Most times I render without GC in poser and do it later in photoshop. Is there a difference if I render with GC in poser or does it not make a difference?

It's a bit like having the exposure set wrong on a camera - (or white balance, or f-stop) - then correcting it in your image-processing software. Why not have it right in the first place?

But, to be honest, it's a lot more than just setting Gamma Correction to 2.2 or whatever. The adjustments one has to make to legacy (or even recent) Poser materials makes the whole exercise a lot more complex than it should be.

Short answer? You are probably going to find your renders are going to look like poo when you set renderer GC on (to 2.2). So, don't, unless you want to invest the time to clean up your shaders and fix your lights.

The information on how to do all that is carefully squirreled away on these threads. You can get reasonably good renders with gamma correction on. And you can get decent renders with it off - many of us have learned to compensate for software design shortcomings, so yes, it is possible. :blink:

GC refers to two translations that need to take place to give each element what it needs.  the render deals with linear math.  sRGB inputs, like images and colors picked on your screen, are gibberish to it.  the screen works in sRGB.  linear input is gibberish to it.  if you correct in Photoshop, you can only deal with what the screen gets, because the renderer has already received and processed gibberish (as understood by it). 

in terms of results, when you render without linearizing your input, our brights come out too bright and your darks are too dark. you've lost any information above white and below black. even within that spectrum, there are ranges that have become single colors.  in the calculations, you have as many levels of value as the accuracy of renderer allows, but in the render you have only 256 values from black to white in any one color. 

to be succinct, even if you linearized your input, you've lost information just by going to an image that isn't a raw format.  Photoshop can't return that information to your image.

KobaltKween says the truth. Using my camera metaphor, if you take an under-exposed photograph into your image-manipulation software, there's only so much you'll be able to correct: over-exposed or under-exposed, information will have been lost. So it is indeed worthwhile to linearise your colours before Poser does math on them.

Interestingly, the very fewest understand this: most will tell you gamma-correction has to do with the monitor. If so, why would Smith-Micro have introduced renderer GC?

Assuming you're using PP2010 with GC enabled:

• incoming colour maps are automatically linearised so they play nicely with the linear maths in the shader nodes
• when you save your render a gamma curve of 2.2 is applied because that's how digital images have to be encoded
• unless, that is, you save your render in HDR or EXR format: these are (I think) 32-bits per colour and remain linear (i.e. no gamma curves are applied)
• this means you have full control over gamma, and lots of other things, in Photoshop and if you use the 'Exposure' adjustment layer it is non-destructive

The best analogy I can think of is when using a digital camera: you have the no-brainer option of shooting to JPEG or the far more flexible option of shooting RAW images. 

Hmmm. Thanks for the in depth explinations:) I will do some renders with GC on and see the difference from a photoshop added GC on a non GC render.

Bear in mind that: 

"The gamma of sRGB is not exactly 2.2, but rather, is a grafting together of two different functions, that when viewed together, may be approximated by a simple 2.2 gamma curve."

I've no idea whether PP2010 uses the simple method or the 'correct' method for its built-in GC.

Simple method - this causes noticeable problems in very dark areas which appear too light.

How do you do gamma correction in Poser6?

Quote - Simple method - this causes noticeable problems in very dark areas which appear too light.

Which is better than having them be too dark, since you can fix that in photoshop. (I think by increasing low-end contrast.)

Quote - Assuming you're using PP2010 with GC enabled:

• incoming colour maps are automatically linearised so they play nicely with the linear maths in the shader nodes
• when you save your render a gamma curve of 2.2 is applied because that's how digital images have to be encoded
• unless, that is, you save your render in HDR or EXR format: these are (I think) 32-bits per colour and remain linear (i.e. no gamma curves are applied)
• this means you have full control over gamma, and lots of other things, in Photoshop and if you use the 'Exposure' adjustment layer it is non-destructive

The best analogy I can think of is when using a digital camera: you have the no-brainer option of shooting to JPEG or the far more flexible option of shooting RAW images. 

You will also find you need a lot less light than you needed before. This has a knock-on effect since anything which is self-illuminated becomes too bright.

I recommend trying a test render with all lights off. This will show you what has non-zero ambient, translucent, alternate diffuse, or alternate specular. You can either zero these (or disconnect them), or rework the shader tree. (I'm fond of multiplying the alternate specular or alternate diffuse input with a diffuse node, so that it only has that effect where there is light falling on the surface.)

Quote - How do you do gamma correction in Poser6?

Actually for all non-PoserPro versions, you can do gamma correction with a very simple node set, developed by Bagginsbill... just do a search user Bagginsbill and "gamma correction" for longer than 45 days ago, and you're bound to find it.

There is another (somewhat more complex) formula that will also linearise colour information (and correct it prior to rendering) but you would need Matmatic to sort-of invoke it.

Anti-gamma incoming material.

Add together diffuse and specular.

Gamma correct the result.

Anti-gamma is Pow with Value_2 = 1/gamma , i.e. usually .454545

Gamma is Pow with Value_2 = gamma, i.e. usually 2.2

Color_Math must be used.

There's a Wacro posted somewhere that sets this up for you on simple shaders. More complex ones could be automated but would be a lot of work.

Quote - Anti-gamma incoming material. Add together diffuse and specular.

Gamma correct the result.

Anti-gamma is Pow with Value_2 = 1/gamma , i.e. usually .454545

Gamma is Pow with Value_2 = gamma, i.e. usually 2.2

Color_Math must be used.

There's a Wacro posted somewhere that sets this up for you on simple shaders. More complex ones could be automated but would be a lot of work.

This discussion will point you there.

I noticed I reversed the instructions again. Anti-gamma is Pow 2.2, gamma is pow 1/2.2

2.2 is for Macs. PC monitors are usually "corrected" to 1.8 (I use the quotes because present day LCD/LED monitors are actually capable of linear response but, for comptibility reasons, warped to behave like analogic tubes).

I think that the best thing is to create a grey level ramp from pitch-black to pure-white and check that it appears to you uniform and that you can see it change uniformly.

Monitor setting have a profound effect: e.g. I have calibrated contrast and luminosity of  my Samsung 226BW LCD monitor the best I could with online tools and Vue tells me that my monitor gamma is roughly 2.0 (it should be more like 1.8).

for bad renders, exposure control in APS works better than gamma IMVHO.  but doing good render is better than having to fix it in APS.  mac and PC standard may now be 2.2, but is user-adjustable (in OS X, maybe in win 7).  back in the old days it was common to see poser 4 renders that were too dark to see the details, because the people were using it in a darkened room at 3 a.m.

Quote - 2.2 is for Macs. PC monitors are usually "corrected" to 1.8 (I use the quotes because present day LCD/LED monitors are actually capable of linear response but, for comptibility reasons, warped to behave like analogic tubes).

Exactly the other way around, PC 2.2, Mac 1.8 (at least it was).

On the topic: Often one uses Photoshop to do alpha-compositing on the rendered images. Alpha-compositing (with the alpha channel in e.g. PNG-output) is an inherently linear operation, so you normally would have to linearize the images anyway when getting them into Photoshop. So it is probably easier just to render without GC and do it once after the compositing. Unless Photoshop supports image operations of gamma corrected channels, but i do not have Photoshop to check, maybe it does nowadays, in any case it is always best to know what you are doing (and what photoshop is doing :-)

Quote - Exactly the other way around, PC 2.2, Mac 1.8 (at least it was).

Sorry, you are right; I did remember that they were different (just to make life easier) but I switched them. Anyway, your actual gamma depends on specific monitor settings so things are terribly variable.

People who are seriously in this stuff (e.g. professional photographers) use dedicated devices (photometers) to make objective measures and use the monitors in ambients with controlled lighting.

Recent mac's are 2.2, or whatever you decide to change it to via a monitor calibration.

No, yours is right. The link was to Bantha's wacro IIRC.

Why would one want conservation of energy?

Realism.

Erm, not to be nitpicking here, but this particular shader setup inverts the output of the blinn-node and stuffs it into the diffuse node, which means (putting all the gamma nodes and image asside) the calculated function is like:

Alternate_diffuse := diffuse (1, 0.8 * (1 - blinn)) + blinn
== 0.8 * diffuse - 0.8 * diffuse * blinn + blinn.

so, if your image map is pure white, it only takes a light intensity of around 2.25 from the shader-nodes to cancel the effect of the blinn and diffuse nodes and any light added thereafter makes the image darker. This is not what is commonly referred to as "energy preserving" :-)

I think in general you have to be suspicious if shader outputs are multiplied instead of being added. (Put one shader output into another is the same for that matter). Attached is a render of that shader with light intensity of 1000%

conservation of energy is the oft-ignored rule of optics: EMR in >= EMR out, unless posersurface is lite emitter.  in real life, EMR in is always > EMR out, excepting lite bulbs and that.

Quote - KobaltKween says the truth. Using my camera metaphor, if you take an under-exposed photograph into your image-manipulation software, there's only so much you'll be able to correct: over-exposed or under-exposed, information will have been lost.

That's a good metaphor but not compeltely accurate. While it's true an underexposed image can have major problems when it's being brought to the correct exposer, it never loses information if you're talking about DSLR images. It may look ugly but you'll always have the details there once it's brought up unlike an overexposed image. Once it's overexposed to white with blown highlights, you can never have those details back.

Quote - While it's true an underexposed image can have major problems when it's being brought to the correct exposer, it never loses information if you're talking about DSLR images

unless it clips solid black