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Bengt Carlsson
New member
Username: Bengt

Post Number: 1
Registered: 03-2009
Posted on Saturday, March 07, 2009 - 07:41 am:   Edit Post Delete Post

Hi,
Just started using raw format combined with jpg. I have a Nikon D300 where raw=nef. When I have edited the image in PWPro4 how can I save the image in raw or DNG? The original nef is 12MB, the jpg is 2.5 MB and if I save in tif the size will be 64MB which is to much for me.
Thanks
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MJDL
New member
Username: Mjdl

Post Number: 4
Registered: 01-2009
Posted on Saturday, March 07, 2009 - 01:35 pm:   Edit Post Delete Post

Generally, camera raw format is not supposed to be edited and saved in its original form. It is just the raw data from the camera's sensor: look on it like a kind of "digital negative", which has to be converted to one of the conventional "output" formats (JPEG, TIFF, etc.)

In fact, like negatives in the old film world, you can't really change them, just archive the ones you really want to keep.

I believe Adobe, the originator of the DNG format, wanted to create a common archival digital negative format, independent of camera manufacturer's raw formats, that would also allow a lot of metadata (captions, keywords, processing parameters, etc.) to be stored in one container defined by an open public specification.

This is what Adobe's Photoshop Camera Raw processor (ACR) actually does, it stores the user-defined raw processing settings for each picture when you save a raw picture as a DNG. The next time that DNG is opened in ACR, all the processing settings are restored for that picture. (I must admit I only have experience with ACR in the form of Adobe Photoshop Elements 3.0.)

Adobe even suggested that camera manufacturers start using DNG as the native camera raw format, but few have actually done this. And in any case, the DNG format still allows private manufacturer data to be stored in the container, so we're back to square one in terms of future archival accessibility.

Anyway, TIFF, whether compressed or not, is always going to be relatively large, especially with recent camera and their huge picture size, since it is intended, after all, to be a lossless image storage format.

An alternative might be to save your PWP work in the lossy JPEG format at 100% quality factor and with 4:4:4 color sub-sampling.

This will result in a significant compression ratio versus the original image data (roughly 1:6 for PWP, I think), while keeping JPEG compression artifacts to a minimum and preserving maximum color information.

As long as you resave such JPEGs with exactly the same compression settings after reopening it in PWP for further processing, there won't be a huge impact from the inevitable JPEG recompression--although I haven't really tested this.

PNG is another lossless format with usually better compression than TIFF, but I'm not sure if PWP saves all the metadata present in the edited image or is able to attach or interpret a colur profile--I haven't tried it.
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Bernard Leverd
Member
Username: Bernard

Post Number: 181
Registered: 08-2002
Posted on Saturday, March 07, 2009 - 03:12 pm:   Edit Post Delete Post

Bengt,
With Capture NX2 fron Nikon, you can save the edited Raw image in Raw format. 'non destructive' edit commands are in fact stored together with the original raw image, and re-applied when you later on reopen the raw image. You may even store multiple edit versions within the same raw container.
Bernard
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Douglas Haag
Member
Username: Doug

Post Number: 22
Registered: 06-2004
Posted on Saturday, March 07, 2009 - 03:48 pm:   Edit Post Delete Post

MJDL .....
I HAVE tested the loss (change) due to successive saves of JPEG files. I opened a JPEG, did no editing and saved it under a new name (generation #1). Then I opened Generation #1 and saved it as Generation #2. Etc. Etc.

After up to 3 generations I couldn't visually detect any difference from the original JPEG. I used the COMPOSITE transformation with an "Absolute Difference" setting to compare pixel-by-pixel any differences and could see hardly anything but black in the comparative result -- even with "brightness" highly exaggerated.

But when I compared the original with Generation #10 -- WOW what a difference. I could readily detect, visually, significant differences from the original image. When I did an "Absolute Difference" comparison, the differences were so dramatic that you could see an actual image in black and white.

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Douglas Haag
Member
Username: Doug

Post Number: 23
Registered: 06-2004
Posted on Saturday, March 07, 2009 - 04:02 pm:   Edit Post Delete Post

MJDL ...
Forgot to mention that all the JPEG saves were at the highest possible quality setting.
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Len Merkel
Member
Username: Lenmerkel

Post Number: 18
Registered: 10-2007
Posted on Sunday, March 08, 2009 - 12:36 am:   Edit Post Delete Post

Bengt, the simple answer is you can't. I don't know of a single 3rd-party imaging application that will update or write-out a raw file (or save edits made to a raw as a DNG). Your raw file is not an image file in the sense that a TIFF or JPG is an image file. It is simply a dump of your camera sensor's data with some shooting metadata added. You can't view a raw file - you can only view an image synthesized from the raw file by a viewing or editing application.

Your D300 raw files have 4288x2848 pixels. When you synthesize an image with 16 bits per channel (e.g. 16/48-bit TIFF), it will need 4288x2848x16x3 bits to store it (or 69MB approx). If you synthesize it with 8 bits per channel (e.g. 8/24-bit TIFF), it will need 4288x2848x8x3 bits (or 35MB). There's no escaping it - that's just how much data your image has once it's been synthesized from the raw file).

Now, if you save as JPG, you can of course create a significantly smaller file - because you are throwing away a significant amount of the data. As has been mentioned earlier, if you continuously save and re-save an edited JPG, you will eventually throw away so much data that you effectively destroy the image.

Large image files are simply a consequence of a large pixel count in your camera's sensor. I recommend just buying a large external drive - disk is very cheap, and getting cheaper by the day!
Len Merkel
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MJDL
New member
Username: Mjdl

Post Number: 5
Registered: 01-2009
Posted on Sunday, March 08, 2009 - 05:41 pm:   Edit Post Delete Post

I should have been clearer: I wasn't advocating using JPEG as a working file format for saving several intermediate versions in a series, for the reasons Douglas Haag pointed out, nor for archiving your raw files (throwing information out isn't archiving...), but purely as a way of saving the end stage (e.g. ready for printing) in less storage than a TIFF would take.
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Bengt Carlsson
New member
Username: Bengt

Post Number: 2
Registered: 03-2009
Posted on Wednesday, March 11, 2009 - 07:07 am:   Edit Post Delete Post

Thank you all for your answers. They made me understand a lot mora about raw. I will now save my original raw files and the edited files as jpg until dng is 'global' accepted. What are your procedures?
/Bengt
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MJDL
Junior Member
Username: Mjdl

Post Number: 6
Registered: 01-2009
Posted on Wednesday, March 11, 2009 - 02:16 pm:   Edit Post Delete Post

Guillermo Luijk's tutorial for the command-line version of DCRAW gives a really detailed view of the various transformations required to go from raw camera sensor data to the final RGB output.

Picture Window uses the camera-specific demosaic routines of DCRAW, I'm not sure about the other elements of the "Raw Settings" dialog (camera profile, contrast expansion, gamma, etc.) use the relevant DCRAW routines or not--I really need to search this forum more carefully for that information, I'm sure it's been discussed before.

Most other raw image converters do a lot more hidden processing than either DCRAW or Picture Window, often using somewhat mysterious terminology, e.g. "vibrance". I think that complexity may be sometimes a disadvantage in terms of experimentation with, and understanding of, the whole process of creating a satisfactory final image. Picture Window's "transformation" building-block approach yields benefits here.

I'm very much a beginner both at photography and Picture Window, so I'm concentrating on the basics right now and don't have any advice to offer on processing raw camera images.

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