P: 100% or 1:1 Zoom

I see, interesting. Indeed @ proven. I imagine the 200% issue wasn’t addressed simply because it wasn’t reproducible. I had not seen that error before forcing it to trigger, so it’s possible that was the case for them.

In regard to the inaccurate 100% zoom, I just checked the App Store and Lightroom requires iOS 11 or later. Which means that SDK limitation issue isn’t relevant (it was addressed in iOS 11). Now I’m pretty sure its just simply incorrect math. After realizing that, I checked LR CC desktop (not classic) and it’s also not true 100% (didn't know which aspect you were saying also happens on Classic, but now I see). Wish I could see those portions of the zoom calculations code.

@ first link ... there should be a small semi-transparent overlay in the bottom left corner or something that shows the level when zooming (the overlay could fade out / disappear after a few seconds). That way users could see the level while pinching to zoom, instead of just guessing. Never saw the need until this thread, but as I was eyeballing / guesstimating the zoom level a few times, I realized how annoying that was, lol. That would be like Photoshop not showing the zoom level.

Does Lightroom Classic show the zoom level?

Great points, and I'll guess we'll see. Thanks for helping to reproduce issue. There are other reports of this issue. Below are some examples:

https://forums.adobe.com/thread/2561677

https://forums.adobe.com/thread/2406683

https://forums.adobe.com/thread/2530270

I guess some reports have been dismissed due to the Smart Preview caveat, but in my case I have now proven that the zoom behavior and inconsistency is the same regardless of whether I am viewing a smart preview or original file. Was looking for an additional link that I can't find where the Smart Preview zoom exception was brought up but the OP stated he was also only working with directly uploaded original files. So, yes there are other reports out there.

I wanted to define predictable triggering so it could be troubleshot. A precise triggering method might illuminate where to look, as it could be due to an overlap of events. Hopefully it'll help them get to the bottom of the problem. Or maybe they can just redo the zooming math, since it's inaccurate anyway.

There's a limitation with the iOS SDK in relation to screen size (UIKit's UIScreen nativeBounds property). If the "base SDK" being used for the sake of device compatibility, is too low, it will cause the screen of newer devices to be reported as smaller than reality. It's possible that wasn't compensated for. -- Ultimately, it could be any number of reasons, not necessarily inaccurate math.

Great that you took time to investigate this in detail! So, we can clearly state that based on our findings that a true 100% zoom is not available in Lightroom Mobile on iPad, although it is supposed to be a supported feature. That is when defining true 100% zoom as matching one image file pixel to one iPad display pixel and assuming all else is equal.

I always view my photos with iPad in landscape orientation as I am also using Apple keyboard. I don’t need to change iPad orientation to trigger the jump to 200% zoom and for me doesn’t require a great deal of effort to trigger.

Thanks again. I’ am very interested to hear Adobe’s feedback on this matter.

The resolution of my files are 24mp (6000x4000) Leica DNG, and 12mp (4032x3024) Lightroom DNG (taken with my iPhone). On the 11" iPad with a resolution of 2388x1668, 100% zoom on the 24mp image would be 39.8% of the image displayed. It came to mind that I could use Lightroom's 100% calculation behavior itself to trigger the glitch, by forcing it to calculate while changing the orientation of the device. I was able to successfully get the 200% zoom to trigger, and narrowed the steps down to:

1. With Lightroom CC on iPad completely exited from the open tasks, I opened Lightroom CC while holding the iPad in landscape orientation. If Lightroom hasn't been completely closed yet, open an image ... and make sure to close any open panels. Exit the image to get back to grid view. Then completely close the app from the task switcher while you're in grid view, and open it again.
   
   
2. With LR open, I opened one of the 24mp landscape images using a single click. The photo opened in "fit" mode.
   
   
3. Double-tapping the photo caused it to zoom in so that the 1/2 of the image could be seen at once (which is actually less than true 100% zoom).
   
   
4. Double-tapping the photo again causes the image to zoom out to "fit". Subsequent double-taps just cause it to go back and forth between zoomed-in and fit.
   
   
5. While the image was zoomed-in I rotated the iPad to portrait orientation.
   
   
6. While the iPad was in portrait orientation I opened the info panel with the image zoomed-in.
   
   
7. With the info panel open, double-tapping the photo resulted in it zooming out to "fit".
   
   
8. Double-tapping it again causes the image to zoom to 1/4 of the photo's width.
   
   
9. Double-tapping it again causes it to zoom out to "fit".
   
   
10. I closed the info panel while the image was in "fit" and the iPad is held in portrait orientation.
    
    
11. Double-tapping the photo again causes the zoom behavior to break. In my case the zoom showed 1/8 of the image or double the previous 1/4 it was giving. Thus becoming a 200% zoom (not a true 200%, just 200% relative to the previous 100%).
    
    
12. Once the zoom behavior breaks it stays that way, whether the iPad is held in portrait orientation or landscape. It consistently goes back and forth between 200% and "fit".

Those steps do not always trigger the break, but it does it consistently enough for me to call it reproducible. If those steps do not work, exit the app completely and try it again. Or just add rotation to the double tapping to increase the probability of triggering the break. The opening of the panel introduces another level of complexity in calculating the position while calculating the zoom level, further increasing the chance of a break.

Point is, it's reproducible despite having never used Lightroom Classic.

My previous assumption that it was doing a 100% zoom is because I was eyeballing the lower resolution images on a smaller screen rather than actually measuring it. But having measured it I see that at no point was the 100% zoom truly 100%.

I imagine the zoom calculation is taking ppi into account, causing the 100% zoom to be incorrect due to the variance of ppi in displays (that or doing something like dpi to ppi math). If the math were based purely on resolution, I doubt there would be room for glitching.

I’ve been on the road a few times and uploaded images directly to my iPad from camera and prior to images being synced with Lightroom Classic have exhibited same zoom behavior I have described above. So don’t think the sync to Classic is responsible for the issue. Yes, the normal behavior should be as you describe, but in my case I am indeed getting two different zoom levels.


I’ll clearly summarize how all different types of image tapping options behave for me:


1) Single tap on image toggles between regular view (with menus) and full screen fit - this works fine


Rest below assumes full screen mode as starting point:


2) First time double tapping on newly opened image (two taps in very quick succession) yields a zoom factor < 100% and depends on image file resolution, e.g., in my case with 13” iPad Pro zoom factor is 75% for D500 and 50% for D850 full resolution NEF files respectively. This is the main issue. According to Lightroom Mobile documentation this should provide a true 100% view, but it does not.


3) Repeat double tapping after zooming in returns image to full screen viewing size


4) If I then repeat double tapping to zoom in and out multiple times the zoom factor will eventually pop to 200%. Behavior is same regardless of image file resolution. I will see 200% zoom factor on both D500 and D850 NEF files. The big variable here is there is no consistency in number of repeated double taps for zoom factor to jump to 200%. Sometimes it happens quite quickly, other time I have to repeat double tap many times to get it to happen. However once zoom factor has jumped to 200% then further double tapping will always toggle between full screen view and 200% zoom, never the lower zoom factor that occurs initially. Also seems that jump to 200% zoom happens more readily with Apple Pencil rather than with finger tapping, but can also be induced with finger tapping.

Odd, it sounds as if you’re getting more than two zoom levels upon double-tapping repeatedly. However, I only get two, “fit” and then something that I thought was greater than 100% before, but in hindsight realize it was the smart preview. Upon downloading the original I saw it’s probably 100% . Repeated double-tapping just causes it to go back and forth between “fit” and what I assume now is 100%.

I am using the new iPad Pro 11”, on the latest Developer Beta of iOS, and the iPhone 7 also on the latest Developer Beta. Behavior is the same for both devices, only two zoom levels. I do not use Lightroom Classic and never have. So it causes me to wonder if although the files originated from iOS import, something about Lightroom Classic is mucking up the zoom levels.

So, I have compared zoom behavior of original files directly uploaded to my iPad from camera to Lightroom mobile with smart previews originally uploaded to my desktop and synced via Lightroom Classic, and the zooming behavior is identical. In Lightroom Mobile on iPad (and in this case with D500 NEF files) double tapping on a newly opened image shows about 2/3rd’s of image along the long axis. On 13” iPad Pro this is a zoom factor of approximately 75% give or take. This zoom factor remains the same regardless of whether I am reviewing original images or smart previews. Repeated double tapping will, as discussed above, eventually result in a significantly higher zoom factor of about 200%. Once again I see exactly same behavior with both smart previews and original files. No difference.

> (unless she really wants to see them...)

I can live without them! 😉 Getting it in front of the team was my main aim, so thank you!

I initially entitled my thread with wording "feature request", but an administrator must have removed that wording. Point is true 100% zoom is supposed to be a supported feature with Lightroom Mobile already, so in that sense it was correct to call this a "problem".