Photoshop: Support more accurate 16 bit/channel display even when zoomed out below 66.67% magnification

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It is rather abysmal that photoshop still has this critical bug, given that is has been reported for years now. It is a software for professional imaging yet you cannot work on an image at print resolution and have accurate color displayed on the screen.



Steps to reproduce:
-For full effect, open an image with dark shadows you would like to lighten
-Again, to dramatize, we are going to add two curve adjusment layers
--Make one curve to set your black and white points and your gray balance
--Make another curve to open up the dark shadows
-You should see that at 66.67 magnification you will get the true colors while at 50% below colors suddenly change, meaning you cannot look at the image as a whole and make color adjustments. This applies to any image that is more than 4/3 your screens total resolution, which, for a 1080p monitor that is beyond the average, would be 3MP. Yes, that is three megapixels as in DSLRs of 14 years ago.

Perhaps you could have an option to 'render proxy at this magnification' which would render a 16bit cache level at a specified magnification at which curves et al could be calculated from there on.

Shame on you for not having addressed this despite pleas from multiple professional fields for so long.
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derin korman

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Posted 5 years ago

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Chris Cox

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That is because 50% you are seeing an 8 bit/channel preview instead of 16 bit/channel.

Would you like to change this to a request to support more accurate 16 bit/channel display even when zoomed out?
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derin korman

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Hello Chris,
Thank you for taking the time to recognise this and saying hi :) I know the underlying reason for the problem, and yes, to support more accurate display while zoomed out is essentially my request, but I think to call it a 'feature request' is a bit problematic.

I say that because it is currently an implicit default without a warning as it has great consequences for the unknowing user. If anything, it should be the compromise in accuracy for performance that should be optional, given that Photoshop caters to users in professional imaging.

The performance tab could have a checkbox that reads 'Render 8bit previews below 66.67 magnification', even if it comes checked, this would be an explicit feature.

cheers,
d
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Chris Cox

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Performance and memory usage are also important - and using 8 bit upper pyramid levels improve performance and reduce memory usage.

What you describe is not a bug or mistake. It can only be changed through pretty extensive code changes and testing. Yes, that makes it a feature request.

As a bug report, this isn't going to go anywhere.
But as a feature request, it has a much better chance to make some changes.
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derin korman

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Of course I understand that 8bit upper pyramid levels improve performance, what I meant to say that since there is no notice anywhere that tells you what you see is not exactly what you get, this is a bit of a problem for general use.

I guess we can make it a feature request then, do you need me to edit the original post?
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Chris Cox

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Hmm, the behavior of the pyramid levels used to be in the manual/help files.

Nope, Jeff already changed it to a request. (and now we have something we can present to our product management :-).
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derin korman

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Thank you. Feel free to contact me if I can be of any help in the future in regards to this. I can forward a draft of the changes, if you need feedback, to the global museum imaging community.
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Tim Parkin

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The proposed solution to allow 16bit previews would be fantastic.

This is a particular problem when inverting colour negative scans too. The colours are extremely screwed when applying the massive curve adjustments needed to provide a decent inversion.
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Chris Cox

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Yes, any adjustment with an extreme change will show more banding in 8 bit/channel, which is what you get when zoomed out.
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Stefan Klein

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Chris,
if a 16bit image is only displayed with 8bit/channel, AT LEAST some kind of information/warning should be displayed! And, of course, 16bit/channel should be supported in all zoom levels.

BTW. (and this may be off-topic), there should be a more realistic display of layer-styles at zoom levels below 100%. Depending on the style, the difference to 100% view can be rather extreme.
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Chris Cox

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We're already doing the best we can with downsampled layer styles. Anything more would require compositing at 100% and downsampling after (which would be really slow if you have more than a few layers).
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Tim Parkin

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Yes - however this is exaclty what i have to do when adjusting files. Copy to a new file, flatten stack, resize to monitor size, zoom to 100% and then make my curve adjustment and copy back to the main file. get's tiring pretty quickly
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Chris Cox

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You don't need to copy to a new file. Just zoom in to 100%, or open another window for the document and change the zoom on it.
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Tim Parkin

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But i then need to get the curve adjustment i make back to the full size document',,.
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Chris Cox

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There is no "full size document" - just use ONE document, and different views of it.
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Tim Parkin

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Yes but I can't make the adjustments i need at 100% and hence i have to resize the document to do so. I cant resize the original document as i then cant get back to the fulll size document. Hence i dupe the document, flatten, resize to fit screen at 100%, make curve adjustments and then copy curve adjjustments to original document. Long winded but the only way to do what i need
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Chris Cox

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Don't duplicate the document. Just make another window for the document, and set it's zoom to 100% to judge the results.
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christoph pfaffenbichler, Champion

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Tim Parkin, did you get that Mr.Cox is referring to Window > Arrange > New Window for ...?
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Tim Parkin

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Yes - the fundamental problem is I that I need to make global adjustments whilst seeing the whole frame which means 16% zoom. At this zoom level the preview is 8 bit and so I can't trust my edits. The only way to trust edits is at 100% and hence I need to resize my original document to apply to appropriate curves. Then I can't get the curves back to my full size document. Make sense?
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christoph pfaffenbichler, Champion

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Not exactly.
Adjustment Layers on a downsampled copy do not necessarily produce results that appear identical when applied on the original image so your »trust« seems to be misplaced.

What kind of Adjustments, Masks, Styles, ... are you talking about anyway?
Could you post an example?
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Tim Parkin

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Yes, i have to flatten them too. I'll change tack as I dont seem to be getting my problem across. How do i accurately colour correct a large image with multiple adjustment layers whilst viewing the whole image (e.g. Not at 100%)
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Tim Parkin

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P.s. At the minimum all i want to so is make a basic curve adjustment but if i duplicate the original document (with a simple 1 point tweak on the green curve) and resize the duplicate to fit the screen and zoom out on the original to fit the screen they look different!
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christoph pfaffenbichler, Champion

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You can try setting Preferences > Performance > Cache Levels to 1 and restart Photoshop.
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derin korman

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Christoph, that slows photoshop to a crawl for large documents, and therefore not a solution. The problem is well outlined and exemplified above, and acknowledged. Are you playing Socrates for any reason?

As Tim also pointed out, the fundamental task of color correcting photographs using adjustment layers, especially in working with film scans and negatives that require dramatic change, cannot be performed with Photoshop as it stands. You cannot correct overall color balance while looking at your photograph through a loupe.
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christoph pfaffenbichler, Champion

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I just got involved because I got the impression (possibly mistakenly) one of the posters did not understand the multiple view option or employ a work-around that would not actually produce reliable results.
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david

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This reply was created from a merged topic originally titled Photoshop: Why don't I see 16 bit quality previews when zoomed out?.

why aren't 16-bit previews possible? i use layer adjustments and i end up seeing a lot of color banding mainly in the sky that is gone when i flatten the file. the problem is it sometimes appears that there is a color cast when there really isn't. it makes color correcting very tedious. i would think that PS could display what the file will look like when flattened, but keep the layers, no?
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Golden Crop

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This reply was created from a merged topic originally titled Photoshop 2015.0.1: 16-bit image with adjustment layers banding on some zoom leve....

There is a problem with rendering 16-bit images on different zoom levels. See the picture for example:



Can someone confirm the problem?

Steps to reproduce:

  1. Create an empty RGB image in 16-bit color mode.
  2. Add any gradient layer
  3. Add a curve layer. Set the right point to Input 255, Output 4
  4. Add another curve layer. Set the right point to Input 4, Output 255
  5. Change zoom level - zoom in. The gradient should look fine.
  6. Now zoom out - at some point the 8-bit banding wil appear.


Configuration:

Adobe Photoshop Version: 2015.0.1 20150722.r.168 2015/07/22:23:59:59 CL 1032107 x64
Operating System: Windows 7 64-bit
Version: 7 SP1System architecture: Intel CPU Family:6, Model:10, Stepping:9 with MMX, SSE Integer, SSE FP, SSE2, SSE3, SSE4.1, SSE4.2, AVX, HyperThreading
OpenGL Drawing: Enabled.
OpenGL Allow Old GPUs: Not Detected.
OpenGL Drawing Mode: Advanced
OpenGL Allow Normal Mode: True.
OpenGL Allow Advanced Mode: True.
NumGLGPUs=1
NumCLGPUs=1
glgpu[0].GLVersion="3.0"
glgpu[0].GLMemoryMB=2304
glgpu[0].GLName="Intel(R) HD Graphics 4000"
glgpu[0].GLVendor="Intel"
glgpu[0].GLVendorID=32902
glgpu[0].GLDriverVersion="10.18.10.3958"
glgpu[0].GLRectTextureSize=16384
glgpu[0].GLRenderer="Intel(R) HD Graphics 4000"
glgpu[0].GLRendererID=354
glgpu[0].HasGLNPOTSupport=1
glgpu[0].GLDriver="igdumdim64.dll,igd10iumd64.dll,igd10iumd64.dll,igdumdim32,igd10iumd32,igd10iumd32"
glgpu[0].GLDriverDate="20140930000000.000000-000"
glgpu[0].CanCompileProgramGLSL=1
glgpu[0].GLFrameBufferOK=1
glgpu[0].glGetString[GL_SHADING_LANGUAGE_VERSION]="1.30 - Build 10.18.10.3958"
glgpu[0].glGetProgramivARB[GL_FRAGMENT_PROGRAM_ARB][GL_MAX_PROGRAM_INSTRUCTIONS_ARB]=[1447]
glgpu[0].glGetIntegerv[GL_MAX_TEXTURE_UNITS]=[8]
glgpu[0].glGetIntegerv[GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS]=[96]
glgpu[0].glGetIntegerv[GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS]=[16]
glgpu[0].glGetIntegerv[GL_MAX_TEXTURE_IMAGE_UNITS]=[16]
glgpu[0].glGetIntegerv[GL_MAX_DRAW_BUFFERS]=[8]
glgpu[0].glGetIntegerv[GL_MAX_VERTEX_UNIFORM_COMPONENTS]=[4096]
glgpu[0].glGetIntegerv[GL_MAX_FRAGMENT_UNIFORM_COMPONENTS]=[4096]
glgpu[0].glGetIntegerv[GL_MAX_VARYING_FLOATS]=[64]
glgpu[0].glGetIntegerv[GL_MAX_VERTEX_ATTRIBS]=[16]
glgpu[0].extension[AIF::OGL::GL_ARB_VERTEX_PROGRAM]=1
glgpu[0].extension[AIF::OGL::GL_ARB_FRAGMENT_PROGRAM]=1
glgpu[0].extension[AIF::OGL::GL_ARB_VERTEX_SHADER]=1
glgpu[0].extension[AIF::OGL::GL_ARB_FRAGMENT_SHADER]=1
glgpu[0].extension[AIF::OGL::GL_EXT_FRAMEBUFFER_OBJECT]=1
glgpu[0].extension[AIF::OGL::GL_ARB_TEXTURE_RECTANGLE]=1
glgpu[0].extension[AIF::OGL::GL_ARB_TEXTURE_FLOAT]=1
glgpu[0].extension[AIF::OGL::GL_ARB_OCCLUSION_QUERY]=1
glgpu[0].extension[AIF::OGL::GL_ARB_VERTEX_BUFFER_OBJECT]=1
glgpu[0].extension[AIF::OGL::GL_ARB_SHADER_TEXTURE_LOD]=0
clgpu[0].CLPlatformVersion="1.2 "
clgpu[0].CLDeviceVersion="1.2 "
clgpu[0].CLMemoryMB=1195
clgpu[0].CLName="Intel(R) HD Graphics 4000"
clgpu[0].CLVendor="Intel(R) Corporation"
clgpu[0].CLVendorID=32902
clgpu[0].CLDriverVersion="10.18.10.3958"
clgpu[0].CUDASupported=0
clgpu[0].CLBandwidth=1.80273e+010
clgpu[0].CLCompute=126.832
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Aric Guité

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This is also an issue with some of the tools, such as the healing brush, you'll get artifacting if you're working on a smooth gradient. Goes away when you zoom in past 66.7%.
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Charles Lanteigne

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Are there workarounds for this?! I'd be willing to take a hit in performance or practicality, because the alternative is that I can't rely on what I'm seeing.

I am dismayed that this would be considered merely a "feature request", when in fact it's the most basic core feature: showing me my image properly! At the very least this should be clearly indicated so the user knows he is looking at an approximation.
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Jim Ainsley

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I recently began using 16-bit mode and just couldn't work out why the quality of my images was so poor.

After a lot of confusion and testing, I finally figured out that Photoshop doesn't display the image properly UNLESS you zoom in close on a photo!

I find it simply INCREDIBLE that this is not considered a bug! How can photographers work in 16-bit mode when we can't even see what we're doing? THIS NEEDS FIXING IMMEDIATELY!

Please see my screen grab of the problem:


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Jeffrey Tranberry, Sr. Product Manager, Digital Imaging

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I'm not seeing the kind of banding you're seeing. Here's a 16-bit image shown at 50% and I'm not seeing the kind of banding you're seeing:



I'd suspect there's something else wrong like a bad color profile or a bad graphics driver. It may help if we could see your Photoshop System Info. Launch Photoshop, and select Help > System Info... and copy/paste the text in a reply.
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Jim Ainsley

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Sorry, I should clarify that the banding only appears as a result of adjustment layers.

In my example, I used two simple curves layers as shown below. This is perhaps an extreme example in order to make the banding very obvious, but I've noticed banding in my regular projects and found it totally confusing.



I agree with the poster above who noted that most people who work in 16-bit mode would settle for a performance reduction in order to see the image in full quality. If nothing else, I think there should be an option in the prefs to enable "true 16-bit view mode" or something.

To me, the point of using 16-bit mode is that it lets you "go crazy" with adjustment layers without having to worry about banding. Though I will add that the problem of banding wouldn't exist in 8-bit mode if Photoshop didn't round down its calculations to 8-bit for every layer. It would be nice to have that option too: "16-bit calculations in 8-bit mode, to reduce banding"
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Jeffrey Tranberry, Sr. Product Manager, Digital Imaging

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OK. Gotcha. Correct. As Chris pointed out earlier, the current implementation, where pyramid levels above the base (that is, the 50%, 25%, levels) of a 16 bit document are in 8 bit. The thinking at the time was that zoomed out representations are previews (inaccurate for a number of reasons including interpolation, etc) and  speed/performance was more important than accuracy. It might be something we can revisit as compute power increases and we refactor and improve our drawing code.
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David Converse

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I have a couple of images that look TOTALLY different at 50% and 100%. I mean, major content changes. I was tearing my hair out over it last night, in fact. I'll post samples on this thread when I get home tonight.

Add my vote for this being a problem, as I always work in 16-bit.
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Jim Ainsley

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Thanks for your reply, Mr Tranberry.
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David Converse

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This is the same file- 16 bit on the left, converted to 8 bit on the right. No other changes. This is consistent with what I get zooming in and out on the (much larger) original between 50% and 66.7%. I've seen this before with multiple layers set to Difference blending.

Is this behavior expected? Doesn't seem right to me.

(Edited)
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Jeffrey Tranberry, Sr. Product Manager, Digital Imaging

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Official Response
As Chris pointed out earlier, the current implementation, where pyramid levels above the base (that is, the 50%, 25%, levels) of a 16 bit document are in 8 bit. The thinking at the time was that zoomed out representations are previews (inaccurate for a number of reasons including interpolation, etc) and  speed/performance was more important than accuracy.

It might be something we can revisit as compute power increases and we refactor and improve our drawing code - but it's not 'free' - it takes a lot more compute power.

If you want accurate 16-bit previews at all levels of the zoom pyramid, you can go to Preferences > Performance... and set the "Cache Levels" to 1 (close all docs and reopen them). You can see how 16-bit at all zoom levels affects performance and why this decision was made.

(Christoph pointed this out earlier in the thread but I wanted to capture it in an official answer)
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David Converse

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What about my post above where there is actually a big change when converting a file from 16 to 8 bit? IOW, its not just a cosmetic difference but different actual pixels. I've seen this happen one other time with layers and Difference blend mode.
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Jeffrey Tranberry, Sr. Product Manager, Digital Imaging

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I'd need to get your sample file that reproduces the problem so I can get it in front of engineering.
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Charles Lanteigne

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Changing the Cache Levels to 1 does not fix the issue for me, there's still a shift in color when I zoom in/out. (I also notice no difference in performance.)

To be clear, I use adjustment layers when I see the issue. "Flattening" the image (or placing a composite of the stack at the top) makes the difference go away (regardless of the cache levels), but obviously this is not convenient.
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derin.korman

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You have to restart Photoshop after doing that but it will also slow photoshop down to a crawl for general use.

To Adobe: What would be useful perhaps is a toggle on a panel that can switch to 16bit rendering without restarting photoshop so that we can enable it as needed for a task and disable it afterwards, not dissimilar to 'high quality previews' found in some tools.

On a similar note, what would be great is to have a 16 Bit curve adjustment option, the current one is rather limiting in precision for setting the black point in common color spaces.
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David Converse

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I can send you that file, let me know how to get it to you. Thank you!
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Charles Lanteigne

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I did restart Photoshop, no dice.
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Jeffrey Tranberry, Sr. Product Manager, Digital Imaging

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David, will send you an email to get the file. Thanks.
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derin.korman

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A suggestion: put a toggle on a panel that can switch to 16bit rendering for all levels without restarting Photoshop so that we can enable it as needed for a task and disable it afterwards, not dissimilar to 'high quality previews' found in some modal tools.