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PNG metadata
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billseymour
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« on: August 25, 2008, 03:19:05 PM »

(posted in iView, and also posted here, to see if EM users have different experience)

I've just noticed that after adding metadata to PNG files in iView, and Sync-annotating back to the file:

Applications using these PNG's do not show ANY metadata in the PNG file. I opened these annotated PNG's in Photoshop CS3 and Fireworks CS4- the 'File Info' for both applications is completely blank- none of the metadata I entered (and annotated back to the image file) shows up.

Anyone else encountered this? Is this a peculiarity of iView? Is this not an issue in EM (or iDimager, for that matter)? Does entering metadata to PNG files in another app, like Bridge, 'take' properly so that metadata is retained?

This is very confusing. In the iView catalog, all the metadata for PNG's is present (but I'm guessing this is metadata in the catalog itself; my question relates to using a copy of a PNG image which I thought I'd properly added metadata to).

Thanks for any insight. (Also posting this in EM area).
--Bill
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Dierk
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« Reply #1 on: August 26, 2008, 12:26:31 AM »

From Wikipedia:

Quote
That said, PNG does not provide a standard means of embedding Exif image data from sources such as digital cameras, which makes it problematic for use amongst amateur and especially professional photographers.

Are you talking about original PNGs or do you create them via Convert Images?
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Dierk

IDimager on Windows XP/SP2; 3.2 GHz, 2 GB RAM, loads of storage space.
Other: Nikon D2x, Nikon D200, Capture NX 2, Adobe Creative Suite 3
billseymour
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« Reply #2 on: August 26, 2008, 05:22:56 AM »

Two sources of PNG's:

1. images from internet (for example, a bunch of texture images put up for personal/commercial usage, that are in PNG format)

2. images with transparency created in Photoshop, saving in a format that preserved transparency. (Say, using a 'cutout' application like Fluid Mask within Ps to create an object cut out from its background).

I understand that iView's catalog maintains the PNG metadata, which is great. But I see two serious problems remaining with this 'no metadata in PNGs':

a. Changing DAM software: with PNG, the whole concept of 'export metadata to original image file' is frustrated. In the new DAM catalog, one (I guess) has to recreate the metadata for transferred PNGs.

b. Using a PNG for use with some Ps project: the only information I have about the PNG is the file name, unless I am willing to go back to iView and read the metadata there that is in the catalog.

So: If PNG is not a metadata-friendly form, then what is best way for me to store transparencies that is DAM-metadata safe? Best idea I have so far:

Store a transparency as a 1 layer PSD file. Advantage: metadata can be written to the file (in Ps, Bridge, iView, etc); Disadvantage: a much larger file (a PNG might be 1 MB, same PSD file might be 3 MB).

I am thinking of opting for the PSD route, since storage is ultra-cheap (3 MB is not even one digicam image in size).
--Bill
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billseymour
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« Reply #3 on: August 26, 2008, 06:58:10 AM »

BTW, another observation, about Photoshop PSD format:

The 'Maximize Compatability' election when saving as PSD file almost doubles the file size.
So, re question of saving a PNG in a PSD format to allow metadata to be saved, as an example:

Original PNG size:                          4.5 MB
PSD save, Maximize compatability: 12.8 MB (!)
PSD save, NO max compatability:   6.58 MB

I'm not exactly sure what I am giving up by not selecting Max Compatability. Realizing this is not a Photoshop forum, still, does anyone know?
(I will post this particular Q on a Ps forum as well).
--Bill
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Dierk
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« Reply #4 on: August 26, 2008, 07:40:50 AM »

PSD get roughly double the size with Max Comp because a flattened version is saved in the file, that's all. You do not give up anything but storage space [and probably speed under some circumstances].

Saving PNGs as PSD seems to be a strange route though I do not know what you actually do with them. I'd go for TIFF or even GIF. Mind, GIF is not lossless unless you discount the 256-colour limit. TIFF supports everything PSD supports [at least since CS], it was recommended by Bruce Fraser and David Blatner in their Real World Photoshop book. In theory TIFF has a broader support base. If transparency, an Alpha channel, is the only extra in your PSD - that is, no layer - you should be alright saving PSD without Max Comp; MediaPro and xMedia can handle that.
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Dierk

IDimager on Windows XP/SP2; 3.2 GHz, 2 GB RAM, loads of storage space.
Other: Nikon D2x, Nikon D200, Capture NX 2, Adobe Creative Suite 3
billseymour
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« Reply #5 on: August 26, 2008, 08:00:39 AM »

Dierk-
Thanks for the information. I'm just interested in having metadata travel with the transparencies (at least those files of particular importance to me); and I was astounded to see that the metadata simply did not get into the original PNG files at all.

My interest in having metadata with the transparency is:
- if I change DAM applications, I want the transparency files' metadata to transfer as well (rather than only residing in the catalog, as I guess is the case for PNGs catalogued in iView, EM, or any other DAM app)

- when I am doing a Ps project, I often copy source files for the project into an 'Originals' project folder. It is a pain in the you-know-what to have a PNG file called wcs_080825_001.png, and have absolutely no metadata available for the file (since it is a PNG) unless I separately bring up iView and look up the file.

I think I will just leave PNGs I am not concerned about 'as is' (in PNG form); and those I really want to preserve metadata for, I will put into PSD with Maximize Compatability turned off.

Thanks. --Bill
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