Lossy DNG?

Lossy DNG?

I see in the new DNG format specifications, Adobe has added a lossy compression option. For the life of me, I'm not sure I understand this thinking. With the cost of memory storage still plummeting, is it really that urgent to save storage space by having a lossy DNG file format? Perhaps so. Perhaps I'm just not accumulating images like others are — maybe wedding photographers and such. I guess I always thought the purpose of the DNG format was to have a universally accessible RAW file that preserved everything the camera recorded without compromise. If I wanted a lossy format to compress file storage space requirements, why wouldn't we just use JPG?

Obviously, I'm missing something here. I use DNG in all my workflow variations, but the full, uncompressed variation for universal compatibility. For any of you who think a compressed, lossy DNG is a useable idea and one you'll embrace, please share your thinking. Curious minds want to know!

Comments

[O.Thomas]

I'm with you on the full size, uncompressed DNG files.

If I remember correctly, isn't lossy DNG being put forward for DNG video files? I'm sure I read that somewhere, can't remember where though.

[Jason]

This might explain it. http://www.popphoto.com/gear/2012/10/adobe-adds-lossy-dng-to-dng-specifications

[Neil]

I'll bite. I use lossy DNG all the time. I shoot professional basketball in RAW format for all the reasons people typically shoot RAW. I can't see any visual difference between regular RAW and lossy DNG, other than a 66% (average) file size savings.

Given the volume of images I shoot and how they wind up getting used, converting to lossy DNG is an easy choice. Unlike JPEG, which is lossy and continually so on every re-save, lossy DNG doesn't degrade with each change. I get all the benefits of RAW, with a file 1/3rd the size. What's not to love?

Neil

P.S. For my landscape work I still stick with plain old RAW :)

[richardplondon]

We can consider this from the other end, maybe.

If offered an improved variant on JPG, which did not commit the white-balance setting, sharpening and so on - and gave (as close as makes no visible difference) the same tonal freedom and exposure latitude as Raw...

Would you say "yes please, that might be handy" or, "JPG's role is only to be as small as possible, and I need NOT to be presented with any option that relaxes some of its technical limitations"? (grin).

[Jim Bullard]

It's useless to me. The only time it might have been useful was when I went on a three day trip and forgot to take all my memory cards.

[Cemal Ekin]

There is Raw, medium-well, and very well-done; DNG, Lossy DNG, and JPEG ;-) A high quality JPEG, if not repeatedly opened and saved, will retain its quality. I too do not get the benefit of lossy DNG.

[Beau]

For those who missed Jaon's helpful link...

Talking to DPReview, Hogarty explained:

"Lossy DNG allows something in-between the two in terms of size but retains the flexibility in terms of adjusting White Balance and preserving detail. For example, the out-takes from a wedding shoot, that the photographer is unlikely to ever be able to sell or make any money from. This gives them a way of reducing the amount of storage space they need, but they still have the file if they do ever need it.

It's based on standard JPEG compression. What's lost is some of the range of the adjustments you can make - if a file is four or five stops underexposed, you'll find it's not quite as flexible as the full file. You can still do a lot, though and it's only in extreme case that you might notice."

[Ac Ekin]

I am going to revise my prior position that I did not get the benefit of lossy DNG. I have thought about it and found several points that may give advantage to the new lossy DNG.

1. JPEG is an 8-bit format DNG can be extracted as 16 bit
2. Lossy DNG is compressed once and processed as many times as needed
3. Although the "white balance" of a JPEG file can be changed, this comes at a potential loss where losssy DNG white balance is changed at RAW level

Although the space savings are not that important in my workflow I can see this could be important in some workflows. Of course the biggest advantage of JPEG is that is the lingua franca of image presentation on the Web.

I now see some benefits of lossy DNG, although I will not have much use for it myself.

Cemal

[Henrik Helmers]

I do see the value of lossy DNG. For my images with the lowest rating it makes sense to sacrifice a bit of editing latitude and quality for space savings. Great photos are not candidates for lossy compression. But there are many photos I keep for other reasons than artistic merit.

Do not confuse lossy DNG with normal JPEG compression. You can recover much more information from a lossy DNG than you can from a JPEG. The data stored is based on what the sensor recorded before white-level adjustments, and the range is sampled intelligently.

I guess the goal is to make DNG more attractive as an in-camera option. It could be a great fit for a point-and-shoot camera, or as a way to increase burst speed on DSLRs.