Hi folks,

Please excuse me if this sounds stupid, but I'm quite confused about this.
If I have a figure posed in between the camera and a mirror, then set the focus distance to the figure, should the reflected image in the mirror be twice as out of focus as the mirror itself? Focus can happen in a mirror, right? It's not just seen as a flat 'image' in Poser, is it?

Cheers,

Glen.

Your physics is right, your renderer is not. Poser's focal blur is fake and has nothing to do with the physics of lenses.

Interesting, thanks. So, what would be the best thing to do then, in your opinion? I guess two renders and Photoshop would come in.

Should my character be in the same focus in the mirror as she is in the camera, ignoring the fact that the mirror itself is further away and, thus, out of focus?

(I'm guessing that numbers are going to crop up soon... I'm rubbish at those, lol!).

Glen,

just draw a triangle on paper, A = from figure to camera, B = from figure to mirror, C = from mirror to camera and A < C . Now the optical distance from figure to camera via the mirror equals B + C that's quite larger than C and even more larger than A. So when B+C is in focus then the figure at A is the most unsharp and the mirror is somewhat in between.

In Poser: render 1 without focal blur producing a sharp image in the mirror, render 2 with focal blur for focal distance B+C.

Personally I don't like the Poser focal blurred renders at all, rendedr times are far too long and quality is far too low. I just make the sharp render plus a Z-depth map and use the latter for a mask on the photoshop blur effect - in your case while masking out the mirror reflection to keep that one sharp. The z-mask should be inverted to give most blur to the most nearby objects in the scene, and could be adjusted in contrast and brightness to regulate the effect your want.

"Never do in 3D what can be done in 2D" is the motto. 

As BB says, Poser blurring is a somewhat post effect. Make a reflective steel ball with blurred reflectivity and look at that ball through a (blur-less) mirror as well. Same for skin scattering. All those effects work on rays directly towards the camera only. One just needs other tools for better results.

Have fun. 

Ok, thanks. So, would I be right in thinking, then, that the reflected image would be sharp, or would the distance of the mirror from the camera affect it? I'm having a bit of trouble getting my head around it and haven't found any images online to use as examples.

say you're not using focal blur, but just blur reflections as such.

say a reflective metallic ball is blurring to an amount X while a mirror (which is reflective metallic too, after all) is blurring to an amount Y. Then in real life you'll get a blurred reflection of a blurring ball, the blurring adds up (X+Y or something alike). But in Poser the ball in the mirror will be blurred to an amount Y only, as the blurring by the ball itself is not showing directly to the camera (but via reflection instead) and hence will not be performed in the render.

Now you're just using focal blur, and the objects reflect sharp. You focus on the ball reflected in the mirror.

Then in real life, the scene seems to continue behind the mirror and the ball in there is at some serious distance. That will be sharp, and the mirror - which is closer to you - will be somewhat blurred while the ball itself - which is closest - will be most blurred. Poser instead will blur the ball as expected, and will blur the mirror accordingly too. But... it will blur the reflection in the mirror as much as the mirror itself, and the ball in the mirror will never get sharp. You need an unblurred (area) render for a Photoshopped replacement.
Note that this is a Firefly thing. Unbiased, physics renders like Octane do get the right image and - like the octane plugin - make you focus interactively as well.

Now you're having both: focal blur on a blurring ball in a blurring mirror. Poser will combine both kinds of blur independantly. This gets you the amount of blur by the mirror only, and the amount of focal blur on the mirror, for the mirror as well as its reflection. And you'll get the blur of the ball and the focal blur on the ball, for the reflection from the ball to the camera. The sharp version to be Photoshopped will still not give you the blur of the ball through the mirror. It's a Poser no-go. 

Hmmm... looks like I'm going to need to learn to use this Octane renderer then... never could figure it out, lol!

Thank you very much for your info!

The render in question is now up on my DA page, though I couldn't seem to get around the mirror issue, even with all focussing turned off. I thought it might be the shader I used for the mirror, which was the EZ Metals chrome shader, as that's the closest I've currently got to a mirror. Still, I'm pleased with how it turned out besides the mirror. :)

http://glen85.deviantart.com/art/Bathroom-001-530765376

my Octane doing mirrors Rose Garden

Nice! I've really got to get on with Octane, lol!

"say a reflective metallic ball is blurring to an amount X while a mirror (which is reflective metallic too, after all) is blurring to an amount Y. Then in real life you'll get a blurred reflection of a blurring ball, the blurring adds up (X+Y or something alike). But in Poser the ball in the mirror will be blurred to an amount Y only, as the blurring by the ball itself is not showing directly to the camera (but via reflection instead) and hence will not be performed in the render."

Sorry but this is not true. (It used to be how Poser worked, but not anymore.)

Here a pair of pawns - left has no blur, right has blur.

Then look behind - we see them in a blurred mirror.

It is apparent that the reflections of the two pawns are not identical. The reflected blurred pawn is more blurry than the reflected unblurred pawn. Therefore the X+Y blurring actually does happen, contrary to what you said.

Also, I did not say "As BB says, Poser blurring is a somewhat post effect." I said it's fake. Poser's focal blur is accomplished by collecting and averaging multiple samples for every pixel, but moving the objects around randomly for each sampling. This is also how it does motion blur. The two forms of blur differ only in the movement, and neither has anything at all to do with post processing. It happens during the 3D rendering. The focal blur is accomplished by having the random movement in proportion to the distance from the in-focus plane, whereas the motion blur is accomplished by having the random movement fall somewhere within the indicated motion of the object in question. Poser's motion blur movement is defined by calculating the appropriate "circle of confusion" and then moving micro-polygons randomly within that circle. This is also why Poser's bokeh doesn't look like real lens bokeh - there is no aperture involved with a shape to it.

A physical blur would not be based on moving micro-polygons around randomly - it would happen by following many sampling rays through different paths of the optical lens system. 

Poser's reflection blur has nothing at all to do with those other blurs, but it is done in a similar way - by perturbing the normal randomly (instead of positions) around the true normal, and taking lots of samples and averaging them. Originally the blurred reflection of a blurred reflection was flawed because whoever built it forgot to perturb the normal on those secondary reflections. But that has been fixed as is apparent in my render above.

However, this is an area where Poser still needs improvement. For very large amounts of reflection blur, there is always some ugliness due to insufficient samples. The "quality" parameter can be set higher than 1, but values above 1 are implemented the same as 1. This is a serious flaw, IMO. It's not a flaw of the technique - it's just a stupid programming flaw that the developer thought he knows better than us how many samples we should use.

Indeed, it was broken in Poser 5,6,7,8 / pro2010,9 / pro2010 and is sort of fixed in Poser 10 / pro2014. Sort of as in: at least it looks good.

However, I do wonder: the environment is reflected in the mirror which is blurred reflected at the back of the figure. Then this back of the figure is reflected in the mirror again, and so blurred reflected at the back of the figure again. Now, is this last result double blurred indeed (as it should), or just single blurred (improved but still fake)? Can someone show me a proof of it?