Since there are a lot of opinions on how to work with RAW files I thought I’d write a journal entry explaining what I know about RAWs and how I work with them.
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This is a direct quote from my Olympus Camera manual; “RAW data is the unprocessed data from the camera’s sensor that has not undergone any changes or modification in white balance, sharpness, contrast or color.”
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Generally speaking RAW is uncompressed relative to a compressed format such as JPEG.
However, RAW is compressed relative to TIFF (tagged image file format).
The difference between RAW and TIFF is that TIFF is completely uncompressed. When I shoot in RAW the file size is 13.5 megabytes. When I convert this to a TIFF the file size balloons to 23 megabytes. The reason for the size difference is because RAW uses what is called a “Lossless” compression algorythm similar to a compressed zip file. This method of compression preserves all image data with no losses.
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JPEG ( joint photographic engineering group) uses what is called “Lossy” compression in which data is discarded or deleted in order to make room for the file compression. This results in loss of quality. Even at the highest quality setting there is still some loss of quality when converting a RAW or TIFF into a JPEG.
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TIFF is the absolute best format for printing. In a TIFF all image data is there and there is no loss of quality when converting from a RAW to a TIFF. But TIFFs consume a lot of space on the Hard Drive relative to RAW. So TIFFs are not practical if you have a large number of TIFF images to store.
Another disadvantage is that TIFF is not uploadable on some websites and not all web browsers can read TIFF.
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One solution is to use another format known as PNG (portable network graphic).
The PNG format uses the same lossless compression algorythm as a RAW making a PNG identical to a RAW in terms of file size and image quality preservation.
The main difference between a RAW and a PNG is that not all photo editing programs can read RAWs, but PNGs can be read by all photo editing programs including Photoshop. And some sites, such as RedBubble will accept PNG files but not RAWs or TIFFs.
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It should be noted that Photoshop can read a RAW if you obtain what is called a “Plug-In” from the manufacturer of your camera and install it in the Photoshop Plug-Ins folder. This is necessary because one of the attributes of a RAW file is that there is extra data from the camera manufacturer in the RAW file that acts like a lock to prevent other programs from opening a RAW file. The Plug-In to Photoshop acts like a key that enables Photoshop to open the RAW file. Only then will you be able to use Photoshop to edit RAW files.
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Some newer versions of Photoshop such as CS2 and CS3 may already have the Plug-Ins while older versions will have to be manually installed. I got the Plug-In when I logged onto the Adobe site and updated my CS2 version.
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Now, the way I work with the RAWs is first I open it with Photoshop and then make all the necessary adjustments such as white balance, sharpness, contrast and so on.
Once all the adjustments are complete I then save the adjusted RAW as a PNG. This preserves the image quality of the RAW but as a PNG I can now upload it to internet sites that accept PNGs such as RedBubble.
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By using PNG instead of JPEG your prints will be superior in color and clarity.
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As an experiment I made a pair of prints off of my own printer to see if there was a visual difference. The result was interesting.
The print made from the PNG had brighter and more vivid colors than the version printed from the JPEG.
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The JPEG version seemed more subdued in terms of overall brightness and color saturation. This is probably due to the compression of a JPEG. Even at the highest quality setting the JPEG has to discard some data to compress the image file.
It would appear that image brightness and color saturation is the first data to be discarded even with the JPEG quality at its highest setting.
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My conclusion is the following;
If you want superior prints but also need to save space in your computer save your RAW as a PNG.
Use JPEG only if you have a slow dial-up connection or if the site your uploading to will only accept JPEG, otherwise PNG is the best.
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Well, that’s how I handle RAWs.
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If any of you have any additional information about RAWs that I did not cover here feel free to add them as a comment.
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Thanks for taking the time to read this.
Steven Love
HOW I HANDLE RAW IMAGE FILES
Written by:
Steven Love
January 5, 2008
Suni Pruett, 4 months ago
Thank you for the information.
aphoto4you, 4 months ago
I am thinking to start series of these journals with all kind a helpful information for people on RB….This is fantastic Steven…lots of folks here would appreciated….FANTASTIC INFO…
aphoto4you, 4 months ago
so u save RAW into PNG?
aphoto4you, 4 months ago
OOOOOOOOOOOOOps…..that is if you open in Photoshop u save RAW into PNG? then when u done what u wanna do with it in order to upoad to RB ..you would save PNG into JPEG in Photoshop? is that right?
Steven Love, 4 months ago
Bianca;
You can upload PNG to Redbubble. I have many of my images here as PNG for best prints. But PNG is hard to upload if you have a slow connection so you might want to archive a PNG version on your computer for storage but send a JPEG copy to RB because JPEGs are a little easier to upload if you don’t have a high speed connection.
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If you’re just selling cards and small prints the quality difference won’t be that noticable.
But if you want to sell large prints, such as 13 by 19 inch or bigger, then I would upload it as a PNG for best color reproduction.
Steven Love, 4 months ago
One other thing;
You should also be able to convert RAW to PNG using your camera’s software.
My camera came with a program called “Olympus Master” which has that ability. But I only use that to convert large numbers of photos at one time and only if I have a few adjustments to make, otherwise I use Photoshop.
aphoto4you, 4 months ago
Okay i been using for years Nikon Capture and just recently started to conver in photoshop into PNG’s…like u instructed in email to me…But now i know why i wasnt able to get into JPEG….i owe u one steve….Lunch in Phoenix???????when i get there…
On the other hand is it true that then PNG files are better for printing because they are saved in 16 bits? and JPG’s are only 8 bit??
Steven Love, 4 months ago
Bianca;
I take it by your invitation to lunch you solved that problem you sent me an email about?
To answer your other question; PNGs can be saved in either 8 bit or 16 bit mode, but JPEGs are restricted to 8 bit only.
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I save my PNGs in 16 bit for best prints because the higher the bit depth the more colors available for printing.
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However, the main reason PNGs are better for printing than JPEG is not because of bit depth but because PNGs preserve the original true color of the adjusted RAW. JPEGs discard data in their compression process which is why they lose some color and brightness if made in large prints.
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Hope that helps.
aphoto4you, 4 months ago
yes steven…i see that….Now not much is been talked about 32 bit…i also noticed these PNG files are large wholy cow…lol…
I know this laptop i am using to access internet will not handle 32 bits..but other laptop will…because this one only has 2 gig of rams…
Yes problem solved…hey this is great thread….
Steven Love, 4 months ago
Yes, I am afraid that when you add more bit depth that will enlarge the file size. That is why I suggested sending a JPEG to RB if you only need small to medium prints made.
A 16 bit PNG may be too much if you don’t have a high speed connection and some sites may actually limit the file size.
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On the matter of 32 bits; that is relatively new because it is only used for HDR images.
According to my Photoshop manual 32 bit mode is used if you want to create effects that look more realistic than normal photography or other digital renderings.
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In 32 bit mode you can use Photoshop to merge different photos together that have different exposure ranges. The procedure is to complicated to explain here but you can probably look it up by googling or going to the Adobe site.
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However, not all desktop monitors can display 32 bit images and not all printers can handle them. Most websites cannot display 32 bit images either. For now 32 bit depth images will have only specific applications.
Kathie Nichols, 4 months ago
Thankyou so much Steve, your post has really helped my to understand a lot more about files. Wow!!!
randmphotos, 3 months ago
A very good explanation, Steve, and of great value to Bubblers. I like the suggestion of using PNGs too. May I add 2 extra notes? Firstly, Nikon RAW files (.NEF extension) do in fact inflict a form of lossy compression, in the form of “quantization” of highlight data, in order to reduce file size (and to speed up card writing in multi-shot sequences). The general consensus among geeks is that this has little if any visible impact on image quality. You can disable this on high-end Nikons (D200 and upwards), but not on my D80, D70, etc. Secondly, a problem with JPEGs is that, even with the highest (“100%”) quality setting, most applications will still cause some image loss and when multiple edits are done to an image there may well be visible damage to spatial resolution and/or colour. Thanks again for the article.
Steven Love, 3 months ago
Thanks for the additional info about Nikons.
I use Olympus so I don’t know about the limitations of Nikons.
JulieMahony, 2 months ago
Great info Steven. I have found that the program called Picasa from Google will also open RAW files but will only save them as JPEG.