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That's exactly the problem many photographers have struggled with for years in real life. I used to be a fashion photographer, and shadowless lighting was one of the holy grails of photography. (Not always, but in many cases).
As someone else posted, your best bet is to create a diffused light setup with as little shadow as possible and save it as a light set.
"IF" ? are you joking? this is one of the most interesting threads I have ever seen in this forum
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After a fair bit of recent reading on Iray I recognized that the crazy lumen values recommended in early tutorials didn't make sense given the intent of the Iray engine.
To follow on Andy's discussion, here's a sample with more realistic lighting values. Scene only lighting. 2 1 square meter mesh, each 1200 watts. These are not out of the range of studio lights.
Roughly 1.5 meters from model. Tone mapping F4, 800 ISO 1/125 shutter (realistic camera settings). No post work, 326 iterations NVidia GTX780
I couldn't find the old Luxrender image...so I ran this one overnight.
It doesn't have the IES profile I wanted to use, so I ended up trying a different one...added bloom and the 'rays' through Lux....if I can convince my son to let me borrow his computer, with it's nice shiny 4 GB 970, I'll repeat the scen in Iray.
Or Fluorescents.
Those are fairly easy to find profiles for...I had a site a few weeks ago that I though I bookmarked that had a whole bunch of IES profiles for various studio/photgraphic lights...but it seems I didn't bookmark it, after all.
@latego ... thank you - seeing that this thread has a lot of views and comments - i am sure many good tips and sugesstions also from other members will follow. I am a little bit bussy right now... (earning my living costs :-)... so .. i must slow down a little bit with posting here....
But here is what i do right now, and what will follow:.. candle ligth, fire.. nigthshots, portrait and photostuio lights... Iray is devinitly way slower in low ligth .. so it is harder for me to post renders rigth now.....
i modeled a candle as real as possible yesterday... and try to find correct values...
I face different problems. 1: when i add a profile to a mesh: the lumens and the profiles are distorted (not real)... it goes even more difficult when i add textures/map... so to get" real values" i must do a lot of test renders - because the needed ligth values are not equal to reference datas anymore...trial and error
Example: a candle has 15 lumens.. a point ligth with 15 lumens doesnt look like a candle (but has correct values)... a candle flame is a mesh ) = the ligths geometry is allreay there (the flame)... a texture (the flame has different colors) takes away a lot of ligth power ( the lumens dosent make any sense anymore.... But i am in the process to have very real looking candle ligth: testing and compearing with values which i know....
Example attached:
A room 3x3meter (room reflections are a must or there is nearly no ligth with a candle)...
Camera: F-stop 1.4, shutter 60, ISO 3200.... (that's a really expensive lens
It's a dark image.. but i am happy with the result... because it is similar to what i get with a real shoot and the same values - but i still think iray goes to dark one or two stops, (the ligth rays distribution should be higher, the room a little bit brigther....well more tests are needed. to be continued....
@fastbike1 your image is well lite.. but the camera values are to sensitive for your result ,which is fine - (in my experience about 2 -3 stops) - i think it has to do with the mesh... i could not figure out yet how mesh / lumen really work in iray.. is the ligth still 1500 lumen /m2 or ligth source / absolut.. the lumens now just spread over the whole mesh? (that's why it goes diffuse).?.. i have open questions here ... because i get mixed results .. and it goes way more complicated when i add textures on a mesh ligth.
@mjc1016
nice render - can you do the same with a wall 1meter away and tell me the values you need for the flame and camera ? .. i just did a test today with a REAL candle... 1 - 1..5meter distance to a wall, the ligth/shadow is clearly to see then it falls off very fast...
I won't be able to run it tonight...just got back from an awards dinner with my wife and I'm not much in the mindset for setting up a render. Plus I want to get the Iray render in, too...so I'll need to transfer the scene file to the Iray machine (I really need a NAS for content storage...)
@mjc1016 we are not in a rush
... candle ligth renders are so sloooowww ... my example did run 2 hours and it is far from beeing finished... i need a son with two titans 
Here's where the IES file for the candle is found...I'm cutting the gain down to .333 to get it down to about 15 lumens,
I need to find a nice brass for the Iray render. I'm using a brass nk file for the Lux render and there doesn't seem to be a brass in the included Iray shaders. I transcribed it from an old US Army book...it had nk tables for several brass compositions. I wish I could find the old scene file...I was using a candelabra and it looked really great.
After about 8 hrs in Lux, I called it 'done'...here it is with the candle being 1 m from the wall. I still need to transfer the scene to the Iray machine.
Lux Camera settings....
ISO:200
Shutter: 1/15
f-stop: 5.6\
The color temp is 1900K on the light.
it will be great to see if iray's exposure with similar values result in a darker or brigther image...
I just did a bracket exposure using a 30mm prime lense..... candle 50cm and 1meter away from a wall....
here the camera values which gave me the best result....but a narrow DOF...
Shutter 1/30
F-Stop 2
ISO 800
Your image seems to me to brigth for your camera settings... but it is a nice candle ligth render :-)..... Do you have the same material for the walls as for the floor?
The candle is sitting on a table...it's got a glossy wood surface, the walls are light grey flat 'paint'...if I were buying paint, I'd call it "apartment white...eggshell"...that not quite white enough to be white, not quite glossy enough to be semi-gloss stuff that almost every apartment has between occupants (I've probably put a couple of hundred gallons of that stuff on walls over the years). The holder is brass...and if you look closely, you'll see some reflections from it on the wall. Now to transfer it to the Iray box and render...I wish there was an easy way to do the IES profiles in3Delight...but the only 3Delight version that can use them is for Maya, I think...and then it's not easy.
It's hard to zero in on exact lumen values in Lux...
ok - based on my reference picture i came up with this (following) real world values... and suddenly i understand more about the mesh ligths
Realworld Camera Settings Reference:
Shutter 1/30
F-Stop 2
ISO 800
I set up a wall corner - each wall is 2x2 meter.... the ligth is in the middle 1meter away....
Picture 1 is a pointlight 10cm above the floor - i used for wall and floors - IRAY stucco.... i dont take care about the scale of the materials texure - but the reflection comes realtively close to my photo test....
Picture 1 = pointlight 15 lumen - color 2000k.
Picture 2 = candle flame (no wax body, just the flame)...
The light colors come from the added (as real as possible flame texture)... because i use real colors (improving here, see the added modelled flame) i need to set emission color to a cold white (aka a thungsten color neutral 5000k)
The flame is about 2 cm2 in a 2d projection... so i must set 7-8 luminance and change to cd/cm2 (means now approximative lumen/cm2) and come close to a 15 lumen candle.... when i am happy with my candle flame i will post reference image and the flame as a download here.
Picture 3 - the flame mesh SCALE gives me now the lights power - .. to show that - i just scaled the flame with factor 10....not bad for animated flackering or variations..
Because the flame is a mesh - a normal IES profile will be distorted (dosent make sense).... but still i think the ligths fall-off is not 100% correct - need to do more work on the flames mesh and maybe create a custom fall-off Ies profile.
double posting - delete
@mjc1016 "the walls are light grey flat 'paint'."
That's what confused me on your render - i use for my ligth tests - neutral white (stucco is not bad) ... because i want to see the ligths fall-off as good as possible. Knowing now your materials - your render seems to come close to real world values too.
@AndyGrimm "but the camera values are to sensitive for your result "
I think you're right. I was trying to model a pair of actual CFL softboxes but I think I didn't model the luminous efficiency correctly. I've done quite a bit of reading about the various lighting parameters since then and have concluded that I missed some. As far as the camera values, I was just trying to duplicate some that I would/could use. I've nver used softboxes with that kind of power so I don't really know what camera settings would give me that exposure.
The tone mapping parameters still seem to be not quite right though. If I leave the shutter and F stop at default and change ISO from 100 to 200 the Exposure Value indicates a darker image and renders that way. However in the real world, doubling ISO while leaving everything else constant will give me a brighter image. So what am I missing?
@AndyGrimm "i could not figure out yet how mesh / lumen really work in iray"
I think a way to do it, provided you're trying to model something like a commercial light with a mesh, is to do the following:
1. create a primitive. If a plane use Z negative
2. Assing the Uber Iray shader
3. Set the Emission channel coloe other than black
4.Set the luminance units to your preference (I like watts so I can model a real light)
5. Set the luminous efficiency to match your real world light, e.g. 50-70 for a CFL)
6. Set the Luminance to the value of your light, e.g. 350 for one of the 7 bulb cfl studio lights.
I'm still experimenting, but I think this gives you a realistic light. I remind myself that the studio photography tutorials I have seen almost lasway have 5 to 7 different lights for a simple fashion shot.
Moral being that a scene need a lot more light than we think. I conclude that Iray models a camera more than a human eye.
I could just as well be full it, but this seems to be consistent with both my reading and my limited Iray experience.
@fastbike1
- i also just figured out a lot while working on candle simulation which interacts (other then a electric lamp) with the size and form of the flame....
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yes - mesh ligths are tricky without a tutorial - but we come now closer
and yes - if you know the luminous efficiency of your photolight - then watt is absolut ok
Many lights or not depends on your photo style - personaly i like dramatic portraits with ONE light.. and hard contrast - for fashion you need two softboxes, a keylight, and a backligh, and one more for the hairs.... and maybe a assistent with a reflector to bring some gold or silber shine on the skin ... well today with photoshop it is easier.. but still.. some simple looking shots need many ligths.
But many great famouse shoots are token with just the rooms interior light - or natural light coming from a large window. So it really depends - not everybody aims for the glossy magazin style
I think it is phantastic that we can do now all this simulated with a free Iray.
does work correctly in my tests... are you sure?
I discovered a major flaw in my last couple of renders...I'll explain after I post the image.
I have a small piece of the mesh as a separate material zone for the emitter. The rest of the flame is a translucent volume. But, the flaw was the direction of the normals of the emitter.
I was noticing odd shadows and such as played around with it more...then it dawned on me. I flipped the normals and the image above is 15 minutes worth of rendering! The old set up wasn't this clear in 3 hrs. And the shadows are now what I think are correct...and the light is more responsive/controllable.
yes - now the walls are to see
i really think you matched it downwards - the shadow, the brigther directligth circle- and the diffuse rest light on the table - looks like a candle to me - while on the wall the light is to even. .The distance to the wall looks like about 50cm to me? correct? then there should be direct ligth.. all my real world tests showed the fall-off to diffuse is about 1m away from the flame.
It's 1 m.
Here it is after an hour and a half.
PS:looks better with the dark theme
ok - then it is a realtively large candle - and my eye got tricked by the scale...
with 1m your example is exactly what i expect from a candle - the light goes diffuse about where the wall starts..
Yep...if I move it closer the light washes up the wall.
I found that as is, with out trying to cut back or anything that most 'candle' LED bulb IES profiles work 'best' for oil lamps/kerosene lamps and, I haven't tried any, yet, torches. Something that has a bigger/brighter flame.
Here's a lamp render....
great light - looking good...
I did not have much time for renders the last days - hope to continue tonigth and over the weekend.
I've been playing about with lights inside an enclosed building. The lights are emitters on the head and tail lights and I have got it this far, now I am trying to get some ambient light from an HDRI plugged into the Environment Map.
In an enclosed space, an HDR isn't going to do much of anything. It's lighting the OUTSIDE of your 'building'. You either need to remove a piece (wall/ceiling/etc) or add windows/doors/other openings.