Are 16 bit scans = 8 bit scans converted to 16 bit in CS2?

<p>Friends, I have an Eversmart Pro II which I use to scan 6x6cm and 4x5 chromes. The Oxygen software scans in 8 bit, though there is, I understand, a plugin that converts to 16 bit. My question is whether an 8 bit scan that is converted to 16 bit in CS2 responds to color management in the same way as a file originally scanned in 16 bit. FWIW, I do most all the color adjustments prescan with very modest adjustments in CS2. Since I am scanning 4x5 chromes, the 16 bit scans would be twice the size of already processor choking files in 8 bit.<br />Thanks,<br>

David</p>

<p>I think there is a theoretical loss to having been in 8 bit then upconverted into 16 bit. The numeric stair steps between tonal or color changes are coarser in 8 bit, and putting it into 16 bit doesn't smooth them out automatically.</p>

<p>However, most of the drastic tonal demands take place in the editing process (curves, levels, etc) so as long as you're editing in the 16 bit world you should be okay.</p>

<p>It's not like a native 8 bit 4x5 scan is likely to show significant banding/posterizing in the raw scan. It's only when you push around an 8 bit file that it would have problems.</p>

<p>Your scanner produces a 14 bit output that is mapped onto 16 bits (two bits of zero.) The software is discarding 6 of those bits. If you convert back to 16 bits, you now have 8 bits of data and 8 zeros. Get different software for the scanning.</p>

<p>The above post is wrong, you are pushing around 8 bits even in 16 bit mode if you threw away the other 6 bits of data.</p>

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<p>The above post is wrong, you are pushing around 8 bits even in 16 bit mode if you threw away the other 6 bits of data.</p>

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<p>Not so fast, Jeff. There is an advantage to converting an 8 bit file to 16 bits before drastic editing: rounding off errors in the various editing steps will be smaller for the 16 bit file, even if originally it started out as an 8 bit file.</p>

<p>You get an extra bit at most. Rounding errors aren't going out very far. There's really no reason to zero out the last 6 bits in the original file.</p>

<p>Actually, the practical difference between starting with an 8 bit file and editing it in 16 bit mode vs starting with a 16 bit file is not as drastic as you suggest. Try it yourself in Photoshop, use this article as a guideline for how to massively compress then stretch an image in 2 steps using the levels tool.</p>

<p>http://www.photoshopessentials.com/essentials/16-bit/page-2.php</p>

<p>Create 3 new image files in PS and add the same gradient (color or B&W) in each. One file should start out in 16 bit with a full 16 bit gradient. The other two files should start out in 8 bit with an 8 bit gradient. One of the 8 bit files stays in 8 bit, the other gets changed to 16 bits to complete the edits (even though it's still only an 8 bit gradient). If you don't want to use a gradient, then just grab any color image from a RAW file - render one copy in 16 bit and two copies in 8 bit.</p>

<p>The result is that the 8 bit file gets massively posterized, the 16 bit file still is a smooth gradient, and the 8 bit gradient edited in 16 bit mode looks pretty much like the 16 bit gradient. I know that this is somewhat of a contrived test to show the difference between 8 bit and 16 bit, but I can't imagine a scenario where you would be pushing a file more than this in PS.</p>

<p>A couple side notes... an 8 bit file is not a 16 bit file with 8 bits of extra zeros. If it was it would take up the same amount of disk space as a 16 bit file. A 16 bit file takes up more disk space because it uses greater precision to describe the number of tonal transitions between pure white and pure black (65,536 steps between white and black vs 256 for 8 bit). When downconverting an image from 14 or 16 bits to 8 bits all that is happening is the RGB color values are each getting rounded off to the nearest integer between 0 and 255. It's not a question of throwing away the last 6 bits, it's a question of converting to a less precise scale of color measurement/description. However, an 8 bit image can still diplay 16.8 million colors - more than the human eye can see.</p>

<p>Anyhow, not trying to be disagreeable. I agree with everything you have recommended - Scan in the highest bit file possible (16 bits), get new software if your current software limits you to 8 bits. There is no reason to throw away 14 bit data and save the raw scan as an 8 bit file.</p>

<p>I scan my film as 16 bit TIF's in ProPhoto RGB color space.</p>

 

<p>You want high bit data from the get go (not sampled up which buys you nothing). IF indeed, the device provides more than 8-bits per color, you absolutely want that data! We now have output devices (at least on the Mac OS) that can send 16-bit data to the print driver. </p>

<p>http://www.digitalphotopro.com/gear/imaging-tech/the-bit-depth-decision.html</p>

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<p>sampled up buys you nothing</p>

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<p>I have to disagree. As Sheldon and I have maintained, converting 8 bit to 16 bit has an advantage. Of course it is best to not throw any data out to begin with.</p>

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<p>I have to disagree. As Sheldon and I have maintained, converting 8 bit to 16 bit has an advantage. Of course it is best to not throw any data out to begin with.</p>

 

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<p>Fine. You have something empirical to demonstrate this (and doing so without using dither on) which affects all things in such comparisons?</p>

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<p>Fine. You have something empirical to demonstrate this (and doing so without using dither on) which affects all things in such comparisons?</p>

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<p>I'm not going to regurgitate what others have demonstrated so effectively. Study the material that Sheldon referenced and the related material in Real World Photoshop and do some tests yourself. You'll be amazed what you can learn if you really try.</p>

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<p>I'm not going to regurgitate what others have demonstrated so effectively. Study the material that Sheldon referenced and the related material in Real World Photoshop and do some tests yourself. You'll be amazed what you can learn if you really try.</p>

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<p>Then your answer is no. FWIW, Bruce was a dear friend and business partner, I've got every version of the book published. Maybe you can point out where padding values with interpolated data is such a benefit.</p>

<p>As for Histograms themselves, a very easy way to make them look improved (smooth) is apply a nice dose of Gaussian Blur. Of course, this hoses the image but heck, at least your Histogram looks nicer....</p>

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<p>Then your answer is no.</p>

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<p>I've run my own tests and you may want to do the same before claiming that there are no benefits to sampling up before editing.</p>

 

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<p>I've run my own tests and you may want to do the same before claiming that there are no benefits to sampling up before editing.</p>

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<p>You have something empirical to demonstrate this??? Or this is going to be a religious debate? If you've got the science, I'm all ears. </p>

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<p>You have something empirical to demonstrate this??? Or this is going to be a religious debate? If you've got the science, I'm all ears.</p>

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<p>I'm not going to hold your hand. You're a big guy, you can try it out for yourself, but please do so before claiming that there are no benefits.</p>

 

<p>I'm going to call this one a difference in semantics...</p>

<p>In some situations (like my "example" referenced above) where you take 8 bit data, crush it, then stretch it, there's a huge difference in whether you edit in 8 bit or 16 bit, and not much difference whether you start with 8 bit or 16 bit data.</p>

<p>However if you take a big long gradient that covers a more narrow range of tones (ie. blue to light blue) then stretch the heck out of it, the 8 bit file is much more likely to show banding than the 16 bit file. The 8 bit file may only start with 20 numerical steps with which to describe the transition between colors, regardless of whether you are editing in 16 bit. The native 16 bit file has thousands of numerical values with which to describe the color transitions and when it is stretched it will fare much better.</p>

<p>So, it depends on the image and what you are doing with the image as to whether there is a noticeable or practical difference.</p>

<p>FWIW, I defer to Andrew on these things. He has written more and knows more about Photoshop and color management than I ever will.</p>

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<p>I'm not going to hold your hand. You're a big guy, you can try it out for yourself, but please do so before claiming that there are no benefits.</p>

 

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<p>OK, religious debate. In science on the other hand, there's something called peer review where someone such as yourself if confident in your tests (which obviously you're not) could submit them to others to provide actual evidence of your theories. This doesn't seem to be something you can provide so I'll stick with my original comments above of which you disagreed but provided nothing to back up your disagreement. I think we're done here gang. </p>

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<p>OK, religious debate. In science on the other hand, there's something called peer review where someone such as yourself if confident in your tests (which obviously you're not) could submit them to others to provide actual evidence of your theories. This doesn't seem to be something you can provide so I'll stick with my original comments above of which you disagreed but provided nothing to back up your disagreement. I think we're done here gang.</p>

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<p>Spend a couple of minutes, run some tests and you'll have all the actual evidence you so desperately seem to look for. I ran these tests many years ago, now it's your turn.</p>

<p>In research if someone states what others have shown shown to be true and they believe. It is not up to them to prove they are correct, but up to those who challenge them to submit the tests and data to prove they are wrong.<br>

He did not state it was "his" theory, but what he had read and believes to be true.<br>

<br /> Why don't you, Andrew submit evidence that he or the website quoted is incorrect?<br>

<br /> In science we accept the hypothesis until it is proven to be wrong.<br>

<br /> Just saying he is wrong, is not proof or ANY different than what you call a "religious" belief. Especially when it looks like several others are disagreeing with your "religious belief or debate" and you have proven nothing.<br>

You do not even quote any source materiel for your beliefs, but just insist that you are right.<br>

It does not even appear that you have read the page quoted. <br /> http://www.photoshopessentials.com/essentials/16-bit/page-2.php</p>

<p> </p>

<p>Andrew the science is pretty obvious, they've already shown how it works. Just think about it a little bit and I think you'll get it. Perhaps your misreading what they've said. When you convert a 8 bit file to 16 bit you don't instantly get more rage, but you get the possibility for more range. So when you edit the file that has been upsampled there are more discrete values to work with while editing. If you're not doing much editing then you're right, upsampling buys you nothing, but if you are editing a lot you have a larger working space with more colors to work with. When applying curves and other adjustments this allows there to be more in between tones which makes posterization and blocking artifacts less likely. Of course starting out at higher depths will produce better results.</p>

<p>In response to the original question, upsampling will help if you edit a lot, but since you said you use the scanner settings mostly, I'd agree with everyone else who said use the highest you can get.</p>

 

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<blockquote><br />In research if someone states what others have shown shown to be true and they<br />believe. It is not up to them to prove they are correct, but up to those who<br />challenge them to submit the tests and data to prove they are wrong. He did not<br />state it was "his" theory, but what he had read and found to be true.<br />Why don't you, Andrew submit evidence that he is incorrect?<br /></blockquote>

<br /> Hold his hand? Sure. And I disagree that he's not responsible to prove his point! <br />1. First step. Download DNG document from my iDisk* in the folder called ProPhotovsAdobeRGB files <br />2. Next, open in ACR using default settings described in the DNG (there's no reason to mess with the rendering for these tests but you can if you so desire). Set the workflow options for ProPhoto RGB, 16-bit data. <br />3. Next, go into the Photoshop color settings, uncheck the Dither check box (this is CRITICAL for providing apples to apples results in conversions). <br />4. You now have a 16-bit document from Raw. Duplicate that image (Image>Duplicate). Convert that copy to 8-bit. Now back to 16-bit for the "data padding". <br />5. Pull nice curve, I've provided one in the above folder with the DNG. Do the same on the "real" 16-bit document. <br />6. Convert 16-bit Document to 8-bit for next step (analysis using Apply image which only works with images in the same bit depth). Shouldn't matter, you applied the curve on the so called better, 16-bit data. <br />7. Set whichever image isn't listed as the target as the source. Set the Channel as RGB. Set the Blending to Subtract, with an Opacity of 100, a Scale of 1, and an Offset of 128. <br />If the scans/test images were truly identical, every pixel in the image would be a solid level 128 gray. Pixels that aren't level 128 gray are different by the amount they depart from 128 gray. You can use Levels to exaggerate the difference, which makes patterns easier to see. <br />What do you see? Are the two equal, identical? No. If indeed the so called benefits of converting 8-bit to 16-bit provided the same results, we'd see it. And more importantly, how does this prove there's a benefit? That's the 64,000 question! When you convert from 8-bit to 16-bit, you're padding data with nothing new in terms of actual data, unlike the data from a high bit capture. So it IS up to those who say there's a benefit to PROVE somehow that doing this conversion is beneficial (I've proven they are not equal/identical). <br />I said converting to 16-bit buys you nothing, Frans says there is. Where's the proof? Again, I'm all ears but Frans apparently doesn't wish to provide a means to empirically prove this. And we haven't even defined "benefits" in this workflow which would kind of be useful no? <br />As to Jamie's point about range, that's got nothing to do with bit depth. More bit depth doesn't equate into dynamic range. Its simply the number of steps in the staircase, not the overall height of the staircase. <br />*My public iDisk: <br />thedigitaldog <br />Name (lower case) public Password (lower case) public <br />Public folder Password is "public" (note the first letter is NOT capitalized). <br />To go there via a web browser, use this URL: <br /><a rel="nofollow" href="http://idisk.mac.com/thedigitaldog-Public" target="_blank">http://idisk.mac.com/thedigitaldog-Public</a></blockquote>

<p>Andrew,<br>

I didn't mean dynamic range I meant the range of tones available, or as you say the number of stairs. That fact that your experiment shows that there IS a difference between the two files shows the fact that there is more data for your editing program to work with.<br>

Who's to say what's better? It depends what you want, but with 16bit there are more colors to use. Upsampling itself doesn't gain you anything, just like upsizing your pixel dimensions won't, unless you do some processing to make use of the extra. By expanding your color pallet you have more colors to play with. If you just upscale and then print it's pointless. True, upsampling is not as good as a high bit depth scan, but if your making use of the extra colors it can help.<br>

Just like making a file larger (in terms of pixel dimensions) can help for making large prints if you properly sharpen and blur the larger file. It's not as good as having higher resolution to start with, but it's better than using the unsharpened low res file to make a large print.<br>

It all depends on what you do with the extra headroom once you have it. There's no reason to make the file larger unless you're actually going to make use of the extra data.</p>

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<p>That fact that your experiment shows that there IS a difference between the two files shows the fact that there is more data for your editing program to work with.</p>

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<p>No, it only shows they are not the same. There's nothing yet to suggest there's "more real data," better data" etc. Someone (Frans) still needs to make proof of concept here. What's apparent is, they are not the same.</p>

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<p>Who's to say what's better?</p>

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<p>Frans (or anyone else who's yet to prove its "better").</p>

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<p>Frans</p>

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<p>I don't feel the need to prove anything; I did my homework already many years ago and you can either believe me, continue to claim that I'm wrong without supporting data or run some tests yourself. For those interested, here's the explanation: when you start with more levels there will be less damage done with editing (particularly those editing steps that require rounding off and most editing steps require rounding off) and the resulting image will have more levels, less missing values in the histogram and there will be less posterization. Whether or not you will see this depends on the subject matter; blue sky and other large areas with little change in color/tonality are notorious for posterization. Many years ago I did some simple tests, similar to the ones described in the article Sheldon referred to and the 8 bit file that was first converted to 16 bit before editing showed less posterization in said areas than the 8 bit file that was not converted but received the same editing steps.</p>

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<p>For those interested, here's the explanation: when you start with more levels there will be less damage done with editing (particularly those editing steps that require rounding off and most editing steps require rounding off) and the resulting image will have more levels, less missing values in the histogram and there will be less posterization.</p>

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<p>Now I wonder why I purchased that 5DMII to replace my 5D. All that extra <strong>real</strong> resolution. Just interpolate the data. Here's the explanation: when you start with more (interpolated) pixels, there's more data and less damage done and the resulting image will have more pixels. </p>

<p>The original comment was, interpolated bit depth buys you nothing. I'm still waiting for proof, on an actual image, with steps that illustrate there is any advantage in doing this. </p>

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<p>Now I wonder why I purchased that 5DMII to replace my 5D. All that extra <strong>real</strong> resolution. Just interpolate the data. Here's the explanation: when you start with more (interpolated) pixels, there's more data and less damage done and the resulting image will have more pixels.</p>

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<p>Nobody claimed that interpolating is just as good as capturing more data to begin with.</p>

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<p>The original comment was, interpolated bit depth buys you nothing. I'm still waiting for proof, on an actual image, with steps that illustrate there is any advantage in doing this.</p>

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<p>I and others have maintained that interpolation before editing results in less damage, less posterization. Sheldon posted a link to an article on that subject. I have described the tests I did many years ago and the results. If you don't believe others that clearly have done their homework and reported on the results, then maybe you should stop arguing and start conducting some tests of your own.</p>