Author Topic: Extract JPGs fm NEFs and profile change ?  (Read 3286 times)

Offline denkea

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Extract JPGs fm NEFs and profile change ?
« on: December 22, 2008, 06:29:50 PM »
Mac OSX 10.5.6  and PM 4.5.4
I'm having a problem after editing NEFs in Capture NX and saving.  The edits show up fine in PM.  When I extract a JPG from the NEF in PM the two thumbnails look identical but the profile in the JPG is ProPhoto.  When I use the 'embed ICC profiles into JPG' in PM from the Tools menu it changes the profile in the folder in finder but the thumbnails in PM look terrible.  It's driving me nuts trying to figure out where I'm going wrong.  Any help would be greatly appreciated.  I'm attaching a screen shot of the NEF and JPG side be side.
Thanks




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Offline dennis

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Re: Extract JPGs fm NEFs and profile change ?
« Reply #1 on: December 22, 2008, 08:09:20 PM »
Do you have your color space in Capture NX set to ProPhoto (I think that's an option)?  Is that what you intend?  When you first extract the JPEG from the NEF in PM, you say it looks OK?  What does PM show for the profile at that point (e.g. ProPhoto (embedded) or just ProPhoto or maybe AdobeRGB)?  Is the screen shot you posted with the extracted JPEG after you embedded the ProPhoto profile (apparently so)?

Why are you extracting the JPEG in PM when you could just save a JPEG from Capture (it would presumably be higher quality than the JPEG Nikon embeds into a NEF)?

If you embed a profile then PM doesn't of course change the color space of the pixels.  Therefore you only use this embed profile command when you know for sure that the pixels are in a given color space and you want to make it clear by embedding the profile explicitly within the JPEG.  With Exif 2.21 you can clearly indicate sRGB or AdobeRGB color spaces without the need for an embedded profile, but if you really have ProPhoto pixels then a JPEG needs to have a ProPhoto profile.  I'm wondering if the extracted JPEG is really in AdobeRGB.  Try embedding AdobeRGB into the extracted JPEG and if it looks right then the pixels are really AdobeRGB.

Also, I have nothing against the ProPhoto color space, but because it has a larger gamut, the 8 bit precision of a JPEG photo in that color space means that you better be careful with subsequent editing or changing color spaces.

--dennis


Offline denkea

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Re: Extract JPGs fm NEFs and profile change ?
« Reply #2 on: December 23, 2008, 05:40:17 AM »
Hi Dennis and thanks for the reply.  It looks like I left out a few details.  Long day/too late at night?!?


Do you have your color space in Capture NX set to ProPhoto Yes (I think that's an option)?  Is that what you intend?    Yes. I edit in NX in the ProPhoto space.  When you first extract the JPEG from the NEF in PM, you say it looks OK?  What does PM show for the profile at that point (e.g. ProPhoto (embedded) ProPhoto (determined by the info button in Finder for the appropriate image or just ProPhoto or maybe AdobeRGB)?  Is the screen shot you posted with the extracted JPEG after you embedded the ProPhoto profile (apparently so)?  Yes, and then changed in PM to embed the SRGB profile.

Why are you extracting the JPEG in PM when you could just save a JPEG from Capture (it would presumably be higher quality than the JPEG Nikon embeds into a NEF)?  I thought it would be easier.  Here's what I do.  Go thru all the photos in a PM contact sheet, tag the ones for editing, view only the tagged and then edit in NX2, save, close and then ,after editing all, extract JPGs in PM, then change the embedded profile to SRGB. I might need to rethink my step by step process.

If you embed a profile then PM doesn't of course change the color space of the pixels.  Therefore you only use this embed profile command when you know for sure that the pixels are in a given color space and you want to make it clear by embedding the profile explicitly within the JPEG.  With Exif 2.21 you can clearly indicate sRGB or AdobeRGB color spaces without the need for an embedded profile, but if you really have ProPhoto pixels then a JPEG needs to have a ProPhoto profile.  I'm wondering if the extracted JPEG is really in AdobeRGB.  No. The extracted JPEG is in ProPHoto and then changed to SRGB via the tools menu. Try embedding AdobeRGB into the extracted JPEG and if it looks right then the pixels are really AdobeRGB.

Also, I have nothing against the ProPhoto color space, but because it has a larger gamut, the 8 bit precision of a JPEG photo in that color space means that you better be careful with subsequent editing or changing color spaces.

--dennis

Offline Hayo Baan

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Re: Extract JPGs fm NEFs and profile change ?
« Reply #3 on: December 24, 2008, 06:23:40 AM »
Denkea,

If I understand you correctly, here's what you do:

1. Edit in Capture NX in ProPhoto RGB. Nothing wrong here; I do exactly the Same.
2. Extract JPGs in PM. Thumbs should look fine and profile as indicated by PM should be PM.
3. Use PM to embed the JPGs with sRGB.

Step 3 (if that is what you are doing), is where you go wrong: this step assigns the sRGB profile to a file that is really an ProPhoto RGB file. What you need to do is convert the colour profile of the files.

The best way to do this is to use Capture NX for this task as this would work on the original RAW bits of the file. All you need is create settings file with the edit step "Convert to sRGB" and batch apply this to the NEF files you want to convert, saving the results as JPGs as you go along.

Alternatives are:
  • The save-as function within PM (currently this won't work on the NEF files directly, only on the extracted JPGs, version 4.6 is supposedly capable of doing this on the NEFs directly). In the save-as dialogue you can specify to convert the files to sRGB.
  • Use the export facility within PM
Hayo Baan - Photography
Web: www.hayobaan.nl

Offline denkea

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Re: Extract JPGs fm NEFs and profile change ?
« Reply #4 on: December 24, 2008, 09:11:53 AM »
Hayo ~~~~~ You nailed it.  That is exactly what I am doing.  And reading you comments about #3 I had an "Aha! moment".  The old "assign" vs "convert" jumping up again. 
Thanks for your help.
All the conversion to jpg and sRgb will be done in NX from now on.
Thanks again.

Dennis

Offline dennis

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Re: Extract JPGs fm NEFs and profile change ?
« Reply #5 on: December 26, 2008, 01:19:40 PM »
Dennis & Hayo,

Glad you worked this out.  Yes it is not a good idea to embed a profile unless you know the pixels are indeed in that color space.  So embedding sRGB is not good.

I would be careful about options such as using PM to save as to an sRGB JPEG.  The ProPhoto color gamut is large and converting color spaces in 8/24 bits (JPEG) may give you undesirable results.  If you do this in CNX keeping the source at 16/48 bit (ProPhoto) then your results (saving to sRGB/AdobeRGB) should be much nicer.

--dennis


Offline Hayo Baan

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Re: Extract JPGs fm NEFs and profile change ?
« Reply #6 on: December 27, 2008, 05:49:16 AM »
Dennis,

Yeah, completely agree with Dennis on this one: 8 bit ProPhoto RGB files are not a good idea as the gamut is too big to fit in 8 bits. Therefore it is also better not to use the embedded JPG file for any quality work as this then also is 8 bit ProPhoto RGB.
Note that I do use the embedded JPGs for creating the images on my website though as these are fairly small and low quality anyway.

Note: all actions within PM creating an image out of a NEF file (e.g. the export function, save as, mail, extract, etc.) will work on the embedded JPG and hence suffer from the same problem! (ok, unless you are on a Mac and let he MAC RAW converter generate the images, but you don't want this if you work with Capture NX as this will let you lose all your edits…)

Cheers,
Hayo Baan - Photography
Web: www.hayobaan.nl