Re: Dispute with model over Trade for Copies photo shoot

On 2010-09-15 17:11:13 +0100, Floyd L. Davidson said:

Pete <available.on.request@xxxxxxxxxxxxxxx> wrote:
<...>
Ok, nothing "views" JPEG, GIF, TIFF, or PNG data
either. They all have to be converted into an image, resized to fit the
display, and colour managed. A "viewer" combines these separate things.

Not true. JPEG, GIF, TIFF and PNG are all *image formats*. The data
defines a single image. To the degree that it is accurately displayed,
all displays will be the same (which does not mean that all displays are
the same, just that what they attempt to display is the same).

If you want to *change* the image, that data has to be changed.

Compare that to a RAW data file, which is not an image
and from which an infinite number of *different* images
can properly be produced. The data set is not changed
to produce different images, because there are an
infinite number of *correct* ways to interpolate the
image data from the exact same sensor data.

I don't wish to be argumentative and I realize that "correctness" depends on whether one's perspective of a subject is microscopic or macroscopic, detail or essence, beginner or master. I learn a lot from your posts and I find the quickest way to learn is by presenting my opinions, having them challenged, and being prepared to change them. With that in mind, here are my thoughts.

As you know, a NEF file is not just a wrapper for RAW data. It is Nikon's proprietary *image file format*.

A NEF file fully specifies the one and only image that the file *currently* represents. It may also contain multiple specifications in the file metadata, called "versions", to represent a selection of the almost infinite possible renditions. Notwithstanding, there is only one *current* version therefore there is only one currently valid image of the RAW data it contains. The underlying principle of data+metadata = image is the same for all image file formats and this principle is what enables file "viewers" to be made.

Making a format proprietary always has pros and cons as do both the cast-in-stone and the ever-changing formats/standards. HTTP and XML being wonderful examples of the latter.

ViewNX is a NEF, TIFF, and JPEG file viewer plus basic editor.

It does not "view" or "edit" an NEF file's sensor data.

I've never implied that it does. I fully understand that with most image file formats the only changes that can be made via metadata are things such as colour-space and rendition size.

ViewNX and Capture edit the specification for the rendering steps necessary to create the image from the contained RAW data. The specification is stored in the metadata. When a NEF file is saved the specification that is responsible for rendering the currently displayed image is written into the version named "Last Saved". The camera wrote its specification into the version named "Original", which cannot be edited thereby giving NEF the capacity for non-destructive editing.

When NEF metadata has been edited, ViewNX will display one of two possible icons in thumbnail view: one indicates that "Quick Adjustments" have been applied and can be changed by either ViewNX or Capture, the other indicates that only Capture can make further adjustments.

If you "view" an NEF file it is the embedded JPEG image
that is viewed. While Nikon says it is to "edit" NEF
files, they also specifically say that by "edit" they
mean it converts the RAW data to an image format (JPEG
or TIFF).

Obviously, it must contain the required RAW and other converters. The
small JPEG embedded in the NEF is used only to produce the thumbnail
view.

The "small JPEG" is a full sized JPEG. It is commonly
used to "view" an NEF file. And yes sometimes that is
also done by actually interpolating the RAW data too,
but not usually because that is slow by comparison, hence
it is generally only done when the expectation is that
the data will also be manipulated as it is converted to
an image format such as JPEG.

We are both right and both wrong, Nikon is the odd one out by being only wrong :-)

You are usually correct so I've been investigating further. It seems that the camera embeds two JPEGs in EXIF fields: the small one is for thumbnail view, the large (low quality) one is for a file "viewer", the default viewing mode for ViewNX. The low quality is to conserve camera buffer and file space. The camera also uses these JPEGs for its playback functions. Obviously, it would be pointless for the camera to save a high quality JPEG in the NEF; it would make more sense to always save NEF+JPEG and not embed an image in the NEF.

ViewNX displays the rather poor quality large JPEG. If its "RAW" button is activated the button is animated while the RAW conversion is being performed. The image is then displayed and cached. Next time the same NEF is viewed it will use the cached image and not the embedded JPEG, irrespective of whether or not the "RAW" button is activated. It does not update the JPEG embedded in the NEF (it would be useful if it did).

Interestingly, when a NEF has been edited by Capture the "RAW" button is disabled, suggesting that ViewNX then uses only the embedded JPEG. The NEF file is noticeably larger after the first time Capture saves it, indicating that it embeds a high quality JPEG. What I've read seems to confirm this and others have found that Capture removes the small embedded thumbnail JPEG. The latter point is nothing more than mildly interesting; I can't be bothered to get and use some EXIF exploration software, and it is certainly not worth a debate.

Apple's Quick Look and Preview display a large image, but it is always the original version not the current version, which is both pointless and incorrect. I find it hard to believe that the NEF now stores two large JPEGs; perhaps it does. When requesting Preview to display a NEF at 100% there is a considerable delay before the full resolution image appears, which is not the case for a same-sized JPEG. I've no idea what is going on and I hope Apple will eventually correct this behaviour.

Summary of the large JPEG stored in the NEF: it is only a likeness of the real image. Good enough for a file viewer? Probably.


Thanks for your posts, Floyd. It took me a while to understand the meaning of an original digital image, but I'm very glad that I got there in the end. I'll put it to good use when I create more than one version in a NEF file. My photography will probably never be good enough to need a traceable method for version control, but I'll make it a habit just in case.

--
Pete

.

Relevant Pages

  • Re: Dispute with model over Trade for Copies photo shoot
    ... Ok, nothing "views" JPEG, GIF, TIFF, or PNG data ... just that what they attempt to display is the same). ... a NEF file is not just a wrapper for RAW data. ...
    (alt.photography)
  • Re: JPG or TIFF
    ... without having to open Nikon View, ... so the quality will not be the same as JPEG Fine ... the NEF and JPEG images, the NEF will not lose quality while the JPEG ...
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    ... Nikon provides the NEF + JPEG so one could preview the image ... the NEF will not lose quality while the JPEG ...
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