Why is my image file coming out so large after using photoshop?

It may be counterintuitive, but this is normal, and it should have always been happening on any computer with any application. The file size will change even if no edits are made, because the change is about the nature of each format you are moving it through.

The short answer is that both JPEG and raw are not the “normal” size of any image. JPEG is highly compressed, and raw requires development before it can be used. Those compromises allow the file sizes to be much smaller than normal. We get used to these small file sizes, so we think they get too large when converted to Photoshop or TIFF format. But the truth is that the file size of Photoshop or TIFF format is the real file size for a fully editable, full quality RGB image.

The natural file size of any image is:

Number of bits * number of bits per pixel * number of pixels

Suppose you have a 24 megapixel file (6000 x 4000 pixels).

If you run it through that formula, you get from roughly 70 to 140MB depending on what bit depth you chose and what file options were set. That’s the natural file size of that image, and that’s why it’s the size range you get if you save in Photoshop or TIFF format.

The JPEG file is much smaller because a lot of the original quality has been squeezed out of it, but if you convert it from JPEG to Photoshop format and save, it must be expanded to a full uncompressed document for normal editing. That is what causes the file size increase from JPEG to Photoshop.

The raw file is much smaller for several reasons: It doesn’t have three RGB channels (yet), it’s one channel of raw data. And some cameras compress the raw file, although not as much as JPEG to preserve more quality. But you can’t edit or print that raw file until it’s expanded to three RGB channels. A raw editor such as Lightroom Classic does that expansion behind the scenes as you edit so you don’t see the file size increase there (until you export to Photoshop or TIFF), but Photoshop converts it to three channels up front before editing, which is a big reason behind the file size gain there.

One thing that could be happening with raw files: If Adobe Camera Raw on the old computer was set to convert to Photoshop at 8 bits per channel, but on the new computer is set to convert at 16bpc, the converted file size on the new computer could be twice as large.

Hi there,

Thanks for reaching out; we're here to help.

How many layers do you have before saving the PSD.? Does this happen with images directly opened in Photoshop, or does only editing in Photoshop give these results?
As suggested, you can try and change PSD to TIFF or vice-versa and check the results.

Let us know how it goes,

Regards,

Ranjisha

Conversion to TIF or PSD can cause this.  

https://feedback-readonly.photoshop.com/conversations/photoshop/photoshop-why-are-psds-so-much-larger-than-jpgs/5f5f45044b561a3d422f508f