Hey guys, 
I usually take a series of dark images during shooting low-light time-lapse photography, so that I can reduce noise from the images. 
Using dark subtraction is a useful way to reduce noise and so to increase signal-to-noise ratio, but I can not find a suitable way to apply those in a typical lrtimelapse workflow. 
That's because I can not save dark-subtracted images in raw format which lrtimelapse uses in its workflow. 
Do you have any idea I can apply dark subtraction to my images in lrtimelapse workflow?

No, I've never thought about it because I don't use it. How do you normally substract that dark frames? In which format do you shoot them (i assume RAW too?)

This post was last modified: 2015-10-13, 19:42 by noverain. Edit Reason: some grammatical correction

No, I've never thought about it because I don't use it. How do you normally substract that dark frames? In which format do you shoot them (i assume RAW too?)

Before talking about applying dark subtraction, let me talk about taking dark frame images. Dark subtraction has its origin in professional astronomical photometry, and is a wide-spread technique in astronomical image processong. If I will take a series of shots of 20-seconds with ISO 3200, then I will also take a series of 20-sec and ISO 3200 images with lens covered with its cover. This makes me take frames with no light but only having thermal noise. The dark frame images should be stored in the same RAW format. 

Astronomers usually take dark frames before starting their shots, in the mid of, and after finishing shots. But because I am taking time-lapse images, I take those before and after the time-lapse shots and later take a median of those images to build a master dark frame. 

Then, I arithmetically subtract this master dark frame from every time-lapse shots. Subtracting dark frames can be easily done in Photoshop by importing a time-lapse shot and the master dark frame into two separate layers and setting blending option to subtract, but astrophotographers usually do a batch job using dedicated software such as Maxim DL or AstroArt.

The feature to substract a dark frame (or better to first calculate the average dark frame out of a set of multiple dark frames taken before and after the timelapse shots) from each picture of the timelapse series is also very interesting for me. So far I just can do this with JPG-pictures which is not a good option here.
Do you plan to implement this option maybe based on RAW-images also for a future LRtimelapse version? I could imagine that this feature would be apreciated by a number of users.
Thanks
Regards
Jens

Hi Jens, no, I don't think so. LRTimelapse does nothing to the RAW files, it's not a RAW Converter. LRTimelapse one works on basis of metadata. I see no way to do hard modifications on a pixel basis to RAW files like they would be necessary for a dark frame substraction.

But of course you can try to do this - as long as you end up with a DNG file (could be one created from a tiff file) - you can then use LRTimelapse on those DNG files.