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Automate keyframe exposure matching

#1 alexnail
Hi Gunther,

First off great software, I absolutely love the results! I've only been using LRTimelapse for a little while but here is a thought...

I think you may be able to deskill part of the workflow or at least help people out a little...The most time consuming part of the process (excluding the final render) is undoubtedly the manual intervention in Lightroom, particularly if there are a lot of keyframes. There are essentially 2 problems with the intervention: it requires time and it also requires skill in matching exposures. Lightroom 4s match exposures doesn’t seem to be that great. For example, I will notice it making a -0.6 exposure adjustment when the camera settings would theoretically call for a 0.5 stop change etc. When I adjust the exposure to what the jump theoretically calls for (ie I adjust the exposure by -1 stop for a transition from 0.5 seconds to 1 second) it is often better than Lightroom's guess.

My suggestion is to get LRTimelapse to balance and transition all the exposures in the first part of the workflow. That wouldn’t actually prevent anyone from following the workflow as normal and using match total exposures/manual intervention if necessary, but on some sequences it might make smooth transitions straight away and avoid manual intervention or at least avoid the 'match total exposures' step since the user could do the tiny tweak straight away. All the user would then have to do is add their creative edits on top and synchonise everything except exposure. The transition could then be rerun for all the other effects. This is potentially a big time saver if my initial experiences with Lightrooms match total exposures are representative in general.Clearly the flaw with this process is that the user may wish to start by making all exposures 0.5 stops brighter for example, and that would make all the calculations that LRTimelapse does to correct the exposures redundant .

Perhaps an alternative 'Auto' workflow might be a good way to incorportate this feature. One click of a button could read all the files, transition the exposures and save the metadata so that for some holy grail sequences the result is perfect immediately.

I don’t have a huge amount of experience with the program (I have only been using it for a week) so I might be missing something, but maybe it's worth a thought to speed things up a little?

#2 gwegner
Hi Alex,
I've been experimenting with this already and in fact it would be no big deal to implement the exposure matching in LRTimelapse.
The problem is, and you mentioned already, that the workflow normally starts with editing the first image, including Exposure compensation and then the next one (the left of the first jump) with different exposure (sequence shall get darker but not as dark as the camera renders it). So every keyframe pair will have the left keyframe showing a totally individual exposure set by the user and only the second one would be edited. This would lead to a workflow where the user only edits the left keyframes and LRTimelapse could calculate the right ones automatically - but since the automatic calculation might as well be slightly off (as Match Total Exposures sometimes is) - you would have to correct manually in that cases.
The time saving in comparison to the current workflow would be minimal.
Just my thoughts, but I would like to discuss this with you and the other users. Thank you for bringing this topic up.
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#3 alexnail
Hi Gunther,

Thanks for the response. Lets have another think about this.....

Reading a little more into what 'Match Total Exposure' actually does I read that lightroom is actually doing its calculation based on the exposure settings, not matching brightness. I wonder if Lightrooms inaccuracy is because the camera doesn’t necessary report its REAL settings only the settings it is supposed to have to the metadata. Ie f8 could be f7.8 and IS0100 might be ISO120. Maybe you could experiment with using the embedded jpeg in the RAW to achieve a more accurate exposure match or to augment the camera settings information?

Using this idea you could, as you propose, only show the left keyframes in the first part of the sequence. The user can then go through them making the adjustments for visual effect before saving metadata. The software could then do all the smoothing itself based on the metadata of the saved keframes and the birghtness difference it calculates between keyframe pairs.

I read in a different thread that someone had a problem with highlight clipping switching from say ISO100-200 and shooting into the sun. In order to avoid a highlight clipping flicker you suggest underexposure, whilst another user suggests smaller steps. Your suggestions throws away information (not as much light is recorded) whilst the other solution leads to a 2 or 3 fold increase in work in lightroom. Personally I would prefer to fractionally underexpose as well as using smaller steps and simply do the work on the computer. The interesting thing about making the exposure jumps in smaller steps is that it would also make the embedded jpegs closer to the raw file when doing holy grail matching. (IE if you for example reduced a jpeg by 2 stops it would be wildly different to its RAW equivalent whilst if you only reduced it by 1/3rd of a stop it would be far more similar) so you might very well be able to do better exposure adjustments than lightroom because you are working off image brightness as well as camera settings.

The method above could potentially allow LRT to do all of the exposure work except the initial exposure settings chosen by the user for the 2 star keyframes (which may not require any modification at all). So the workflow could be like this:

User initialises metadata in LRT, calculates 2 star keyframes and saves meta in one click
User reads meta into LR then adjusts 2 star exposures to taste and saves meta (optional step)
LRT does all the transition work and deflickering, saves meta and warns if manual intervention is likely to be required to adjust 3 star keyframes (particularly if there are big exposure jumps likely to cause inaccuracy)
User reloads meta and checks holy grail keyframes in lightroom > If OK then export
If not okay correct in lightroom save meta and run LRT one last time.

Basically if you can get LRT to reliably do a perfect job of keyframe matching based only on the exposure information/embedded jpeg then you will create a process that is faster and more intuitive (editing just the 2 star keyframes would be really nice, it makes more sense to me because that is the creative part, I don’t want to do anything technical!). On the other hand if you cant improve upon Lightroom's accuracy (I think you will be able to) then it's essentially pointless.

One last suggestion….I believe that having a crop transition through the exposure is probably a common wish? I assume this is something that could be set in LRT and written to meta? Crop is really the only thing that you absolutely cant set with the holy grail frames because it would create jerky movement. Things like WB probably are best edited with the 2 star keyframes. Could you perhaps just code a crop feature into LRT? This avoids people having to deal with the 'technical' aspect of checking the correct columns etc in the table (and on that subject, does the user need to independently check the 4 different crop values? Isnt just one crop value enough for the user to see?)

Anyway like I said in my last post I am probably running before I can walk here, but I'm just trying to help! Sorry for the massive mental splurge! The easier you can make this the more popular your software will become!

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