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Old Dec 13, 2013, 10:01 AM   #11
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One of the often overlooked image formats that allow for much smaller file sizes with no loss of quality is PNG (Portable Network Graphics):

http://en.wikipedia.org/wiki/Portable_Network_Graphics

It uses very sophisticated compression and filtering techniques, where you can sometimes get much smaller file sizes that you can with lower quality JPEG, without the inherent loss of quality, especially when dealing with certain color combos used for text with sharp edges. Here's an image showing that kind of thing (loss of quality with JPEG, with comments on file size compared to PNG):

http://www.libpng.org/pub/png/book/fig_C3.html

Here's a multi-page document that goes into a lot about how PNG achieves that kind of thing, while giving you a totally lossless conversion.

http://www.libpng.org/pub/png/book/chapter01.html

It also supports embedded icc color profiles, and can work well as an intermediate image format for editing, as well as a format for posting images online.

But, on the downside, it does not support embedded EXIF information.

PNG is also really great for things like screen captures where you want to maintain readable menu text with downsized images with smaller file sizes (as noted in the above example I linked to showing loss of quality using JPEG).

You'll see PNG used a lot by Linux users, and it tends to be the default format used by many screen capture utilities. For example, I was glancing at a new linux distro this morning for audio editing that includes a Real Time Kernel that had a capture online in PNG format here:

http://tangostudio.tuxfamily.org/en/ts-debian

Just click on the image to see a larger (still downsized version). This is the image you'll see (still downsized if you click on the one on the above page, depending on your browser window size):

http://tangostudio.tuxfamily.org/ima...sd-desktop.png

PNG tends to be well supported by most browsers and editors. Internet Explorer tended to be an exception before IE 9, depending on what PNG features were being used (transparency, etc.). But, from what I understand, IE even works OK with complex PNG images with IE 9 or later.

With many image editors, you can select the amount of compression you want to use with PNG, with it still being lossless, too. Supposedly, the compression time can increase with the smallest file size settings (highest compression level). But, I haven't noticed any perceptible difference in file save/open times when switching from the lowest compression (1 setting), to the highest compression (9 setting) on a 6 year old Dell Laptop I'm using right this minute with a simple image editing app called showFoto.

Note the settings slider for an image save dialog from showFoto below (I used a "mouse over" after clicking the ? button so you could see the help text associated with the compression level).

When saving the the screen capture image linked to above, using a 1 Setting (lowest compression) resulted in a 3MB file size, while saving it at a 5 setting took it down to only 340KB. So, a mid range is usually great for good compression with smaller file sizes, while still being totally lossless the way most image editors implement PNG (although technically, it can also support lossy compression, I think you'll find most image editors stick to compression and filtering algorithms that are totally lossless when using PNG).

IOW, for image editors that support PNG, you should find similar compression settings (slider, or similar for setting compression amount).
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Old Dec 13, 2013, 10:45 AM   #12
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Hi,
My camera (FZ150) uses CW2 as it's raw format. I've never used the raw before, but I was just fiddling with it, and two things jumped out at me....... how much brighter the picture is than the jpeg, and how much brighter the darker areas of the picture are. So, it seems like this is definitely the format to use in low light.
So..... you would both agree that the first thing to do with pictures that you want to keep is convert them to PSD or TIFF?
..... john

Last edited by Shinnen; Dec 13, 2013 at 10:46 AM. Reason: Clarify
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Old Dec 13, 2013, 10:57 AM   #13
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The JPEG image from the camera has already been converted with corrections applied (brightness, saturation, contrast/tone curves, sharpening, etc. etc. etc.).

The RAW file is as the data came from the sensor, and is not a viewable format without being converted first (and a basic conversion is happening when you load it into a RAW converter so you can view changes being made to it).

The results you see on screen from an initial conversion from RAW will vary greatly depending on the RAW converter you're using (as you'll find a variety of conversion algorithms being used, different defaults for image corrections being applied and more). IOW, just because you see something different than the camera produced JPEG with one RAW converter, doesn't mean you'll see something different with another RAW converter, depending on the default settings being applied to the image. But, you can modify many things about the image once it's loaded into your converter of choice.

You'll also find many differences in how much editing you can do to a photo between the many raw converters on the market. Some people may not need to do any further corrections other than what their raw converter of choice provides. Whereas others may want a more sophisticated editor supporting more features for further enhancements. For most of what I do, just sticking with the RAW converter's ability is fine (I'm using Corel AfterShot Pro, which is similar to Adobe Lightroom for RAW conversion and image enhancements) But, there are many more available.

Here's a recent post discussing some of the RAW converters available for Linux (but, they're also available for Windows).

RawTherapee for Panasonic Lumix FZ 18, poor results

I'd decide on a RAW converter (Adobe Lightroom, Elements, AfterShot Pro, etc. etc. etc.) for starters before deciding what kind (if any) intermediate format you want to use for future editing. That's because some of the RAW converters around can track corrections you're making in external files (usually .xmp) without actually modifying the original RAW file. With some converters (like AfterShot Pro, Lightroom and others), you get "non destructive" editing that way, with the ability to back out corrections, make different corrections later, etc., all while leaving the original RAW data intact. Then, when you want to share those image with others, just export to something like JPEG after you're happy with your edits (keeping the original RAW file for when you may want to do something different with the image).

IOW, I keep the RAW file and use it as a starting point, versus using any kind of intermediate format. But, if you wanted to use a different editor later, converting to something like TIFF is usually a good bet.
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Old Dec 13, 2013, 10:58 AM   #14
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Hi Jim,
Thanks for the primer. Yes ..... png does seem to be good, but I depend heavily on exif data especially when I'm experimenting and trying to find out what setting are best, which is ofen. Do you see exif being incorporated into png in the future?
..... john
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Old Dec 13, 2013, 11:24 AM   #15
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Hi Jim,
When you say 'raw converter' do you mean a program that allows you to edit raw files? I use a program called Faststone which is basically a convenient way of viewing a folder and doing minor editing. It's pretty good. It will allow me to save my rw2s to about 10 different formats, among them png, jpeg, bmp, and tiff, but not psd. Man, these are large files, 3 times the size of the rw2, but they open much faster than the raw file. Why is that? However Faststone will not allow me save the changes in raw. Also, I've noticed that the tiff format is the only one that preserves the exif data. (That may be only with this app.)
..... john

Last edited by Shinnen; Dec 13, 2013 at 11:34 AM. Reason: clarification
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Old Dec 13, 2013, 11:52 AM   #16
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View or edit. RAW is *not* a viewable (or editable) image format. It's got to be converted before you see it on screen (unless a viewer is just using an embedded jpeg thumbnail some cameras include inside of a raw file). Now, you do get what some raw converters refer to as "non destructive" edits (for example, Corel AfterShot Pro does that via an external .xmp file). But, the original raw file is untouched (they just store the changes they're making separately so they can be reapplied by the same editor later before exporting to a different file format).

The individual photosites in a camera's sensor are only sensitive to one color each, and with most Bayer Pattern sensor designs, you have twice as many pixels that are sensitive to green. More about how Bayer Pattern sensors work here:

http://en.wikipedia.org/wiki/Bayer_filter

Note this part:

"The raw output of Bayer-filter cameras is referred to as a Bayer pattern image. Since each pixel is filtered to record only one of three colors, the data from each pixel cannot fully determine color on its own. To obtain a full-color image, various demosaicing algorithms can be used to interpolate a set of complete red, green, and blue values for each point."


The raw conversion algorithms take the values from the red, green, and blue photosites and combine them via sophisticated interpolation techniques (using more than one photosite location and combining them) so that all 3 colors are stored at each pixel in order to give you a usable/viewable image.

The raw file has not combined the output of photosites in any way. That's what the raw conversion process does (or in camera processing if you shoot in jpeg). There are a number of different algorithms used, and some are better than others.

So, something like Faststone is actually converting the RAW file to a viewable format before letting you see it on screen so you can save is as a different image format.

Chances are, it's using something like the Open Source dcraw.c code (or a similar library based on it) for it's raw conversion. But, there are many different libraries and conversion algorithms around; which is why different viewers and editors may give you a totally different look to a converted raw file that you see on screen using their default algorithms. Now, Windows started including codecs to perform basic RAW conversion for use with apps like Windows Explorer a while back. But, not all cameras are supported by camera manufacturers' codecs or Microsoft's available codecs (but, there are good alternatives like the FastPictureViewer Codec Pack).

Here's a long post on the subject (RAW files, demosaic algorithms used, etc.) from 2009:

need help..
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Old Dec 13, 2013, 6:20 PM   #17
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Only TIFF and JPEG files have EXIF tags.

RAW, PSD and DNG (Adobe Digital Negative, a camera-independent RAW file format) files contain the information that may eventually make its way into EXIF tags, but they do not have EXIF Tags as such.
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Old Dec 14, 2013, 9:13 AM   #18
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Quote:
Originally Posted by TCav View Post
Only TIFF and JPEG files have EXIF tags.

RAW, PSD and DNG (Adobe Digital Negative, a camera-independent RAW file format) files contain the information that may eventually make its way into EXIF tags, but they do not have EXIF Tags as such.
I don't keep up with PSD files, but RAW files and DNG files contain EXIF tags. Your image editor just needs to know where to find the EXIF table that manufacturers embed in the files.

You can also read the EXIF from a raw file converted to DNG using common tools that support EXIF.

DNG supports lots of metadata, including EXIF metadata tags, as well as TIFF-EP tags, IPTC metadata and XMP metadata.

You can also embed DNG specific info during conversion from raw using either EXIF tags or TIFF-EP tags. But, Adobe's specifications for DNG suggest using EXIF tags for any additional info you want to embed.

You can even read the EXIF from DNG files using some of the online tools if desired. For example, Jeffrey's EXIF Viewer lets you upload a file and reads the EXIF (as well as IPTC, XMP and other info) from it. It uses code from Phil Harvey's ExifTool on the "back end" to get you that information from raw or DNG files.

But, many other image viewers that support EXIF can also show it to you (in the same way you'd see it from a jpeg image) if they also support DNG files.

For example, I can convert a raw file (.arw) from a Sony dSLR model to DNG using an open source DNG converter and see separate sections for EXIF, Makernotes, IPTC, and XMP metadata for it using a simple photo viewer called showFoto in Linux (that allows you to click on a tab to switch between metadata types you want to view), and Adobe's DNG converter should do the same thing (move the EXIF tags from the original raw file over to the DNG file during conversion).

Now, some raw converters and viewers may not be properly transferring the EXIF data during their conversion from raw (as byte offsets for that metadata will vary between raw file types, and a converter needs to support a specific camera model and know where to find it). But, EXIF tags are supported by the DNG specifications.

My problem with DNG is that some raw converters don't support it, unless it's "native" from the camera (for example, some Pentax models allow you to use DNG as the default raw format). Corel AfterShot Pro is one example (it will support DNG files directly from some Pentax models, but does not support DNG files from converted raw formats.

I prefer to keep the original RAW files for more than one reason, and want to make sure I have the original file as produced by the camera.

Even though DNG allows you to do things like embed the original raw file into the DNG file during a conversion, I just don't see the point of converting to DNG for my needs.

Now, some users may want to convert to DNG for compatibility with an older raw converter.

For example, if you're using an older version of Photoshop like CS2, and the Adobe Camera RAW plugins available for it do not support a newer camera model you purchased, you can use a newer version of Adobe's DNG converter that supports that camera model, and then use an older Camera Raw plugin with CS2 to open the DNG file created from that camera's raw file.

But, I'd still suggest keeping the original raw files (as disk space is cheap anymore). That way, you always have the camera produced raw file as a starting point, with no need to worry about any issues that raw to DNG converters might cause.
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Old Dec 14, 2013, 10:21 AM   #19
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Thanks guys,
Well, I'm certainly getting an education here.
If I view my raw files in Faststone, however it does that, I can save them in several formats. (That explains why Faststone is so slow at opening raw files ...... it has to covert them for viewing.) But, I didn't know that each viewer shows raws differently. So...... the question is .... what viewer/converter is best for my raw files, or should I just let Faststone convert them to Tif and do whatever editing I want to do in Tif, then convert them to jpg for sending, posting, etc? I have an old version of PSE6 for tricky stuff, but mostly I just use Faststone.
...... john
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Old Dec 14, 2013, 12:52 PM   #20
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Once you open a RAW file, the application you open it in converts it for viewing, so you can't usually save a RAW file. (Some RAW files permit the saving of changes, but the original data is always still there.) Every program converts RAW files from the same data, and all let you tune the result. Every program is capable of producing the same result; what matters is how easily you can get the result you want.

It seems to me that you're already quite satisfied with Faststone, so why change? But if you want to try some others, many are available as freeware or free trial downloads, so you can actually try many different programs before you decide from among them.
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