work with any of the possible settings properly?
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Hmm, tried the script on the pic I am currently working on but the spot where I put the ball is not seeming to be the focal point. This may be cause I have my camera rotated in my universe. I will set up a new scene with some props and see if I can get a better handle on how the ball placement works.
An f-stop is a measure of how wide the aperture of a camera lens is.
It is intimately tied up with 2 things; the amount of light that is let into the camera (not really relevant here) and the depth of field (which is).
DOF is about how far before and beyond a plane (the focal plane) other objects remain in focus.
The above link helps explain depth of field.
Just what the exact mathematical relationship is I'm not sure, but I don't think it involves the inverse square rule (at least, not in simple cases:-) but it certainly involves some trig:-))
Hope it helps (result of simple google for "depth of field")
Message edited on: 11/21/2004 17:09
Attached Link: http://www.keindesign.de/stefan/poser/index.html
Not really talented enough to be considered for the dork hall of fame. A follower really. Didn't Stefen of http://www.keindesign.de/stefan/poser/index.html make a script to set Depth of Field and Focal distances some time ago? I read such in another thread and downloaded his script some time ago. I had saved the URL in my Faves. Hope this is on topic ...
So it sounds like there isn't really a numerically definable relationship between aperture and "sharp region"? I've been Googling some of that stuff, and I'm frankly lost. Seems to be considerable argument among the various tutorials, with some debunking the others!My python page
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Ockham, the script Rance1 mentions looks like what stewer posted and is used to calculate the distance between the camer and objects in focus or Focal Distance option. Maybe you can take a look at the method outlined by Stephen (on his website tutorial on this, which also has the py script) and see if that helps. I like the idea of being able to either pick a figure or place a ball prop where I want my focal point to be and the script do the calculation to give me the depth of field effect I want. So don't give up on this just yet. :O)
There has to be a formula, I have seen tables on deep of field for real camaras. For a given focal length, focal distance, f-stop and film format, the deep of field is the same for every lens. It has to be a optical formula. Unfortunaly I can not find the actual formular in any of my photography books. :-( Anybody with an optics textbook around? I assume Poser simulates a 36 mm film format.
http://www.schneideroptics.com/info/depth_of_field_tables/ This is for cameras, not sure if it works the same for poser. I haven't tried, but I think to use these you'd have to change the measurement in poser to feet and the focal to the appropriate mm. If python doesn't see anything but PU, then I guess a conversion would be in order. Is that possible with any accuracy? There is an equation, but that's in the realm of physics and I swore off that after college.:) This definitely a thread to watch.
This was just a quickie experiment. It is just my $ .02 for anyone that might be interested in a starting point of reference. I shall try to do a more definative tut on FireFly sometime in the future ... the Good LORD willing and the crick (if you're not from PA, that's creek) don't rise ... too high. ;=] Right now, I've got to worry about some idiot who has installed electronic surveillance equipment right across the street from my new secret (Oops! - I guess it's not secret anymore) laboratory where I do all my Poser experiments. cheers, dr geep ;=]
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