Lightroom subpar performance on a new and powerful computer + Photoshop image scaling artefacts

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  • Problem
  • Updated 3 years ago
  • (Edited)
Hello everyone.  
I need to share my experience with Lightroom CC 2015.4 on brand new and powerful iMac and see if other people experience similar performance issues. Is it my setup or is it indeed the application that needs refinements? Also I want to share a weird bug presented by Photoshop CC 2015.1.2 and see if anyone can reproduce this.

Until 2 weeks ago I was using a 
  • MacBook Pro mid 2012, retina
  • 16GB RAM
  • 2,7 GHz Core i7 processor.
  • 750GB SSD
  • NVIDIA GeForce GT 650M 1024 MB
  • OS X El Capitan 10.11.3
  • Adobe Creative Cloud - applications always up to date
  • Using mostly Lightroom and Photoshop (I'm a photographer, that's my job & passion)
Well, this is a pretty decent computer, but over the last couple of months or a year it has been running progressively slower and slower when running Lightroom. Photoshop was behaving more or less OK having in mind the specs and age of the MAC. But eventually Lightroom became so slow, I cant even describe the slowness. I as looking at the spinning wheel more time than working on an image. Lightroom was slow in all modules. Normally I also have Mail and Safari opened and some times Photoshop. Back in time, some 6 months ago, I first started closing one of those apps to slightly improve LR's performance. Then I had to start closing all applications and only leave LR running. My computer became a dedicated machine to Lightroom, only to try and have some work done at the end of the day. 

Strangely enough, there was always free RAM (I use Bjango's iStat Menus to constantly monitor RAM and CPU in the OS's menu bar)...some times as much as 25%-40% free RAM. But Lightroom was behaving as if there was none. 

So a few weeks ago I decided that my old pal the MacBook Pro has to be retired, although he was performing VERY WELL with all other applications...But I understand that Adobe applications are complex image editing power softwares and resource hungry. So I did a huge investment in the latest and greatest, fully loaded iMac...

Two weeks ago I received my iMac and I've been using it intensively ever since, doing my observations and taking notes. And after 2 weeks I had to reach out to the forums and cry out my frustrations. Because there are such...and as I see, I'm not alone...First the iMac's specs:
  • iMac 5k, late 2015 model, 27", fully tuned and loaded with 
  • 64GB RAM;
  • 4,0 GHz Core i7;
  • 1TB SSD (no fusion drive) by the way it's 4x faster in read & write times than my old MacBook Pro. Performance was measured with Blackmagic Disk Speed Test v. 2.2.2 and the iMac's SSD exceeds the scale with over 1200MB/s write and 1900MB/s read speeds;
  • AMD Radeon R9 M395X 4096 MB;
  • OS X El Capitan 10.11.3
  • Adobe Creative Cloud - applications always up to date (currently LR CC is 2015.4, CR is 9.4, PS is 2015.1.2)
Well, overall performance is better, indeed. But it's far from what I expected. Don't get me wrong -- the iMac is performing AMAZINGLY well with all other applications. But with Lightroom I still see the spinning wheel a lot of times. For the folders with images that I'm currently working on I render full resolution 1:1 previews +  Smart Previews (so in fact I'm working on the internal iMac SSD). Rendering edits lags. The spot removal tool is so badly slow and lagging, that I prefer to export the file to Photoshop and clean it there. How is this possible?

Before I get asked let me answer: yes, I do use the graphics processor (the option is selected). I tried both options.

Now regarding Photoshop:

I don't use it as much and as often as Lightroom, but I did notice that when opening the application, it takes about 35 seconds to get through the welcome screen and to be able to use the program. Some times it takes longer, which is about the same time it took to load Photoshop on my old MBPro. How can this be normal? On another note Adobe Premiere some times takes more that 60 sec to load, Illustrator 20 sec, Indesign 15 sec...

The big, scary problem with Photoshop CC 2015 is this:

I noticed a serious scaling artefacts in Photoshop CC 2015.1.2. This is horrible and scary. The artefacts are not immediately evident in busy pictures, but in uniform B&W photos, the bug is obvious. To showcase the problem I'm using a grayscale image. I did a lot of experiments and reached to the following conclusions:
  1. This only seems to be happening with 16 bit images. I cannot reproduce the artefacts with 8 bit & 32bit images in all situations (but I work entirely with 16bit RAW images as they come like this out of the camera, so this IS a problem for me);
  2. This only happens when the background is a layer. Even if it's just a single layer;
  3. The pattern varies - some times its made up of squares, other times rectangles and other times squares & rectangles overlap, like in the examples below;
  4. If the background is flattened, the artefacts do not occur when resizing (upscaling or downscaling);
  5. The artefacts are much more pronounced if the rescaling is done to an uneven number of pixels. For example, resizing from 3000pix wide to 2111pix is much worse than resizing to 2000pix;
  6. The problem appears to be only an "illusion", because when exporting, the preview and resulting JPG's on disk are OK. See images 4A & 4B below. But this is still a problem, because working on files with such overlaid artefacts is very distracting and...scary
IMAGE 1: normal file before downsizing16bit (as mentioned, this does not happen with 8bit and 32bit images, nor with flattened images). Background is a layer:

 after resizing (Image > Image Size...). Notice the "grid" artefact:

IMAGE 2B: Same as 2A above, but with exaggerated brightness to better show the pattern:

IMAGE 3A: Same as example 2, but slightly zoomed in to show details of the pattern:

IMAGE 3B: Same as 3A above, but with exaggerated brightness to better show the pattern:

IMAGE 4A: On export (Fale > Export > Save For Web (Legacy)...) the preview is OK, but notice the original file behind the dialogue window is not OK:

IMAGE 4B: Same as 4A above, but with exaggerated brightness to better show the pattern:

That's all for now. I hope Adobe will look into this issues.


Kostadin Luchansky

KDL [at]
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Kostadin Luchansky

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  • confused

Posted 3 years ago

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Rory Hill

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I feel for you Kostadin.  Regarding "Is it my setup or is it indeed the application that needs refinements?" have you tried:

1.  Clearing your preferences in Lr.
2.  Using a new Catalog.
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Kostadin Luchansky

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Hi Rory,
Thanks for your reply and input. I use 2 catalogues - one is big and is the one that holds my professional, work images. It has 105.679 photos in it. I've read that this is not so much for Lightroom to handle. But the other catalogue, the one with my private photos with family and friends in it is 1/10 of the other one. I understand that this is a relatively small catalogue. However, working in both I experience the same symptoms.
I have not performed clearing LR's preferences. I had no idea that this procedure existed and I don't know how to do it, but I will do a Google search and give it a try. 
Thanks and do have a nice day.
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Rory Hill

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I don't think the size of the catalog is much of a factor.  However, it is possible Lr is struggling with some corrupted metadata or preview issue.  I'm suggesting you try creating a new catalog and import just a few images fresh from your camera.  That way we can at least determine if it is your catalog(s) that are causing the problem.  Try this after you have cleared your preferences and that did not solve your problem.  If this doesn't work then your problem is above my pay scale :*(
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Chris Cox

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The lines are due to a video card driver bug (it's mixing the low bits of the 16 bit values into the high bits by mistake).  Changing the GPU mode to "Basic" should avoid that until Apple can fix the driver code.