I have a question about focal length. I usually render at Standard PC vertical (3:4). My camera setting is 35 mm, Focus 100.0, Exposure +0.00 (factory settings I think). My characters always seem a bit long and stretched. Can someone advise me on a better camera setting, or is the one I'm using the best there is? I'm using Vue 5 Esprit. Thanks in advance, Denny

Try a 50mm to 55mm focal length, Denny. Cheers

Attached Link: http://www.daz3d.com/support/tutorial/index.php?id=1422

Thanks so much for the info. I've tried the 50mm and it already looks better. Denny

so what exactly constitutes a standard focal length in Vue. There's no notion of film back size in the software; focal length is pretty meaningless without knowing the format of the film or sensor size you're using.

Practically, all the focal length does in Vue is give you a wider but stretched shot when pulled back, and a thinner and more, er, "focused" shot when pulled in. Just experiment with lengths, I just use the default, works fine for me.

It's just for getting a wider shot, without having a wide image size. That's what I think, anyway. Someone may know what he/she is actually talking about ;)

well yes, of course that's what it does. What else would it do. But it's all rather arbitrary. And incorrect, to boot. Supposing you needed to match back to a live action shot or some other software? The point here is that the focal length is meaningless without a knowledge of the format of the back plate. For example, a stills 35mm camera, 24mm is wide angle but if you were shooting, say, 4x5 plate, 24mm is extremely wide. Vue is only giving you half the information. Not really enough unless you're just playing.

"Not really enough unless you're just playing." Playing? I don't think that is true. Maybe I'm not clear about what you are saying, but surely if 3d software was to add format of the film or sensor size it would limit the render resolution? Maybe film or sensor size could be added as an option, but one of the big advantages of digital software is that there is not a restrictive limit to render size...I would put that as a big plus. I've had a good look at C4D and just a quick look at Maya and they don't specify film size...and they have been used extensivly with matching to live action footage. Cheers

Well, I agree with kimaldis, it is really arbitrary. But, you can render at preset sizes, like "photo", "photo vertical", "academy flat standard", etcetera. These automatically modify the focal length, so you could just use those and leave the focal length feature alone completely. s'what I do, most of the time

Seems to me Vue (at least Vue 5i) simulates a 35mm film plane and lenses pretty well.

Here are 3 illustrations from my upcoming eBook for digital artists, done with Vue 5i:

Beginners in photography often think of "non-normal" lenses as causing distortion, but they don't. They just take a different sized hunk out of the world than we are used to, at the typical viewing distance of the photo.
For instance, a very wide angle panorama print looks normal if you move it very close to your eyes and wrap it around your head.
Oh! forgot to mention that the block above is 4X deeper than wide or tall.

HTH
Art Head Start

Message edited on: 09/24/2005 20:21

"For instance, a very wide angle panorama print looks normal if you move it very close to your eyes and wrap it around your head" JC, you do know that my other half will probably leave now, when she sees me try this? lol! Cheers

Good thing i didn't have a going relationship when i was an art student and wore deep red welder's goggles 24 hours a day for 3 days to see how my color vision was affected. BTW, i became more color sensitive. By the 3rd day, i could tell which traffic light was red - without noting it's position relative to the other lights, lol. The colors sure looked intense when i took off the goggles. Did a few vision experiments in art college.

"Maybe I'm not clear about what you are saying, but surely if 3d software was to add format of the film or sensor size it would limit the render resolution? Maybe film or sensor size could be added as an option, but one of the big advantages of digital software is that there is not a restrictive limit to render size...I would put that as a big plus." you're not understanding either focal length or perspective transforms work. Most GP 3D apps - Maya, Xsi, Houdini - don't work in the quite limited way Vue works and with good reason; focal length is meaningless unless you take into consideration the format you're working with. And it's not a plus at all, it's a pain because it's misleading and just plain wrong. http://en.wikipedia.org/wiki/Angle_of_view : calculation of FOV from Focal length. http://en.wikipedia.org/wiki/Perspective_transform : detailed description of how world to screen transformations work.

"Beginners in photography often think of "non-normal" lenses as causing distortion, but they don't. They just take a different sized hunk out of the world than we are used to, at the typical viewing distance of the photo." yes, you're right. Perception of perspective is largely dependant upon viewed distance. The idea of a 'standard' lens is based on a 'normal' viewing distance. the other mistake people often make is that widening or lengthening focal length alters perspective. it doesn't. Moving the camera close or far changes perspective, not changing focal length. http://en.wikipedia.org/wiki/Perspective_distortion_caused_by_lens_focal_length

"The other mistake people often make is that widening or lengthening focal length alters perspective. it doesn't. Moving the camera close or far changes perspective, not changing focal length."

Hey kimaldis - very good point! Someting to add to my eBook text - thanks. Good references too.

Don't understand this though: "Most GP 3D apps - Maya, Xsi, Houdini - don't work in the quite limited way Vue works and with good reason; focal length is meaningless unless you take into consideration the format you're working with. And it's not a plus at all, it's a pain because it's misleading and just plain wrong."

Does it really matter if the math is that of true lenses? Is not the purpose of Vue to simulate reality, rather than to recreate it? In other words, if it looks enough like photographic lenses is that not sufficient, no matter the method? I haven't explored the Vue perspective/aspect ratio render stuff though.

"Does it really matter if the math is that of true lenses? Is not the purpose of Vue to simulate reality, rather than to recreate it? In other words, if it looks enough like photographic lenses is that not sufficient, no matter the method? I haven't explored the Vue perspective/aspect ratio render stuff though". hehe. Remember, under the hood, Vue is doing exactly the same as any other 3D app. View transform is pretty standard and there's only one way to transform 3D into 2D (unless you're using After Effects and god only knows what's going on there). So, it's doing it right, it's just being a bit selective about what it exposes to you. Does it matter? Depends. For most users probably not. But if you want to match to live action or another app then yes, it does because you're probably going to be dealing with FOV, not focal length. For example, my XSI camera I'm using a 34mm focal length but I'm using PAL as the image format. If I decide to work in another format then I need to adjust my focal lenght accordingly. Note, this isn't a limitation of XSI, this is the way real world lenses work, so it's not behaving like real world cameras at all. I'm being picky right now because I do have to match XSI moves back into Vue. I'm also working with kind of an odd aspect ration; 4.4:1, so I'm going to be a bit touchy until I know it works. If it doesn't, expect me to come back and scream a bit more ;-) For most people using this software, it's not an issue but that's not really my point I was trying to make. What I was trying to say is, it's wrong and in my experience, you don't do it properly it comes back and bites you in the ass. I come from a background of film and photography and I've done a lot of movie work, matching CG into live action and vice versa. I like to see things done properly and it bothers me when it's not, because that's when things go wrong. sorry for boring everyone. I'll go back to my box now. see www.cg-soup.com for some of the stuff we do.

Aha, so there are practical issues! Now i understand. Yes, standards are important for keeping one's ass unbitten. You're sure not boring me - learning a lot here, much appreciated.

I too am learning. Been watching this thread. I'm a total amateur at both photography and VUE. I used to use 35-mil cameras a lot. There I learned that the standard (50 mil) lenses worked best for everyday (ie snapshot) photos, but for portraiture, it was better to use 100-150 mil, 'cos it flattened out the perspective considerably and made the photos look more realistic (to the human eye. Had to get back further from the subject tho... I never thought much about the physics/maths associated. just went with what looked good. But recently I got hold of my 1st digital cam. Now all my "knowledge" is irrelevant. It's not 35mil. It's not anything. It has a zoom lense, and I have to work with that -- I'm still struggling.... I have the same problem in VUE. Where's the datum line? I recently tried to import a .obj file into a scene (using the default cam settings). It looked distorted, perspective-wise (sorry for the bad wording there, too tired to think of another way of saying it..) It had 2 normal terrains (stretched) and 3 procedural terrains, all with default texturing. + the .obj file (which was very low poly). So I tried changing the Field Of View. Vue hung up on me (was taking 20 secs to do any change at all), so I gave up, and abandened the attempt. I don't know what went wrong. I just got totally discouraged.. (BTW, V5i, if it helps..) Cheers, Diolma

I mostly set my Vue cameras at 50mm focal length and leave render perspective at defaults. Looks best to me, but have not experimented much - too much else to try in Vue 5i :o)