Linear Workflow in Photoshop Pros and Cons

[NeonMojo]

Are there any advantages with doing Photoshop work in linear space?

 

Currently we are rendering out of max in linear space and converting to gamma corrected space before we do any compositing of people, cars or trees since all our people, cars and trees are already in gamma corrected space.

 

i just wanted to see if anyone has any thoughts on the pros and cons of working in linear or gamma corrected space in Photoshop...

 

Thanks

[STRAT]

what are these 'linear space' and 'gamma corrected space' terms?

[pg1]

Linear and gamma space is to do with how you monitor displays the information from you computer.

 

Monitors apply a gamma curve to the bits and bytes that are the actual image in your computer before they display it.

They do this to all images even though most people dont know it.

 

There is a very long and discussion running on chaosgroup.com about LWF (linear work flow)

 

Neonmojo

 

Normally we render out to an .exr file format allowing using to correct the gamma in real time in photoshop

Best of both worlds

[STRAT]

eh?

[pg1]

It is very important and a bit of a head wrecker to understand but really improved my vray renders.

 

if you go to chaosgroup and go to tips and tutorials there are several threads about this topic (the best is probably on throb.net)

 

This is a reply in one of the many conversations on chaosgroup about linear workflow.

Since there seem to be lots of confusion about the whole linear workflow and gamma settings things, here is a more complete description.

 

The source of the problem is that computer displays (CRT and recently LCD monitors) do not display colors in a linear fashion. That means that if you input a color like medium grey (RGB 128, 128, 128), when displayed on the screen it will *not* be twice as dark as pure white (RGB 255, 255, 255).

 

The result is that the renderings that you see on your monitor do not correspond to the actual colors in your images. To compensate for this effect, the images must be color-corrected so that you see the actual colors.

 

Since each monitor alters colors differently, there must be a way to calibrate different monitors to a common standard so that you can be sure that when you view your images on another monitor, they will look the same. This standard is known as 2.2 Gamma or sRGB color space. It was chosen because CRT monitors on average apply a 2.2-gamma transformation on the input colors. Therefore, correcting for 2.2 gamma requires only a little change in the displayed colors to fit them into the 2.2 curve.

 

Note that for LCD monitors, things are somewhat different. The LCD output is a lot closer to linear. That means that calibrating an LCD monitor for 2.2 gamma output requires very large modification to the displayed colors. When combined with the fact that some LCD monitors still have less than 24-bit color resolution, it means that lots of color resolution is lost during this transformation. Therefore, it is often better to calibrate an LCD monitor to display linear colors, instead of trying to fit it into the 2.2 gamma framework.

 

Here is the thread

 

http://www.chaosgroup.com/forum/phpBB2/viewtopic.php?t=15303

[STRAT]

hmmmm. i'm certainly aware of monitor calibration, but in all my career this has never been an issue for me personally.

 

i'll always plump for a crt over a tft any day of the week anyway due to their superior colour displays and contrasts, but i've never gone in for all this calibration stuff. i usually turn my monitor brightness and contrast all the way up and work this way.

 

my rendering and photoshop output has always printed out as perfectly and predictably as i want it. i've never been dogged by indifferent colour values and calibrations from any of my kit. what i see on my screen is basically what the client recieves. it's never been an issue.

 

some peeps obviously see it differently.

[pg1]

Its not just colour calibration of your monitor.

 

A lot of people on chaosgroup had the same response you just gave and if your happy with your renders then I would stick with that method but if you look at renders by say Zuliban, and ask how in gods name did he get the lighting so subtle and real looking then LWF is a good start to getting the same result.

 

I am a vray user (ask cpnichols about lwf he can probably explain it much better) and with LWF I get better results faster.

No more really dark contrasted shadows

correct colour bleed in gi.

Interior renders, a million times easier to get light in and bounce around a room.

no more having to tweak the colour mapping panel in vray and realistic light falloff.

 

The best example I can think of is if you turn down the brightness and contrast on you monitor to really dark and tried to render you would add more and more lights in 3dsmax to get real result, this would mean longer rendertime (more light bouncing around) and a lot of tweaking to stop colours becoming blown out and to balance the contrast.

 

Now of course you wouldn't make you monitor real dark.

Well thats actually what is happening because you monitor applies a curve that darkens the image compared the actual render that was calculated by vray.

 

Actually all images have to deal with this not just renders,digital cameras video etc.

 

Its very easy to setup in max and very difficult to get your head around whats actually going on.

 

Like I said if your happy with your renders stick with that but have a look in LWF in your spare time.

[STRAT]

i'll certainly look at LWF, but i severely doubt it'll change my imagery or the percieved realism of my work. these things you talk about with interior gi light bouncing and colour bleeding, i've never suffered a lack of ease with this aspect.

 

even though i use cinema and not vray, and they're still governed by similar constraints, perhaps one acts differently than the next.

 

Zuliban's work has always been great, but i never wonder in awe how he gets lighting like that. i'm quite happy matching it.

 

as i say, my screen rendering is identicle to the printed output, as long as i have my home monitor and works monitor set up the same i'm safe.

 

but, i'll certainly look into it.

[pg1]

www.gijsdezwart.nl is a good place to start

 

Happy hunting

[STRAT]

cheers

[pg1]

you have to click on the tutorials page for those who dont speak dutch

[STRAT]

yup, i soon discovered that

[eksg]

hmmmm. i'm certainly aware of monitor calibration, but in all my career this has never been an issue for me personally.

 

 

ehem.....where were you when i was asking how to calibrate my printer to my monitor?

[NeonMojo]

We are about to switch to a linear workflow in max and vray in order to provide more natural lighting. I have read all the posts on this and I understand all the benefits you gain when working in max/vray, but my main question was about staying in a linear space in photoshop. We decided to start out by keeping all our photoshop work (except texture creation) in gamma corrected space since our printers are calibrated for that and all our compositing entourage of cars, people, and plants are all in gamma corrected space and we would have to convert them to linear in order to have a completely linear workflow all the way through the process...

 

So are there any major advantages of doing our photoshop work in linear? or should we just convert our renderings to gamma corrected space (sRGB) and then do all our compositing??

[moshenko]

So are there any major advantages of doing our photoshop work in linear? or should we just convert our renderings to gamma corrected space (sRGB) and then do all our compositing??

 

I think it's not so much "are there any major advanatages?" but rather "is it even possible?" Currently, Photoshop does not support most common operations when working in 32-bit. There is no filter support, no adjustment layer support, only the ability to adjust exposure and gamma, then convert to another bit depth. When using 16-bit colour there are some filter and layer options available but not everything that you are used to with 8-bit. So really, the only advantage is in being able to adjust/expose the initial 32-bit rendered image, if that's the course you pursue. Whether or not you see that as an advantage is something you'll have to experiment with and find out.

[richmondlu]

I have an Apple IIE is there a way I can make my monitor not look so green?

every thing i do on there is green even Oregon Trail?

 

Just kidding just remembering the simple days.

[Crazy Homeless Guy]

I think it's not so much "are there any major advanatages?" but rather "is it even possible?" Currently, Photoshop does not support most common operations when working in 32-bit. There is no filter support, no adjustment layer support, only the ability to adjust exposure and gamma, then convert to another bit depth. When using 16-bit colour there are some filter and layer options available but not everything that you are used to with 8-bit. So really, the only advantage is in being able to adjust/expose the initial 32-bit rendered image, if that's the course you pursue. Whether or not you see that as an advantage is something you'll have to experiment with and find out.

 

agreed. the lack of support for 32 bit in Photoshop is annoying.

 

linear color space is good for controlling color bleed caused by pumping the lighting up to much to light a space that is not in correct color space.

 

your render times will also decrease when you are working in linear color space. since you will not need to create as much light to light a scene, it will take the computer less time to process the light that is being bounced.

 

fortunately, Vray 1.5 makes working in corrected space a lot easier than it was in 1.47, but it is still good to grasp the basic concept of what is happening.

[Sawyer]

I save to HDRI and then resave as a tiff at 8 bit.

[NeonMojo]

I also agree about the lack of 32 bit support in photoshop but you can still work in a linear color space working with only 8 or 16 bits per channel. The bit depth does not effect how colors are mapped in a color space, only how much information you store for each pixel.

 

That said, I have heard about some blending modes and filters such as unsharp mask that work better (introduce less artifacts based on color space arithmetic errors) in linear space then a gamma corrected space... but other then that is there any other benefit to keeping photoshop in linear space?

[IC]

I've just read this post.

If any LightWave users are wondering about this, you can add the Full Precision Gamma (2.2) filter in Effects/Processing/Image Filter.

[sterealkey]

My God this sounds interesting!

 

I'd better check it out.