Routinely, I use the LR Export feature to downsize DNGs to JPEGs. sometimes, like today, that fails. I had 3 of 40 photos fail to export to the desktop file. Error message was "Could not create a JPEG that met your limit of 1500K bytes. Please increase your file size." That's not possible- I need that size for web posting. What's up with that?
LR tries to meet a particular file size limit by upping the image compression, but it can only 'squeeze' things up to a certain point. Probably, you are either Resizing to - or the image naturally has - pixel dimensions that are too large to be squeezed enough.
IOW, that much material can't reliably be packed into that size of box however much you force it.
There are two resolutions: one way is to relax your stated file size limit, and permit LR to produce a larger file (that same amount of material can be squeezed in more comfortably when the box can be bigger).
The other way - more suitable here - is to Resize the image in your Export settings to a moderate appropriate number of pixels wide and high. IOW, make it so there is a more suitable amount of material needing to be 'crammed' into that box - LR will then always succeed, because it won't ever have to push its compression up to absolute maximum.
I'm not specifiying height and with in the export, just the desired file size. And 95% of my 36 MPx DNGs size down just fine. Only a few give me problems. it's hard to predict which ones will be problematic- usually outdoor scens with lots of tree and grass detail.
Did those three photos use Select Subject or Sky masks? A bug causes LR to incorrectly compute the exported size of such photos:
You can work around the bug by selecting the Export option Metadata > Include: All Except Camera Raw Info:
No, none of them used more than a commmon brush adjurmentss. I'm just learning about the new masking tools you mentioned.
"none of them used more than a common brush adjustments."
So you're not tripping over that bug. Then your options are those outlined by Richard.
"usually outdoor scene with lots of tree and grass detail."
That makes sense -- lots of detail won't compress as much.
I've had some success with a workaround- doqwnsizing halfway, taking it back to LR and downsizing/exporting again. That worked for two of these three, and might have worked if I'd used three or more steps. I just want to understand the problem and knjow how to avoid it, reliably. I don't want the big FF sensor I use fighting me at a critical step of the process. I'd shoot 12 Mpx for this job (real estate) if I could do it in RAW, with maximum bit depth.
The usual workflow is to first pick target pixel dimensions (e.g. 2000 x 1500 pixels) and then either pick the quality (e.g. 80) or the limiting size. It sounds like you may be using dimensions that are needlessly too large. What is the intended use for the exported pics -- publishing on a Web site? Web publishing typically needs dimensions much smaller than what comes out of the camera. (E.g. I just checked, and pics on Zillow are 1344 x 895.)
Thanks- I think you might be on to something. I haven't been specifying a target in H & W pixels. I've just been selecting a 1.5 MB file size. When I just exported the same problematic photo and using a 1000x1500 dimension, it worked. Interestingly, when I tried the third possibility, specifying dimensions but not a file size, it came out to 1540 KB, just a smidgen too big.
If you specify dimensions and a particular JPG saving quality (compression) file size results will naturally differ to some extent depending on how compressible the image contents are - as processed - and also possibly depending on the shape proportions of the image. For example if setting max 2000px wide and high, a square cropped image will be fully that size while a 2:1 rectangle will be only 2000px x 1000px resulting in a smaller file size naturally. One the other hand you will have dictated a known JPG compression level at those known dimensions, which you have tested as visually acceptable and consistent.
If this output is also substantially always under 1.5MB file size then you may not even need to impose that file size limit.
When you do impose a file size limit then you are giving up that control and consistency as to the particular saving quality which will be used for each image. "As many pixels as possible" is typically not the sole aim, especially if those pixels will accordingly present in a very processed and compressed way once fully zoomed into 1:1.
Fewer pixels showing a nicer appearance when zoomed 1:1, is IMO a better aim to set.
Thank you, thank you, thank you!! Fixed my problem.