White Balance/Color Space Questions on VueScan DNG & TIFF Files

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After reading both the User's Guide and The VueScan Bible, I am now trying to set up VueScan to give me files that I can both use as digital masters and for any post-processing in LR. The issue that I am trying to better understand is how VueScan's raw file in DNG format differs from an outputted TIFF file with respect to White Balance in LR. The DNG raw file shows me the standard White Balance options for a raw file with the temperature scale displaying the color temperatures. The TIFF file that was outputted shows me the scale that is used with jpeg files and displays a scale from -100 to +100. This makes full sense to me if I was working with a raw and jpeg files from a camera, but I am a bit uncertain about what I am actually gaining from VueScan's DNG raw file format with respect to white balance. Is this file more malleable (like a raw file) when it comes to setting white balance, or is it just displaying the color temperature scale because the file is in DNG format, and it doesn't actually offer me any more leeway that the TIFF output file? I know that the Color Balance setting in VueScan on the Color Tab seems to impact one of the two files (the TIFF I am assuming) as they appear different. I have no objections to working in the DNG format for the master file, but TIFF is a bit easier if I end up sharing the files with people.

Also, one related question regarding Output Color Space. The usual choices are available (including sRBG, Adobe RGB and ProPhoto RGB). I am normally used to working with raw camera files that have no assigned color space and I just assign a space to any derivative file on export, but I am not sure what would be a good color space to assign to these files. I plan on processing them in LR, but they are also master files and it would be nice (but not absolutely necessary) if they were readable outside of LR should they be shared without any LR processing.

Any thoughts?

--Ken
 
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Hi Ken,

Yes it sounds like the VueScan Default Scanner color space is making a best guess of what an "average scanner" colors would be. So exporting the scan into another color space Pro Photo RGB for example would carry forward that "best guess" in to Pro Photo RGB. That is a big difference than simply assigning Pro Photo RBG to the resulting scan which would probably produce all sorts of undesired color shifts.

So if using the generic VueScan scanner input profile (the default) is producing acceptable results no need to pursue a custom profile.

I would be inclined to try to profile my scanner for reflective scans if I had an IT8 target. Good inexpensive ones are available from here Targets coloraid.de. However, they are not currently shipping to US due to COVID-19 postal restrictions. <sigh>

-louie
 
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Hi Ken,

Yes it sounds like the VueScan Default Scanner color space is making a best guess of what an "average scanner" colors would be. So exporting the scan into another color space Pro Photo RGB for example would carry forward that "best guess" in to Pro Photo RGB. That is a big difference than simply assigning Pro Photo RBG to the resulting scan which would probably produce all sorts of undesired color shifts.

So if using the generic VueScan scanner input profile (the default) is producing acceptable results no need to pursue a custom profile.

I would be inclined to try to profile my scanner for reflective scans if I had an IT8 target. Good inexpensive ones are available from here Targets coloraid.de. However, they are not currently shipping to US due to COVID-19 postal restrictions. <sigh>

-louie
I agree. I would like normally profile a scanner, but as this model is very inexpensive and is only being used for this project, I may end up buying an IT8 profile when I can, scan this unit, and then have the IT8 for when/if I upgrade to something like a V600 or V800.

Thanks,

--Ken
 
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Is it also possible to treat a scanner TIFF file as the "negative" and perform non-destructive edits?

To generalize my question, how much additional value is there for a scanner RAW file as opposed to a scanner TIFF file?

Sorry for the late reply. (Time seems to operate differently these days...) As long as the image is in LR, it's non-destructive, so in that sense it's the same as a TIFF - but it's also a lot bigger, and does not contain the same capabilities as a RAW file for re-processing, since so much of the data is now locked down. This also applies to a scanner as a RAW or TIFF.
 
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Regarding color space: RAW files don't have a color space, so it's not a concern. The converted files (JPG, TIF, PSD) need color spaces, and those depend on the eventual uses. For the web, it should be sRGB JPGs at 72 ppi; that's current best-practice. For sending to outside printers, sRGB is generally fine, but if the printer needs a wide color gamut, then Adobe RGB is the standard. For your own printer, anything will work (with a caveat, following). For processing further in Photoshop, for instance, ProPhoto at 16-bits, either as a TIF or PSD, gives the best results in terms of how much you can chew on image; roughly speaking, those color spaces at 16-bit allow for the best changes across tone and contrast.

For all these issues to work correctly, you have to calibrate your screen; that is 90% of color management. It's easy and not terribly expensive to do. If you do your own printing, it's best to calibrate or profile you printer; this will save a lot of money and time, not to mention emotional distress after looking at prints that don't resemble what you see on your screen.
 
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For the web, it should be sRGB JPGs at 72 ppi
Forget the 72ppi. That is one of the most persistent misunderstandings. Resolution in ppi is irrelevant on the web.
 
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Respectfully, I have to disagree. While it is absolutely true that images will render OK at other resolutions, there are two reasons why I stick with 72ppi. The first, and most important for me as a professional, is that 72ppi limits how my images can used if they are stolen, and this is common for me and other professionals - a stolen image is a free image, and I like to choose who gets to use my images for free, since over time "free" is a very poor business model. 72ppi will not print well at anything other than a small size, whereas 300 ppi, which is what I deliver to clients will print well at that resolution, or even at half that resolution, if someone knows what they are doing.

The second reason is how web developers code for the best professional presentation of images, whether for an ad, or for a portfolio, which is that image files should load as fast as possible and look their best at whatever sizes they are supposed to render at. Advertisers also are sensitive to not having images they have paid to license be ripped off.

Any developer will admit that the 72 ppi standard is a legacy of the early web, but that's just the way things turned out, so they code for that, and the better portfolio sites also strongly suggest that's the best. Even Instagram suggests 72 ppi, if I'm not mistaken. So while 72ppi is not, strictly speaking, necessary, it is the standard for good and practical reasons.

So for non-professionals who don't have the kinds of considerations I have, or that advertisers have, any resolution will do - but sRGB as a color space applies for web presentation no matter what, if you want images to render as accurately as possible.
 
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Respectfully, I have to disagree.
Respectfully, I have to disagree with your disagreement. Johan is (as usual) correct - the PPI setting is totally irrelevant. In your example, what will stop the photo thief from stealing your 72ppi image, loading it into Photoshop, and changing the PPI setting to 300? If all the pixels are there, then all the pixels are there and available to the thief, regardless of whether you've inserted the number "72" or any other number into the file (which is all you are doing when making that setting).

This is, however, off topic to this thread ...
 
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My position on resolution is based on the practicalities of how images are used.

For instance, the images on my professional portfolio site are mostly 2000 pixels wide, each of them sRGB 72 ppi.

2000 pixels wide at 72 ppi = 27.7 inches.

If I convert that file to 300 ppi = 6.7 inches wide.

If the image was going to be used for print, this makes the print not very usable for anything above a postcard size; 300 ppi being the standard for delivering images files for commercial and fine art printing, and sometimes for editorial printing. Of course the image could be printed larger than 6.7 inches, but if the photo is, for instance, a landscape or a building, with lots of high-frequency detail, the print detail will break down and it will not be an attractive print. Even skin tones can get unpleasantly blocky.

If the image is only going to be seen on the web, all this is less of an issue. But print is still a viable medium for fine art and commercial and editorial uses. Those uses are not defined by myself, but by the contractual demands of my clients. For commercial use - which can range from large posters to brochures, the size of the file - and the resolution - directly affects quality. In editorial uses, whether the image is printed or appears online, the quality of the image is also important, because in both cases there is money on the line.

Money is one of the factors setting the standard for best practices, which is one of the reasons Adobe and other vendors pay attention to the professional market. For which I'm very grateful!

So, for instance, if someone who sells images at an art fair steals one of my images off my portfolio site and tries to print it at anything larger than 6.7 inches, they are going to have a hard time making any money - which is exactly the result I hope for. And that hope is based on industry standards designed to protect images that are stolen from being able to be monetized by people who do not pay a license to use that image, or by people who do not own the copyright, such as myself.

Obviously, for people who do not make a living from their photography, none of this matters, so I will admit it's a moot point as to how resolution affects image quality.
 
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My position on resolution is based on the practicalities of how images are used.

For instance, the images on my professional portfolio site are mostly 2000 pixels wide, each of them sRGB 72 ppi.

2000 pixels wide at 72 ppi = 27.7 inches.

If I convert that file to 300 ppi = 6.7 inches wide.

If the image was going to be used for print, this makes the print not very usable for anything above a postcard size; 300 ppi being the standard for delivering images files for commercial and fine art printing, and sometimes for editorial printing. Of course the image could be printed larger than 6.7 inches, but if the photo is, for instance, a landscape or a building, with lots of high-frequency detail, the print detail will break down and it will not be an attractive print. Even skin tones can get unpleasantly blocky.
The point is that this is determined by the 2000 pixels image width, not by the 72 ppi resolution. An image of 2000 pixels width @72 ppi is exactly the same as an image of 2000 pixels width @ 300 ppi or an image of 2000 pixels width @ 1,000,000 ppi. And internet browsers ignore the ppi value and show the three above mentioned images at exactly the same size. That is why ppi is totally irrelevant for the internet, period.

And if you do not believe me (you apparently don’t): The 72 PPI Web Image Myth - Photo Cascadia
 
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Again, I do agree with you, as I stated earlier; mostly, resolution is not an issue on the web. Where things are different is in the UX, or User Experience, for the intended audience.

For instance, my portfolio host (PhotoFolio), is run by designers and developers who are focused on being up-to-date with best practices for posting photos on the web, so however they tell me to format images, that's what I'll do. And there is a good reason for that: those developers know that my audience are art buyers from advertising agencies and photo editors at publications who spend all day looking at hundreds of image every day, so their viewing experience better be first-rate. If it's not, I am less likely to get hired (and so will the many other photographers on the site), with the result the developers will be out of a job - these are commercial considerations. So, when they tell me my images need to be sRGB 72ppi, it's not because they don't know the reference above from Photo Cascade - which is an argument all professional photographers are well aware of - it is because their job as developers and designers is to optimize the viewing experience for people whose job is to scan large images in large numbers that render very fast one after the other that look as good as possible. This is where resolution does make a difference, but it is situational. I am not an engineer, but they are, and their reasoning is based on testing and industry best-practices. I'm happy to take my lead from them.

Obviously, for most people, resolution, as you write, does not matter, and images posted at other resolutions than 72 ppi will look OK, but when you're in business of showing your images to potential buyers - as I am - these subtleties make a lot of difference. It's a fine distinction, I will happily admit, but it is a distinction for good reasons.
 
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Barry, the situation is simple. This is what you said earlier:

The first, and most important for me as a professional, is that 72ppi limits how my images can used if they are stolen, and this is common for me and other professionals - a stolen image is a free image, and I like to choose who gets to use my images for free, since over time "free" is a very poor business model. 72ppi will not print well at anything other than a small size, whereas 300 ppi, which is what I deliver to clients will print well at that resolution, or even at half that resolution, if someone knows what they are doing.

Maybe you now have found another reason to use 72 ppi and maybe that reason is even legitimate (I doubt it), but the above quote is what I reacted to. And that is why I said that this is a persistent myth. Setting the ppi value to 72 does not protect your images on the web any better that setting it to 1 ppi or 1,000,000 ppi. I am not going to add anything more to this discussion, because I would only repeat what I already said.
 
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Barry, the situation is simple. This is what you said earlier:

Maybe you now have found another reason to use 72 ppi and maybe that reason is even legitimate (I doubt it), but the above quote is what I reacted to. And that is why I said that this is a persistent myth. Setting the ppi value to 72 does not protect your images on the web any better that setting it to 1 ppi or 1,000,000 ppi. I am not going to add anything more to this discussion, because I would only repeat what I already said.

I agree, I think we've about wrung this subject dry. I will say that in my earlier responses I mentioned both printing issues as well as web-developer best practices.

My larger point is not that technical realities don't matter - they are important to understand - it's more that technical aspects of photography or, really, any kind of image production, ultimately reflect of how images are processed and presented.

For instance, for me, one of the most thrilling aspects of digital photography has been the ability to process and print color images. Black & white images were easy to produce when film was dominant, but color was expensive and could not easily or cheaply be processed and printed in a home office (or bedroom!). Digital not only changed photography, it changed how commercial printing works; it is directly connected to the amazing proliferation of images on the web (which did not exist when film was dominant); it brought high quality photography to everyday products such as phones and point-and-shoots; and made high-quality printing possible for anyone to achieve. Any of these uses of digital imagery requires different kinds of processing and different levels of quality. There is no one-size-fits-all.

But without a handle on some of the basics, there is only trouble and frustration. Forums like this one, and the better books and teachers, have been invaluable to me as I learned how to learn, and learned what mattered and what does not, and why.
 
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Well, thinking of people who may read this thread in the future, I hate to leave misinformation lying around - especially on one of the most respected and authorative informational websites on the internet. So:

Going back to your example of an image 2000 pixels wide, let's assume for the sake of argument that it's also 2000 pixels in height. So there are 4 million pixels in that image file (2000 x 2000). The quality of the image is determined solely by the quality (informational content) of the data in those 4 million pixels. Also contained in the image file will be some extra information about the image: possibly a copyright notice, possible camera metadata, etc., and possibly a DPI/PPI "resolution" setting. That resolution setting is just a single number tacked on to the rest of the data in the file. It is used as a hint (and it is really no more than a hint) in some scenarios to other programs that might want to process the file later on. You can set that DPI/PPI number to 72 or 300 or whatever you like when you export the file from Lightroom or Photoshop. But it has exactly zero effect on the 4 million pixels of image data which is exported and stored in the file at the same time.

A web site and browser combination which wants to display your image will simply ignore that DPI/PPI number. All that a web server and browser want to know is what size of an image to produce to fit on your screen. If they determine that your image needs to be 1000 pixels square to fit on your screen, they will simply convert your 2000-pixel image down to a 1000-pixel image. This is a mathematical downscaling, by a factor of two. There is no need to know, or care about, the DPI/PPI setting, because it's irrelevant. Likewise your hypothetical image thief. If the thief can download your 2000-pixel image, then they've got your 4 million pixels of image information, exactly as you uploaded it. Just having the number "72" tacked on the end does nothing one way or the other. All the relevant information is in the pixels.

I don't understand how any of your discussion has any bearing on this mathematical outcome.

mostly, resolution is not an issue on the web
Resolution is never an issue on the web.
Where things are different is in the UX ...
Things are NOT different in the UX. If you think they are, you need to explain how.
This is where resolution does make a difference, but it is situational
Resolution does NOT make a difference. If you think it does, you need to explain how.
images posted at other resolutions than 72 ppi will look OK
Images posted at other resolutions will look exactly the same (see test images below).
these subtleties make a lot of difference. It's a fine distinction, I will happily admit, but it is a distinction for good reasons.
This "subtlety" makes no difference. What are these "good reasons" to which you refer?

Here's a test. Two images, both exported as JPGs from Lightroom at 600 pixels square, color space sRGB, compression factor 80. One of them exported with a resolution of 10 pixels per inch, the other at 1000 pixels per inch. Should be a big difference, wouldn't you think? I'm not telling you which is which. Can you see any difference? Download both files and open them in Photoshop. You can verify the PPI settings with the "File Info ..." facility. You will note that the files are exactly the same size on disk. In Photoshop, put one of the images on top of the other as a new layer, then set the blend mode of the uppermost layer to "Difference". This will highlight any differences between the two images. There will be none (this will be indicated by a completely black screen). The files are identical apart from the fact that one contains the number 10 and one contains the number 1000 in the PPI field.

Image A:
MapleLeaves_A.jpg

Image B:
MapleLeaves_B.jpg


You seem to put a lot of store in the recommendations of the PhotoFolio website. That's fair enough, as a general rule. I this case, I think they have just been lazy - when exporting, you need to put some number in the resolution box, so they probably figured "72 is as good as anything else, so let's just write that down so we don't get people contacting us all the time asking 'What PPI should I use?'"

Also worth noting is that web site recommendations, even on well-known photo sites, are sometimes wrong because they tend to be written by web designers who themselves do not understand the issues. Web designers are usually not computer scientists or engineers, they simply do things a certain way (probably the way they were taught) and repeat misinformation without thinking about it too deeply.
 
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I wish Adobe would have just left the Resolution box off the Export Dialog window in LR. It is information that is mostly used by legacy software (for convenience) and is confusing at best, as in this discussion. It s value as an instruction seems dated, especially in this era for 4k monitors. If you are concerned about fast load times, then resize your images before posting. If you are concerned about quality on high resolution monitors, then post high resolution images and encourage your viewers to use sites/software than does not compress the files.

Having looked at the Photofolio site and searched for the help/support pages, I found this: Batch Resize Images in Lightroom . Note the following:

Our normal image suggestions are 1860x1140px, but you can adjust the resolution or dimensions to fit your needs. We typically suggest keeping the file sizes in the 250 - 550 kb range, but you can use larger files. Keep in mind, the larger the file size, the slower the image will load on slower internet connections. Finally, select "Export" to resize & save the images.

--Ken
 
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You seem to put a lot of store in the recommendations of the PhotoFolio website. That's fair enough, as a general rule. I this case, I think they have just been lazy - when exporting, you need to put some number in the resolution box, so they probably figured "72 is as good as anything else, so let's just write that down so we don't get people contacting us all the time asking 'What PPI should I use?'"
That was my idea too. Or they just believe the same myth. They would not be the first, or the last.
 
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I wish Adobe would have just left the Resolution box off the Export Dialog window in LR. It is information that is mostly used by legacy software (for convenience) and is confusing at best
I agree with you. However, if you set the image size in length unit (cm or inches), the PPI will be used by LR to calculate the image size (in pixels) of the exported image. Note that I don't see this useful either! Fixing the image size in length unit might be useful if you want to print it later. But in this case, It's better in my opinion to send the image full size and let the print service do the downsizing according to their printer capabilities...
 
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I agree with you. However, if you set the image size in length unit (cm or inches), the PPI will be used by LR to calculate the image size (in pixels) of the exported image. Note that I don't see this useful either! Fixing the image size in length unit might be useful if you want to print it later. But in this case, It's better in my opinion to send the image full size and let the print service do the downsizing according to their printer capabilities...
I did not know that LR uses the resolution box input to calculate if you set the measurement of an exported file in a unit length. I guess I did not know because, like you, I always send as much resolution as I can or as is needed. Or, I resize based on pixels rather than inches or centimeters and the input is not needed. I still think that it could be better labeled if it is going to be used for that purpose. Perhaps "Desired Print PPI"? Now that makes me wonder what happens if the native file does not have the needed resolution? Does LR scale up?

--Ken
 
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Perhaps "Desired Print PPI"? Now that makes me wonder what happens if the native file does not have the needed resolution? Does LR scale up?
Yes, if you leave the "Don't Enlarge" box unchecked. But if you check that box, and the file doesn't have the required resolution, then you end up with an exported file which doesn't have enough pixels to print the required size at the required PPI setting. That could be an obscure bug, of course.
 
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