Photoshop: Why is a JPEG that is saved as a PSD file much bigger?

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Has anyone also a problem with big file sizes in Photoshop CC?
I start with a jpg file of 2MB and end with a PSD file of 130MB.
Layers are flattened and masks are removed.

In the preferences the checkbox 'max compatibility' is checked for preview in Lightroom. This could reduce the size to 30MB but is not an option for me if a preview is not possible in LR.

Files created with an earlier version (PS CS6) are about 20MB with the same image dimensions and same content.

I have a lot of images and this will take up a lot of harddisk space it this continues.
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Stijn Van Rompaey

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Posted 3 years ago

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Chris Cox

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JPEG is a lossy compressed format, lossless formats storing the same image will be larger. But my guess is that you have something else in the document that is taking up space - like metadata.
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Stijn Van Rompaey

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Thank you Chris.
I am aware of the bigger size of a PSD file, but 130MB for one layer and most of it is transparency is very big. Metadata could not take that much size I guess.
FYI, history log is also disabled.
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Chris Cox

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Then without seeing the file, I'm not sure what could make it that large.
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Stijn Van Rompaey

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I figured out that TIF format (zipped and transparency on) is a lot smaller in file size and works perfect in a Lightroom and Photoshop workflow with previews.

To give an idea, here is an example with file sizes in different formats:
JPG : 2MB
PSD : 130MB
TIFF (zipped and transparency on) : 40MB