Work flow and data loss.

[JBW]

Two caveats? This is based upon posting to the web rather than printing. My Sony Alpha a58 shoots and exports in 8-bit JPEG and RAW

If I shoot in RAW I get more information to play with than if I shoot in JPEG.
I also get to work in Sony Express which allows me to use camera and lens specific software and gives me more colour control than GIMP.

Therefore I start in RAW adjust as well as I can and then export in 8-bit Tiff.
I work in Gimp in areas not available in Sony Express and export in 8-bit JPEG to post to the web.

Is my understanding valid?

Brian

[Manfred M]

May I make a suggestion.

1. Shoot in jpeg+raw mode so that you have two versions of the same image.

2. Edit the jpeg in Gimp and the raw in Sony Express + Gimp.

3. Compare your results.

There is no "ideal" work flow and whatever gets you the results you like should be considered. As I said before, this is something need to work out yourself.

[dennybeall]

I use different hardware and software but it sounds like your approach is sound. Shoot in raw in order to capture as much as possible. Save that. Then work with a copy and save in .tiff, also good approach. Use your chosen software to make network quality jpg copies from those. The same work flow I would use just different software.

[tclune]

The one thing that seems questionable to me is exporting in 8-bit TIFF. Do you have the option of 16-bit TIFF? I would expect that your raw data is at least 11 or 12 bits deep, so it makes sense to me to hang on to that range right through the processing cycle and just reduce it to 8 bits for final output.

[JBW]

The one thing that seems questionable to me is exporting in 8-bit TIFF. Do you have the option of 16-bit TIFF? I would expect that your raw data is at least 11 or 12 bits deep, so it makes sense to me to hang on to that range right through the processing cycle and just reduce it to 8 bits for final output.

Gimp can only handle 8-bit.

[mrinmoyvk]

Why TIFF ? what is its importance over JPEG?
Meanwhile I am googling


Edit: Got it leaving aside colour space for technical people. TIFF retains all data where as JPEG looses during compression.
But then I read png is also lossless Then why not png?

I am looking after saving image after final editing for distributing or keeping on my hard disk. I will never ever edit it again. So whats the better way? "There are no space issues"

[Donald]

Whilst references to .tiff files is quite appropriate, GIMP users will also want to note that saving in GIMP's own native .xcf format let's you keep all your workings in case you want to go back and re-edit at a later date. Up until I started using Silver Efex Pro2 and used Elements as the 'mule' to carry it, I had never saved a .tiff file. They were all .xcf files. It was from these that I made my final .jpegs.

Mrinmoy - Have a read of this CiC tutorial. Hopefully it will help you understand the difference.

[xpatUSA]

Gimp can only handle 8-bit.

Not what it says here, Brian.

http://www.gimpusers.com/tutorials/w...w-in-gimp-2-10

"8-bit only" stopped at V. 2.8.x from what I've read. Not an expert, never used it myself.

The GIMP "8-bit only" thing seems like it could be Photographic Lore. Similar to "FastStone Viewer only opens embedded JPEGS" which is untrue. Doesn't stop me being told that by somebody whenever I post de-coded Sigma X3F files (up to SD14/DP1 format) on the Sigma forum on DPR. Whine, whine . . .

[xpatUSA]

Two caveats? This is based upon posting to the web rather than printing. My Sony Alpha a58 shoots and exports in 8-bit JPEG and RAW

If I shoot in RAW I get more information to play with than if I shoot in JPEG.

Is my understanding valid?

Brian, what do you mean by "information" and what "data" do you believe is lost?

There are times when data can be lost even between raw and 16bit TIFF. For example, a red flower with highly saturated colors but not over-exposed will lose data during conversion to a 16-bit sRGB TIFF. The data lost is color information that is out-of-gamut in sRGB. see below ***

This example is just to show how "data" can mean many things.

Same comment goes for "information" which could be meta-data stored in the raw file which gets stripped out when you save for the web - no great loss really.

*** Working and saving in ProPhoto will not help. Sooner or later the image must be converted to sRGB. Not widely known but you can save as ProPhoto JPEG. Still doesn't help - the display driver has to convert your image into 'display space' usually BT 709 = sRGB.

Is it time for someone to play the 'I've got a wide gamut monitor' card?

[DanK]

Brian,

My approach is to discard as little information as possible. It doesn't always matter--Manfred's point--but sometimes it does. I don't find it worthwhile to take the chance.

So, I stay in raw format as long as I can. When I have to export to TIFF, which my stacking software requires, I use 16-bit ProPhoto. My monitor won't display it properly while I am in that software, but I don't care about that. I save as jpeg only for the web or for the rare cases in which I send a file to a lab for printing rather than printing it myself.

I don't have a wide-gamut monitor, so what I see on the screen is what an sRGB jpeg will look like, with whatever compromises that entails, including rendering of out-of-gamut colors. It it looks OK to me, I leave it; if not, I fuss with it in editing. The main situation where I have problems with out-of-gamut colors is in printing, particularly on matte papers. I print directly from edited raw images in lightroom, without saving as a TIFF or JPEG unless other software has forced me to save as a TIFF (stacking software, Nik, whatever), so I use soft proofing to get a rough estimate of how the software will deal with out-of-gamut colors.

Dan

[JBW]

Not what it says here, Brian.

http://www.gimpusers.com/tutorials/w...w-in-gimp-2-10

"8-bit only" stopped at V. 2.8.x from what I've read. Not an expert, never used it myself.

The GIMP 8-bit thing seems like Photographic Lore. Similar to "FastStone Viewer only opens embedded JPEGS" which is untrue. Doesn't stop me being told that by somebody whenever I post de-coded Sigma X3F files (up to SD14/DP1 format) on the Sigma forum on DPR.

It is not lore it is fact. If you read the link you supplied you will find that Gimp 2.10 is not yet out. 2.9 is still in the unstable test version. In simple words if you want a gimp that doesn't crash and burn you use 8-bit. Eventually it will be upgraded but not yet.

[xpatUSA]

But then I read png is also lossless Then why not png?

Huge files, often bigger than the original raw file. Especially for normal photos. Less so for graphs and posters.

I am looking after saving image after final editing for distributing or keeping on my hard disk. I will never ever edit it again. So whats the better way? "There are no space issues"

You might want to look at RawDigger. The raw file remains un-touched but a 7Kb .pp3 'sidecar' file is saved alongside the raw file and is re-used every time you open the raw file. Also, you can optionally save a .pp3 alongside the output file. You can copy and re-name .pp3 files; in other words, while still keeping the truly original image, you can have as many "versions" of it as you want at only 7Kb per version! You can even open any .pp3 file as text and directly edit the settings which are found as plain text therein (a bit anal, that. It's easier to do it by editing the review image).

ACR does the same in Adobe products the (.xmp file) but only for the ACR conversion to Adobe PS or LR working space. After that, subsequent editing is not saved in the sidecar file, unlike RawTherapee which saves everything you do.

If you truly will never edit it ever again (howls of shock and disbelief heard) keep your JPEGs or PNGs and dump everything else.

I can not advise you on a workflow that is best for you. I often dump the raw, any intermediate TIFF and the JPEG if my image is just for posting. Sometimes I regret it but I'm still using an 80GB internal HD

[xpatUSA]

[8-bit GIMP] is not lore it is fact. If you read the link you supplied you will find that Gimp 2.10 is not yet out. 2.9 is still in the unstable test version. In simple words if you want a gimp that doesn't crash and burn you use 8-bit. Eventually it will be upgraded but not yet.

Sorry, Brian - I had heard about it some time back and, to be honest, I only scanned the article before posting the link.

Thanks for the correction

[FeatherMonkey]

I recently discussed this as long as you do all the real pushing and pulling(tone, exposure etc..) before dropping to 8 bit, you should be fine I was told.

Honestly I struggle with this subject, but printing and Web viewing are pretty well covered with the 8 bits aren't they?

I have to confess I've yet to get to gimp I'm finding my first pp software(darktable) does nearly all of it.

[JBW]

Sorry, Brian - I had heard about it some time back and, to be honest, I only scanned the article before posting the link.

Thanks for the correction

[Krawuntzel]

I have to confess I've yet to get to gimp I'm finding my first pp software(darktable) does nearly all of it.

But as far as I know, darktable is not running on Windows; only linuxes and mac.
Erwin

[Krawuntzel]

It is not lore it is fact. If you read the link you supplied you will find that Gimp 2.10 is not yet out. 2.9 is still in the unstable test version. In simple words if you want a gimp that doesn't crash and burn you use 8-bit. Eventually it will be upgraded but not yet.

Brian, you are right.
They say about the Development Series (2.9):
"These builds are of the development branch of the GIMP. They may be very unstable, and as such should not be used in production.
DO NOT use these for any serious work. You have been warned."

However, I use gimp 2.9 now for over 2 months and had no problems with it. Maybe I am just lucky.

As to your original question: as others have mentioned, I prefer to stay with 16bit as long as possible. So I export to .tiff and only in the last moment I convert to 8-bit .jpeg/sRGB.
And no; I do not own a wide gamut monitor
Erwin

[xpatUSA]

I've been thinking about this thread and, so far, not understanding the concern being expressed about the difference between 8 and 16 bit depths. To me, the usage of "loss of information" or "loss of data" has varied confusingly in this thread. Yes, here I go again with a usage mention. So . . .

. . . suppose someone here produces a perfect horizontal gradient 1024px wide by say 50px deep, using the incredibly capable Photoshop (PS), or even four gradients, namely grayscale, red, green and blue. Suppose now we save as 16-bit TIFF and then again but as 8-bit TIFF.

Now suppose we bring the TIFFs up on our output device of choice. Will we see "vertical banding" in the 8-bit version(s) at 100% and at a proper viewing distance . . . . I think not.

Therefore "information" i.e. what we actually see in the form of visible lightness or visible color information, has not been lost - although "data" certainly has because 256 tonal levels got compressed into 1.

If so, then the root fear here must be of the potential loss of visible data. We all know the causes of that and it's various appearances but I claim that they are not caused per se by the simple conversion from 16-bit depth to 8-bit depth.

So, one could convert a raw file directly into an 8-bit file, tweak it a little in GIMP pre-V2.9, e.g. crop, exposure comp, sharpen and save it quite satisfactorily as a 90% quality 4:4:4 JPEG, post it here and I'll bet that nobody would know how you got there

[FeatherMonkey]

But as far as I know, darktable is not running on Windows; only linuxes and mac.
Erwin

Erwin You'd be correct but what I was alluding to is what Ted said better than I could.

I'd imagine there's plenty of software packages to choose from that can do the exposure, tonal manipulations etc for Windows, prior to 8bit.

[xpatUSA]

So, one could convert a raw file directly into an 8-bit file, tweak it a little in GIMP pre-V2.9, e.g. crop, exposure comp, sharpen and save it quite satisfactorily as a 90% quality 4:4:4 JPEG, post it here and I'll bet that nobody would know how you got there

Putting my money where my mouth is but with FastStone Viewer not GIMP:



Sigma DP1s compact 16.6mm FL, 20.7x13.8mm sensor, 2640x1760px raw size, quick test snap, hand-held.

The flow:

X3F file opened in Sigma Photo Pro 3.5.2, +15% (0.3 out of 2) Fill Light to turn off the blinkies and saved with no further adjustments as a full-size 8-bit TIFF.

Opened in FastStone Viewer, adjusted luminosity curve to bring up shadows and increase sky contrast a bit. Downsized to 1280px wide using Lanczos2 (sharper). Sharpened some more in USM, 0.3 radius, 17 amount. Saved as JPEG Y'CbCr, Hoffman optimized, 4:4:4 (no sub-sampling), 90% Quality.

Would you have known?

FastStone Viewer uses cumulative editing i.e. every adjustment includes all previous - so it doesn't take many steps to get posterization, funny colors, etc.

Please note that FastStone does not embed ICC profiles so, color-wise, you'll see what your system thinks sRGB is, not mine.

[postscript]

For those in any doubt, here's the end of the street at 1000% (un-smoothed):



The JPEG artifacts are obvious but just look at those smooth tone transitions in the sky.

I rest my case, m'lud