Subject | Re: Lenses and sharpening |
From | Floyd L. Davidson |
Date | 09/20/2014 03:32 (09/19/2014 17:32) |
Message-ID | <87k34zrs9f.fld@barrow.com> |
Client | |
Newsgroups | rec.photo.digital |
Follows | Eric Stevens |
Followups | Sandman (9h & 38m) > Floyd L. Davidson |
Eric StevensI'll have to admit that when I used JPEG as an example format it just never occurred to me that anyone would try to argue the absurd point this discussion has taken. I did not suggest JPEG formatting was not lossy or that it was reversible, in any way. I did say that sharpen is reversible and unsharp mask is not.
On 19 Sep 2014 07:02:13 GMT, Sandman <mr@sandman.net>wrote:SandmanEric Stevens
In article <na4n1a9tqb8cr0bcsqju244pdvkiui43g8@4ax.com>, Eric Stevens wrote:Eric StevensCorrection:
He never claimed that the JPG can be reversed. As I have already written, he said that the original image can be recovered after sharpening by HPS even after the image has been saved as a JPG.He never claimed that the JPG can be reversed.Sandman
Correction:
He did.Eric StevensSandman
As I have already written, he said that the sharpening of the original image can be recovered after sharpening by HPS even after the image has been saved as a JPG.
Which requires that the JPG compression is reversed as well. Floyd didn't realize this because he doesn't know how these things work.
Unfortunately he knows too much, compared with the rest of us. I did wonder when he threw in that JPEG conversion but I finally he concluded that he was trying to make a point.
The settings for HPS is a set of numbers. The settings for Gaussian blur is another set of numbers. Applying HPS or GB to an image is basically the same process and what you get depends upon the numbers you feed to it.That is true. It would be perfect of course, but it would be close enough for government work.
What I think Floyd was saying that even with the loss of information and image data inherent in a JPEG conversion you can restore the original sharpening by changing the numbers you apply to the image saved as a JPEG.
Image 1 --->Apply HPS settings --->Save as JPEG --->Reverse HPS
gets you to the same place as Image 1 --->Save as JPEG
You can't do that if the original sharpening was USM as it is not fully reversible.That is exactly the point. It just is not reversible.