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Author Topic: Random poor previews  (Read 2269 times)

dchew

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Random poor previews
« on: October 16, 2012, 09:22:13 am »

Occasionally I get really poor previews that show in both Grid and Loupe view, and it is always with the same image.  Here is one example.  If I zoom in redraws a good view, and if I go to Develop it also redraws.

I tried dumping and recreating the 1:1 preview, but that doesn't help.  Is there any way to recreate the little preview?

Dave


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digitaldog

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Re: Random poor previews
« Reply #1 on: October 16, 2012, 10:05:53 am »

Looks like banding from the display or display system to me. Unless you did something really weird when creating the DNG (lossy?). Do you have the original raw? What's it look like. Can you tell us something about the display, OS, etc. Does this show up on all machines assuming you have more than one?
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Fips

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Re: Random poor previews
« Reply #2 on: October 16, 2012, 10:17:53 am »

I can confirm that this is not due to lossy DNG or display issues. Had the same problem a couple of times. As far as I can remember I just updated the preview image and that solved the problem. Occasionally LR has some hickups with preview images. It also happend to me that one image got the preview of another and another time a preview didn't appear at all.
But all the problems disappeared eventually, usually after a catalog optimization following a backup.
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dchew

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Re: Random poor previews
« Reply #3 on: October 16, 2012, 10:36:37 am »

Andrew,
Thank you for the help.  I do have the original raw file, and it's preview looks normal.  Info:
LR4.2
17" MBP 2012 (non-retina) connected to a NEC PA241w.  Laptop calibrated with an i1, NEC calibrated with the X-rite OEM unit.
OS 10.7.4

Just to be clear, when I go into Develop the image redraws and looks fine.  You got me thinking though.  I use "temporary" catalogs for importing raw images then export the selects to a Master catalog as DNG's.  I have a preset for that export with the JPEG preview set to:  Full Size / Embed Fast Load Data, but neither Use Lossy Compression or Embed Original Raw File are checked.  However, it could be that I mistakenly chose the canned LR Preset for "Export to DNG" which has "Medium" selected for JPEG size. Would that do it?  Also, I made some additional Develop changes to the file after importing to the Master catalog.

I could try recreating the DNG from the raw and ensuring I use my preset.

Dave
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digitaldog

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Re: Random poor previews
« Reply #4 on: October 16, 2012, 10:40:51 am »

Develop and the other modules use a different method to provide a preview so it makes sense that in Develop it looks OK (better). Try selecting the image and asking LR to rebuild 1:1 previews. Any difference?

The DNG JPEG isn't used for preview if I'm not mistaken so I don't think your setting for DNG is the issue here but it couldn’t hurt to change it. Then force an update of the DNG (Update DNG metadata and Preview).
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dchew

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Re: Random poor previews
« Reply #5 on: October 16, 2012, 10:54:57 am »

No difference.  I trashed the 1:1 preview, rebuilt, then Updated DNG Preview & Metadata.  I gotta run out now but later I will try exporting a second version into the MSTR catalog.  Thx to you and Fips.

Dave
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Fips

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Re: Random poor previews
« Reply #6 on: October 23, 2012, 11:37:14 am »

Here's an update from my side: The attached image shows a bad preview which LR just produced. I played around a bit bit and came up with a theory. This banding occurs only when I apply a preset in the library module. If I change anything in the develop module the preview gets updated and looks ok afterwards.
This suggests that when you use quick develop in the library module the adjustments are only performed on the small preview jpg. This makes sense as you want the program to be as snappy as possible. Only when you do into 'develop' the chosen preset gets applied to the actual raw file.

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