Photoshop: documents over 2gb automatically save as psb

And if you save your files in .tif with recording of layers? Well the 2 Gb limit would not exist and you would still have your layers available for next corrections! But it's too easy, it is preferable to complicate your life.

I don't have one of the newer cameras 30+MP cameras, maybe never, that is for another day. I have found myself with a file that could not be saved as a PSD and will admit that I did not know it had to do with size. Now when a file was getting to big I would save it as is and then create a 'flattened' version of it saved with some kind of incremental addition to the name of the 'new' file. It helped out most of the time and I could always go back to any previous version. Interesting notes here. I'm still having problems with [copy] [paste]! Good Luck! 

PSB with full size jpeg preview of flattened file by default would be my vote too - that way bridge would not have to parse the whole file to generate a preview.

Why not just save to PSB by default then?

I think what the issue being raised here is that you shouldn't have to tell photoshop to save your file as a psb. If it's over 2gig and you tried saving it as a psd, of course you will still want to save it. It's not like you are surprised and then go into it and start deleting layers to get it under the bar. You just want it saved so you don't lose anything. If photoshop tries to save as psd and realises that it's over 2gig afterwards, then put in a dialogue box saying "this file cannot be saved as a psd file, click cancel in the next 10 seconds if you do not wish to proceed"then it goes ahead and saves the file for you in the format that works.

That's my opinion.

We already do make a guesstimate on the size of the resulting file and warn you if that is too large for the format. But if the guesstimate comes in under 2 Gig, and the file written goes over 2 Gig - then we have to warn you after writing out 2 Gig. There is not way around it without a perfect (and fast) predictor for compression of all your data and metadata.

If you want safety, then just always save as PSB.

PSD cannot go over 2 Gig - the file format is too old, and only handles 32 bit offsets.

PSB is PSD with 64 bit offsets so it can go up to a couple Exabytes without problems.

Chris, I would happily trade the occasional file being saved as PSB that is under 2gb, for the wasted time forgetting to set a 4gb file to psb that fails to save. To make a photoshop guestimate: look at the bottommost pixel layer find the compressed size of that, multiply that by the number of pixel layers, add the ballpark for the number of mask layers and what not. If the answer is over 1.5gb, and someone tries to save as PSD pop up a box in the save as dialogue that says "you might want to save this as a PSB".

I also admit I dont know about the differences in psb and psd file structure. But I can tell you that there will be more and more photographers facing this issue as 30+MP cameras become the norm. It doesn't take many layers in a 16bit 36mp image to get to 2GB

It may be time to look at that file size limit. And please include a full or half-res jpeg preview inside PSD and PSB that bridge can read.

Because there is no way for Photoshop to know ahead of time exactly how much your document will compress when saved.
The size in memory is only loosely related to the size compressed on disk.

Photoshop makes an estimate before saving and if it looks like the document might come in under 2 Gig, tries to save it as PSD. If the estimate is too large, or the file goes over 2 Gig while saving, then you get an error.

Basically, you're asking that Photoshop somehow predict the future, or save the file without going through the task of saving the file -- and neither is possible to do perfectly.