PSD files can be expected to be larger than raw files. A raw file contains readings of some 12 to 16 bits per Photosite (depending on the camera). A "developed" PSD file has pixel values containing 24 or 48 bits each. That's a 2x to 3x increase in data size by my reckoning. But that increase will not necessarily be exact every time because PSD provides data compression, as do many raw formats.
Regarding saving from one place or the other, I just tried the same thing and my Camera Raw-saved PSD file was only 2 kb different in size than my Opened then saved PSD. One was 147,489 KB and the other 147,487 KB.
Are you converting to your working space when opening the file, or changing the bit depth before saving?
What kind of camera?
I may not have been clear in my post. It's not about PSD v. Raw file size, just comparing PSD files.
Starting with a raw file ( in this case a 5DmII CR2)
Using the same settings (mid-bottom of ACR window) when saving a file using the "save image" within ACR or opening the file into PS and then saving. This is where I'm seeing the file size difference.
The second part of the problem is that PSD files that are saved directly out of ACR using the "save image" (bottom left of ACR window) are all set as Maximum Compatibility. As a result opening these files will always be have the extra data and saving time that files with Maximum Compatibility enabled have. The only way to get around this is to have your PS prefs set to Never or Ask and the "Save As" to overwrite the file.
I just reprocessed a folder of PSD's that were saved out of ACR by overwriting as above and the 36 files (with layers, retouching etc) went from 6.9GB to 5.6GB, and the save time is also faster.
This isn't intended to be a discussion about the benefits or disadvantages of the Maximum Compatibiliy "feature", but just a question as to whether it can be turned off in PSDs saved from ACR.
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I did a little more testing. The file sizes DO match almost perfectly if you save from Photoshop using the Maximize PSD and PSB File Compatibility setting set to Always, and different as you say with a setting of Never.
So my thinking now is that the Maximize Compatibility setting is completely responsible for the difference in size.
I know of no way to specify the format of the PSD as saved by Camera Raw.
I would have thought that Camera Raw should have been able to get the configuration information from Photoshop and heed it, but there are actually a lot of things a plug-in just can't get from Photoshop, and I suspect this setting may be one of them. We probably weren't supposed to notice.
The Save As workaround seems to be your only path at this point.
thanks for testing this.
If the file is flattened as they are when they are saved directly out of ACR or PS, I still see a discrepancy in the sizes, irregardless of the compatibility settings.
Saving flat files (no layers) within PS, with either max or not, the sizes are pretty much the same (a couple bytes more.. probably just some data) since it doesn't require the full size preview. The size difference becomes dramatic with layered files as expected, but I don't think it's expected in a flat file.
>We probably weren't supposed to notice.
sounds right : )