Google| Subject | Re: Lenses and sharpening |
| From | Savageduck |
| Date | 09/18/2014 08:10 (09/17/2014 23:10) |
| Message-ID | <201409172310255197-savageduck1@REMOVESPAMmecom> |
| Client | |
| Newsgroups | rec.photo.digital |
| Follows | Eric Stevens |
| Followups | Floyd L. Davidson (32m) > Savageduck |
On 2014-09-18 05:05:12 +0000, Eric Stevens <eric.stevens@sum.co.nz>said:
Eric StevensIt means exactly what he intended it to mean. You are putting words in his mouth when you become his advocate and say that he wasn’t claiming that the JPEG is fully reversible. That is your spin on what he didn’t say.
On Wed, 17 Sep 2014 19:20:02 -0700, Savageduck <savageduck1@{REMOVESPAM}me.com>wrote:SavageduckEric Stevens
On 2014-09-18 01:00:46 +0000, Eric Stevens <eric.stevens@sum.co.nz>said:Eric StevensSavageduck
On Wed, 17 Sep 2014 06:05:14 -0700, Savageduck <savageduck1@{REMOVESPAM}me.com>wrote:SavageduckEric Stevens
On 2014-09-17 09:22:00 +0000, Eric Stevens <eric.stevens@sum.co.nz>said:Eric Stevens
On Tue, 16 Sep 2014 22:27:43 -0700, Savageduck <savageduck1@{REMOVESPAM}me.com>wrote:Savageduck
On 2014-09-17 04:08:19 +0000, Eric Stevens <eric.stevens@sum.co.nz>said:Eric Stevens
On Tue, 16 Sep 2014 07:53:15 -0700, Savageduck <savageduck1@{REMOVESPAM}me.com>wrote:Savageduck
On 2014-09-16 10:36:29 +0000, floyd@apaflo.com (Floyd L. Davidson) said:
--- snip ---Eric StevensSavageduckSavageduckEric Stevens
The reverse process performed on a lossy, compressed JPEG is not going to reverse the HPF to return to the original state. That was lost once the save was executed.
That's why I never included a conversion to JPG in my example of a reversible process.
?but that genius Floyd did.
--- snip ---Eric StevensNo one who understood what we were trying to talk about would claim that a JPG conversion is a reversible process.Savageduck
?but that genius Floyd did.
I've had a look and I cant see where. Could you refer me to the message?
With pleasure.
That wasnÂ’t too tough to find: Posted: Mon, 15 Sep 2014 13:44:18 -0500 Message ID: <8738bs2076.fld@barrow.com>
Wherein Floyd stated the following:
“A non-destructive workflow means you can *undo* and then *redo*.
That is not a reversible function.
For example, you can add sharpening with a high pass sharpen tool to an image, save it as a JPEG, send it to someone else, and they can use a blur tool to reverse the sharpen.
If the sharpening is done with UnsharpMask that cannot be done. USM is not reversible.”
Note, the words, “save it as a JPEG,”.
As I said, that genius Floyd did.
Yes, I found that text, but I don't think that it means what you seem to think it means. He wasn't claiming that JPEG is fully reversible: everybody knows that it isn't.
Here I was hoping you weren’t going to say that he didn’t mean what he said, or that I read it wrong. The problem is, Floyd always says what he means doesn’t he?
Based on what Floyd has been saying all along, the obvious series of processes would be:However, that isn’t what he said. From his statement he said; “For example, you can add sharpening with a high pass sharpen tool to an image, save it as a JPEG, send it to someone else, and they can use a blur tool to reverse the sharpen.â€
1. Sharpen image.
2. Save file as TIFF
That seems pretty clear, and Floyd means what he says.
3. Apply Gaussian blur to TIFF image to recover original image sharpness.However you challenged me to support my claim that he actually said that. Remember? Yo said yourself; “No one who understood what we we trying to talk about would claim that a JPG conversion is a reversible process.†…but Floyd did, and Floyd knows what he is talking about, and he means what he says.
This series of processes is possible if you sharpen with a high pass filter but not possible if you sharpen with unsharp mask. i.e. the original image is recoverable if you sharpen with the high pass filter.
Floyd then went further and, as you quoted, proposed an alternative series of processes:
1. Sharpen image.
2. Save file as JPEG
3. Apply Gaussian blur to JPEG image to recover original image sharpness.
... and claimed that, again, this process also is possible if you sharpen with a high pass filter but not possible if you sharpen with unsharp mask. i.e. the original image is recoverable if you sharpen with the high pass filter.Regardless of what you understood him to mean, what did he actually say? I doubt that Floyd would be please with anybody being so bold as to paraphrase his words. He does mean what he says doesn’t he?
I understood him to be saying that inspite of the losses of a JPEG conversion, recovery of the original sharpness is possible if the original sharpening process used a high pass filter. That while saving as a JPEG will always cause losses, this will not prevent a Gaussian blur operation from recovering the sharpness of the original image.
I certainly don’t have the engineering background you and Floyd have, but I have a solid education in the sciences and I have had years of experience in microbiology and lab work, all of which strangely led me down another career path solidly entrenched in investigation. One of the things I have been quite good at over the last 30+ years is remembering and pinning down inconstancies in statements. They can be revealing. So rather than put words in his mouth, let Floyd's words stand on their own without your interpretation.
-- Regards,
Savageduck
09/13/2014-
