Page 12 of 25 FirstFirst ... 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 ... LastLast
Results 166 to 180 of 363
  1. #166
    Join Date
    May 2005
    Location
    Sydney
    Posts
    866
    Thanks
    200
    Thanked 1,412 Times in 346 Posts

    Painting coloured illumination from the imagination

    I posted this little tutorial yesterday in another thread for someone who was having trouble with making up the effect of coloured lighting, and thought I'd post it here as well, so it won't sink out of sight.

    With Linear Dodge you can easily "clip" the upper limit of your RGB gamut and start getting strange results; if that happens you just need to keep your colours a bit darker.

    Bear in mind that the procedure applies directly only to this simple situation, and will lead you into trouble if you apply it blindly to more complex situations. Try instead to understand the reasons for each step.

    Also bear in mind always that these tips are meant as aids to getting physically correct colour relationships when that is what you are after, not orders to get those relationships. Plenty of lovely painting styles do not use "correct" colour and lighting, or correct perspective or anatomy, for that matter.


  2. Hide this ad by registering as a member
  3. The Following 4 Users Say Thank You to briggsy@ashtons For This Useful Post:


  4. #167
    Join Date
    Mar 2004
    Location
    Australia
    Posts
    767
    Thanks
    60
    Thanked 64 Times in 41 Posts
    Thanks for this David... a very effective tutorial

  5. #168
    Join Date
    Feb 2011
    Posts
    2
    Thanks
    7
    Thanked 0 Times in 0 Posts
    Dear Dr. Briggs,

    Thank you so much for your invaluable website! have been reading it the whole days and i feel like i just had a new birth! I've been painting digitally for a while but always confused by how to pick up colors. Now you made everything so clear to me. Thousand thanks!!!

    Xi
    Last edited by spinor; February 9th, 2011 at 07:17 PM.

  6. #169
    Join Date
    Feb 2011
    Posts
    4
    Thanks
    0
    Thanked 0 Times in 0 Posts

    questions about uniform saturation

    hi and thank you again for taking the time to answer these questions. as per your suggestion in the email, i will post them here so everyone can benefit. these were the major points of confusion that i forgot to ask.

    in faber birren's book 'creative color' he mentions, "the most beautiful of all formal color gradations that is known" as the "uniform chroma scale-which have the same apparent color content but which differ in lightness and darkness." is that in fact, the same thing as your described "uniform saturation shading series?" (if its not, how are they related as to what happens in nature?)

    if so, he also suggests an "easy" method of making one of these scales by mixing a tint, a tone, and a shade of the same hue and then intermixing them for in-between steps. if this is the case it raises questions.

    1. doesn't much care still need to be taken with the tint, tone and shade to ensure they are constant in color saturation amongst themselves? this doesnt just happen naturally, right?
    2. assuming you have step 1(question 1) done correct, is he implying that all in-between steps will then be balanced, saturation wise, inherently? if so, by that logic, couldnt i do away with mixing the tone all together and just use the tint and the shade to make the tone? and if not then it would seem this whole approach falls apart a bit.
    3. lastly, if i use red, add black and then a bit more red again to bring it back on the saturation line, couldnt i have just used less black to begin with or is it not the same thing? how does this affect step one?

    ok, sorry, i guess there is one other thing as well. so what is the proof/evidence that this is actually true and that saturation doesnt decrease or increase in the shadows? im guessing the shoddy results of just color sampling images isnt enough.

    thank you thank you, very much appreciated.

  7. #170
    Join Date
    May 2005
    Location
    Sydney
    Posts
    866
    Thanks
    200
    Thanked 1,412 Times in 346 Posts
    You're welcome, draw and spinor!

    Thanks for taking the trouble, Bob. They're all very good questions.

    Birren's "uniform chroma scales"


    Quote Originally Posted by bbshrmn View Post
    in faber birren's book 'creative color' he mentions, "the most beautiful of all formal color gradations that is known" as the "uniform chroma scale-which have the same apparent color content but which differ in lightness and darkness." is that in fact, the same thing as your described "uniform saturation shading series?" (if its not, how are they related as to what happens in nature?)
    What Birren calls "uniform chroma scales" are the perceptual (or logarithmic) "isochromes" of the Ostwald system, which is not really used any more. Ostwald's perceptual isochromes were in theory lines of uniform saturation in my terminology, though in practice (in the Ostwald colour atlas) they seem to me to be somewhere between lines of uniform saturation and lines of uniform chroma.


    Mixing a shading series

    Quote Originally Posted by bbshrmn View Post
    1. doesn't much care still need to be taken with the tint, tone and shade to ensure they are constant in color saturation amongst themselves? this doesnt just happen naturally, right?
    2. assuming you have step 1(question 1) done correct, is he implying that all in-between steps will then be balanced, saturation wise, inherently? if so, by that logic, couldnt i do away with mixing the tone all together and just use the tint and the shade to make the tone? and if not then it would seem this whole approach falls apart a bit.
    3. lastly, if i use red, add black and then a bit more red again to bring it back on the saturation line, couldnt i have just used less black to begin with or is it not the same thing? how does this affect step one?
    1. Of course, and of course.
    2. Mixtures between successive steps tend to drift off the uniform saturation line, so the steps should be kept close together.
    3. if you are shading red+black+white by adding black, you correct the saturation with red (not red+black+white). If you are shading a pure opaque red with black, there is less of a tendency for the saturation to drop, but if it does you could boost the saturation with a transparent red. Adding some of the opaque red would of course just take you back in the direction you came from).


    Uniform-saturation series and illumination

    Quote Originally Posted by bbshrmn View Post
    ok, sorry, i guess there is one other thing as well. so what is the proof/evidence that this is actually true and that saturation doesnt decrease or increase in the shadows? im guessing the shoddy results of just color sampling images isnt enough.
    I'll answer that by showing you some uniform saturation series and asking what you see. The main rectangle of the attached jpg simply shows seven uniform saturation series (one achromatic). We automatically see it as an image of uniform object colours under varying illumination. To me this simple demonstration neatly proves that
    (1) our visual system recognizes relationships of uniform saturation in the visual field, and
    (2) it uses these relationships in its amazing capacity to separate effects of illumination from effects of object colour (object-colour constancy).

  8. #171
    Join Date
    Feb 2011
    Posts
    4
    Thanks
    0
    Thanked 0 Times in 0 Posts

    uniform saturation series

    Quote Originally Posted by briggsy@ashtons View Post
    I'll answer that by showing you some uniform saturation series and asking what you see. The main rectangle of the attached jpg simply shows seven uniform saturation series (one achromatic). We automatically see it as an image of uniform object colours under varying illumination. To me this simple demonstration neatly proves that
    (1) our visual system recognizes relationships of uniform saturation in the visual field, and
    (2) it uses these relationships in its amazing capacity to separate effects of illumination from effects of object colour (object-colour constancy).
    thanks for the quick reply.

    ... but does this example, starting out with some colors that arent so crisp and saturated to begin with, not work just as well? this reads very natural and as uniform object colors also, no?

  9. #172
    Join Date
    May 2003
    Location
    Hudson River valley, NY
    Posts
    16,206
    Thanks
    4,879
    Thanked 16,686 Times in 5,022 Posts
    Quote Originally Posted by briggsy@ashtons View Post
    What Birren calls "uniform chroma scales" are the perceptual (or logarithmic) "isochromes" of the Ostwald system, which is not really used any more.
    And thank goodness for that! Creative Color is overall a good book, but Birren's big flaw was his attachment to Ostwald.

    Tristan Elwell
    **Finished Work Thread **Process Thread **Edges Tutorial

    "Work is more fun than fun."
    -John Cale

    "Art is supposed to punch you in the brain, and it's supposed to stay punched."
    -Marc Maron

  10. #173
    Join Date
    May 2005
    Location
    Sydney
    Posts
    866
    Thanks
    200
    Thanked 1,412 Times in 346 Posts
    Quote Originally Posted by bbshrmn View Post
    ... but does this example, starting out with some colors that arent so crisp and saturated to begin with, not work just as well? this reads very natural and as uniform object colors also, no?
    Not as natural as when you shade the same colours keeping the saturation uniform:

  11. #174
    Join Date
    Feb 2011
    Posts
    4
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Quote Originally Posted by briggsy@ashtons View Post
    Not as natural as when you shade the same colours keeping the saturation uniform:
    yeah, it appears so. given that its the same illumination range, your colors definitely appear to be passing into the darkness, where mine feel to be coming out of it a bit. thank you thats helpful.

    i was also trying to color sample some HDR images to see what kind of results i would get since they are supposed to be closer to how we perceive reality and i did find mostly uniform saturation throughout them. that said, the saturation was often at 100%. if you will accept the loose terms, why the 'blow out' and are these HDR images better for us to study, from a 'reality standpoint'? are they just constantly pushing the outer limits of the technologies involved, how does this relate to paint?

    thank you.

  12. #175
    Join Date
    May 2005
    Location
    Sydney
    Posts
    866
    Thanks
    200
    Thanked 1,412 Times in 346 Posts
    Sorry, Bob, I'm a bit vague on the details of HDR image processing at the moment, so I'll have to pass on those four(!) new questions for now. A digital camera is in a way a kind of inexpensive spectrophotometer, and you can very usefully investigate some things using digital photos, but I'd be much more inclined to use a straightforward image, aware of its limitations, than one that is higly manipulated in a way I don't fully understand.

  13. #176
    Join Date
    Feb 2011
    Posts
    4
    Thanks
    0
    Thanked 0 Times in 0 Posts
    ok, thank you and sorry for the bombardment. so much to know and so little time.

  14. #177
    Join Date
    Jun 2008
    Location
    Philippines
    Posts
    520
    Thanks
    102
    Thanked 204 Times in 81 Posts
    I decided to go back to the basics and learn as much as I can about value, saturation and hue, and I would just like to say that, as much as how your site gave me a headache trying to understand it on my own, thanks so much for such an invaluable resource Briggsy.

    As of the moment, I'm alternating between Gnomon Workshop's Light and Color and your website for studying, and already, my brain is trying to understand the difference between chroma and saturation, and I feel my brain bleeding. I'll continue my reading and studying and hopefully, once I get familiar with the technical aspects of the subject, everything will be that much clearer for me.

    Thanks!

  15. #178
    Join Date
    May 2005
    Location
    Sydney
    Posts
    866
    Thanks
    200
    Thanked 1,412 Times in 346 Posts

    Saturation

    Everything about colour is more complicated than many people assume, so a little bit of bleeding is probably a good sign! Saturation especially is a word that requires caution, because it has several different meanings, which people using the word are often not conscious of.

    Some people use the word "saturation" for the purity of colours of surfaces, with these colours being considered as mixtures of white, "pure colour", and black, and saturation as the proportion of the "pure colour" component in the mix. People who say that chroma is "very similar" to saturation may simply be confused, but they may also be using saturation in this sense, which in effect means relative chroma - i.e. chroma as a percentage of the chroma of the "pure colour". This concept of "pure colour" is very problematic in relation to surfaces, however, so the open ended scale of chroma is much better.

    In Photoshop, saturation is the colour purity of the light that is emitted from the screen. Any light can be considered to be a mixture of a certain percentage of white light, plus coloured light: saturation in this sense is simply one minus the proportion of white light. I use saturation in this second sense, as explained on this page:
    http://www.huevaluechroma.com/093.php

    Colours like B and C in Figure 9.8 on that page have low chroma, and low saturation in the first sense, because as surface colours they contain a lot of black, but they have high saturation in the second sense, because the light given off is pure red (only the red phosphors are glowing).

    Not sure if that will help or not, but anyway a close study of the figure I just mentioned usually seems to get the idea across.

  16. The Following User Says Thank You to briggsy@ashtons For This Useful Post:


  17. #179
    Join Date
    Feb 2005
    Location
    Croatia, Europe
    Posts
    86
    Thanks
    6
    Thanked 2 Times in 2 Posts

    light and shadow

    I'd like to pose a technical question. I am quite familiar with the color theory in general (we had that class back at Academy), and rules and guidelines in particular, yet there are some instances in which I am not 100% certain about the correct procedure.

    For instance, one of those guidelines is that the lightest dark is darker than the darkest light. (It is not always valid. I mean - it only applies to certain kinds of light under certain conditions. In overcast light, such rules do not apply. Even in sunlight, a very light ground surface can significantly raise shadow values.)

    What I'd like to know is how one shoud draw an area in light which local hue is equally dark or darker than the shadow? Take an apple for instance (or people with really ruddy cheeks). Apple may be yellow/green in hue, appearing rather high value in light, but there is large dark red spot which is partially in light and partially in shadow. That intense, dark red is of equal value as adjacent shadow. If one draws it as he sees it, the drawing may look somewhat odd; the apple will appear flat with oddly looking shadow. I mean - form shadow will go nicely around the form, creating the illusion of roundness, but the shape of adjacent red spot of equal value will confuse the viewer. What one should do in that case?

    Should one neglect what he sees in order to create a convincing illusion of form? Should he draw the mentioned dark spot (or say, ruddy cheeks) lighter than it appears, in order to prevent merging it with the shape of the shadow ?
    https://www.behance.net/Valentino_R
    blog: https://tinoradman.wordpress.com
    www.valentinoradman.com

  18. #180
    Join Date
    May 2005
    Location
    Sydney
    Posts
    866
    Thanks
    200
    Thanked 1,412 Times in 346 Posts

    "Always keep the lightest dark darker than the darkest light".

    I'm really glad you brought this up Valentino, because this particular piece of advice is doled out far too often on these forums. It's not just that it's wrong factually, it's also very bad teaching to hand out simplistic "rules" instead of encouraging analysis and understanding.

    You're perfectly correct that the rule only applies under certain conditions. The brightness of any point is the brightness of the illumination multiplied by the reflectance of the surface. It should be clear from this diagram that the rule can not possibly hold if there are dark and light local colours involved, unless the contrast between the illumination in the light and in the shadow is very high. If the rule has any validity it is as a statement of aesthetic preference, not physical fact.

    The Dimensions of Colour - a colour theory discussion thread

    It would be better to say "Always make your lighting so contrasty that the lightest shadow is darker than the darkest light". At least that would make the limitations of the "rule" more obvious.

    I don't agree that painting your subject as it appears, ignoring the rule, will make it "appear flat" or create an "oddly looking shadow". All it will do is cause the pattern of lights and darks in your picture to differ a little from the pattern of light and shadow. That's it!
    Last edited by briggsy@ashtons; June 2nd, 2011 at 09:10 PM.

  19. The Following User Says Thank You to briggsy@ashtons For This Useful Post:


Page 12 of 25 FirstFirst ... 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 ... LastLast

Similar Threads

  1. Colour theory and lighting?
    By Gesturing Stream in forum Art Discussions
    Replies: 8
    Last Post: October 6th, 2011, 02:50 PM
  2. Colour theory?
    By StylesArt in forum Artist Lounge
    Replies: 5
    Last Post: January 2nd, 2011, 04:20 PM
  3. help, colour theory.
    By wilko2112 in forum Art Discussions
    Replies: 2
    Last Post: December 3rd, 2007, 04:00 PM
  4. colour theory
    By MerQueen69 in forum Art Critique Center
    Replies: 2
    Last Post: July 3rd, 2007, 05:11 PM

Members who have read this thread: 90

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

Developed Actively by the makers of the Best Amazon Podcast