"Merged result exceeds maximum size" in ACR

[Nero Stilbe]

I run two systems on a Mac Pro Desktop with 32 gigs of ram. One system is running OSX High Sierra 10.13.6, the other is running OSX Mojave 10.14.6. Both are running the most current version of Photoshop CC 2020 and its version of ACR. Within 10.13.6 I can merge 3,4, 5 or 6 raw files to a single DNG without any problem. Within 10.14.6, when trying to merge the same files I get, "Merged result exceeds maximum size." In both cases the preference option is set to 21mp at 16 bit per individual raw file. I have run through the ACR preferences and can find no setting that changes the outcome in 10.14.6. I have no problem running the automated merge in Photoshop CC 2020, but I want the DNG from ACR first for possible future readjustment, and then I can dump the raw files and recover a lot of storage space. What am I missing here?

[Chuck Uebele]

I don't recall what the limit is, but ACR does have a file size limit, and it has nothing to do with your system. There is nothing you can do about it, unfortunately.

[blindhout]

i have just started to have that problem with the new update of photoshop on 9/10/20, cant even merge 2 dng files in raw anymore

[Jao vdL · Accepted solution]

The limit is 65000 pixels on both sides and 512 megapixel maximum. You can't control the resolution of the merged image so it is possible to hit this limit. If you go over that the merge should fail. If it fails way below that (i.e. just a few raw images) something else is wrong and could be a bug.