Lossy DNG shows strong visible differences but JPG not, is this a bug?

[biriem]

Hello,

I tried out the lossy DNG format with a lot of pictures.

For most pictures I can't find any visible differences.

But I found also some pictures with very noticible visible differences between lossless and lossy DNG.

It seems that the lossy DNG format has problems with dark pictures with small light sources for example

the stars in the dark sky or the red lights of an aeroplane in the dark sky.

I have an example where you can see red security lights of a great antenna on top of a mountain.

Surprisingly with this extreme example the JPG versions looks much better as the lossy DNG version of my source lossless DNG.

Here is the cropped JPG from the lossless DNG (file size 10877KB):

Between this JPG and the lossless DNG file is no visible difference.

And here a JPG from the lossy DNG (file size 13261KB):

Between this JPG and the source lossy DNG file is no visible difference.

The source of both DNG files was a NEF File from a Nikon D7100.

Also interessting is, that for this excample the file size of the lossy DNG is  greater than the lossless DNG. This seems crasy IMHO.

I was very surprised, that JPG result is is much better than the lossy DNG for this case.

Perhaps there is a hidden bug in the lossy DNG conversion process.

I hope Adobe can look in to this. If you need the original NEF file let me know.

[joeh35702813]

Interesting post, I have been using DNG lossless files for over 10 years and using DNG lossy files a lot in the last year so here is my 2 cents.

I started using the lossy DNG format as lossless DNG files (from Fuji raw files) were just so big (30-35mb) it slowed down my workflow and was taking up too much space. At first i only made lossy DNG for my B-roll pics, but then after a while I went all in with lossy.

I have ran a number of tests between the lossy and and lossless DNG and can say that 90% of time time you cant tell the difference, even in high ISO lossy looks the same as lossless. The only photos i have noticed a issue with lossy is high contrast scenes with a wide scale of bright and dark (e.g. clouds in below pic), In these scenes i noticed a small increase in noise in the dark areas at 200% zoom, so nothing major really.

If you want something in the middle between huge raw and fragile jpeg, lossy is a pretty good middle ground.