The Dimensions of Colour - a colour theory discussion thread - Page 11
 
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  1. #301
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    Quote Originally Posted by Ixyra View Post
    Good question! I don't fully understand the answer to this either, but from what I've learned this is what information I can pass on:
    The sun is just pure energy, which emits a perfect spectrum. The atmosphere (bunches of particles) prevents a lot of that spectrum from coming through. The color from light we see are also particles that are being emitted/rejected, and not absorbed, from the atmosphere (Hence being able to "pass through"). For some reason that I can't remember but is related to particle emissions, the closer the sun gets to the horizon, the more it allows the red light to bounce off particles for us to see. It's the exact same reason to why we see the white/cyan at the horizon, but the exact science behind it I can't recall. I may be able to find my notes somewhere and post what I've found at some point! I just know it deals with particle scattering.
    hey, thanks for the respond, let me know if you found the reason, i will do so as well!

    is it possible that one color still be the same under 2 different light sources? it should from my standpoint, if both colors matches the maximum color of the material, lets say we've got this dark gray R:100 G:100 B:100, and 2 light-sources that got much more color, an orange light R:255 G:155 B:100 and a cyan R:100 G:155 B:255. but it seems to be so wrong, and its hard to test this in reality cause of little speculars involved on almost every material.

    €: okey, my RGB calclations like "a material reflect what it gets" does not work out somehow, ugh, ... :/

    Quote Originally Posted by briggsy@ashtons View Post
    Hi Idiot Apathy! Time for some more briggsy colour fun!



    Careful there, intensity and saturation are not synonyms. The guideline seems to be: going from the half light to the full light, the saturation stays exactly the SAME, which means of course that the intensity or chroma always becomes GREATER.

    Got a headache yet?

    Actually, while terminology can make things confusing, the concepts themselves are really simple, and MUCH easier to put into practice in Photoshop than in oil paint. I'll try to explain what I said a bit more fully.

    Imagine you have a white light shining onto a bright red jaffa, whose centre light you decide to paint using a nearly maximum-intensity red, say R 240 G 000 B 000. What colours would lie on a shading series down from that red, i.e. would look like the same colour turning into less light?

    Well, the colour of the light bouncing (diffusely) off the jaffa is the product of the local colour of the jaffa and the colour balance of the light source. As long as we are turning under the same (white) light source neither of these factors change, so all the colours in the series will have the same balance of wavelengths, and will differ only in brightness or amount of light. We control the balance of wavelengths by the ratio of R to G to B, so all the colours should have the same ratio, in this case 1 to 0 to 0.
    So all of the following colours would lie on the series:
    R 240 G 000 B 000
    R 230 G 000 B 000
    ...
    R 100 G 000 B 000
    and so on

    Can you see now that if we wanted a brighter colour on the same series then R 255 G 000 B 000 actually is the limit, because there just isn't any colour brighter than R 255 G 000 B 000 with R/G/B equal to 1/0/0?

    In Photoshop, all of the colours in this series have the same hue (H = 0) and the SAME saturation (S = 100%). Think of saturation as PURITY of colour of light. All of the colours in this series have the same purity - they are all made by just the red phophors glowing - but they differ in brightness and therefore in chroma (intensity). Think of brightness as the AMOUNT of coloured light and of chroma as the STRENGTH of colour.

    R255 G 000 B000 has the maximum chroma of any red in RGB space.
    Maximum Saturation (PURITY) x Maximum Brightness (AMOUNT) = Maximum Chroma (STRENGTH).

    By the way, if the ball is a desaturated red, say R250 G100 B100 in the full light, the story is still the same. We could make a shading series for this ball using all the colours in which R/G/B were equal to 5/2/2:
    R 250 G 100 B 100
    R 200 G 080 B 080
    R 150 G 060 B 060
    etc.
    Again, in Photoshop all these colours have the same hue (0) and the same saturation (60%). As I said in my first post, shading series in Photoshop seem to fall along lines of uniform saturation. The brightest possible colour with this hue and saturation (i.e. with R/G/B = 5/2/2) is R255 G102 B102.

    I know that many authors use the terms saturation and intensity interchangeably as you apparently did, but hopefully you can see that this masks an important logical distinction.

    Idiot Apathy, you would do me a huge favour if you could let me know the sources where you got the idea that the full-light should be less saturated than the half-light. I am aware of the passages in Loomis' "Creative Illustration" to that effect, but if there are others please let me know the references, or even better, post some quotes or page scans. I've decided to try to write up some of this stuff as a tutorial and it would be great to be able to refer to them (in the section on "colour myths", that is ).
    such detailed explanation would be awesome for colored light in R G B values!

    Last edited by Mister Janchichan; December 31st, 2013 at 01:42 PM.
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  3. #302
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    So just looked through the thread and it looks like most my questions have been answered. so thanks!

    Mister Janichan: actually i think there is an explanation on this very forum, have a look for LINRAN color tutorial he goes into how to work out the correct values, hue etc using just the rgb slider.

    Im really gutted about the whole band of saturation before the terminator not being the case, are there any specific circumstances when this would happen? (apart from the large light source)

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  4. #303
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    Quote Originally Posted by Siphonophores View Post
    So just looked through the thread and it looks like most my questions have been answered. so thanks!

    Mister Janichan: actually i think there is an explanation on this very forum, have a look for LINRAN color tutorial he goes into how to work out the correct values, hue etc using just the rgb slider.

    Im really gutted about the whole band of saturation before the terminator not being the case, are there any specific circumstances when this would happen? (apart from the large light source)
    whoa, i didnt knew about it, thanks a lot! i just recently started to use RGB sliders, awesome!

    still like to know if its possible that one object looks the same under 2 light-sources.

    @siphonophores: somehow i dont get what you are trying to ask, what do you mean?

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  5. #304
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    MJ: no problem the question was pretty vague. Basically there seems to be two schools of thought when it comes to shading.

    1.) principle of uniform saturation

    and

    2.) highest contrast at the terminator.


    However to my knowledge the first option is actually the realistic 1, while the second confuddles the specular and diffuse highlights. I just was hoping there might be a case where this whole band of saturation existed in reality, although i havent seen it as of yet.

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  6. #305
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    Quote Originally Posted by Siphonophores View Post
    MJ: no problem the question was pretty vague. Basically there seems to be two schools of thought when it comes to shading.

    1.) principle of uniform saturation

    and

    2.) highest contrast at the terminator.


    However to my knowledge the first option is actually the realistic 1, while the second confuddles the specular and diffuse highlights. I just was hoping there might be a case where this whole band of saturation existed in reality, although i havent seen it as of yet.
    i know that this has been discussed here a while ago, have a look at idiot apathys thread, there are great lessons with simple scenes with spheres:

    http://www.conceptart.org/forums/showthread.php?t=53517

    also have a look at this thread, this has been discussed a few times.

    but i tried to illustrate an example of one situation with speculars involved where this band of saturation occures, hope ill get corrected if someones knows better:

    Attachment 1884212
    Attachment 1884214

    so, this is how i create such situation, on the red sphere, where its lightest (on the upper edges) its more desaturated because of the specular from the white surrounding. the intensity of the specular decreases as the angle changes, so its weaker where your eyes are straight on (shall be around 0-10%). so where the specular is weaker you see more of the balls local color, hence more saturation in this case.

    the local color is a very pure red, so the color wont be much affected by the reflecting blue light of the pillow.

    because of that i created the orange ball, which contains more blue and green in its local color, so it will be affected by the pillows reflected light. now you've got the following:

    low saturatuion on the upper edges, higher saturation in the half-tone and lower saturation in the shadow

    my thoughts on this: break it down into steps - first local color, shadow and light, then add speculars, think about surrounding light that bounces into you spheres shadow that could change your color/saturation in the shadows.

    if i misunderstood someting and told you stuff you already know - i am sorry, but probably it helps!

    but i would like to here someones thought on this!


    ---------------------------------------------------------------

    i got something here:

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    it looks really plain, but i guess that it would look plain if it is lit 360° equally. i just lit the edges a bit cause of specular light from the surrounding.

    is this something a white tower looks like on the shadow-site? i just took the blue from the sky and painted the tower with it...from my understanding -> if white gets lit by blue light it reflects blue..so in photos the shadows are always very greyed out and darker, but i dont trust the camera, a darker/grey would result from cloudy skies and/or 2nd-light reflect into the shadow.

    Last edited by Mister Janchichan; January 2nd, 2014 at 10:57 AM.
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  7. #306
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    somehow my attachments in the post above are broken:

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    Name:  2.jpg
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  8. #307
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    MJ: I think those spheres are nice u r really making progress in this area. however I think you are having trouble with specular reflections. basically specular reflections are mirror reflections of the surrounding environment (the clarity of this reflection depends on many factors. the material is a big factor). The white dot u see usually on spheres is the light source (i.e the sun or a lamp etc) However i think i understood fro your answer why there is this band of saturation. (the specular reflection interacting with the lambertian/diffuse ref)

    thanks!

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  9. #308
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    Quote Originally Posted by Siphonophores View Post
    MJ: I think those spheres are nice u r really making progress in this area. however I think you are having trouble with specular reflections. basically specular reflections are mirror reflections of the surrounding environment (the clarity of this reflection depends on many factors. the material is a big factor). The white dot u see usually on spheres is the light source (i.e the sun or a lamp etc) However i think i understood fro your answer why there is this band of saturation. (the specular reflection interacting with the lambertian/diffuse ref)

    thanks!
    what exactly is wrong with my speculars? please explain! if the white dot appears depends on the level of glossiness of the material, see this:

    http://udn.epicgames.com/Three/rsrc/...y_specular.jpg

    so i wanted to paint my spheres with very low specular-power,see the white desaturation on the edges which is weaker in the middle of the ball

    i found a quote from david in another thread that explains exactly what i've done:

    Quote Originally Posted by briggsy@ashtons View Post
    Kitsu

    Great work on the notes and movie. Maybe the lit area on the sphere in the movie should be more crescent-shaped (like a new moon) when the sphere is approaching the backlit phase? The lit shape looks a little too straight-edged in those positions to me, and seems to completely disappear in the fully backlit position. Love it nonetheless.

    I'll quote below some of my own notes on specular and diffuse reflection in case they're helpful to anyone, although you and Chris have already covered many of the points:

    The Dimensions of Colour - a colour theory discussion thread

    "We see the red ball by virtue of light reflected from it. Like most surfaces, the ball reflects light in two different ways, called diffuse and specular. The shiny highlight is the most obvious specular reflection; the red light coming from the rest of the ball is the diffuse reflection.

    In specular reflection, light bounces off the surface like a super-elastic ball, obeying the law of angle of incidence = angle of reflection. In diffuse reflection, light penetrates the surface, and emerges equally in all directions.

    The highlight is a specular reflection of the light source. It is seen wherever the surface is at just the angle needed for the angle of incidence from the light source to equal the angle of reflection to the observer. Its position therefore moves as the observer moves. The position of the diffuse reflection does not depend on the position of the observer: it is always brightest facing the light source, and diminishes as the surface turns away from the light source, receiving and therefore reflecting less light per square centimetre. The diffuse reflection thus creates the modelling that we use in drawing and painting to describe form.

    A polished surface creates a crisp highlight that is an image of the light source. Because of their slightly different locations, the eyes of the observer each see this image at a slightly different point, and the brain traces these two images back to an apparent position below the surface of the ball (just as the image in a mirror appears to be behind the mirror).

    Close inspection of a polished object will also reveal specular reflection of the entire surroundings, not just of the light source. This specular reflection of the surroundings tends to be strongest on the receding planes around the edges of the object. This is because the specular reflections in these regions are created by light from the far side of the object hitting the surface at a low angle, and when light hits a surface at a low angle, a relatively high proportion of it is reflected in a specular manner. Specular reflection of the surroundings usually tends to dull the apparent colour of an object, and so this dulling effect tends on average to be greatest on the receding planes.

    If surface is textured (like an orange), the highlight is "fuzzy", as tiny points that are at the angle needed to reflect light to the observer are spread over a broad area.

    Occasionally one encounters the mistaken idea that smooth surfaces reflect light in a specular way, and rough surfaces in a diffuse way. As I said at the start, most substances reflect light in both ways simultaneously, by quite different processes. No matter how highly polished most substances get, they will still reflect in a specular way only a relatively small percentage of the light hitting them. Metallic substances, on the other hand, characteristically reflect a very high proportion of light in a specular way (close to 100% in the extreme case of a mirror).

    Finally, the diffuse reflection is commonly changed in colour by the object (in the case of the ball, becoming red), but in specular reflection from most substances the light retains the colour of light source. The main exceptions to the latter rule are the coloured metals such as gold and copper, which do change the colour of light reflected specularly from them."


    by the way, have a look @skin-tones, usually you will find this band of saturation in the half-tones as well, for the same reasons as explained OR because of subsurface-scattering of the blutvessels

    Last edited by Mister Janchichan; January 2nd, 2014 at 04:35 PM.
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  10. #309
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    mJ: thanks ill check that out.

    Your light source seems to be coming from above but your specular seems to be like the ball is back lit. i thought it was the fresnel effect. Yea it def does depend on the mat to change the strength of the specular, i think the description u posted describes this


    edit: also, i tried looking, im pretty sure this is floating around the net i just thought id throw it out here. Color vibrancy? does it only effect saturation or can it effect hue and value as well? thanks again

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  11. #310
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    Hi Briggs (or anyone who has the answer) ALso just wondering what do you think is better the colour triangle or color square for hsv? Or are they the same.

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  12. #311
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    SO i did some color balls recently and was wondering what people thought about them, they are meant to be in direct sunlight.

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    hey siph, these look great, but you could challenge yourself a bit more and tease a background and a groundplane so its better to tell if your effects are right. also you could vary the power of the specularity, i find this very challenging.

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    thanks MJ! I think thats a good idea i might try that soon. I think i missed how strong direct sunlight is.. so i did an edit.

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    here are some BALLZ! some are more glossy, some less

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    dood, all my posts disappear and stuff, wtf... next try...

    and one question that REALLY REALLY gets me into trouble, i mentioned it before, but describe a bit simpler:

    if a color reached its maximum of reflectance under skylight, how will it look under sunlight? the same right? i dont know..since i am working in RGB instead of HSB i stumble upon this alot. and i just mean diffuse reflection!

    Last edited by Mister Janchichan; January 4th, 2014 at 03:59 PM.
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  16. #315
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    sry i dont know that one, nice balls

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  17. #316
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    Hi guys, my post from yesterday seems to have vanished permanently, but anyway I seem to have managed to get my email notifications working again. It's great to see so much activity here, but by far the most important thing I can say is to repeat what I said to Mr J on the last page:

    Quote Originally Posted by briggsy@ashtons View Post
    Make sure you do plenty of observation of actual objects in different situations to develop a sense of how the theory works in practice, such as as how strong to make the various component reflections contributing to the appearance. You'll learn much faster if you let nature answer your questions.
    I think you could improve a lot of your efforts and answer a lot of your own questions by taking the trouble to create suitable setups to compare them with what you expected, and perhaps photograph them and analyse the colour relationships in Photoshop. This will do you much more good in the long run than getting answers from someone else.

    If you are trying to paint simple objects from imagination make sure you actually understand the theory properly, for example with regard to the position of the highlight on a sphere (it has to be on a line from the light source through the middle of the sphere, not off to one side) and the importance of shading series.

    Siphonophores: I hope you can see that due to your decisions regarding the colouring, you've made your spheres look highly translucent, which I don't think was your intention. Also, to show strong sunlight on an opaque object requires a strong contrast between the light and shadow sides. Did you examine a coloured sphere in sunlight when doing the exercise?

    For the exercise of painting spheres into a photograph, I'd like to draw attention to this post, also on the last page:
    http://www.conceptart.org/forums/sho...20#post3653620

    In my attempt at one of Mr J's photos below, I first painted a white sphere under the lighting I inferred on the left, and then a coloured version on the right, using the procedure set out in that post. To follow this procedure, it is essential that you closely examine your photograph for clues that tell you about the relative strength and colour of the different light sources. I've marked in some of the clues I found useful for this into the photo, but I want you to see if you can follow for yourselves how I used this information.

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  18. #317
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    Quote Originally Posted by briggsy@ashtons View Post
    Hi guys, my post from yesterday seems to have vanished permanently, but anyway I seem to have managed to get my email notifications working again. It's great to see so much activity here, but by far the most important thing I can say is to repeat what I said to Mr J on the last page:



    I think you could improve a lot of your efforts and answer a lot of your own questions by taking the trouble to create suitable setups to compare them with what you expected, and perhaps photograph them and analyse the colour relationships in Photoshop. This will do you much more good in the long run than getting answers from someone else.
    hey david, thanks a lot for taking the time once again. i do alot of observations and lately painting from live too, but some stuff i want to understand, not just taking for granted and use this for my paintings. probably i am something like a nerd on this, but so far my understanding on things really helped me in my own work. ive made myself simple rules to paint whatever i want, i can tell how water looks if its clean, turbid, when the sky is this and that bababa... but now it seems that ive got a big misunderstanding when it comes to reflectance of materials and i just try to solve it with knowledge, so please dont take it amiss that i ask further on this topic:

    you've noted the rgb distribution on my screenshot, it has a lot of color, very bright, the left ball, even in your version has less RGB color in sunlight than the sky has to offer, so why should it get darker in the shadows? i solved alot with just observation without asking anybody, but i am running at a wall with this.

    is it just because sunlight penetrates the material more than the skylight or something?

    if there is no answer to this i probably should rely more on the values than RGB-Distributions and create my shadows first of all on this information (sky value compared to white/sunlight) and alter the local-value at this factor.


    Edit: Probably i got a Solution, Needs some validation, but i am optimistic

    Last edited by Mister Janchichan; January 5th, 2014 at 06:54 PM.
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    Briggs: Thanks! I did not see that at all. I really struggled with trying to increase the contrast. I couldnt find many refs for direct sunlight in fact one i saw was a tennis ball which might explain the translucency thing. I will keep experimenting and seeing how to do this

    Edit: i think i wanted a little translucency but not as much as i had there.

    MJ. Im not sure i understand completely what u mean but i will try answer. Also Great job on those balls the yellow one to me really looks like direct sunlight.

    Ok so I think you are on the right track. There is less light hitting those areas of the sphere. Also the reflected light due to the ANGLE, is less powerful (45% of the original intensity) keeping in mind that it is already reflected and therefore much weaker than the original lightsource that i think might explain it.

    Also you can figure out the values in the rgb slider using linrans method tho personally i prefer the triangle thing.

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  20. #319
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    Quote Originally Posted by Mister Janchichan View Post
    hey david, thanks a lot for taking the time once again. i do alot of observations and lately painting from live too, but some stuff i want to understand, not just taking for granted and use this for my paintings. probably i am something like a nerd on this, but so far my understanding on things really helped me in my own work. ive made myself simple rules to paint whatever i want, i can tell how water looks if its clean, turbid, when the sky is this and that bababa... but now it seems that ive got a big misunderstanding when it comes to reflectance of materials and i just try to solve it with knowledge, so please dont take it amiss that i ask further on this topic:
    I think it's really great that you want to understand things, and of course I'm not advocating the ignorant "just paint from life" rubbish that infected ca.org over the last few years (I mean in the free forums, not in the paid courses of course). It's just that it often seems to me that you go to the other extreme. For example, if you have a go at predicting what the shaded side of a white tower would look like, why not take the next step of taking a white cylinder outside and looking at it?

    Quote Originally Posted by Mister Janchichan View Post
    you've noted the rgb distribution on my screenshot, it has a lot of color, very bright, the left ball, even in your version has less RGB color in sunlight than the sky has to offer, so why should it get darker in the shadows? i solved alot with just observation without asking anybody, but i am running at a wall with this.

    is it just because sunlight penetrates the material more than the skylight or something?

    if there is no answer to this i probably should rely more on the values than RGB-Distributions and create my shadows first of all on this information (sky value compared to white/sunlight) and alter the local-value at this factor.


    Edit: Probably i got a Solution, Needs some validation, but i am optimistic
    Always remember that you are painting colour relationships. If you have a sphere under an ambient skylight and a concentrated spotlight, the colour you use to paint the skylit side depends on how bright the spot light is. The brighter the spotlight is, the darker you need to paint the skylit side to get the contrast - the relationship - right. So you end up having to organize your painting so that the lightest and brightest things are within the range of paint, and then paint everything else dark enough that the relationships to those lightest and brightest things are working.

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  21. #320
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    Quote Originally Posted by Siphonophores View Post
    Briggs: Thanks! I did not see that at all. I really struggled with trying to increase the contrast. I couldnt find many refs for direct sunlight in fact one i saw was a tennis ball which might explain the translucency thing. I will keep experimenting and seeing how to do this .
    You really couldn't find a coloured ball?! (And I don't mean a picture of one on Google!). Or couldn't you find direct sunlight?

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  22. #321
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    Its been a long time since ive seen the sun.... It forgot these lands, went south for the winter

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  23. #322
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    Quote Originally Posted by Siphonophores View Post
    Its been a long time since ive seen the sun.... It forgot these lands, went south for the winter
    Fair enough, then. This is what it looks like:

    Name:  direct-sunlight.jpg
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  24. #323
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    i slightly changed how i establish my colors based on the last talk. if i want to paint something under very colored light i first have to paint the locals compared on white to better think of how it would change after colored light, but i am sure after some time i am able get more confidence.

    here are 2 of my latest little results

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    even if those sphere-studies are fun im looking forward to paint something more vauleable finally

    edit: oops, didnt realise how small they are

    as mentioned i compare the colors to whire first, thought it would be a nice excercise like i did here, no multiplymode or such:

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    Last edited by Mister Janchichan; January 6th, 2014 at 06:51 AM.
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  25. #324
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    brigggs: Thanks! changed my approach on this now heh. time to go back to it

    MJ: 1st one looks excellent! very representative

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  26. #325
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    Ok so I tried to take what was said on board and came up with these. Now the first bunch were done before the crits were given so they are off. hopefully i got closer with the second batch. Then the third batch was a little light adjust to simulate that burning retina feel.

    Edit: they were posted in the wrong order. No 1 is the burning retina.

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  27. #326
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    So i was wondering, i was reading about the eye and specifically in regards to its ability to compress brightness in order to adjust the image.

    Would you know how much they adjust the brightness for different times of the day like sunrise and sunset etc?


    Heres what I found out so far.

    There is a Logarithmic relationship between luminance and subjective brightness perception in the human eye.

    Human eye uses a low pass filter and the band pass filter to compress the illuminance coming into the eye.

    The fall off for light compression is halved every time the frequency doubles.
    it can also divides 1/4 every time between the frequency doubles.

    But how does the frequency apply to the amount of light in the eye? Is the frequency the amount of light in the eye?

    From what i understood i thought there may be a significant decrease in the amount of compression that happens in low light circumstances.

    thanks again

    Edit: FOund the info i was looking for.

    Last edited by Siphonophores; January 12th, 2014 at 08:18 PM.
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  28. #327
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    New question,

    How does the principle of uniform saturation account for the brezold brucke shift? Does it account for the abney effect? and if it doesnt how could we incorporate this?

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  29. #328
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    Mister Janichan,

    The striped sphere in white light looks really good, but your method only seems to be letting you paint setups where the main light and the shadow illumination are the same colour. The way I showed lets you show multiple light sources of different colours.

    Siphonophores,

    Great, those last blocks look a lot more convincing than the spheres. One thing to at least be aware of though is that the gamut of digital colours is quite differently shaped to the range of commonly occurring natural colours, and extends well beyond the latter for many hues, especially in the greens and in the red-magenta-deep blue range (not so much in the yellows and greenish blues). So unless you tone down some colours below the maximum brightness and saturation possible, they'll tend to look a bit unnatural or even fluorescent (as in your green and magenta blocks).

    Quote Originally Posted by Siphonophores View Post
    New question,

    How does the principle of uniform saturation account for the brezold brucke shift? Does it account for the abney effect? and if it doesnt how could we incorporate this?
    My guess is that you'll get the same perceptual hue shift (if any) in the series of RGB colours of a given [I]digital[/I] "Hue" (H) and saturation as you would get in a series of colours of the same chromaticity in nature; in other words I think you'd automatically get the same hue shift happening.

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    thanks! yea this is definetly something to consider, I was thinking about it but i wanted to keep the high saturations in to simulate artificial colors and surfaces.

    Now i read somewhere that a way to compensate for it could be to select your shading series in a kind of curve rather than a linear selection. The one question i had after reading your post was,

    If the shift happens naturally would it only happen if your computer monitor was in Direct sunlight or is it a property of the Intensity of the light itself?


    So say we select a color with 100 brightness (which i think equals 1000 Lux) Will this because of its intensity automatically create the brezold brucke effect, or is this only effect of the high (v high) intensity of Direct sunlight?

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  31. #330
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    Sorry, I haven't really gone into the BB effect in great detail myself because to be honest it seems a rather arcane issue in the context of practical painting. There's even some debate over whether the effect exists at all in object colours, as opposed to lights. I just meant that within the range of brightness of RGB colours, if there is any BB effect then I assume you would get that automatically as colours of a particular "Hue" and "Saturation" got brighter. If what you are concerned about is how to depict the BB shift of a light that gets brighter than that (?), then yes presumably you would have to adjust the hue appropriately. Any BB effect would of course be overprinted and possibly swamped by a difference in colour of the illumination between the shadow and light areas.

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