Re: color adjustment to sky.

Question

what's the best way to change a gray/dirty white sky to blue? 

Answer 1

edwardfromrehoboth wrote:
     BTW, a genius in my local Apple Store says that Aperture 3 is not a "pro app", that it cannot, in many cases, turn a white or gray sky to a satisfactory blue, and that I will have to get Photoshop Elements or NIK Vivezza.  Live and learn!
Please ask him/her to get in touch with me.  S/he does not understand Aperture, and probably doesn't know that the difference between DAM/Digital Photograph Developers and Graphics Programs is compositing.  Live and learn, indeed.  You can print this and take it to your Apple Store.
The Tint Brush can be used to change the hue of any pixel.
Let's clarify some terms:
Color -- an observed phenomenon, precisely specified by Hue, Luminance, and Saturation
White -- no color data, 100% luminance
Black -- no color data, 0% luminance
Gray -- a color of any luminance value in which all color channels have identical luminance values
Hue -- a specific part of the spectrum, generally understood as a range from red to violet by way of orange, yellow, green, and blue
Luminance -- the degree of lightness and darkness
Saturation -- the degree to which a color deviates from a gray of the same luminance
Mid-tone -- any color with a luminance that falls within the broad middle of luminance values
Dark -- any color with a low luminance
Light -- any color with a high luminance
Highlight -- a very high luminance color, often reflecting a light source directly to the viewer (a/k/a luster light)
Shadow -- an area of diminished luminance caused by an object obscuring light
So -- you wish to change lights in part of your image to somewhat saturated blues.  The first thing to realize is that this is either a photography problem (you blew out the lights and there is no data there) or, perhaps, a graphics problem (you wish your photograph to vary from the data you recorded).  Aperture does not _add_ data to a photograph.  It _adjusts_ what's there -- that is, outside of organizing your photos, its entire remit.  If you need to add data, you will have to use a graphics program (that's what they do).  If adjusting the data that you captured with your digital camera is sufficient to your needs, then Aperture can likely do so.  You will most likely want to lower the luminance (so that you can saturate the color), change the hue to blue (if it is not) and increase the saturation.  Lowering the luminance can be done a number of ways; many users prefer one way over another.  The Tint Quick Brush can be used to change the hue, but I would first try changing it using the (mis-named) "White" Tint control that is part of the Enhance Brick.  Then I'd try to increase the saturation of the sky using the Vibrancy Quick Brush.
Message was edited by: Kirby Krieger -- format change.