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JPEG Vs. RAW
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Jan 10, 2019 22:31:22   #
Gene51 (a regular here)
 
sbohne wrote:
Opening a jpg and the saving it without editing does NOT cause any loss.


After you hit save, when you close it, the recompression of the image will cause some very minor degradation - even if you don't edit the image. If you do it a lot, artifacts become more evident. That's just common sense, and why they call jpeg a lossy format.

https://petapixel.com/2010/02/04/saving-jpeg-photos-hundreds-of-times/

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Jan 10, 2019 22:37:14   #
sbohne
 
Gene51 wrote:
After you hit save, when you close it, the recompression of the image will cause some very minor degradation - even if you don't edit the image. If you do it a lot, artifacts become more evident. That's just common sense, and why they call jpeg a lossy format.

https://petapixel.com/2010/02/04/saving-jpeg-photos-hundreds-of-times/


Sorry. I don't agree. This information comes from people like Claude Jodoin, a technical writer for PPA and a product tester for many digital imaging companies. I have posted the sources that back this up. Basically, I think the point is moot. How many times do you open a file and save it HUNDREDS of times?

But I'm pretty much done debating this topic. But I am amazed that after 20 years, these old misconceptions still hang on.

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Jan 10, 2019 23:06:22   #
rochephoto
 
It's actually very simple. The raw file contains millions of bytes of color information that can be preserved with Hires and high capacity files like Tiffs. They can also be outputted to compressed and clipped Jpegs. They can also be reprocessed in the future by ever more powerful Raw processing programs. Images that are shot in Jpeg are fixed in their limited information set. Although they can be approved in some ways, they can never utilize the much broader information set that a raw file embodies. Another way of thinking of it is that a Raw file is like a roll of film that can be processed over and over again with different and better developers. A Jpeg is like taking your roll of film to a one-hour photo lab. What you see is pretty much what you get...

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Jan 11, 2019 09:13:34   #
rmalarz (a regular here)
 
It would seem that the Joint Phototgraphers Expert Group and a few others disagree with you, your degrees, awards, references, and oblivious expertise. Oh, I might also mention David A. Huffman. He'd probably disagree, as well.

Opening a jpg image and simply closing it doesn't change it, I've proven that for myself. Opening and then simply saving it changes it. I've proven that, as well. Thus, it is referred to as a lossy format. However, if you wish to continue along with your oblivious ignorance, I'm not going to stop you. This isn't a topic for debate, as it's not an opinion. It's fact.
--Bob

sbohne wrote:
Sorry. I don't agree. This information comes from people like Claude Jodoin, a technical writer for PPA and a product tester for many digital imaging companies. I have posted the sources that back this up. Basically, I think the point is moot. How many times do you open a file and save it HUNDREDS of times?

But I'm pretty much done debating this topic. But I am amazed that after 20 years, these old misconceptions still hang on.

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Jan 11, 2019 09:14:42   #
rmalarz (a regular here)
 

--Bob
rgrenaderphoto wrote:
Absolutely, and the recipe choices were made by the camera, not the photographer. And furthermore in my very, very biased opinion, which is based on the dramatic improvement in my output from switching 100% to RAW, refusal to understand the possibilities is tantamount to refusing to learn how your camera system works.



I don't' care how perfect your in camera exposure is, don't care how great your compositions are.

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Jan 11, 2019 11:37:20   #
DirtFarmer (a regular here)
 
sbohne wrote:
Sorry. I don't agree. This information comes from people like Claude Jodoin, a technical writer for PPA and a product tester for many digital imaging companies. I have posted the sources that back this up. Basically, I think the point is moot. How many times do you open a file and save it HUNDREDS of times?

But I'm pretty much done debating this topic. But I am amazed that after 20 years, these old misconceptions still hang on.


I'm an experimentalist.
Using Win10 and IrfanView I took a jpg from my photopile and saved it. I then checked the properties, which include the number of bytes in the file.
I then opened the jpg again and saved it again (without making any changes). Checking the properties, the number of bytes in the file were not the same as they were the first time.
Tried it several more times. Each time the number of bytes in the file changed. Sometimes higher, sometimes lower.
No difference in the images were visible to the eye. I did not try subtracting images to look for differences.

I do have to agree with your point: "How many times do you open a file and save it HUNDREDS of times?"
When I was learning postprocessing I probably saved interim edits several times in the process but I seriously doubt that I ever saved an image more than 25 times.

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Jan 12, 2019 01:12:26   #
flashgordonbrown
 
Gene51 wrote:
After you hit save, when you close it, the recompression of the image will cause some very minor degradation - even if you don't edit the image. If you do it a lot, artifacts become more evident. That's just common sense, and why they call jpeg a lossy format.

https://petapixel.com/2010/02/04/saving-jpeg-photos-hundreds-of-times/


There is a difference between 'saving' and 'closing'. If you open,view, and close,there is no loss of dsta. If you save without having made any changes, there will be some negligible loss of data. Done enough times,that process could have an effect on the quality of the image. I do a fair amount of adjusting my images using Picasa, even though it is no longer supported by Google. None of the adjustments in Picasa have any effect on the original file. When I have used Photoshop, I always made a copy of the original file and made my adjustments on that, leaving the original file intact. I don't claim to be an expert in post processing, but I know what has worked for me, and I'm comfortable in sharing.

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Jan 12, 2019 13:26:09   #
PHRubin
 
DirtFarmer wrote:
I'm an experimentalist.
Using Win10 and IrfanView I took a jpg from my photopile and saved it. I then checked the properties, which include the number of bytes in the file.
I then opened the jpg again and saved it again (without making any changes). Checking the properties, the number of bytes in the file were not the same as they were the first time.
Tried it several more times. Each time the number of bytes in the file changed. Sometimes higher, sometimes lower.
No difference in the images were visible to the eye. I did not try subtracting images to look for differences.

I do have to agree with your point: "How many times do you open a file and save it HUNDREDS of times?"
When I was learning postprocessing I probably saved interim edits several times in the process but I seriously doubt that I ever saved an image more than 25 times.
I'm an experimentalist. br Using Win10 and IrfanVi... (show quote)

Personally, if I open a file to look at it but don't change anything, I don't save it, I just close it. EVERY SAVE reevaluates and comes up with a new version, closing doesn't. I haven't the courage to see what happens after hundreds of SAVES.

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Jan 12, 2019 13:37:28   #
TheShoe (a regular here)
 
sbohne wrote:
No, it doesn't and I posted the link that backs it up. You are free to think other wise. Your mind is made up, I'll stop trying to confuse you with the facts.
If you open a JPEG and save it at a differentn compression, opening and saving will lose data; however, that would be saving an altered file. If you open and simply save using the same compression, there is no loss.

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Jan 12, 2019 14:07:11   #
PHRubin
 
TheShoe wrote:
If you open a JPEG and save it at a differentn compression, opening and saving will lose data; however, that would be saving an altered file. If you open and simply save using the same compression, there is no loss.


I disagree. Each SAVING can change the file, regardless of whether you made a change or not. It does depend on what program (app) you used to view the file.

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Jan 12, 2019 14:16:10   #
DirtFarmer (a regular here)
 
PHRubin wrote:
I disagree. Each SAVING can change the file, regardless of whether you made a change or not. It does depend on what program (app) you used to view the file.


Agree.
That was the point of my experiment described above.

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