First thing you need to understand is what convergence means. In a few words it means that the last iteration did stuff all to change the current image. To be honest, it is a horrific way to measure how well a render has gone.
I've read even your explanation several times, but still didn't fully understand what convergence is
Maybe you could rephrase it some other way?
EDIT: Okay, I think(?) I started to understand something about this word. If I set it to 95%, it would mean that if pixels in say iteration 999 and iteration 1000 are the same for 95%, rendering will stop. Something like that? And overall image quality might still be bad, but desired convergence is achieved. Eh?
But I got your point that it's a bad way to measure final image quality.
Learn what is required from lighting to get scene converge and live by those rules.
But
what is required? Atm I just understand it as "if the scene looks lit well enough for my eyes and adequately to the place, it's good to go". But even if it is not, instead of adding more light with for example ghost lights, I can just bump up exposure value, or F/stop, or ISO, or shutter speed, etc, in tone mapping tab. I don't quite understand the difference.
If you are rendering at final resolution, you need to get away with less than 1000 iterations.
Okay, so. Here's my example. I have indoors scene, daytime. I have HDRI lightning, I use Iray Indoor camera and sometimes regular daz camera for POVs, since Iray Indoor camera can't have focal length less than 60mm for some reason (the latter requires some tweaking with lights, removing ceiling and/or walls, and mentioned tone mapping). My tone mapping settings are: Exposure value 12.75, F/stop 8, shutter speed ~100, ISO 100, other sliders untouched, if I remember correctly. I also blindly added Nominal Luminance in Filtering tab, just because I read about it somewhere here, set it to 1000 or 10000 (also, I don't see any difference at all with it). Also I have 1-3 simple sphere ghost lights around the character. They have emission value about 4000 to 20000 depending on the scene. I render to final resoultion which is 1080p 16:9.
I read about rendering in 4k and than downsampling to 1080 to get same quality or better, faster, but I usually do batch rendering overnight, so I thought - why bother.
Since before your reply I rendered with convergence reaching method, 95% convergence was reached after 1500-4000 iterations. If you are saying that I should reach good quality in less than 1000 and I don't - what does it mean, what should I do? The obvious answer for me for now is: add more light! But that the scene would look overly exposed. Do I need to add more light into the scene and then reduce stuff such as Exposure value etc? And it should lead to faster... c-converging... better converging? I really still don't understand the meaning of that word.
- add more light that shines directly into the grainy areas (use a dark blue color in your light to illuminate "shadow" areas if you need that effect)
I actually do that, again with ghost lights, but I thought that's, like, unprofessional? Because since it's a game where you click through the images, and if in 50 images in the same room the lightning changes 10 times - it's kinda strage if not annoying.
Sorry for a wall of text and thank you guys for already quite detailed answers!
