Luminous Landscape Forum
Raw & Post Processing, Printing => Digital Image Processing => Topic started by: DonaldSmkn on February 09, 2010, 05:52:59 am
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I am unsure as to whether this constitutes a beginners question or not, but thought it might stimulate some discussion.
From the moment I started using photoshop, curve adjustments were basically relatively straight forward s curves to boost contrast - for images that require it that is.
This wasn't an entirely straight forward process.
Only recently I started using the whitepoint, black point dropper, or manually shifting white points or black points according to where the information "begins" for each point in the histogram.
This is providing some great results, universally across the image. It may not save all highlights (if already blown) or shadows (if already clipped) but it is much more straight forward and consistent than a standard s-curve as preached by many online tutorials. Colours also "pop" a lot more and the whole photo looks like it appeared to me at the time - minimal curve adjustment also seems to reduce the likelihood of dreaded posteris/zation.
This then begs me to question - why would you apply a s-curve if this powerful tool is producing these great results?
Also, with regards to clipping, if I turn my rgb image to "difference", add a clipping mask, "apply to image" and check invert, then turn the layer to normal again, I'm seeing some details regained in bright clouds and dark shadows - most of my work is done?
I can understand that detailed curve manipulation and multiple layers can be used to put life into heavy shadows, etc - but the method I have provided above seems to work quite well for urban snapshots and the like and general fluff I add to flickr.
I wouldn't mind your opinions in regards to the above. Please note I am a newbie to image processing, so please try not to over complicate the matter.
Thanks!
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After getting the White Balance right (in raw) my tactic has always been to start with levels first, so adjusting white point and black point and only go and manipulate curves if it's still needed to suit my liking to change the overall tonal balance (many times not needed). Adjusting curves before levels feels very much reverse to me (but don't know if that's just me).
Next step after that is any local dodging and burning.
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After getting the White Balance right (in raw) my tactic has always been to start with levels first, so adjusting white point and black point and only go and manipulate curves if it's still needed to suit my liking to change the overall tonal balance (many times not needed). Adjusting curves before levels feels very much reverse to me (but don't know if that's just me).
Next step after that is any local dodging and burning.
It may not be "just you", but it's also not usually necessary to use Levels. Shifting the end points of Curves does the same white and black point work as Levels does, then while in Curves you make most other luminosity adjustments. If anything, Levels could be more convenient for shifting overall brightness by using the middle input slider.
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I am unsure as to whether this constitutes a beginners question or not, but thought it might stimulate some discussion.
From the moment I started using photoshop, curve adjustments were basically relatively straight forward s curves to boost contrast - for images that require it that is.
This wasn't an entirely straight forward process.
Only recently I started using the whitepoint, black point dropper, or manually shifting white points or black points according to where the information "begins" for each point in the histogram.
This is providing some great results, universally across the image. It may not save all highlights (if already blown) or shadows (if already clipped) but it is much more straight forward and consistent than a standard s-curve as preached by many online tutorials. Colours also "pop" a lot more and the whole photo looks like it appeared to me at the time - minimal curve adjustment also seems to reduce the likelihood of dreaded posteris/zation.
This then begs me to question - why would you apply a s-curve if this powerful tool is producing these great results?
Also, with regards to clipping, if I turn my rgb image to "difference", add a clipping mask, "apply to image" and check invert, then turn the layer to normal again, I'm seeing some details regained in bright clouds and dark shadows - most of my work is done?
I can understand that detailed curve manipulation and multiple layers can be used to put life into heavy shadows, etc - but the method I have provided above seems to work quite well for urban snapshots and the like and general fluff I add to flickr.
I wouldn't mind your opinions in regards to the above. Please note I am a newbie to image processing, so please try not to over complicate the matter.
Thanks!
Pulling in the white and black points to just before clipping is a normal practice, provided of course the scene warrants the resulting tonality accross the range. It does accentuate contrast nicely and the added bit of black adds vibrance to colours. I don't recommend clipping highlights in your white point adjustment, but if you want a linear contrast and brightness boost by shifting the level 255 end point leftward beyond the clipping point, you can often protect highlights containing needed detail bv painting these highlights grey or black on the Curves layer mask.
The paragraph about turning the rgb image to "difference" is unclear. Could you explain in exact detail and correct sequence precisely the steps you are implementing here?
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Hi Mark,
The sequence is as follows:
In the curve adjustment layer, I turn the blending mode to "difference".
Then, I go to layers, and add a clipping layer.
Then, I go to images, apply image, use the default setting, however check "invert".
Then I will go back to the curve adjustment layer and set the blending mode back to "normal".
This appears to save some detail in highlights that were lost in the initial tone curve adjustment.
Let me know what you think.
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In the second step, there is no such thing as a "clipping layer". Do you mean "Add Clipping Mask?
In the third step, there are no "default settings" for Apply Image. The settings are what you used the previous time you used it. What specific setting are you using, in particular the blend mode?
Anyhow, I tried all this by adding a clipping mask and leaving the Blend Mode of Apply Image at "Normal". The end result is that it darkened the image a bit, likely because it picked up some of the luminosity of the Background Layer thereby toning down the brightness created by the Curve adjustment. From what I observe so far, the same thing could be achieved more straightforwardly by proper use of Curves. Where did you get this "technique" from? Or what reasoning process took down that path? I'm curious!
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Thanks for giving that a go Mark, and apologies for the confusion.
I came up with this technique myself - I've just been playing with it now and it doesn't seem like the be all and end all afterall.
All I really am looking for is to gain back the tonality and punch of, say for instance, a film stock like provia or velvia without going into too much detail.
To tell you the truth, I have trialled exposure 2, but I was not liking the generic rgb contrast ajustments as it blew highlights and clipped shadows too much! (As you can imagine, not all photos are the same and won't beneft from heavy curve adjustments) I don't mind clipped shadows and so forth - I am not a lazy photographer, but I don't like to spend a lot of time editing photos.
I'm really looking for something to punch up my images a little without too much hassle.
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It may not be "just you", but it's also not usually necessary to use Levels. Shifting the end points of Curves does the same white and black point work as Levels does, then while in Curves you make most other luminosity adjustments. If anything, Levels could be more convenient for shifting overall brightness by using the middle input slider.
The levels adjustment was convenient in previous versions of Photoshop to set the black and white points, since Levels offered a histogram preview and one could set the white and black points using the histogram. Now, curves also has a histogram and preview, enabling one to easily set the white and black points and also to adjust the tone curve to add contrast.
This image has very low contrast and needs setting of the black and white points as well as a contrast boost to the midtones with an S curve:
[attachment=20144:079_Histogram.png]
After adjustment:
[attachment=20145:Snap079_curves.png]
An important additional point is that one should make such adjustments using as much information in the image as is possible. In post processing, one should use 16 bits per channel. Even better, one should make the adjustments in the raw converter. The raw converter has an S curve built into its default tone curve, but that curve may not be ideal for all images. If he uses ACR, the reader could look at the ACR tutorial by Michael and Jeff Schewe or Mr. Schewe's camera raw book.
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Thanks for giving that a go Mark, and apologies for the confusion.
I came up with this technique myself - I've just been playing with it now and it doesn't seem like the be all and end all afterall.
All I really am looking for is to gain back the tonality and punch of, say for instance, a film stock like provia or velvia without going into too much detail.
To tell you the truth, I have trialled exposure 2, but I was not liking the generic rgb contrast ajustments as it blew highlights and clipped shadows too much! (As you can imagine, not all photos are the same and won't beneft from heavy curve adjustments) I don't mind clipped shadows and so forth - I am not a lazy photographer, but I don't like to spend a lot of time editing photos.
I'm really looking for something to punch up my images a little without too much hassle.
Try the Vibrance Adjustment Layer in PSCS4, or do a local contrast enhancement - the technique I recommend is John Paul Caponigro's, which you should be able to access by becoming a member of his website.
With digital photography, you have a choice of letting the camera make your decisions by outputting JPEGs, or shooting raw and spending some time optimizing your images. How much time is "a lot" is of course a personal judgment, but you miss out on much of the promise of digital photography unless you are prepared to put some real effort into adjusting raw images.
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It may not be "just you", but it's also not usually necessary to use Levels. Shifting the end points of Curves does the same white and black point work as Levels does, then while in Curves you make most other luminosity adjustments. If anything, Levels could be more convenient for shifting overall brightness by using the middle input slider.
Mark, good point but unfortunately not for me. I use an old copy of Photoshop CS (version 8) as I cannot justify upgrading given the very basic tools I only use. The advantage of using levels is you can use the clipping warning (holding the alt key while touching the lever) which in my old version doesn't work when you grab the curve end-points.
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Only recently I started using the whitepoint, black point dropper, or manually shifting white points or black points according to where the information "begins" for each point in the histogram.
This is providing some great results, universally across the image. It may not save all highlights (if already blown) or shadows (if already clipped) but it is much more straight forward and consistent than a standard s-curve as preached by many online tutorials. Colours also "pop" a lot more and the whole photo looks like it appeared to me at the time - minimal curve adjustment also seems to reduce the likelihood of dreaded posteris/zation.
If you really want convenience, you might as well just use the "auto" button of curves/levels as it will pretty much do this for you automatically, and with less of a chance of user error. (Referring here to needing to do your apply image thing to bring back highlights you might have clipped by incorrectly choosing your white point.)
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Using auto functions can be a starting point, but it will seldom suffice for completing a quality image edit.
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Using auto functions can be a starting point, but it will seldom suffice for completing a quality image edit.
Who'd a thunk?
But the guy was looking for a quick way to add pop and gray balance without clipping. Guess what auto does.
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I'm trying to encourage him to approach the editing of raw image files in a serious and systematic manner. But yes, if he wants quick-and-dirty Auto Everything will do that - no question about it.
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Thanks Mark - yes I am looking to extend beyond the realm of auto adjustments. The one outcome I am looking for in this exercise is gaining a superior knowledge of curve adjustment to that presented in online tutorials and a lot of bookstores. Surely if I understood the implications of curve adjustments, I could quickly process images.
In other words, I want to understand, have the knowledge as a tool I can use at any time, but not necessarily all the time or for every image.
I hope this makes sense.
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Thanks Mark - yes I am looking to extend beyond the realm of auto adjustments. The one outcome I am looking for in this exercise is gaining a superior knowledge of curve adjustment to that presented in online tutorials and a lot of bookstores. Surely if I understood the implications of curve adjustments, I could quickly process images.
In other words, I want to understand, have the knowledge as a tool I can use at any time, but not necessarily all the time or for every image.
I hope this makes sense.
Donald, I really don't want to over push "auto" on you, but lets just see it thru to it's logical conclusion. Open one of the images where you manually set the B/W endpoints and gray balance. Turn off that layer and create a new curves adj layer above and apply Auto. Compare the curves it makes (channel by channel) to yours. See which you like better or worse and why. If you notice yours are generally more contrasty, see where your endpoints are compared to it. And are you adjusting each channel or only the master curve?
Dan Margulis' color correcting books are probably the most extensive description of curves out there. You can probably pick up an old edition used for cheap. Curves haven't changed much over the years.
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Donald, I really don't want to over push "auto" on you, but lets just see it thru to it's logical conclusion. Open one of the images where you manually set the B/W endpoints and gray balance. Turn off that layer and create a new curves adj layer above and apply Auto. Compare the curves it makes (channel by channel) to yours. See which you like better or worse and why. If you notice yours are generally more contrasty, see where your endpoints are compared to it. And are you adjusting each channel or only the master curve?
Dan Margulis' color correcting books are probably the most extensive description of curves out there. You can probably pick up an old edition used for cheap. Curves haven't changed much over the years.
Thanks Smahn.
With regards to Curves, does Dan consider RGB adjustment or does he only work within the L*a*b mode. From what has been posted and from what I can find online, he seems very one sided and relies extensively on L*a*b adjustment. Correct me if I am wrong.
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There are tons of free articles on the internet amd indeed on this website about the appropriate use of Curves and much of it is clear and understandable. Margulis doesn't only discuss L*a*b curves - he deals with RGB and CMYK as well - his favorite mantra is that every image has ten channels, and this is correct; but you don't need to buy his books to understand them. As well, he comes from a pre-press background and in many of his presentations he inverts the direction of luminosity on the axis to mimic the CMYK convention eventhough he may be discussing RGB. This just adds a layer of unnecessary baggage to understanding the concepts. I don't know whether he still does it - haven't looked at any of his stuff for several years. But as I say, there is a lot out there which is very good on this subject.
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Mark, could you point me in the direction of some good information on the matter? I have tried simple google searches but I find the information very basic.
I will endeavour to look for some of Dan's books, but would rather explore the free alternatives.
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Well, I'm not sure what you find too basic, so it's hard to know where to point you. I wrote a couple of articles about Curves published on this website here (http://www.luminous-landscape.com/essays/curves.shtml) which are probably not very basic, but may not be directly responsive to what interests you. (BTW they deal with a fair bit of Margulis' positions too.) Have you checked Ben WIllmore's material and anything of interest at Cambridgeincolour.com? There's also interesting material on Curves at Lobster and Curvemeister, as both are selling "Curvy" products which they explain in some detail.
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You can try the tutorials at Digital grin (http://dgrin.smugmug.com/gallery/6885600_qzSwN)
or this thread at
Digital Grin (http://www.dgrin.com/showthread.php?t=48066) about Margulis' book
You might find these useful too:
Developing images that pop pdf version (http://www.thelightsright.com/files/tutorials/DevelopingPhotosThatPop_Part1/DevelopingPhotosThatPop_Part1.pdf)
or
html version (http://www.outbackphoto.com/workflow/wf_45/essay.html) with comments by Uwe Steinmueller
This is a 4 part series links to all 4 parts in pdf can be found The Lights Right Tutorials (http://www.thelightsright.com/view/tlr_tutorials_menu)
Les