Mental Ray Exposure Modifier

[Crazy Homeless Guy]

Does this work for Mental Ray wishes also. How about making the camera exposure part of the modifier stack, that can be applied to a camera. This way I don't have to change the exposure when I am changing views.

[Justin Hunt]

I like this one, would be very handy

 

jhv

[Crazy Homeless Guy]

Do you know where I can find Zap's scripts? I have searched for them, but can't seem to locate them.

[Dave Buckley]

i am not familiar with the vray physical cam but zap's script was basially a mental ray version, in fact i actually think it was called mr physical camera.

 

when you say so that you don't have to change exposure when you change views??? why would you need to change exposure when you switch to another view anyway???

 

surely another view would just be a different camera angle of the same scene, in which case, if it is the same scene then the lighting solution remains the same and therfore if the exposure is correct in one view it would be the same at all angles providing the lighting solution doesn't change (and also providing you are not meaning change from interior view to exterior view)???

 

or

 

do you mean setting one cam on the interior and one on the exterior and then applying interior exposure settings to the interior cam and vice versa with the exterior cam??? if thats what you mean then yes that would be very useful because then we could use one switch from an exterior to an interior in the viewport without having to dial in new exposure parameters to compensate for the change in lighting scenario (interior and exterior being the lighting scenarios)

 

sorry if that was a bit long winded

[Crazy Homeless Guy]

i am not familiar with the vray physical cam but zap's script was basially a mental ray version, in fact i actually think it was called mr physical camera.

 

when you say so that you don't have to change exposure when you change views??? why would you need to change exposure when you switch to another view anyway???

 

surely another view would just be a different camera angle of the same scene, in which case, if it is the same scene then the lighting solution remains the same and therfore if the exposure is correct in one view it would be the same at all angles providing the lighting solution doesn't change (and also providing you are not meaning change from interior view to exterior view)???

 

or

 

do you mean setting one cam on the interior and one on the exterior and then applying interior exposure settings to the interior cam and vice versa with the exterior cam??? if thats what you mean then yes that would be very useful because then we could use one switch from an exterior to an interior in the viewport without having to dial in new exposure parameters to compensate for the change in lighting scenario (interior and exterior being the lighting scenarios)

 

sorry if that was a bit long winded

 

Both. If I am facing the building with the sun behind me for one camera, and the next camera I am on the other side of the building facing the sun, more than likely I will need to key in different exposure settings. Or, it I move to a view that is entirely in shadow, I will probably need to key in different exposure settings for the camera.

 

If I am doing an interior scene with multiple views, maybe a few different rooms in the same model, etc... There is a good chance that I will need different exposure settings. Maybe one room is getting light from the outside, maybe one isn't. They will need to be exposed differently.

 

I can do all this with scene states and such, but in reality that is extra steps where things can get screwed up. If they are attached to the camera, and change automatically when I switch to a different camera, there is less coordination needed on my part, and therefore less of a chance I will come in a morning before a deadline only to find out that I forgot to switch something when sending a different camera to render.

 

There is the BO physical camera script from the German Mental Ray forum. It is more robust than the standard Mental Ray exposure, or at least it ties several features of the Mental Ray exposure into one roll out in an effort to make it easy to work with, but this also creates a condition where I need to switch more than just my camera when switching views.

[Crazy Homeless Guy]

Hey Travis,

 

In such scenario I am not to sure I would give the extra

time to setting up multiple exposures in Max??

using Floating point and tweaking exposure after the fact

in Combustion (or such) seems a quicker/more flexible

approach to such a multi cam set up!

 

Regards

Bri

 

I am trying to get away from using floating point due to the bloated file size. Yes, I can always convert everything to a different format after I have it where I want, but again, that is additional steps.

 

But anyway... Can you really correct a floating point to that degree in Combustion?

 

I have used PhotoShop in the past with floating point files, but decided that the degree to which they were adjustable was dissapointing, and not worth the extra steps. Especially since the DMVC where I learned Lon's camera raw trick, which I do not think works with either EXR's or HDR's.

 

I have Combustion 4 sitting on my shelf, but have not worked it in to my production work flow yet.

[Dave Buckley]

bloody hell, just when i thought i'd mastered exposure etc, you now throw something new into the mixer for me to think about haha.

 

back to the drawing board eh?

 

if i setup an interior camera and sunlight is coming through the window, i set my exposure etc and render, voila.

 

if i then change the time on the daylight system so that the sun is facing away from the window, or if i just rotate the compass 180 degrees, i will then need to change my exposure. i was under the impression that my exposure would be fine left alone, yes the render would be darker than the original render with light coming through the window but wouldn't that be how it appears in real life anyway???? if i adjust the exposure for the room with no direct sunlight then surely that would just be to brighten the room which would then be unrealistic according to the real world???

 

if that is the case then do you change the exposure for visual beauty/physical correctness or photographic correctness???

 

i am confused

[SandmanNinja]

...Especially since the DMVC where I learned Lon's camera raw trick, which I do not think works with either EXR's or HDR's...

 

Can you describe this process? It sounds interesting.

 

I haven't compared a 32-bit render to a 8/16-bit file size, but I'm guessing it's 2 or 4 times the size (that extra info has to go somewhere).

 

HD storage is cheap - just curious why the filesize is an issue.

 

I'm very comfortable with photoshop and am always on the lookout to learn something new (especially from someone experienced), thus my questions.

 

After I was exposed (forgive the pun.. hehe) to 32-bit frame buffer and Image -> Adjust -> Exposure in Photoshop, I'm a huge fan of it. While maybe not perfect, it's certainly acceptable (to me, anyway). The ability to take a completely overexposed and blown out render, move a slider, and it looks pretty darn good... is remarkable.

[Crazy Homeless Guy]

 

if that is the case then do you change the exposure for visual beauty/physical correctness or photographic correctness???

 

i would change it to what looks right to you. i would say that you are trying to simulate nice photography. if you are unexperienced, you leave the camera in auto mode, and as you pan around, the camera automatically adjusts the exposure based on how much light is coming into the lens. if you are experienced, then you have a decent idea of the exposure settings you need, but you would adjust them per view.

 

....i am not sure that you can for physical correctness since our eye adjusts depending on the condition also. it makes it hard to say what is physically correct.

 

i would say that beauty and photographic correctness should be paired together.

 

 

Can you describe this process? It sounds interesting.

 

In PhotoShop... File... Open As... select Camera Raw, and then locate your TIF file. It gives you a lot of the settings that Adobe Aperture has. Pretty sweet.

 

Yes, hard drive space is cheap. We have about 200 people in our office, the majority on Revit, and several people rendering. Hard Drive space seems to go really fast, and I often have a couple of gigs of undeleted EXR's on the server, so I was trying to move away from them.

[Dave Buckley]

yep i'm with you now, i guess i've been doing that anyway, i've never really setup multiple cameras in one scene (camera in each room)

 

i usually just setup my light and position it where i want, and then adjust my exposure until the light levels look right.

 

i guess this is what you are doing just in the same scene.

 

i have one more question (well probably more than one - but we'll get to them later )

 

i have been using my digital camera to help me when it comes to exposure, it has a lot of built in presets for different scenarios, eg, moving water, sports, day, night, portrait, fireworks etc.

 

i was switching between the different presets to help me get exposure right, but when i check the settings on each one, the f-stop seems to be set at 2.8 regardless of which setting i choose, it only seems to be the ISO and shutter speed changing for each preset??

 

surely the f-stop will change aswell?????

 

but then again i have heard that i can leave the shutter and ISO at the same value and then just alter the f-stop????

 

and then i've heard i can adjust all three??

 

once again i'm confused

 

with regards to my digital camera, the setting of f2.8 means my aperture is open quite wide therefore letting a lot of light in. but i also read that the lower the f-stop number then the blurrier the image will be, unless compensated for with the other values?

[Crazy Homeless Guy]

I will allow someone with more knowledge than myself answer the actual camera questions. I know there are several enthusiasts on this board.

[Dave Buckley]

so was i right with the first part of that post then??

 

about me adjusting my exposure the way you do, just that i do it subconsicously??

[Crazy Homeless Guy]

so was i right with the first part of that post then??

 

about me adjusting my exposure the way you do, just that i do it subconsicously??

 

yes.

 

i have had one model where i shot somewhere in the neighborhood of 70 exterior images. usually it is only a a handful of shots, but there has been more.

[Dave Buckley]

cool so all my hard research hasn't gone to waste haha how do we move this thread to a different topic (as its now more of a mental ray thread rather than wishlist) i think this could become quite a useful thread if we keep it up.

 

i'm going to make a few quick tests tomorrow using the dwayne ellis bathroom scene, i'm going leave the exposure settings i have at the minute, and then adjust time of day and rotate compass etc to see how the final renders look, i've never really tested it i guess.

 

when you say you change the xposure controls for different views, would it be things like altering burn amounts for scenes where light hits walls and then where it doesn't etc, or are you talking about actual aperture, shutter and iso?? or are you talking about all of them as a whole???

[Dave Buckley]

maybe this is what you were after homeless_guy

[SandmanNinja]

i was switching between the different presets to help me get exposure right, but when i check the settings on each one, the f-stop seems to be set at 2.8 regardless of which setting i choose, it only seems to be the ISO and shutter speed changing for each preset??

 

surely the f-stop will change aswell?????

 

but then again i have heard that i can leave the shutter and ISO at the same value and then just alter the f-stop????

 

and then i've heard i can adjust all three??

 

once again i'm confused

 

with regards to my digital camera, the setting of f2.8 means my aperture is open quite wide therefore letting a lot of light in. but i also read that the lower the f-stop number then the blurrier the image will be, unless compensated for with the other values?

 

Finally something I know about!!

 

The lower the f/stop the more light is let in, and the DEPTH OF FIELD is shorter. So, if you are shooting a photo of something that is very deep, or many of them, then some will be out of focus.

 

The lenses on ..er.. less-than-higher-end digital cameras aren't the best in the world optics wise, and the electronics aren't that smart either.

So if they make one variable ..er.. constant (i.e. keep the f/stop the same), then it'll help the camera figure out how to properly expose the scene.

 

Also, the majority of 'fun pics' are taken in dark settings - night time fire works, pubs, clubs, etc - so it helps to have the f/stop cranked as open as you can.

 

In the real world, the iris valve (f/stop) will open and close a whole lot. In the scene described above, the aperature would have been fairly open, but when he turned around it would have cranked closed a lot to stop most of the (excess) light from getting through.

 

In a film camera, you'd never vary the ISO - it's set by the film manufacturer! Rule of thumb:

ISO 64 = outdoor

ISO 100 = outdoor

ISO 200 = indoor/outdoor

ISO 400 = indoor

ISO 1600 = indoor, in a dark closet, taking a photo of an ice cube with the lights turned off

 

Generally, I'd leave ISO alone (use the guide above), the shutter on 1/30 or 1/60 (1/30 is the de facto slowest you can go without a tripod or flash) and play with the f/stop. When you run "out" of f/stop, play with the shutter speed.

 

Hope that helps.

[Dave Buckley]

thanks for that, so as far as using exposure in 3d, can i follow the same rules?????

[SandmanNinja]

With Mental Ray and mrPhotographic settings, these are all valid guidelines.

 

With Mental Ray, since it's just "math" following a "forumula", you can punch in an ISO of 32 or 16 - it doesn't really exist in the real world, but it will have the same effect mathematically.

 

[Crazy Homeless Guy]

maybe this is what you were after homeless_guy

 

This is perfect.... Well almost perfect. It would be nice if it had White Balance on the roll out also.

[Dave Buckley]

glad i could be of assistance

 

only problem is i don't know how to use it.

 

does this mean that you don't need to use the mrphotographicexposure anymore, can we leave that deactivated and just adjust the exposure per camera???

 

and due to the fact there is no white balance control on the cam, then how would you get around that? PS maybe??

[Crazy Homeless Guy]

actually, i only had a chance to install it. my initial reaction was that it was the solution to the problem, but on closer inspection, it actually is not. i read Zap's blog post about it, and he clearly outlined that he created the script because this is where he felt the information needed to be rather than the environment roll out. he also made it clear that the script he created simply called the ones in the environment, and was in no way a solution, but more of a concept.

 

here is the basics of how his the script works...

 

you go to the camera create panel as you normally would. if you have the script installed, there will be an option to create a mr camera. you create that, and the camera controls are then part of the modifier tab. you can adjust the shutter speed, f-stop, ISO and a couple of other things.

 

the shutter speed, f-stop, and ISO in the modifier panel are scripted to change the information in the environment roll out. when you change the number here, it changes the number in the mr photographic exposure settings in the environment roll out. so yes, you need that enabled.

 

i was wrong in saying you could not control the white balance. since you still use the mr photographic exposure enabled, the white balance is still in place.

 

where this script fails for me... it is not on a per camera basis. i was hoping that the camera settings were attached tot he camera. if it was on a per camera basis, then when you switched cameras, the f-stop, shutter speed, ISO would all change to the settings needed for that camera.

 

to me this script suggests that a per camera might be possible if i had a little knowledge in the scripting department. which i do not.

[Dave Buckley]

ah sorry, was worth a shot anyway, my bad for not reading (or understanding) the blog post in the first place

[Crazy Homeless Guy]

well i don't consider wasted time by any means. to me it appears that there might be a way to pull this off through scripting. i may be easier to use the 'basis optmize exposure photographic' shader by Thorsten Hartman to achieve it though. i really need to learn Max scripting.

[Camby1298]

well i don't consider wasted time by any means. to me it appears that there might be a way to pull this off through scripting. i may be easier to use the 'basis optmize exposure photographic' shader by Thorsten Hartman to achieve it though. i really need to learn Max scripting.

 

 

Its not Max scripting in this case that you need to know. Its how to develop mr shaders for this specific instance. There are many tutorials on the web on how to develop shaders; I'll have a look into it as well.

[Crazy Homeless Guy]

Its not Max scripting in this case that you need to know. Its how to develop mr shaders for this specific instance. There are many tutorials on the web on how to develop shaders; I'll have a look into it as well.

 

Possibly, it would certainly give you more options. That is how the BO script is set up, but Zap clearly states that he called the existing MR Photgraphic controls via scripting, not by developing a new shader. It is a '.ms' file, and not a '.mi' file.

 

http://mentalraytips.blogspot.com/2007/10/max-2008-physical-camera-with-dof-and.html