The 1st attached pic is a screen shot of part of an image zoomed 11:1 in library module, 2nd is same thing done in develop mode and looks more pixelated. Am I correct in believing the image shown in library mode is a preview / jpeg one and the one one in develop is the actual raw image? If so why does the develop module one look less detailed than the library one? By the way if I turn on 'use graphics processor they both look pixelated.
1 Correct answer
At the link provided by I explain why the Library and Develop module previews look different. I've copied that text below.
"The Develop module uses a simpler algorithm for creating the Loupe preview to prevent adjustment slider lag. The Library module creates a Preview file, which is created using the Bicubic algorithm (same as the Export module), which provides much more accurate interpolation. BTW- The most accurate view in the Library module are the pyramid Zoom settings 1:16, 1:8
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Replies
Knicker wrote
thedigitaldog wrote
Knicker wrote
The question is: which way is the unintended/buggy behavior?
That should be fairly obvious; the behavior that matches Photoshop.
Yes, of course, and it's been "fairly obvious" to me from the beginning of the DPR discussion as well.
If it's "obvious", why continue? 
Knicker wrote
One of the reasons I don't use LR is because it doesn't always match the behavior of Photoshop.
Well as illustrated, it does and can. I hardly believe I'm the only person who's previews match and know I'm not.
I can't assist in your buggy system hence, maybe as suggested, you start a new topic asking for help in doing so. As shown, it can and does work bug free for some of us.
Knicker wrote: In its efforts to simplify things and protect LR users from some of the complexities of PS, Adobe has created some FUD for those of us used to how PS does things. This didn't strike me as one of those instances, though.
I shouldn't ask what FUD?: it works correctly, it was illustrated several times it works as it should without a lick of FUD. But all software has bugs.
With default settings, LR and PS match. I don't know how Adobe can make that any easier.
Knicker wrote
I remember the first time I tried the zoom function in FastRawViewer, I was really thrown for a loop. Zooms past 100% are interpolated/smoothed. I still scratch my head about why they programmed it that way. A question for Iliah, I suppose, in another time and place...
Indeed.
Knicker wrote
I remember the first time I tried the zoom function in FastRawViewer, I was really thrown for a loop. Zooms past 100% are interpolated/smoothed. I still scratch my head about why they programmed it that way. A question for Iliah, I suppose, in another time and place...
I don't think so. There IS a major difference in rendering (contrast and saturation). To be expected. But you should ask him about this concept of interpolated and smoothed, I think he'll tell you otherwise because it makes no sense to me to do so. The differences are seen below on a system I know previews correctly pretty close if you discount contrast, saturation etc:
200% in each.
thedigitaldog wrote
Knicker wrote
I remember the first time I tried the zoom function in FastRawViewer, I was really thrown for a loop. Zooms past 100% are interpolated/smoothed. I still scratch my head about why they programmed it that way. A question for Iliah, I suppose, in another time and place...
I don't think so. There IS a major difference in rendering (contrast and saturation). To be expected. But you should ask him about this concept of interpolated and smoothed, I think he'll tell you otherwise because it makes no sense to me to do so. The differences are seen below on a system I know previews correctly pretty close if you discount contrast, saturation etc:
200% in each.
Go to 1000% in FRW (the max). Do you see any pixelation at all? I don't on my iMac, but at 1000% you should definitely see the pixel structure.
Knicker wrote
Go to 1000% in FRW (the max). Do you see any pixelation at all? I don't on my iMac, but at 1000% you should definitely see the pixel structure.
And indeed, I do see the pixel structure! And if you read the manual and set your preference's 'correctly', you may as well. Proof of concept below (zoomed in to the max DEFAULT of 1000% one can go higher).
Anyway, I've already emailed Illiah because I like to get facts from the source, rather than speculate. Like how some thought interpolation algorithm's in PS affected the previews. 
Knicker wrote
Well, for whatever reason, the bilinear interpolation on zoom setting is how my version of FRW was defaulted.
Yeah, that's what default means.
Knicker wrote
Until you mentioned above that it's configurable, I wasn't even aware of it and hadn't tried to look for it, let alone change it in the preferences. (I confess that I never made it to page 113 in the user manual.)
RTFM, don't speculate.
We didn't have to go down this path but you insisted so yeah, we're seeing that a lot of this back and forth is user misunderstandings. 
Stop assuming about interpolation algorithms you don't have nor possibly would understand IF you had them! That's not debatable.
Yes, when one zooms out, there is some resampling of the zoomed out data, that's WHY it's always recommended to view at 1:1 (one image pixel for one display pixel) or greater zoom ratio. This is really not news to anyone who's studied this stuff (and I've been a beta for Adobe since version 2.5 of Photoshop, a quarter of a century and a beta for Lightroom when it wasn't even called Lightroom). Zoomed in? You really just don't know what is happening under the hood.
And yes, now that you've actually read the FRV manual in terms of zooming, you've seen it does indeed allow differing algorithms because it actually states that:
Image Resampling method – sets the method to be used for calculating zoom-in (going above 100% view):
• No resampling – for large zoom factors, the image will look as if it is constituted of small square tiles.
• Bilinear resampling – fast, mid-quality method.
• Bicubic resampling – high-quality method, a relatively fast vast video card is recommended.
Knicker wrote
What was not clear here (until I dropped into the discussion today) was whether interpolation algorithms apply to zoomed-in previews. Until I mentioned it, nobody questioned the "Answer" that zoomed-in previews (in LR's library module) should be interpolated.
It wasn't clear to you. 
And you're of course, still speculating about interpolation algorithms with zoomed in previews in any LR module.
Some here can ask specifically what's going on, to an Adobe engineer via email.
Not really necessary.....
EDIT: And you're of course, still speculating about interpolation algorithms with zoomed OUT previews in PS.
Knicker wrote
thedigitaldog wrote
Knicker wrote
What was not clear here (until I dropped into the discussion today) was whether interpolation algorithms apply to zoomed-in previews. Until I mentioned it, nobody questioned the "Answer" that zoomed-in previews (in LR's library module) should be interpolated.
It wasn't clear to you.
And you're of course, still speculating about interpolation algorithms with zoomed in previews in any LR module.
Some here can ask specifically what's going on, to an Adobe engineer via email.
Not really necessary.....
The running editorializing isn't called for and isn't appreciated.
I'm sorry the facts and having you actually learn how products work (like RFV) are ruining your day.
I've shown that, on a system without GPU bugs, everything you've speculated about and reported isn't so. Maybe you should spend some time fixing your hardware?
- In PS, some form of (probably bicubic) interpolation is applied when zooming out at odd percentages.
The key word that outlines more assumptions from you is probably (Bicubic). But it doesn't matter on systems that operate without bugs in terms of previewing image data.
- In PS, nearest neighbor or something similar is used when zooming in to preserve the pixel structure appearance.
The key word that outlines more assumptions from you is something similar. But it doesn't matter on systems that operate without bugs in terms of previewing image data.
- In ACR, some different form of interpolation is applied when zooming out at odd percentages. This is one reason why sometimes users are confused by the difference in appearance of zoomed out images in ACR compared to the same images zoomed out in PS.
The key word that outlines more assumptions from you is some different form. But it doesn't matter on systems that operate without bugs in terms of previewing image data.
It is clear why some users here are confused . It's been illustrated a number of times. And yet, you wish to continue which seems pointless. Which is why my suggestion you start a new thread which fell on deaf ears has you upset by facts you call editorializing.
"Facts are facts and will not disappear on account of your likes."
-Jawaharlal Nehru
Knicker wrote
thedigitaldog wrote
Knicker wrote
The referenced 2017 thread discussed how, when zooming out, there may be differences in the appearance of the displayed image between the Library and Develop modules. That's correct.
It's also true in Photoshop vs ACR, depending on how Photoshop's image interpolation preference is set in the Preferences > General tab.
I don't believe that's at all correct either; this setting in Photoshop's preferences has no role over previewing data on-screen when zooming, nor do I see any difference doing so. It's used for actually resizing (interpolating) the document data.
It's my understanding that the interpolation method used in zooming out in ACR is fixed. You can, however, change the interpolation method in PS itself by changing the setting in preferences. (Like Todd advised for testing LR, you need to be sure to close and restart PS to see the difference).
The interpolation in both ACR and LR isn't fixed, it's actually an adaptive algorithm based on a number of factors. For actually interpolating the image data. What you are trying to state is, the user doesn't alter this as they can in Photoshop. And for good reasons! There are times when in Photoshop, users really DO want to use nearest neighbor or differing algorithms; I do this all the time.
The facts are, the settings for Photoshop's interpolation settings in pref's have NO role over the preview on-screen for normal viewing while zooming EXCEPT in cases where you can see the update while altering settings when optional. For example (and this has nothing to do with 'normal viewing' or the preferences) Image Size and the dropdown for the resample algorithms:
Altering the resample algorithm's above will, in this dialog, update based on what you set. By design.
thedigitaldog wrote
Knicker wrote
Try setting the preference to Bicubic Sharper in preferences, close/reopen PS, zoom out to an uneven percentage and do a screen grab. Rinse and repeat with Bicubic. The screen grabs should show a noticeable difference.
It absolutely doesn't on this end. No matter the interpolation algorithm in preferences, the zoom uneven percentage or not, the image previews identical no matter how set, no matter how many times I relaunch Photoshop.
It makes absolutely no sense that Adobe would make the product behave this way anyway and they didn't.
Now that isn't to say a bug somewhere may produce this utterly undesirable effect. Fortunately for me, it doesn't. Again, it makes absolutely no difference in what you see zoomed on-screen based upon the resample algorithms in Photoshop. And Adobe makes it perfectly clear what those algorithm's affect:
new pixels based on the color values of existing pixels.
You're right. I was trying a number things last night and mislabeled my findings and accidentally attributed the change I was seeing to the default interpolation setting in the PS preferences, when in fact it was due to toggling the GPU on/off in the PS preferences. To recap: it's not changing the interpolation preference setting in PS that's causing a change in the interpolation method when zooming out on my iMac. It's changing the GPU on/off status that's causing the change. I've now confirmed (on my iMac, at least) that the zoom-out interpolation algorithm is fixed to whatever it is in PS regardless of the preference setting. It's also fixed in ACR. What remains true, however, is that the zoom-out algorithm used in PS is different from the one used in ACR. And, of course, this is a different set of issues than the zoom-in behavior settled earlier in this thread.
What's odd and kind of depressing is that my generic iMac using only it's embedded GPU is displaying visibly different zoom-out behavior in PS when the GPU is on compared to when it is off. The gpu off setting looks worse. Weird. If anything, you'd expect the GPU turned on to be the source of any problems, not the reverse. Here's an example of what I'm talking about (note the strange repeating box like structure introduced by the gpu-off version of the DPR test scene (opened from ACR into PS) and displayed at "Fit on Screen" size (approximately 23% on my 27" iMac):
The crop on the top is GPU-on and the crop on the bottom is GPU-off
By the way, if you're interested in a good test image to use for quickly comparing different interpolations for downsizing or zooming out, try the one below. The grid will look dramatically different with different interpolation algorithms applied when downsized/zoomed out to odd percentages:
Knicker wrote
To recap: it's not changing the interpolation preference setting in PS that's causing a change in the interpolation method when zooming out on my iMac. It's changing the GPU on/off status that's causing the change. I've now confirmed (on my iMac, at least) that the zoom-out interpolation algorithm is fixed to whatever it is in PS regardless of the preference setting.
No. As explained, the differences is due to bugs with GPUs. I don't know how you keep missing that fact but perhaps this will help: On my Mac, GPU on or OFF produces and IDENTICAL preview at 200%. BECAUSE as I've attempted to illustrate to you over and over again, my system doesn't exhibit GPU bugs:
Knicker wrote
thedigitaldog wrote
Knicker wrote
To recap: it's not changing the interpolation preference setting in PS that's causing a change in the interpolation method when zooming out on my iMac. It's changing the GPU on/off status that's causing the change. I've now confirmed (on my iMac, at least) that the zoom-out interpolation algorithm is fixed to whatever it is in PS regardless of the preference setting.
No. As explained, the differences is due to bugs with GPUs. I don't know how you keep missing that fact but perhaps this will help: On my Mac, GPU on or OFF produces and IDENTICAL preview at 200%. BECAUSE as I've attempted to illustrate to you over and over again, my system doesn't exhibit GPU bugs:
You're still mixing two separate issues. When zooming IN, my iMac behaves correctly like yours does - ie., no difference in the display whether or not the GPU is on and no interpolation applied. What I've confirmed this evening after reviewing my tests from last night is that, on my iMac, when zooming OUT in PS there is a visible difference in the interpolation applied (see my crops in my prior post above from the DPR studio scene).
Nope, try again: on my system, zoomed out at 33.3 percent, a match (again).
No need to even label which is which but if you really must, check the date/time, I started with GPU on, then turned it off, quit and reopened the image again:
I'm mixed up? 
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