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Tutorial on a curves technique to avoid dark prints

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Post time: 2015-7-13 16:42:42 |Show all posts
Red River Paper hosts this brief Photoshop tutorial by Tim Grey
http://www.youtube.com/watch?v=tb-ugPMUFhs
Summary: Raise the shadow end of a luminance curve about six percent of the y-axis, then apply brightening contrast to the midtone region (pull the curve up slightly around lowerr quartile of the x-axis and up a bit more at the upper quartile).
I didn't do a comparison, but one print certainly showed shadow detail with a pretty good overall look. I still believe in Norman Koren's advice that every photo should have some black; could select an area with a blurred boundary to exclude from the adjustment.
Question:
The video is basically a stream of the screen while Grey does what he prescribes. I noticed that the color coordinate system was RGB. But: "Normally the RGB color space is a poor choice for lightening or darkening an image. When you use this color space, the same curve is applied to each of the three components of the image (red, green, and blue). This can result in unwanted hue or saturation changes in different parts of the image. Working in HSV or HSL avoids this problem." (Jonathan Sachs, "Using Curves and Histograms," Digital Light and Color) )
Is it unusual that the expert blithely uses RGB?

Post time: 2015-7-14 09:20:25 |Show all posts
stlsportscom wrote:
What I want, more than anything else, is the software equivalent of 'fill flash'...to brighten the faces in the pictures, pictures that were taken outdoors and in bright overhead sunshine (or bright backlight)--without the benefit of an actual flash.
Can you supply a thought or two aimed in this direction?
Oh boy! That's a tall order, but here goes. First, I almost never use flash, so I run into this very situation a lot with my own photography. There may be some nifty piece of software or plugin to LR and PS that does this in a more automated "slider bar" approach, but I'm so comfortable with the tools in LR and PS, that I've never bothered to try to look for one. It can be done very elegantly, albeit with higher skill levels required using LR, or LR in combination with PS, or PS without LR. So, I'll share my LR and PS approach to this problem as best as I can in a written description (really needs a video tutorial to make it all easier).
Preliminary: Shooting RAW helps with this "fill flash" task big time because it opens up the full DR of the camera sensor, much of which gets thrown out when redacted by the camera to a JPEG output.
Work the problem in successive stages as necessary in order to get the "fill light" in the faces or other key areas where you want it, but taking care to keep the whole image still looking natural rather than overcooked! Here's a brief description of the incremental stages I use.
Stage 1 "fill flash". Use The LR develop module's (or Adobe ACR's) "Basic" set of controls over "exposure" "highlights", "shadows", "blacks" and "whites" to perform a global increase aimed at lightening the shadow areas of the image, taking care not to go so far that the global effect looks fake or overdone. The key control is "shadows", but if you experiment, you will find that there's an important interaction going on between the exposure slider to drive all tones lighter, the highlight and white sliders to pull back highlights and preserve highlight detail, and the black and shadow sliders, to anchor the deepest blacks while opening up the shadow tones that aren't quite so dark (e.g, typically those face tones exposed in shadow without the benefit of flash).
Stage 2 "fill flash" : While keeping the whole scene natural looking with stage 1 controls you may not get the faces opened as bright as you might like, so then move to the LR adjustment brush, adjust the same controls, and paint in the effect to the areas in the image that need even more shadow boost. Gain a little skill and this selective local control on top of the stage 1 global control is all you will usually need to achieve a very natural "fill light" effect.
Stage 3 "fill flash". If you are still struggling to get to where you want to go after stage 1 and stage 2 LR edits or it's becoming too difficult to keep everything looking natural, then it's time to move to PS. With PS, you can now add very careful adjustment layers (like the ones that started this thread". But you have way more control on how to feather and apply them to those areas of the image that still need more dodging or conversely burning than is practical to achieve in LR. The precision and feathering of all adjustments is far more delicate in PS than in LR. You can even use luminosity masks to really isolate the areas you want to feather in more brighenting without wrecking the rest of the image. That said, luminosity masks are a tutorial in and of their own right. Typically, Stage three fill flash does not need this level of luminosity mask sophistication to complete the "fill flash" effect you want to achieve. It just needs the more basic dodging and burning techniques carefully brushed into the local image areas by adding an ordinary mask to the curve adjustment layer. This mask used in conjunction with the adjustment layer in PS gives you incredible control on your dodging and burning including reversibility and fade in/fade out opacity tuning to get each layer to have as aggressive or delicate an effect as you desire.
I should say that the methods I'm describing are indeed more advanced ones that may frustrate the newcomer to LR and/or PS, but practice makes perfect and once you get good at it, it takes only a few minutes to accomplish with incredible control on any particular "keeper image". Stage 1 and to some extent stage 2, of course, can be broadly applied in LR to a whole sequence of near frame images at once (the primary advantage of LR over PS) and these initial two stages I've described are very often all you need to achieve the "natural fill light" effects you are looking for.
I hope my explanation helps give you some insight as to how to tackle the issue. It's much easier to show friends and colleagues how this is done when they are sitting at my computer along with me...much harder to put into words for a forum discussion.
cheers,
Mark
-- hide signature --Mark McCormick
http://www.aardenburg-imaging.com

Post time: 2015-7-14 08:06:55 |Show all posts
Mark McCormick wrote:
Charles2 wrote:
Question:
The video is basically a stream of the screen while Grey does what he prescribes. I noticed that the color coordinate system was RGB. But: "Normally the RGB color space is a poor choice for lightening or darkening an image. When you use this color space, the same curve is applied to each of the three components of the image (red, green, and blue). This can result in unwanted hue or saturation changes in different parts of the image. Working in HSV or HSL avoids this problem." (Jonathan Sachs, "Using Curves and Histograms," Digital Light and Color) )
Is it unusual that the expert blithely uses RGB?
In PS, use the curves tool as an adjustment layer as shown in the video. Then, if you want the change to only affect luminance values in the image and not shift hues or saturation, simply choose "luminosity" rather "normal" as an option in the layers panel. PS uses the mathematics of the CIELAB model and the chosen RGB working space (sRGB, aRGB, proPhoto) to confine the appearance changes to the underlying L* values rather than changing all the RGB values based on the simpler RGB model. Same principle applies if you choose "Saturation" or "hue" in the layer panel dialoque box.
cheers,
Mark
-- hide signature --Mark McCormick
http://www.aardenburg-imaging.com
Mark, thanks for your response.
I have one need (above all else) which sort of relates to this thread.
All manner and form of vacation pictures include people, faces of people, and landmarks/beaches/streets/buildings.
What I want, more than anything else, is the software equivalent of 'fill flash'...to brighten the faces in the pictures, pictures that were taken outdoors and in bright overhead sunshine (or bright backlight)--without the benefit of an actual flash.
Can you supply a thought or two aimed in this direction?

Post time: 2015-7-14 06:41:13 |Show all posts
Charles2 wrote:
Question:
The video is basically a stream of the screen while Grey does what he prescribes. I noticed that the color coordinate system was RGB. But: "Normally the RGB color space is a poor choice for lightening or darkening an image. When you use this color space, the same curve is applied to each of the three components of the image (red, green, and blue). This can result in unwanted hue or saturation changes in different parts of the image. Working in HSV or HSL avoids this problem." (Jonathan Sachs, "Using Curves and Histograms," Digital Light and Color) )
Is it unusual that the expert blithely uses RGB?
In PS, use the curves tool as an adjustment layer as shown in the video. Then, if you want the change to only affect luminance values in the image and not shift hues or saturation, simply choose "luminosity" rather "normal" as an option in the layers panel. PS uses the mathematics of the CIELAB model and the chosen RGB working space (sRGB, aRGB, proPhoto) to confine the appearance changes to the underlying L* values rather than changing all the RGB values based on the simpler RGB model. Same principle applies if you choose "Saturation" or "hue" in the layer panel dialoque box.
cheers,
Mark
-- hide signature --Mark McCormick
http://www.aardenburg-imaging.com

Post time: 2015-7-14 05:09:54 |Show all posts
Thanks for this update, that's great news.  I definitely want to get a copy of the Color Mechanic plug-in.
Cheers,
Peter

Post time: 2015-7-14 04:03:15 |Show all posts
ppage wrote:
Speaking of Picture Window Pro... Has Digital Light and Color gone out of business? The site is still there but whereas products and manuals could be downloaded just a month ago now those links do nothing. A great shame if that's the case.
Don't worry. I posted a query on DL&C's forum about this. A staff person soon replied, "We are experiencing a problem on our host site and working to get it fixed."

Post time: 2015-7-14 02:19:19 |Show all posts
Charles2 wrote:
Howard Moftich wrote:
there's a difference between color-space and color-model. In PS, the curves adjustment is based on the color-space you're using (which is 98% of the time RGB) and you simply do not have access to HSL (although you could do a Hue/Sat layer w/ mask if you want).
So another advantage for Picture Window Pro over PS: it offers convenient choice of HSV, HSL, or RGB and their components for its curves and levels dialogs.
Speaking of Picture Window Pro...  Has Digital Light and Color gone out of business?  The site is still there but whereas products and manuals could be downloaded just a month ago now those links do nothing.  A great shame if that's the case.

Post time: 2015-7-14 00:39:32 |Show all posts
Charles2 wrote:
Red River Paper hosts this brief Photoshop tutorial by Tim Grey
http://www.youtube.com/watch?v=tb-ugPMUFhs
Summary: Raise the shadow end of a luminance curve about six percent of the y-axis, then apply brightening contrast to the midtone region (pull the curve up slightly around lowerr quartile of the x-axis and up a bit more at the upper quartile).
I didn't do a comparison, but one print certainly showed shadow detail with a pretty good overall look. I still believe in Norman Koren's advice that every photo should have some black; could select an area with a blurred boundary to exclude from the adjustment.
Question:
The video is basically a stream of the screen while Grey does what he prescribes. I noticed that the color coordinate system was RGB. But: "Normally the RGB color space is a poor choice for lightening or darkening an image. When you use this color space, the same curve is applied to each of the three components of the image (red, green, and blue). This can result in unwanted hue or saturation changes in different parts of the image. Working in HSV or HSL avoids this problem." (Jonathan Sachs, "Using Curves and Histograms," Digital Light and Color) )
Is it unusual that the expert blithely uses RGB?
Yep. And would throw up a caution flag to some.
-- hide signature --Steve Bingham
www.dustylens.com
www.ghost-town-photography.com

Post time: 2015-7-13 22:47:25 |Show all posts
Scott Eaton wrote:
... What I do in situations like this is generate a severe tone mapped imaged (the post step used in HDR) and then apply it *conservatively* to the trouble areas.
Interesting. Raw Therapee has a tone-map operation with sliders for several parameters. RT can apply it to a TIF or JPG saved near the end of post processing in another program, and you can save the result as a TIF or JPG to blend selectively back into the source image.

Post time: 2015-7-13 21:42:03 |Show all posts
I also prefer to work in a non RGB space if I'm doing a lot of brightness alteration. If it's a small amount though, and also the fact we're dealing with the limited brightness range of a print it's not that big a deal.
I like the example of the image being used because it illustrates the tricky problem nicely, but totally disagree with the solution. Their solution just makes things muddier, and if printed on matte paper would look arguably worse.
What needs to happen is the areas in shadow need an increase in brightness and elevate contrast while the overall print is left alone. Globally reducing the black level just makes things worse. At worst the shadowed areas should have been selected and adjusted alone (dodge and burn), but still, the absolute black level in the shadow area need not decrease. This just makes things worse.
What I do in situations like this is generate a severe tone mapped imaged (the post step used in HDR) and then apply it *conservatively* to the trouble areas. Basically I'm just increasing the contrast and brightness in the darker muddy areas but being lazy about it. A curve approach would work as well, but the curve is relative to each image. An example is in my gallery linked at the bottom with a very similiar problem and the tone map blend to solve it without looking artificial. Had I access to the original image used in this tutorial the result would look like a million bucks.
http://www.dpreview.com/galleries/7030893105/photos/2472844/ice7

Post time: 2015-7-13 20:06:00 |Show all posts
Howard Moftich wrote:
there's a difference between color-space and color-model. In PS, the curves adjustment is based on the color-space you're using (which is 98% of the time RGB) and you simply do not have access to HSL (although you could do a Hue/Sat layer w/ mask if you want).
So another advantage for Picture Window Pro over PS: it offers convenient choice of HSV, HSL, or RGB and their components for its curves and levels dialogs.

Post time: 2015-7-13 18:26:29 |Show all posts
there's a difference between color-space and color-model.  In PS, the curves adjustment is based on the color-space you're using (which is 98% of the time RGB) and you simply do not have access to HSL (although you could do a Hue/Sat layer w/ mask if you want).
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