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Author Topic: dng-file size and Photoshop  (Read 599 times)

Eric Brody

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dng-file size and Photoshop
« on: January 17, 2020, 11:30:07 pm »

In my quest to deal effectively with the rather large files from my Sony A7RIV, I thought I had an idea... first convert to dng, smaller file size, then to Photoshop.
The uncompressed ARW files are 117MB, when sent to Photoshop after working on them in Lightroom Classic they are 344MB. Then with layers they start to get really large.

I thought if I first converted them to dng with Adobe's dng converter, where they are smaller, in the 70-80MB range, import them into Lightroom, work on them and then send them to Photoshop that they would be multiplied by 3 or so, just like the ARW files, eg 210-240MB. For some reason, they come into Photoshop at 344MB, just like the basic RAW ARW files.

Am I doing something wrong, is there no free lunch here, can someone more knowledgeable than me explain this?

Thanks.

[moderator: changed subject from "dog-file" to avoid disappointment among puppy-lovers. Jeremy]
« Last Edit: January 18, 2020, 03:34:00 am by Jeremy Roussak »
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digitaldog

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Re: dng-file size and Photoshop
« Reply #1 on: January 18, 2020, 12:16:21 pm »

The DNG’s are raws, and converted and usually a bit smaller due to better compression (lossless if so selected). But that raw data has to be rendered into RGB for Photoshop and that’s producing a much larger document, especially in high bit with layers. So no free lunch when you render and add layers in PS. IF you stick with DNG and parametric edits in LR, they data takes up a lot less space and unless you print directly in LR, at some point, you’ve got to render the data and you end up with a 2nd, larger document.
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Andrew Rodney
Author “Color Management for Photographers"

Eric Brody

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Re: dng-file size and Photoshop
« Reply #2 on: January 19, 2020, 12:06:32 am »

Thanks Andrew. As so often is the case, you make sense out of my misunderstandings. So, it appears that using the dng converter will shrink my files (ARW to dng) so long as I stay in Lightroom. Should I go to Photoshop, as I do for all my "master" files, I'm back to huge files. Maybe someday Sony will come through with a proper lossless compressed RAW as Nikon, Canon, and Fuji all have done.
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Bart_van_der_Wolf

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Re: dng-file size and Photoshop
« Reply #3 on: January 19, 2020, 06:14:43 am »

Thanks Andrew. As so often is the case, you make sense out of my misunderstandings. So, it appears that using the dng converter will shrink my files (ARW to dng) so long as I stay in Lightroom. Should I go to Photoshop, as I do for all my "master" files, I'm back to huge files. Maybe someday Sony will come through with a proper lossless compressed RAW as Nikon, Canon, and Fuji all have done.

Hi Eric,

Nikon, Canon, and Fuji are no different. All the Raw formats that are based on Bayer CFAs (or other sparse sampling) only capture a fraction of the full RGB data. Add some (lossless or not) compression and one gets an efficient storage that will drastically increase in size the moment they get demosaiced, and get increased in bit-depth.

The in-camera Raw captures need to be written to storage fast, and compact, in order to be able and achieve/maintain a fast frame-rate with a limited capacity buffer, and to capture many images on a compact storage medium. The demosaicing is where an attempt is done to recreate an as complete as possible dataset from that smaller efficient proxy.

Cheers,
Bart
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DP

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Re: dng-file size and Photoshop
« Reply #4 on: January 19, 2020, 11:05:32 am »

All the Raw formats that are based on Bayer CFAs (or other sparse sampling) only capture a fraction of the full RGB data.
how many errors & inaccuracies did you manage make in just one line ? Foveon, no "RGB data" readout from sensor (and no "color" till color transform), cameras w/o CFA at all, ...
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Bart_van_der_Wolf

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Re: dng-file size and Photoshop
« Reply #5 on: January 19, 2020, 01:56:49 pm »

how many errors & inaccuracies did you manage make in just one line ? Foveon, no "RGB data" readout from sensor (and no "color" till color transform), cameras w/o CFA at all, ...

I didn't say all Raw formats, I spoke about all those with a Bayer CFA, like the one the OP uses.

Foveon is not a Bayer CFA sensor, that's why I focused on the majority of current sensors, those with a Bayer CFA. There are other configurations than the typical RGGB mosaic as well, but they are a minority. IThe Foveon sensor captures something vaguely reminiscent of RGB data per Photosite, but with very much channel overlap, and also dependent on chief ray angle (because a longer travel distance through silicon registers at a different depth/color than perpendicular rays). A monochrome (or rather achromatic) sensor doesn't capture RGB data, it instead captures a mixed spectrum per photosite.

None of these exceptions are relevant to amswerig the OP, unless he shoots with such a sensor.
« Last Edit: January 19, 2020, 02:01:17 pm by Bart_van_der_Wolf »
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digitaldog

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Re: dng-file size and Photoshop
« Reply #6 on: January 19, 2020, 02:23:37 pm »

I didn't say all Raw formats, I spoke about all those with a Bayer CFA, like the one the OP uses.
I concur based on this statement pasted from your reply: “All the Raw formats that are based on Bayer CFA...“
When considering all raw formats based on a Bayer CFA, these formats are based on a Bayer CFA.  :D
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Andrew Rodney
Author “Color Management for Photographers"
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