So it looks like the PEF is not really compressed at all, just different. The DNG probably just contains more generic, less efficient code.

Interesting, but very much windows/office/general computing with generic compression that doesn't suit all things, especially raw data from a sensor.
I'm talking about my own vaguely remembered observations using cameras with relatively small buffers and relatively small SD cards (8, 16, 32 MB) and JPEGs TIFFs RAWs on an SSD (hard drive) being opened up in Photoshop or similar.
I suspect the results will be very different from the example above. But I'm happy to be proved wrong as I use DNGs anyway

Steady on Algi; it's not nonsense, that's why compression exists and why data communicating is so fast. However, it remains to be seen whether in the real word of cameras optimised for proprietary compression, not bloody winzip and SSDs (which I have), dealing with actual pictures, the results will be so clear-cut.
I am happy to be proved wrong with relevant test both capturing and saving an image and reading it into Lightroom.
It was just a thought. I'm pretty sure I've noticed PEFs opening quicker in the past
And full-sized JPEGs of course are near instantaneous to display, but RAWs and TIFFs are very sluggish. Remember, once opened, a JPEG is as big as any other comparable file, so why would it be so much more responsive to open and save?

AH, great minds
I haven't done any tests but I suspect PEFs are faster to capture and to work with.
Generally, compression and decompression is faster than writing to disk.

Today PEF has support but what about tomorrow?
What you could do, and I might try this myself, is use PEF and get Adobe to convert the precious ones to DNG for archiving.

Thank you Neil and David.
Incidentally, it's the same lighting as for human models wanting to look like they're on the beach

That's essentially it, compression.
I choose DNG because it is the de facto standard and is always going to be supported in the future. PEF could become obsolete with fewer and fewer applications recognising it.
I get round the size issue by ruthlessly culling the negatives after I've finished processing.
BTW, Lightroom is definitely worth the money

Thank guys,
Incidentally Nigel, the Flash was on full power, like the sun
I have 2 very capable Metz 58s and a couple of old Pentax 540s, but the Yongnuos keep getting the gig I love those things

Thanks guys

Posts crossed. Thank you Lennybloke