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Archive 2013 · Preserving file quality
  
 
SylviaLWright
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p.1 #1 · p.1 #1 · Preserving file quality


Hello all, I'm new to fredmiranda forums.

Just returned from a photo trip to Yosemite NP (where I met Landscape forum moderator Jim Fox, who pointed me here).

I shot RAW + large JPGs, and hope to use them to teach myself how to improve images in post processing.

I read that every time you open and close a JPEG file, it loses some data. Is this true of RAW files?

What do you do to preserve those lovely fat files -- work on copies and leave your original files alone?

Many thanks.

Sylvia

Edited on Feb 21, 2013 at 07:21 PM · View previous versions



Feb 21, 2013 at 05:00 PM
howardm4
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p.1 #2 · p.1 #2 · Preserving file quality


JPG is by definition a lossy format so yes, you do eventually lose data on each save but it takes a while to actually be visible. Since you also have RAW (yeah!), you should start from there.

Since RAW files need to be 'rendered' into an actual image, you don't actually manipulate them directly. For example, in Photoshop, you'd dump the RAW file into their converter (ACR) and you'd get a .psd (which is a variation of the TIFF format) which is NOT lossy.

Of course, you should always make safety copies - just in case!



Feb 21, 2013 at 05:13 PM
WAYCOOL
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p.1 #3 · p.1 #3 · Preserving file quality



Just opening and closeting a jpg will do no harm. Like Howardm4 said if in the coarse of editing your photo
you just make changes and close the file 4 or 5 times your not likely to see any change that you didn't make. Personally I think shooting both raw and jpg is a waste of space raw is superior in every way. If for no other reason the ability to convert to 16 bit psd or tiff I stay with raw.



Feb 21, 2013 at 05:57 PM
Ian.Dobinson
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p.1 #4 · p.1 #4 · Preserving file quality


SylviaLWright wrote:
Hello all, I'm new to fredmiranda forums.

Just returned from a photo trip to Yosemite NP (where I met Landscape forum moderator Jim Fox, who pointed me here).

I shot RAW + large JPGs, and hope to use them to teach myself how to improve images in post processing.

I read that every time you open and close a JPEG file, it loses some data. Is this true of RAW files?

What do you do to preserve those lovely fat files -- work on copies and leave your original files alone?

Many thanks.

Sylvia


A couple of things :

1: as mentioned , just opening and closing a jpeg does nothing to it. But resaving will loose you some info.
You can test this by opening and saving a jpeg over and over again. Even if you don't touch the the compression slider you will see the file size reduce .

2: raw is raw . When you edit it you don't touch the raw file .

3: shooting raw+jpeg . Yes to a certain extent its pointless . But as an iPad user in the field I find it much better to load the jpegs into the iPad and save my raw files for when I get home.
However if the first time you will view and use your jpegs is at a computer then yes you are just wasting space (and on most cameras buffer/fps) . There is a very fast little utility that you can use on. PC (maybe mac as well) called 'instant jpeg from raw' . It strips the embedded jpeg from a raw file (you camera uses that jpeg to display the image on the cameras screen) , and as long as you are using a recent(ish) camera the jpeg is usually full sized (old cameras used a very small jpeg) .
Eg my 7D produces a full sized 18mp jpeg, its highly compressed (about 2-3mb ) but to tell the truth I'd be hard pressed to tell the difference



Feb 21, 2013 at 11:52 PM
Peter Figen
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p.1 #5 · p.1 #5 · Preserving file quality


"1: as mentioned , just opening and closing a jpeg does nothing to it. But resaving will loose you some info.
You can test this by opening and saving a jpeg over and over again. Even if you don't touch the the compression slider you will see the file size reduce . "

Having done this test several times, all I can say is that it's not true. I've gone up to fifty successive saves, done by copying the file and saving, not merely doing a straight Save As, which would be invalid. The original file and the fiftieth are identical, and layering one on top of the other using Difference blending mode yields a pure black result indicating there is no difference between the files. This only works if you use the same compression and don't change a single pixel value. As soon as even one pixel value has changed, the compression is reconfigured and the losses start piling up, so to speak.



Feb 21, 2013 at 11:57 PM
mhayes5254
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p.1 #6 · p.1 #6 · Preserving file quality


As was said, although you loose a bit every time you work on a file, you really do not need to worry about it. The losses are far too small to matter. Where the limitations of JPEG may matter is if you are doing significant editing (big changes in brightness for example). Since JPEG has only 8 bits of luminance data per pixel, you MAY get banding or other artifacts when editing. Working in Raw PSD or TIFF gives more bit depth and this extra information allows much more significant editing changes without getting strange things happening.

If you are just starting out there are two different schools of thought 1) The simple approach of not worrying about it and use JPEG until you run up against its limitations 2) use RAW from the start and have the benefits available if they are needed. I did 1 but recommend 2

The choice between JPEG and or RAW can be influenced by what software you are using. Things like Lightroom make it easy to just work with RAW without the need to keep track of different versions of a file. RAW definitely gives you more power for PP



Feb 22, 2013 at 06:23 AM
MissMouse
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p.1 #7 · p.1 #7 · Preserving file quality


When working on an image I save my work using PSD format which preserve my work. Layer, adjustment mask etc. I save Print jpeg file from my PSD documents. When you save a Jpeg while editing a PSD Photoshop temporary flatten the document and converts to 8bit color it needed to be able to save a Jpeg image file. Once save Photoshop reverts the document back to state it was in before you used Save As jpeg. You Layers and color bit depth is back as before without any color lost because it was reverted back not converted back.

RAW file are always still intact and a copy or two may be in smart object layers embedded smart objects in a PSD....



Feb 22, 2013 at 03:28 PM
 

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SylviaLWright
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p.1 #8 · p.1 #8 · Preserving file quality


Howard, waycool, Ian, Peter, mhayes, MissMouse:

All your replies are terrifically helpful. Each of you gives me a bit more understanding of what a RAW file and a JPG file is/isn't; why shooting both may not be helpful; what Lightroom and PhotoShop offer; how your workflow goes. And it's all really interesting; I can't wait to get started this weekend.

So, now that I'm no longer paranoid about even opening my files, my next question is (should I make this a new post? if so, I'll edit; pls let me know) --

How did you learn all this stuff?? How did you choose your editing software? Do you also use HDR software? Can you suggest any print or online tutorials specifically for photographers?

My tech specs: I work on Macs. I have Adobe CS 5 on my work laptop, and Photoshop Elements on my home iMac. (I haven't used either, so "layers" etc. are all new territory.)

I want to do my photo editing on the home iMac, for the large monitor.

And I shoot Canon, and I see the RAW files from my camera are named Canon Raw (.CR2). Does this affect my editing?

OK, sorry, that's five questions. I'll stop there for now.

Thanks!
Sylvia



Feb 22, 2013 at 04:09 PM
15Bit
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p.1 #9 · p.1 #9 · Preserving file quality


Welcome to the forums Sylvia.

Moving beyond the jpeg loss issues, there are some other advantages to using RAW. The most important being that RAW files generally hold "more" data, particularly dynamic range, and are much more malleable in processing. You can do more editing to a RAW file before it begins to show artefacts, particularly in terms of adjusting exposure parameters.

With a RAW file you also have the choice to use different RAW converters for the initial rendering of the image, and different converters tend to have different "looks" in terms of contrast curves, colour rendition etc. This is an advantage, as it gives the choice to pick software that gives a "look" that you like, rather than relying on the in-camera jpeg processor, but picking between RAW converters can add extra confusion when you are first trying to learn how to do PP.

If you shoot RAW and use Adobe Photoshop or Lightroom you can also get camera calibration kits (search "colorchecker passport") to make sure that colours are exactly correct in your images.

In terms of learning how to do it - well there are numerous books available for PS and LR, and lots of online resources (videos, tutorials etc). Ultimately though, i think most here would agree that it is a "learning by doing" exercise. The more you do, the more you learn.



Feb 22, 2013 at 04:18 PM
cgardner
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p.1 #10 · p.1 #10 · Preserving file quality


CS5 (which I also use) comes with two companion applications: Bridge and Bridge Downloader.

Bridge is a file review / organizer for Photoshop. The user interface mimics a transparencies on a light table. By selection a thumbnail and hitting the space bar provides a full screen view you can scroll through with arrow keys or run as a slide show. With cmd + 1.. 5 you can rate the files while reviewing with a start rating. I mark keepers with one start, selections for editing with two, completed editing with 3, etc. Filters allow selection by star rating, color label, file type, etc.

Clicking on a thumbnail in Bridge opens RAW files in ACR where you assign color space and bit depth and correct exposure and adjust contrast. From there it opens in Photoshop as a .PSD file

One of the more useful things about RAW is you can correct one file then copy the settings to the others in the batch. That's done by right clicking the little circle icon that appears the thumbnails in Bridge then selecting "Develop > Copy Settings" from the menu of the file that is corrected. Then select the others and right click and select "Develop > Paste". The actual RAW data isn't changes, only the meta data (record of the adjustments)

Bridge downloader works with Image Capture the OS app. In Bridge preferences set it to open whenever a CF card is detected. It will save the files to your Photo folder or anywhere else you specify.



Feb 22, 2013 at 09:10 PM
SylviaLWright
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p.1 #11 · p.1 #11 · Preserving file quality


Thanks, all. I see this is gonna be a long learning curve. I'm starting at such a basic level -- didn't even know that one must have Photoshop or Lightroom to use the HDR products such as HDR Efex Pro 2.

15Bit, thank you for the add'l benefits of RAW.

cgardner, thank you for the 1-2-3's of basic Bridge actions.






Feb 24, 2013 at 04:04 PM
Eyeball
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p.1 #12 · p.1 #12 · Preserving file quality


Sylvia - You can use the Canon Digital Photo Professional (DPP) software that came with your camera to develop the raw files if you want. It will still give you better dynamic range than the camera Jpeg. Some people actually feel that DPP has slightly better quality in raw development than PS or LR. It just doesn't have as many bells and whistles.


Feb 24, 2013 at 09:03 PM
SylviaLWright
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p.1 #13 · p.1 #13 · Preserving file quality


Eyeball, I had not thought of this. I had installed DPP when I started using the camera, but did not use. I've now downloaded the latest DPP updates and will explore. Thanks!


Feb 25, 2013 at 06:16 PM





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