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12/29/2012 12:48:22 PM · #1 |
Just trying to understand because I'm clearly missing something......
Why does the whitebalance affect an images that has been converted to black & white so dramatically. I'm trying to understand the channels more around B&W and just confused so something is not twigging (I'm converting to B&W thru the channel BW tab)........ |
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12/29/2012 01:08:38 PM · #2 |
I have not played with this at all, so take my opinion as "theoretical ponderings only."
I think what's happening is that the WB setting is applied as the RAW data is de-mosaiced. The B+W conversion settings are then applied. Because the WB setting affects the relative amounts of the R, G and B channels present, and the B+W settings use, by default, specific percentages of these channels, the results *should* be different, given different WB settings. |
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12/29/2012 01:40:28 PM · #3 |
| lets use HSL for example. when you convert to B/W you are turning down the saturation portion of the color, white balance adjusts the color temperature and thus the HSL of any color in an image. different color temperatures correspond to different values of HSL, so when you desaturate a color the remaining hue and luminance values determine what shade of grey the color now appears as. |
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12/29/2012 03:40:09 PM · #4 |
Originally posted by mike_311:
lets use HSL for example. when you convert to B/W you are turning down the saturation portion of the color, white balance adjusts the color temperature and thus the HSL of any color in an image. different color temperatures correspond to different values of HSL, so when you desaturate a color the remaining hue and luminance values determine what shade of grey the color now appears as. |
This seems a reasonable point of reference
desaturating HSL and emphasising Red Contrast used in conjuction with selecting the correct White balance will give you worse or better contrast... first select your WB before applying B&W, so that it becomes clearer starting point. |
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12/29/2012 04:01:07 PM · #5 |
Yeah... because the shot was a "color" image and the white balance is affecting the underlying colors.
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12/29/2012 04:01:09 PM · #6 |
B/W conversion, at the simplest level, just removes all color information from an image without changing luminance levels at all. Color balance, on the other hand, noticeably adjusts the relative luminance of the different color channels as well as their color.
Prove this to yourself by opening ANY colorful RAW image and adjusting saturation to zero, then dragging the WB slider back-and-forth and watching the relative luminance values change dramatically.
In fact, the BEST way I've found to do a B/W conversion is exactly that: if you know it's gonna be N/W in the end, zero the saturation and adjust the white balance to what you think is going to work best. THEN return the saturation level to normal and open the image as a color image on PS. From that point on, use your preferred tools to make the B/W conversion. I use Nik's Silver Efex Pro. |
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12/29/2012 05:28:03 PM · #7 |
Thank you all... That makes sense.
I have a couple of presets and that Nik stuff looks interesting (I have one of their PS plugins) but I try and avoid presets unless I understand what it's doing.... I would prefer to understand and will use them after I understand what they are doing but it bugs me just using them without understanding..... Control freak I guess :-) |
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