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mattd67431277
Participating Frequently
February 6, 2023
Question

People detection happening too often

  • February 6, 2023
  • 2 replies
  • 799 views

I absolutely love the new people detection feature in Lightroom -- it makes selecting commonly selected objects incredibly simple, fast, and easy. I have noticed a significant uptick in the amount of time my graphics card fan spins loudly while I edit in Lightroom, however, and I'm experiencing a bit more lag on my computer. I happened to have the masking toolbar open as I was making global adjustments to a photo, and I noticed that it redetects the people in the photo after every change, including adjusting blacks/shadows/exposure/highlights/whites with the Add New Mask window open. I know it's possible adjusting global lighting could theoretically allow Lightroom to detect a new person out of the shadows of a picture, but I kind of doubt it's all that likely. I can't tell if it's also redetecting the people in the image with the people tab collapsed on the Add New Mask window or with the Add New Mask window closed, but if it is it seems like that behavior should be replaced with a button where you can request it redetect people after making changes to cut down on a lot of unnecessary processing if so.

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2 replies

johnrellis
johnrellis
Legend
February 6, 2023

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How are you observing that the People masks are being redetected?  

 

I don't observe actual redetection of people as I edit with the masking panel open.  AI masking uses the GPU for detection, and when I first open a photo with lots of people, I see a spike in GPU activity:

 

But I don't see similar spikes in GPU usage as I change Basic sliders such as Exposure and Shadows.  

 

I do see the thumbnails of the faces change as, say, Exposure is changed.  But that doesn't indicate redetection -- LR is just updating the thumbnails based on the current rendering of the photo, which consumes very little GPU or CPU.

 

Do you see repeated GPU spikes as you edit? On Mac, you can monitor GPU usage in Activity Monitor > Window menu > GPU History; on Windows, Task Manager > Performance tab.

 

You can stop LR from detecting people automatically when you first open the masking panel keeping the People section collapsed:

 

 

 

 

    M
    mattd67431277Author
    Participating Frequently
    February 7, 2023
    I do see a small bump in GPU activity each time I adjust one of the
    lighting levels, but that could be it calculating the lighting change. I'll
    have to do some more editing later today and open up the observation tool
    when I hear the fan blowing.

    If you open the Add New Mask panel on an image with no mask already there
    (shift+w) and have the People section expanded, every time you adjust any
    lighting setting using the histogram, the people list disappears and is
    replaced by a spinning wait icon with "Detecting people..." text beside it
    for a second before it reloads the detected people. You could be right that
    it's not actually redetecting people and just updating the preview images;
    if that's the case it might be better to have the text say "Generating
    previews..." rather than detecting people to clear up that confusion.

    Thank you for the response!
    johnrellis
    johnrellis
    Legend
    February 7, 2023

    [This post contains formatting and embedded images that don't appear in email. View the post in your Web browser.]

     

    A little more detail on what I see:

     

    When I first open the mask panel, I see a big GPU spike as it shows "Detecting people" (A). As I adjust the histogram, I see "Detecting people" and the people thumbnails flash for the briefest  moment, but I see just small bumps in the GPU (B):

     

     

    Those small bumps are comparable to what I see when I adjust the Basic sliders (exposure, shadows, etc.) (C):

     

    I think the brief flash of "Detecting people" when the histogram is adjusted results from refresh logic of the mask panel, which probably goes like this (based on my experience coding UIs):

     

    1. You adjust the histogram.

     

    2. LR refreshes the rendered image, the histogram, and the masking panel.

     

    3. The masking panel refreshes the detected people. That code repaints the text "Detecting people", examines the cache of AI masks, finds the detected people masks in the cache (so it doesn't have to compute them), re-renders the people thumbnails, then cleares "Detecting people".  

     

    If my understanding is correct, then I agree it would be better not to flash "Detecting people" if the people masks have already been computed.

      GoldingD
      GoldingD
      Legend
      February 6, 2023

      And are you not pausing Face Detection?

       

      johnrellis
      johnrellis
      Legend
      February 6, 2023

      "And are you not pausing Face Detection?"

       

      Pausing Face Detection doesn't affect People detection in the Masking panel.

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