TIFF to DNG?

[Jeff Charles]

An RPP processed TIFF can be converted to a DNG in Lightroom. The DNG
is much smaller than the TIFF, and the Lightroom lens correction
profile can be applied to the DNG.

Is there any disadvantage to converting a TIFF to a DNG?

Jeff

[RPP]

Yes, because this DNG is not Raw anymore and there is not much left
for RPP to work with, i.e. colors, WB and details are going to be
Adobe style and RPP will not be able to help much.
Usually people do it in reverse order - convert with RPP and process
resulting TIFF in LR - f.e. cropping, lens corrections.

Andrey

[Jeff Charles]

Thanks for your response.

To be clear, I would be converting with RPP and then processing the
resulting file in Lightroom. My question is are there any negatives to
converting the RPP-produced TIFF to DNG.

Jeff

[Joel Craig]

Resending to the list so all can see my response as I mistakenly sent previously to just Jeff (sorry Jeff)…

I think maybe you're misunderstanding what a DNG is. Your camera's RAW file is a camera-specific or model-specific "digital negative" upon which no processing has been done. The Adobe DNG file format is simply a standardized digital negative file format. Adobe created the format as a way to future-proof your RAW files from software incompatibilities, something that can happen when you deal with proprietary file formats.

The preferred work-flow would be to use Adobe DNG Converter to convert your proprietary RAW files to DNG. The DNGs are now informationally identical to the previous RAW files, they are simply no longer in a proprietary file format. The DNGs can now be archived, or processed with RPP, then proceed with your normal work-flow.

Hope this clarifies a bit.

Joel

> --
> You received this message because you are subscribed to the Google Groups "Raw Photo Processor" group.
> To post to this group, send email to raw-photo...@googlegroups.com.
> To unsubscribe from this group, send email to raw-photo-proce...@googlegroups.com.
> For more options, visit this group at http://groups.google.com/group/raw-photo-processor?hl=en.
>

[Iliah Borg]

> The preferred work-flow would be to use Adobe DNG Converter to convert your proprietary RAW files to DNG. The DNGs are now informationally identical to the previous RAW files

This is not a given. It already happened more than once that files converted to DNG were missing significant information that was contained in original raw files.

--
Iliah Borg
i...@pochtar.com

[Jeff Charles]

I do understand what a DNG is. Lightroom will convert a TIFF to a DNG,
and the resulting DNG does look identical to the TIFF, while being
much smaller. I am just wondering if there is any downside to doing
this.

Jeff

[Brian Fitzgerald]

My understanding that DNG adds some metadata and applies a lossless compression algorithm to the image data. Neither of those is detrimental as long as the next bit of software in your workflow understands DNG headers and compression, even if your workflow changes over the decades.

[Jeff Charles]

That's my understanding too. Also, the TIFFs and DNGs and their
histograms look the same to me.

Adobe does say that they do not include undocumented manufacturer tags
when they convert raws to DNGs, but that's likely not relevant for
TIFF to DNG conversions.

I guess one problem could be finding the DNG later and thinking that
it is a raw file, which it is not.

[Brian Fitzgerald]

agreed

[Brian Fitzgerald]

To clarify… A DNG of a RAW or CR2 or NEF or whatever real RAW file is a RAW file inside a protective metadata Matroshka doll. If you convert from RAW of whatever kind to TiFF with a "RAW Converter", I believe you lose the RAW data at that point. That's life as I see it. If there are exceptions, I'd like to hear them.

On Sep 27, 2011, at 10:05 PM, Jeff Charles wrote:

[dmdimon]

This is incorrect. DNG itself CAN be losless, but tiff to dng
conversion is lossy it two ways at least. Same for DNG to tiff
conversion

On Sep 28, 3:18 am, Brian Fitzgerald <talking...@gmail.com> wrote:
> My understanding that DNG [skip] applies a lossless compression algorithm to the image data.

[Brian Fitzgerald]

Interesting. Please mention at least two ways.

[dmdimon]

fast and dirty:
1) converting raw-dng or dng-raw is converting from one non-linear
tristimulus space to other non-linear tristimulus space IN INTEGER
DOMAIN - this is lossy operation if spaces are effectively different.
2) converting raw-dng or dng-raw is converting 16(8) bit to some
10(12,14) bit with different type of encoding for source and
destination - there are no miracles in digital kingdom - it is lossy -
and both ways lossy(or at least altering) due to quantization-bound
posterization.