Down sample DNGs Prior to conversion

One feature that I would love to be added to the scanner to NLP workflow would be the ability to down sample the DNG prior to importing into Lightroom.

As many of you know none of the scanners commonly used can actually resolve the ridiculously high DPI settings as advertised. However, In order to get the highest actual DPI you must set the DPI to maximum when scanning.

This results (for my plustek 8200) in file sizes over 400MB! On top of the increased file size the “high resolution” scans also slow down lightroom and cause general performance to suffer.

It would be beneficial to down sample before importing rather than after in order to speed up the workflow.


Hmm… I don’t think there is a way to downsample a DNG before importing to Lightroom… maybe someone else in the forum will have an idea of how to do this?

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Lightroom’s DNG export has a somewhat hidden feature that could be useful early in a person’s workflow. By default lossy compression is turned off on the DNG export and the resize option is greyed out:

However, if you check lossy compression, that enables you to resample the DNG to a lower-megapixel image (or specify a pixel count for your long edge):

It seems to me that users needing to downsample could export & re-import a lossy DNG at the maximum resolution they’re still comfortable with, and then apply NLP to that small DNG.

I just tested this on a 250-megapixel image (D850 3x3 pano stitch of a 6x9 negative). I exported a lossy DNG at 24 megapixels. The file size went from 1 GB to 10 MB. :slight_smile:

You can take a look at it here:

It’s just a test image from my first roll of film. At first glance, NLP handled the lossy DNG just fine.


I should note that I forgot to resize the image on my first lossy DNG export, and the full 250 MP image went from 1 GB down to just 85 MB.

I don’t know much about the image quality trade offs. Here’s a few articles for those who are curious:


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Ahh, brilliant! I had no idea you could enable resizing of DNG exports this way!


I never knew LR had this feature thanks! should I run the Vuescan DNG conversion before re-exporting? NLP doesn’t seem to recognize that the raws came from Vuescan after importing the compressed DNGs Thanks!