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Automatic white balance correction for (very) long-term jpg timelapses

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#1 lightatwork
Hi Gunther,

Thanks for developing this great product. During a few of my last productions, I ran into a very time-consuming process that might be possible to automate. Hear me out:

I know that shooting RAW is by far the best option for creating good quality timelapses and having maximum control over things such as white balance. However, there are a lot of situations, especially in the field of very long term (more than weeks or months), where having the raw files available is not an option because of logistical or technical restrictions. Take for example the systems of PhotoSentinel. They have a new system that can record RAW, but their main service and ALL of their legacy products are based on JPG capture. For the purpose of those systems (very long term, remote installations) that is fine, but it creates challenges during post-editing.

For me, there are two main variables that make for a smooth, good-looking long term timelapse. 1 is of course exposure. Plenty of tools to get that right, using the features of LRT. 2 is (constant) white balance. The white balance that is baked into the jpg is fixed and whatever white balance setting on the camera, you are going to have shifts in white balance due to the actual changes in light and white balance during the day(s).

Right now, when I edit a long term jpg sequence (exported to DNG using LR), I make two sets of keyframes. One set to control (correct) the extreme differences in exposure. The fine correction is done by visual deflicker. The other set of keyframes is to correct the white balance. Once in lightroom, I use these keyframes to set a similar white balance for those frames and let LRT interpolate between these keyframes for Color Temp en Tint. With very long timelapses, where I am forced (because of activities to be captured) to also use shots from early morning and just before sunset, this results in a very, very timeconsuming process.

It would be fantastic if I could do the following:
- Convert JPGs to DNG's in LR
- Initialise the DNGs in LRT
- Correct for exposure and other basic settings
- Perhaps make visual previews and then:
- Pick a point in the image which should be neutral grey (sort of like the reference area for exposure, but then a point for white balance)
- Have LRT/LR run a process similar to the "White Balance Selector" in LR for each image separately
- Have the option to offset the entire image range in terms of white balance. This could be useful if the point you picked is not 100% grey or because of artistic reasons.

This feature would be very useful for JPG-based workflows, but I think RAW-based long-term workflows could benefit as well. It is not a matter of not being able to correct the white balance, it is just automating a very time-consuming and currently manual process of correcting for changes in the white balance of the actual light, during the morning, day, evening, etc.

Thanks for looking into this.

Regards,
Jorrit Lousberg
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#2 gwegner
Hi Jorrit, thanks for your suggestions and insights in your workflow.


Quote:- Convert JPGs to DNG's in LR

Unfortunately Adobe does not allow this by now. Please support my request to Adobe: https://feedback.photoshop.com/photoshop...-converter

Quote:- Pick a point in the image which should be neutral grey (sort of like the reference area for exposure, but then a point for white balance)
- Have LRT/LR run a process similar to the "White Balance Selector" in LR for each image separately
- Have the option to offset the entire image range in terms of white balance. This could be useful if the point you picked is not 100% grey or because of artistic reasons.

The problem is that LRTimelapse only works with Metadata. This would mean analysing the preview for the color temperature (how?) and transform that into a WB correction. For RAW that had to be an Absolute WB value (how to figure out?) and for JPG a relative WB value. Without having thought very deeply about this, it seems rather complicated to do.

Most of the long term users of LRTimelapse use the filter options in the Long Term Module, which allow for a Hue filtering. The idea is to remove images that do not fit into the desired look.

I'll keep this in my mind, but I cannot promise that I'll be able to find a way to implement this, sorry...
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#3 lightatwork
Hi Gunther,

Thanks for checking the request. For starters, I have supported your request to Adobe.

I understand your concerns for implementing this. You know better than me what the limitations and restrictions of the LR/LRT combo are. For me the Hue-filter is specifically NOT what I am after, since it removes the images from the sequence. I don't want that, I want/need to keep them and (automatically) adjust the WB of those frames to fit into the rest of the sequence.

In LRT you probably wrote the system that analyzes the exposure on a certain chosen part of the image (reference area) yourself, since it is not a standard metadata thing. My guess was that in theory it would be possible to approach the white balance analysis in the same manner:
- Have LRT set a (very small) reference area that should be neutral grey
- Have LRT analyze that reference area for RGB values
- Have LRT adjust metadata WB and Tint so the RGB values are the same
- Do this for every frame

Just like the exposure reference area, this probably requires a lot of programming on your side, since it is not something you can have Lightroom do.
I suppose having LRT adjust the metadata would require iterations, since the system can not know beforehand how much to change the values to get the desired. There MUST be a software-solution for this, since it is exactly what Lightroom is doing with their Whitebalance color picker tool. Both for RAW and JPG files.

Thanks again for your great product and I wish you all the best.

Regards,
Jorrit
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#4 gwegner
Unfortunately mapping Whitebalance to toning is much more difficult than exposure. I will think about it but won't make any promises. For adobe it's much easier in lightroom, since they have access to the raw data of the images, which I don't have in LRT.
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