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]

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]

Er, is there a Doctor in the house???

Message edited on: 11/21/2004 15:13

Wow! you are fast! I will give this a try now and let you know how it does. Thanks a bunch [grovels in obeisance]

I think the length should really be based on crow-flies distance from current camera, but this will at least give your hand-eye coordination some exercise until we hear from somebody who knows cameras.

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? :)

I'll experiment with the script tonight and see if I can get a good handle on the relationship between real life photography and Poser-ese, btw. ;) (I'd do it now, but I'm leaving in twenty minutes, so I won't have the chance... I can't work as quickly as you. :P )

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?

" 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[0] + p2[0]-p1[0], -p3[1] + p2[1]-p1[1], -p3[2] + p2[2]-p1[2])
mag = math.sqrt (d[0]*d[0] + d[1]*d[1] + d[2]*d[2])

Btw, here is a good reference to give you an idea what the relationship is, shadownet and Ockham:

http://www.mir.com.my/rb/photography/fototech/htmls/depth.html (The link includes both technical and layman's explanations)

Message edited on: 11/21/2004 15:50

Bookmarking this thread : I'm really in need of something understandable to set the focus in my pics.

Is the var you've labeled as 'mag' the same thing as focal length? Or does it need another formula?

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.

Oops; crossposted with stewer!

So could it be possible to have one ball to be positioned on the point of focus, then its scale expanded or reduced to get the boundaries of the "sharp zone" ? (sorry if it doesn't make sense : I know nothing about real life cameras).

So could it be possible to have one ball to be positioned on the point of focus, then its scale expanded or reduced to get the boundaries of the "sharp zone" ? In pmath terms, you would want the target object's scale to be directly or indirectly proportional to f-stop?

'mag' is the final value in PNU - I just named the value like that because it's the magnitude of the vector between the object and the camera.

sorry. 'indirectly' should be 'inversely' in my above statement. (running late, excited about topic... arggh)

thanks for the link softriver, definitely will be useful. And a lot easier than rummaging through the storage boxes trying to find my old photography books. Stewer - okay you qualify as a GOD too. Scratches head and leaves it up to Ockham to understand godspeak. :O)

Edit: Is there a numerical relationship (linear or otherwise) between the f-stop number and the area or diameter of the "sharp region"?

okay, too many grey cells at work here, I'm going to sit back and look on worshipfully

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.

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

I B A Dork too! (he says with swelled chest) :O)

bookmark.

Dork? I thought it was Nerd! That's what I used to call them. Well, till I became one too! LOL.

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?

Nerd is the right word, dork is a certain body part. ;)

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.

Can I just say before I leave that this script is a brilliant idea. Translating a skill that in real life often equates to "fiddling with your camera" (for people who aren't professional photographers) into Poser is long overdue. THANK YOU OCKHAM!

Attached Link: http://www.cs.mtu.edu/~shene/DigiCam/User-Guide/950/depth-of-field.html

Hope it helps (result of simple google for "depth of field")

Cheers,
Diolma

Message edited on: 11/21/2004 17:09

Attached Link: http://www.keindesign.de/stefan/poser/index.html

Does it matter, what I've selected in general preferences? Poser Units, centimetres, feet... ? No, it doesn't matter. The internal values (which Python sees) are always in PU.

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!

Nothing like reinventing the wheel or building a better mousetrap. :O) Cool link Rance01 looke like a lot of useful info for folks new and ignorant to P5 - of which I B #1

The way I heerd it, a nerd is one who has no social skills and knows it. A dork is one who has no social skills and doesn't know it. (I've run into a lot of salesmen in computer stores who are purebred dorks, for some reason.)

LOL @ Ockham!!! BTW - it's not limited to computer stores.... Cheers, Diolma

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)

Dorks, nerds, or gods, I think you are ALL wonderful. I love these threads ... Rance

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.

Shadownet, I wasn't all together sure if that's the tool you were thinking about or not. I've a number of Ockham's scripts and know that he's one of the Poser GREATS. I bow low and slowly walk to the next thread. Rance

Rance, I was not familar with that script so thanks. It is useful. I am hoping the great Ockman whose name must be held in awe can do it one better. :O)

Saved the thread to faves. Along with Shading Rates I think Focal Points and Depth of Field are some of the most interesting features of FireFly. Thanks for kicking this thread off. Rance

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.