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Author Topic: Confusion Over Options For RAW Image Processing  (Read 6928 times)
John R Smith
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« Reply #20 on: February 28, 2011, 04:48:07 AM »
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Jim

Just a few observations on the topic of B/W digital work - these are my opinion and and my experience only, and are certainly not meant to be set in stone.

* If you shoot RAW and set the camera to auto white balance, there will be no need to mess with white balance in LR or ACR for a B/W conversion. Very slight colour temperature changes will make negligible difference to the B/W result.

* If you have come to digital B/W from the wet darkroom, then Lightroom 3.x can replicate almost anything that you could have done in the darkroom for B/W (with the exception of solarisation or posterisation). You really only need CS5 if you have a wish to go beyond that.

* When it comes to the thorny issue of converting a colour RAW to B/W, you should be aware that my experience shows that any strategy other than a flat grayscale conversion will increase colour noise in the output file. This is not necessarily an insurmountable probelm, but it is something to be aware of. Noise of this type is often masked in landscape work by the nature of the subject's high-frequency detail, but it is nonetheless there.

John
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« Reply #21 on: February 28, 2011, 07:48:31 AM »
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Not true...in Photoshop you can have the red, green and blue channels of a color image work as layers (technique ala JP Capnigro and myself see: Art of B&W pdf) and use opacity blending and layer masks to get a B&W conversion that you can't do in LR/ACR.

I remember your paper from 2005 and went back to it. It's a great paper, but I have two observations: (i) in my remarks above what I had in mind was a direct comparison of using the channel mixer compared with using the more current techniques in LR/ACR and PSCS5 B&W Adj Layer, and (ii) yes indeed, one needs to be a bit less definitive saying what can and can't be done in PS, because - as we all know - there's really no limit. That said, it may be interesting to research with the image you used in that paper, seeing to what extent one could achieve very similar outcomes in LR/ACR versus what you show there, recognizing of course that the raw converters don't have the layering and masking capabilities of Photoshop. 
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Mark D Segal (formerly MarkDS)
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Slobodan Blagojevic
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« Reply #22 on: February 28, 2011, 09:55:59 AM »
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...
* When it comes to the thorny issue of converting a colour RAW to B/W, you should be aware that my experience shows that any strategy other than a flat grayscale conversion will increase colour noise in the output file...


Could it be that only screen rendering appears noisy?
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Slobodan

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« Reply #23 on: February 28, 2011, 10:01:26 AM »
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I remember your paper from 2005 and went back to it. It's a great paper, but I have two observations: (i) in my remarks above what I had in mind was a direct comparison of using the channel mixer compared with using the more current techniques in LR/ACR and PSCS5 B&W Adj Layer, and (ii) yes indeed, one needs to be a bit less definitive saying what can and can't be done in PS, because - as we all know - there's really no limit. That said, it may be interesting to research with the image you used in that paper, seeing to what extent one could achieve very similar outcomes in LR/ACR versus what you show there, recognizing of course that the raw converters don't have the layering and masking capabilities of Photoshop. 

With the parametric editing ability of ACR/LR and the Adjustment Brush with its control point technology, much of the need for layers and masks is obviated.
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« Reply #24 on: February 28, 2011, 10:02:49 AM »
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With the parametric editing ability of ACR/LR and the Adjustment Brush with its control point technology, much of the need for layers and masks is obviated.
that is if you have time to work it manually - if you have a good toolbox of plugins to automate your work then LR is quite impotent just because it does not support layers, etc directly
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« Reply #25 on: February 28, 2011, 10:06:09 AM »
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recognizing of course that the raw converters don't have the layering and masking capabilities of Photoshop. 
LR/ACR may be don't, but there are raw converters outside Adobe realm that have layering and masking... Bibble, Lightzone... it seems that C1 is slowly moving into that direction, albeit they lack the resources to implement fast.
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« Reply #26 on: February 28, 2011, 01:38:05 PM »
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* When it comes to the thorny issue of converting a colour RAW to B/W, you should be aware that my experience shows that any strategy other than a flat grayscale conversion will increase colour noise in the output file. This is not necessarily an insurmountable probelm, but it is something to be aware of. Noise of this type is often masked in landscape work by the nature of the subject's high-frequency detail, but it is nonetheless there.

John

I don't understand this statement. When you use the raw converters (LR/ACR) to move from colour to B&W, one is engaging an instruction set making the program render the colour data in grayscale, wherein the use of the colour group sliders influences the luminance of the gray tones representing those colour groups. If this is what we are talking about, I have never ever seen any colour noise in printed images from such a process. Nor have I seen this problem in fully converted colour images converted to B&W using the Photoshop CS5 Black and White Adjustment Layer, nor have I seen it using Nik Silver Efex Pro versions 1 or 2. I've made B&W images using any of these techniques. Conversions are neutral and not showing colour noise in print sizes ranging between 13*19 and 17*22 inches. Are there other processes you have been using which do show such a problem, and if so what are those processes and in what viewing conditions do you see it?
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Mark D Segal (formerly MarkDS)
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« Reply #27 on: February 28, 2011, 01:39:26 PM »
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that is if you have time to work it manually - if you have a good toolbox of plugins to automate your work then LR is quite impotent just because it does not support layers, etc directly

Don't use plugins. 

WRT other RAW editors, while there are some others out there, their functionality is limited compared to Photoshop.  Even Lightzone, as good as it is, isn't Photoshop. 
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« Reply #28 on: February 28, 2011, 01:41:11 PM »
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Don't use plugins. 

Really? Why not? Even if they do great stuff for me very easily? What am I missing here?
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Mark D Segal (formerly MarkDS)
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John R Smith
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« Reply #29 on: March 01, 2011, 02:40:09 AM »
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I don't understand this statement. When you use the raw converters (LR/ACR) to move from colour to B&W, one is engaging an instruction set making the program render the colour data in grayscale, wherein the use of the colour group sliders influences the luminance of the gray tones representing those colour groups. If this is what we are talking about, I have never ever seen any colour noise in printed images from such a process. Nor have I seen this problem in fully converted colour images converted to B&W using the Photoshop CS5 Black and White Adjustment Layer, nor have I seen it using Nik Silver Efex Pro versions 1 or 2. I've made B&W images using any of these techniques. Conversions are neutral and not showing colour noise in print sizes ranging between 13*19 and 17*22 inches. Are there other processes you have been using which do show such a problem, and if so what are those processes and in what viewing conditions do you see it?

Mark and Slobodan

I probably shouldn't have made this comment, but I just assumed that it must be a well-known issue. Specifically, I am talking about my Hasselblad 3FR files, imported into Lightroom and converted to B/W using the grayscale conversion tools within LR. When I first started doing this, I made up a set of B/W LR pre-sets which emulate the spectral response of various B/W film stocks, and some others which replicate the effect of various coloured filters (yellow, green, orange etc). This was by no means an original idea, I simply studied how trial versions of Convert to B/W Pro and Silver Efex worked and rolled my own.

All was good, but then I started to notice that even at 100 ISO or 50 in some images I had serious colour noise in areas of flat tone and low detail. Clear blue skies are the obvious area where you see this first, and of course you only see it on screen at 100% when applying capture sharpening and noise reduction. With the 'Blad files, there is always a tiny bit of luminance noise, but normally that is no problem. One area which showed up the colour noise issue big time was skin tones in semi-shade, where massive blotchy noise was apparent. In a complex landscape with lots of grass, trees, and a cloudy sky you will barely notice a problem, as the high-frequency detail masks the noise.

Now the noise reduction in LR is very good, and will deal with the issue, but I couldn't understand why I had so much CN at low ISO. So I examined an area at 100%, and switched the file around through my presets and also back to a flat grayscale conversion (all sliders set to zero). Lo and behold, when the grayscale was set flat, the noise completely vanished. Smooth skies, smooth skin tones. Further investigation showed that the main culprit was boosting yellow and orange in the grayscale panel, which either introduces this noise or makes what CN is already there much more visible, I don't know which. And of course, the spectral response of a typical B/W film (like FP4) has this "kick" in the yellows, which gives it that look. And when I shoot B/W film, 90% of the time I have a yellow filter on as well, which in the English landscape lightens foliage and darkens skies. So all my LR presets tend to boost yellow and darken blue in varying degrees, which gives me a really nice film-like look, but also has this unforseen noise side-effect. So these days I tend to think rather more carefully about how much digital filtration to apply to a given image, and modify my pre-sets to suit.

I had just thought that all of this must be a well-known problem (except to me, of course), and I was trying to save others just starting out from finding out the hard way.

John
« Last Edit: March 01, 2011, 09:17:31 AM by John R Smith » Logged

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« Reply #30 on: March 01, 2011, 03:13:28 AM »
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John are you actually seeing colour noise or am I right it thinking it's at the noise reduction stage that you have to remove colour noise to clean up the image.
Wayne
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John R Smith
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« Reply #31 on: March 01, 2011, 03:31:20 AM »
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John are you actually seeing colour noise or am I right it thinking it's at the noise reduction stage that you have to remove colour noise to clean up the image.
Wayne

Wayne

Well, you don't actually see the noise in colour, of course, because you are working in B/W. What you see is a nasty blotchy load of gray porridge which should not be there. You see it alright at 100%, whatever you are doing. It is colour noise, because the colour noise removal in LR gets rid of it.

John
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« Reply #32 on: March 01, 2011, 07:07:12 AM »
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Mark and Slobodan

I probably shouldn't have made this comment, but I just assumed that it must be a well-known issue. Specifically, I am talking about my Hasselblad 3FR files, imported into Lightroom and converted to B/W using the grayscale conversion tools within LR. When I first started doing this, I made up a set of B/W LR pre-sets which emulate the spectral response of various B/W film stocks, and some others which replicate the effect of various coloured filters (yellow, green, orange etc). This was by no means an original idea, I simply studied how trial versions of Convert to B/W Pro and Silver Efex worked and rolled my own.

All was good, but then I started to notice that even at 100 ISO or 50 in some images I had serious colour noise in areas of flat tone and low detail. Clear blue skies are the obvious area where you see this first, and of course you only see it on screen at 100% when applying capture sharpening and noise reduction. With the 'Blad files, there is always a tiny bit of luminance noise, but normally that is no problem. One area which showed up the colour noise issue big time was skin tones in semi-shade, where massive blotchy noise was apparent. In a complex landscape with lots of grass, trees, and a cloudy sky you will barely notice a problem, as the high-frequency detail masks the noise.

Now the noise reduction in LR is very good, and will deal with the issue, but I couldn't understand why I had so much CN at low ISO. So I examined an area at 100%, and switched the file around through my presets and also back to a flat grayscale conversion (all sliders set to zero). Lo and behold, when the grayscale was set flat, the noise completely vanished. Smooth skies, smooth skin tones. Further investigation showed that the main culprit was boosting yellow and orange in the grayscale panel, which either introduces this noise or makes what CN is already there much more visible, I don't know which. And of course, the spectral response of a typical B/W film (like FP4) has this "kick" in the yellows, which gives it that look. And when I shoot B/W film, 90% of the time I have a yellow filter on as well, which in the English landscape lightens foliage and darkens skies. So all my LR presets tend to boost yellow and darken blue in varying degrees, which gives me a really nice film-like look, but also has this unforseen noise side-effect. So these days I tend to think rather more carefully about how much filtration to apply to a given image, and modify my pre-sets to suit.

I had just thought that all of this must be a well-known problem (except to me, of course), and I was trying to save others just starting out from finding out the hard way.

John

If we are talking about film scanning, another idea would be to convert the image to B&W at the scan stage. For example, using SilverFast Ai6, you can select 48-bit Grayscale and it will scan and render a luminance-only image from which you will have none of these problems. You can then use an application such as Silver Efex Pro to create a multitude of B&W interpretations and effects from it.
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Mark D Segal (formerly MarkDS)
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John R Smith
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« Reply #33 on: March 01, 2011, 08:06:40 AM »
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Yes, well film scans are another matter altogether. You don't get noise issues, you get grain aliasing instead, which is just as nasty in its own way.

There are all sorts of issues when converting colour RAWs to B/W, not all of them terribly obvious. A straight conversion is almost always very flat and far too low in contrast for for a B/W image. Very similar to the problems you have in the darkroom if you try to print a colour negative as B/W, actually. The process of normalising the histogram and bringing contrast up to a believable level (believable in the context of B/W film, that is) has the effect of increasing any inherent flaws and artefacts in the original image file.

At 100% it is often possible to see unpleasant artefacts which manifest themselves as a kind of geometric breakup of the image, which don't look like a noise problem but in fact are, and they can be smoothed using the LR colour noise removal. Usually this happens when the image has been really pushed in the shadow areas because of under-exposure in the field. Although the LR noise removal is very good, obviously it is better to do as little as possible.

John
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« Reply #34 on: March 01, 2011, 08:14:28 AM »
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John, in post 29, were you talking about digital film or both?
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Mark D Segal (formerly MarkDS)
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« Reply #35 on: March 01, 2011, 08:33:20 AM »
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John, in post 29, were you talking about digital film or both?

Just digital, Mark. Specifically Hass 3FR RAW files imported directly into Lightroom 3.2 Sorry, what I wrote towards the end of the post was a little confusing. I was trying to explain why my LR pre-sets tend to boost yellow and orange - to mimic the response of film and filters. I didn't mean that I was processing film scans.

John
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« Reply #36 on: March 01, 2011, 09:39:14 AM »
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Wayne

Well, you don't actually see the noise in colour, of course, because you are working in B/W. What you see is a nasty blotchy load of gray porridge which should not be there. You see it alright at 100%, whatever you are doing. It is colour noise, because the colour noise removal in LR gets rid of it.

John
I can reproduce what your getting by upping the yellow orange and reducing blue, presumably ACR see's a greyscale image in colour as far as noise is concerned, I assume it's only really rendered proper greyscale on opening in photoshop, in camera raw it's still seeing the full raw image.
Wayne
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« Reply #37 on: March 01, 2011, 09:49:17 AM »
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... you don't actually see the noise in colour, of course, because you are working in B/W... It is colour noise, because the colour noise removal in LR gets rid of it.

Isn't that a good reason to use the color noise removal slider before you convert it to b&w? Btw, it is on by default, at 25 value. Are you saying you are zeroing it before the conversion to b&w?
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« Reply #38 on: March 01, 2011, 10:22:37 AM »
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Could the noise be posterization?

http://www.photography.com/articles/digital-photography/posterization/

When using ACR on images with 1SO 200 - in effect no noise - and I raise saturation I find that I have to be careful when raising the blue saturation, especially in skies. The effect looks very much like posterization.
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« Reply #39 on: March 01, 2011, 10:31:12 AM »
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Just digital, Mark. Specifically Hass 3FR RAW files imported directly into Lightroom 3.2 Sorry, what I wrote towards the end of the post was a little confusing. I was trying to explain why my LR pre-sets tend to boost yellow and orange - to mimic the response of film and filters. I didn't mean that I was processing film scans.

John

AH, OK, so my comment on film scans was not relevant - just wanted to verify that.
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