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Author Topic: Using ACR after scan stage  (Read 10091 times)
roa5100xx
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« on: January 18, 2013, 11:15:03 AM »
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Hi,
Can ACR be used after the scan stage(35mm slides) for processing (capture sharpening, noise reduction,color, etc). What would be the downside? What would be the upside? Good idea or bad?

Thanks
Herbert

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digitaldog
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« Reply #1 on: January 18, 2013, 11:18:17 AM »
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Unless the scanning application kind of sucks, you'd be best served doing as much there as possible. It's faster, it doesn't involve any data loss. If the scanning software is not so good, then ACR would be the next place to alter the color and tone. After that, Photoshop proper.
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Andrew Rodney
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« Reply #2 on: January 18, 2013, 11:29:24 AM »
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Yes you can, the major precaution being that you do not sharpen the image at the scan stage and then resharpen it in ACR/LR. As well, it is a good idea to normalize the histogram in the scan software at least to prevent unrecoverable clipping once you send the image to an application from which you can print it. Further editing in scan software that brings the image closer to a finished state is a good idea, because that gives you further editing headroom if you need it in other applications in which you may subsequently open it. Scratch and dust removal is best done at the scan stage if your scanning application and scanner allows for infrared detection and removal. Beyond that, each of these applications (scan application, Adobe applications) have their respective comparative advantages, so it is useful to experiment with both and choose the workflow that best suits you.I have much discussion and illustration of these options in my ebook on SilverFast - largely in relation to Lightroom and Photoshop, but the image editing engine and features are mostly the same in Camera Raw and Lightroom.
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Mark D Segal (formerly MarkDS)
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dmerger
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« Reply #3 on: January 18, 2013, 04:44:14 PM »
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Herbert, I disagree in part with the prior advice.  Also, it appears that Andrew and Mark previously have given inconsistent advice.  Both of them, I believe, have advocated custom scanner profiling, but making the type of adjustments you’re considering would make any custom scanner profile almost useless.  Perhaps Andrew and Mark can explain their apparently inconsistent advice.

In any event, let me explain why I believe that some of Andrew’s and Mark’s advice above is wrong.  First, it’s necessary to have a basic understanding of how a typical scanner operates.  A scanner uses a CCD (like a digital camera) to digitize your slides.  You can change what the CCD records by adjusting exposure and focus (i.e., hardware adjustments), but things like capture sharpening, noise reduction, color, etc (i.e., software adjustments) must be done, after the physical scan, to the data produced by the CCD.  Just because you set your software adjustments in your scanning software before you do your scan does not mean that those adjustments are part of the physical scanning process.  They are not.  Those adjustments are applied by your scanning software to the CCD data after the physical scan.

The point I’m making is that software adjustments are not a part of the physical scanning process. All software adjustments merely adjust the pixel data produced by your scanner’s CCD. As you noted, you can make your software adjustments with your scanning software or in ACR. 

If you make your software adjustments with your scanning software as part of your physical scanning process, it’s kind of like shooting jpeg’s.  Your adjustments are baked into your scan (i.e., destructive with data loss).  You do not get the advantages of a nondestructive workflow as with ACR. 

Another consideration is whether you prefer ACR or your scanning software’s image adjustments.  I’m a big fan of ACR and LR, and much prefer them to scanning software.  So much so that I can’t imagine why anyone would rather use scanning software, but I realize it’s a personal choice.
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Dean Erger
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« Reply #4 on: January 18, 2013, 04:58:10 PM »
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I’m a big fan of ACR and LR, and much prefer them to scanning software.  So much so that I can’t imagine why anyone would rather use scanning software, but I realize it’s a personal choice.

The question is, have you ever used really good scanning software ala say, LinoColor or ColorQuartet? I've used both for years driving high end desktop drum scanners and both provided functionality that we don't even have today in ACR or Photoshop (example, a saturation curve UI. Far more powerful selective color controls).

As I mentioned above, if you have a good scanning interface, it's going to be a lot faster and there's going to be less data loss doing it at the scan stage. If the software sucks, well, you have to fix the turd somewhere. ACR is preferable to Photoshop for a number of reasons, just as a good scanning interface is going to be preferable for the same reasons.

The best scanner with crappy software is an expensive door stop.
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Andrew Rodney
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« Reply #5 on: January 18, 2013, 05:36:21 PM »
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Herbert,

Before you have a chance to become confused, you may wish to consider the following:

Dean's first paragraph is irrelevant because we are not discussing scanner profiling. Scanner profiling is a "good thing to do" for dealing with reflective scans and positive transparency scans for the same reason that any device profiling is worthwhile, and that advice is valid regardless of what image editing options you elect to perform. Your question wasn't about profiling the scanner, so let's move on from there.

Dean's second paragraph is correct, except for scanner-dependent operations such as lamp control (in Nikon scanners) and infra-red scratch and dust removal on colour transparent media (positive and negative) using scanners and applications that support it. Unless the scanner has user-adjustable lamp-control, exposure adjustment is not a scanner dependent operation. It is software controlled. For dust and scratch removal, both SilverFast and Vuescan support it for a range of scanners. You can check on the SilverFast website for the scanners that allow for infrared detection; SilverFast's iSRD tool is much more granular than the infrared detection tool offered in Vuescan, but both can do it and removing all this debris at the scan stage is a vastly superior solution to scratch and dust removal in Photoshop or any raw converter.

Dean's third paragraph is correct, but you knew that and you are asking where it is better to make these adjustments.

Dean's fourth paragraph can be correct, depending on the kind of scan you produce. If you produce an adjusted scan in the scanning software and export it to your hard-drive he's right. All the adjustments done in the scanning software are baked-in. That is either OK or not so OK, depending on the quality of the adjustments and how permanently you want to keep them.

SilverFast and Vuescan both offer the facility to make a "raw" scan (in SilverFast called "HDR"). These scans are not "raw" in the same sense as a raw data file from a digital camera. These scans are fully rendered, three channel pixel-based images by the time you see them (and that is true in Vuescan too, whether they have a "DNG" container or not). They are only raw in the sense that nothing else is done to them except to dump everything read by the scanner's sensor into a processed, linear, but UNedited image file, so nothing has been destroyed that you have any control over. You can keep this as a master file and never damage it by never saving over it. For example, you can call it up in Photoshop, make any adjustments you want, then do a "Save As", the original file you were working on goes back to sleep as it was - unaltered and undamaged, while the newly created file has your adjustments.

The other way of doing this "non-destructively", which is where Dean's point is correct, is to open the scanned image in Lightroom or Camera Raw and make your edits there. Nothing happens to the file until you export it, if you ever do, because all that happens within the raw converter is that a metadata instruction set with all your edits sits with or in the image file, and only when you do something such as printing it or exporting it for whatever purpose, those edits get implemented on the fly ON THE EXPORTED IMAGE, so the original remains unaltered/undamaged, but the exported image has been altered.

Turning to Dean's final paragraph, there can of course be differences between Dean's preferences, factual considerations and what suits you. The factual consideration is that each digital image editing application only has so much "adjustability" built into its controls. So the more you can safely edit within the scanning software, even though it is baked in unless you use the raw scan option I defined above, the better the starting point of the image for the next level of adjusting you may wish to do in another image editing application, and the less further editing will be required. This is logically unambiguous and proves itself in reality too, especially for very difficult images.

One reason why you may wish to deploy software outside the scanning application for image editing is simply because it can often do stuff that you can't do in the scanning software because the scanning software wasn't designed for it. For example, no scanning software allows you to correct pin cushion or barrel distortion or to implement perspective controls, whereas Lightroom/ACR do. Another reason to consider the options between the scanning software and say ACR/LR, is that much of what you should do between these applications depends on which tool is best for the job at hand, and that varies; so my basic point, and what I emphasize in my book, is not to be dogmatic about this. There is NOT "one size fits all". SilverFast, for example, has a white balancing tool that is quite unique, insofar as it lets you balance four separate zones in one image where each one needs different balancing, at once, with four mouse clicks. It can work really well, and I haven't seen another application that does this. Lightroom I would contend is much stronger than ANY scanner application in teasing out shadow detail while maintaining and even enhancing the quality of deep shadow tones. Don't look for uni-dimensional recipes in this work. It's horses for courses. Some things work better in some places than others. Have the options available, experiment, and use whatever gives you a more satisfactory final result.

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Mark D Segal (formerly MarkDS)
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dmerger
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« Reply #6 on: January 18, 2013, 05:38:19 PM »
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I haven't used a drum scanner, and I assumed that Herbert's question wasn't about drum scanners.  My comments are about typical consumer scanners and related scanning software.
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Dean Erger
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« Reply #7 on: January 18, 2013, 05:45:04 PM »
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I haven't used a drum scanner, and I assumed that Herbert's question wasn't about drum scanners.  My comments are about typical consumer scanners and related scanning software.

You're missing the point. The hardware isn't under discussion here. The high end drum scanners of past just spent considerable time and effort providing excellent and powerful scanning software. They didn't' expect customers to spend ten's of thousands of dollars on hardware and mate with crappy software. Again, a great scanner with bad software is a huge waste.

Scanning software like a raw converter can be OK, good or superb. If you have a crappy scanning interface, pass the processing onto something better. That said, about the only software I've played with recently that comes close to providing the tools I would expect for scanning as I had in the past would be SilverFast. IF you had this software AND you knew how to use it, I don't think ACR would be useful outside of the corrections Mark discusses in terms of pin cushion or barrel distortion. And even then, I'm not sure ACR deals with rendered images to the same degree/quality as feeding it a raw.
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Andrew Rodney
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« Reply #8 on: January 18, 2013, 05:54:35 PM »
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Andrew, I fully agree with you that SilverFast is the best of the lot in scanning software and makes sense to do lots of stuff there, but I still recommend a pragmatic approach to the use of tools for image editing. Actually, in preparing my book, which is based on years of experience, I did/do edit high-bit rendered TIFF images from the scanner in Lightroom and it does an excellent job, as much as SilverFast also does an excellent job for the functions where it has comparative advantage.
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Mark D Segal (formerly MarkDS)
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« Reply #9 on: January 18, 2013, 06:50:33 PM »
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You're missing the point. The hardware isn't under discussion here. The high end drum scanners of past just spent considerable time and effort providing excellent and powerful scanning software. They didn't' expect customers to spend ten's of thousands of dollars on hardware and mate with crappy software. Again, a great scanner with bad software is a huge waste.

Scanning software like a raw converter can be OK, good or superb. If you have a crappy scanning interface, pass the processing onto something better. That said, about the only software I've played with recently that comes close to providing the tools I would expect for scanning as I had in the past would be SilverFast. IF you had this software AND you knew how to use it, I don't think ACR would be useful outside of the corrections Mark discusses in terms of pin cushion or barrel distortion. And even then, I'm not sure ACR deals with rendered images to the same degree/quality as feeding it a raw.

I’ve used Silverfast (and know how to use it), but I prefer ACR and LR.  With respect to software edits, SilverFast and ACR can start with the same pixel data from the scanner CCD. You like the way SilverFast edits that data.  I like ACR/LR. 
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Dean Erger
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« Reply #10 on: January 18, 2013, 09:49:06 PM »
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Do setting black and white points at the scan stage provide more data than scanning "flat" and doing those adjustments in Post?
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Mark D Segal
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« Reply #11 on: January 18, 2013, 10:17:39 PM »
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What do you mean by "data"? Luminance levels? Pixels? For any given resolution setting, a completely unadjusted linear scan contains the most output data you can get from the scanner at that resolution.
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Mark D Segal (formerly MarkDS)
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« Reply #12 on: January 18, 2013, 11:21:44 PM »
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Both?  Any?  All?  IS it better to leave the points alone during the scan?
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dmerger
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« Reply #13 on: January 18, 2013, 11:44:28 PM »
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Do setting black and white points at the scan stage provide more data than scanning "flat" and doing those adjustments in Post?

The short answer to your question is – No. 

A black and white point setting in your scan software does not affect the actual physical scan or the data produced by your scanner’s CCD.  It merely causes your scanning software to edit that data in accordance with your settings.  In other words, setting a black and white point can be done in your scanning software or PS, for example, and the results would be similar.

To amplify Mark’s answer, your scanner’s CCD outputs 16 bit linear unadjusted data.  (Only hardware adjustments can change the data your CCD outputs.) That linear data is the starting point for all subsequent edits regardless whether those adjustments are done with scanning software, PS, ACR, other image editing software.   It’s not practical to work with linear data, however, so most people at least output a gamma adjusted file from their scanning software.  Some people, however, output the 16 bit linear unadjusted data and then make a gamma adjustment and color correct the data via a scanner profile or other method.
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Dean Erger
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« Reply #14 on: January 18, 2013, 11:44:53 PM »
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Both?  Any?  All?  IS it better to leave the points alone during the scan?

There is one significant advantage the ACR/LR has regarding tone and color control over ANY scanner software I know is the ACR/LR has the ability to do both global (like in a scanner software) AND local image adjustments...if you think about it, this is a major difference.

As it relates to black and white point adjustments I think it's 6 of one, 1/2 dozen of the other for black point adjustments but I would suggest that ACR/LR has the best set of tools for adjusting white point. Yes, a scan ain't a raw file and you can't recover any clipped data from a scan but the ability to adjust highlights and white in ACR/LR added to the ability to adjust curve end points adds a degree of control I don't think ANY scanner software I am familiar with, has...so, setting the black and white points in the scanner software should be done very, VERY carefully to avoid wasting and usable image data that may be there and used by ACR/LR.

The fact you can globally set black and white points and then do local adjustments makes a real good case for doing very open (flat) scans in the scanner software and rely on the ACR/LR toolset to optimize the overall tone mapping. If you can get a decent full range scan with a decent color balance, that would be the best starting point for ACR/LR tone and color adjustments post scan.
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Mark D Segal
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« Reply #15 on: January 18, 2013, 11:49:01 PM »
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Alan, you asked: Both?  Any?  All?  IS it better to leave the points alone during the scan?

Not necessarily. It depends on where the end points of the histogram sit. If the luminance range of the prescan doesn't stretch to the end points of the tonal range, by remapping the deepest gray to black and the lightest gray to white, you are increasing contrast. If the resulting image looks better that way, and the quality of the remapping is good (because you are working in 16-bits per channel with good scanner software) there is no clipping of black or white and no harm done. In fact you end up with a better looking image straight from the scan stage. BUT if the tonal range of the prescan is already bumping-up against the walls of the histogram panel, any remapping that would sacrifice data from the end points of the tonal range is usually not a good idea, because you would be clipping luminance levels. No scan software I'm familiar with can rebuild highlights or rescue shadows as well as Lightroom/ACR can. SilverFast's "AACO" tool, if used VERY conservatively, and combined with SilverFast's Multi-Exposure (which does a second pass for adding exposure to dark areas), can help give shadow rescue a decent start at the scan stage. Apart from, or in addition to that, for those cases where shadows look hopelessly blocked and highlights look clipped, you'll get further exporting the scan to Lightroom/ACR where you can often rescue highlights and continue rescuing shadows there more effectively. I find combining the capabilities of software at both stages of the image-making process can be very helpful. Often it is not a case of "either-or", regardless of what some would have us believe. Once you've tried these various permutations and combinations yourself, you'll see the point.
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Mark D Segal (formerly MarkDS)
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« Reply #16 on: January 19, 2013, 12:00:51 AM »
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To amplify Mark’s answer, your scanner’s CCD outputs 16 bit linear unadjusted data.  (Only hardware adjustments can change the data your CCD outputs.) That linear data is the starting point for all subsequent edits regardless whether those adjustments are done with scanning software, PS, ACR, other image editing software.   It’s not practical to work with linear data, however, so most people at least output a gamma adjusted file from their scanning software.  Some people, however, output the 16 bit linear unadjusted data and then make a gamma adjustment and color correct the data via a scanner profile or other method.


I think Alan is asking where it is best to edit what the scanner produces. That is what Jeff Schewe and I addressed. I largely agree with all that Jeff said, except in my experience I think LR/ACR can also have value-added over scan software at the lower end of the tonal range. It isn't true that it isn't practical to work with linear data, for the reason Jeff stated. You don't want to end up there because it usually looks pretty flat, but as a starting point - as you said yourself - that's where the scans start, and as Jeff mentioned, often a good starting point for working in LR/ACR. Here again, there is no one-way truth in this. It depends on the image, it depends on the scan software, it depends on the operator not over-doing the adjustments - you can export images with gamma = or >1.0 and be fine either way.
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Mark D Segal (formerly MarkDS)
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« Reply #17 on: January 19, 2013, 12:42:31 AM »
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Do setting black and white points at the scan stage provide more data than scanning "flat" and doing those adjustments in Post?

I think Alan is asking where it is best to edit what the scanner produces. That is what Jeff Schewe and I addressed.


Of course, I must have misread Alan’s question and didn’t properly address his real question.  My apologies.  Roll Eyes  

It isn't true that it isn't practical to work with linear data, for the reason Jeff stated. You don't want to end up there because it usually looks pretty flat, but as a starting point - as you said yourself - that's where the scans start, and as Jeff mentioned, often a good starting point for working in LR/ACR.

Looks like I also misread Jeff’s reply since I don’t see where he talked about linear data. Are you sure, Mark, that Jeff recommends staring in LR/ACR with linear data from the scanner?  Linear data doesn’t just look pretty flat; it looks extremely dark with horrible color.  That’s why with camera raw files LR/ACR provides a gamma adjusted view for editing photos.  I don’t think it’s practical to make color and tone adjustments directly on and viewing linear data.  But if Jeff and you are able to do so, I must be wrong.  Shocked

By the way, what profile would be embedded with a linear file?

I'd also say that I agree with what Jeff wrote, but apparently I'm not capable of accurately reading today, so I'll take a fresh look tomorrow.  Cry
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Dean Erger
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« Reply #18 on: January 19, 2013, 12:58:21 AM »
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Looks like I also misread Jeff’s reply since I don’t see where he talked about linear data. Are you sure, Mark, that Jeff recommends staring in LR/ACR with linear data from the scanner?

I never mentioned "linear" data from the scanner...pretty sure that was Mark and maybe Andrew. Regardless, whatever image you get out of a scanner–ICC profiled to a specific color gamut and gamma or a "raw" linear output, it doesn't really matter. Doing the tone and color correction in ACR/LR is superior because of the ability to do both global and local adjustments.

I have two scanners, an Imacon 848 and an Epson Perfection V750-M Pro Scanner. When I'm scanning 4x5 film or smaller, I use the Imacon 848 and optimize the scan in Flexcolor and output a 16 bit image with the custom scanner profile I've made. If I'm scanning on the Epson I tend to do do flat scans in 16 bit Adobe RGB and optimize the image in Photoshop (and ignore "profiles"). I'll bring either scan into LR to do final tone & color corrections. That seems to work very well. BTW I don't do any sharpening in either scanner software! In the Imacon you actually have to turn sharpening on but move sharpening to -120 to defeat sharpening (turn it off).
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Mark D Segal
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« Reply #19 on: January 19, 2013, 08:31:14 AM »
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Jeff, where you said above "very open flat scans" I thought you had in mind linear because that's what you get from a gamma setting of 1.0 in the scanner; however one can also produce open flat scans that are not necessarily linear so your point is well taken.

Dean's point that linear scans start life looking dark and ugly is correct, but in the newer versions of LR/ACR they can be handled well even though when you first look at them it's depressing. I still elect most of the time to move them upwards of gamma 1.0 in the scan software to provide more editing latitude in post-scan software. There's nothing sacrosanct about linear gamma.

It's true that ACR/LR is advantageous in respect of handling both local and global corrections. I should point out however that a number of SilverFast's tools provide for creating masks and doing localized editing with them. It is, however, not as fully-featured as LR/ACR in these respects.

I also generally think it's suboptimal to bake either sharpening or grain reduction into in a scan; one wants the flexibility and quality of the sharpening workflow from capture to output sharpening, and reversibility in respect of grain mitigation. However there are people who wish to do their complete editing in the scan software without buying anything else, and for those folks, SilverFast does offer a complete workflow including these tools. It's sharpening algorithms have improved in version 8.

Where you say you ignore profiles with the Epson scanner, I find if not using a scanner profile at the scan stage, the image starts life more corrected in the post-scan stage of image editing by assigning the scanner profile on opening it in Photoshop and converting to the working space.

Interesting that you go to Photoshop and then to LR/ACR. If I need to do any work on the scan beyond what I can do in the scan software, I'll first go to LR/ACR, then if I need something neither SilverFast nor LR/ACR can do I'll open it in Photoshop, then bring it back to LR for printing, where the print module is just an easier trip than Photoshop's.

Well, Herbert, you see - you asked a seemingly simple question and as often happens, you find out that the answers are not as short as the question! That's fine and normal, because image editing provides multiple paths to outcomes, some better than others - depending - and it's in the "depending" where all the fun is.
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Mark D Segal (formerly MarkDS)
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