Forums


Go Back   The TrekEarth Forums >

Notices

Reply
 
Thread Tools
  #21  
Old 12-07-2009, 11:43 AM
feather's Avatar
feather feather is offline
TE Expert
 
Join Date: Jun 2005
Location: North Yorkshire, England, UK
Posts: 3,381
Default Re: Deterioration of photos posted in TE

I sort-of understand. There is also the matter of jpeg always reduces quality every time it is saved, which is why it is recommended that when working on a photo you always should save in a non-loss format like Photoshop's own or even tiff if there are no layers and only save the final image as jpeg. If you keep going back to a jpeg to do different adjustments and save each time it will end up as useless. If you have worked on any of your photos quite a lot, there is the possiblity that on the ones where you notice the deterioration on TE it has just reached the point where the loss is noticable to the eye???
Kath
Reply With Quote
  #22  
Old 12-07-2009, 05:47 PM
Longroute's Avatar
Longroute Longroute is offline
TE Expert
Thread Starter
 
Join Date: Jan 2008
Location: Cagliari, Italy
Posts: 2,000
Default Re: Deterioration of photos posted in TE

Thanks to Kaths hints and the very helpful collaboration of a friend I finally found out the cause (at least in my case) of the quality deterioration of some of my photos. Because the matter can interest other people too Ill try to explain it as clearly as possible.

Yes Kath, you were right! The problem was the RGB stuff!
When first you hinted at it I was sure my photos were all sRGB I had checked it but only the original files. Then a doubt came to my mind and I checked the resized copied for TE with a program which reads the exif data and it said: colour space: uncalibrated!!

That wording comes out every time the colour space is not sRGB. So it was evident that while the original files were ALL sRGB, some of them had the colour space changed when processed with Photoshop.
That drove me crazy because I was sure that my PS settings were fixed in sRGB!!! And actually most of my pp photos have that setting.

After a long search I found out that the changing occurred in Adobe Camera Raw, a program I use for opening the raw files before converting them into jpg files in PS. At the bottom of the main window in this program there is a small unnoticed link for changing the colour space. I had set it initially as sRGB but for an unknown reason now I found it to be Adobe RGB!! I only needed to switch it to sRGB and the pp files now have that colour profile! Solved!

Thanks to you all for your participation in this forum.

Donato
Reply With Quote
  #23  
Old 12-07-2009, 09:00 PM
guillaumejm's Avatar
guillaumejm guillaumejm is offline
TE Junior Member
 
Join Date: Nov 2005
Posts: 407
Default Re: Deterioration of photos posted in TE

Hello donato and you all.

"je donne ma langue au chat!". Sorry but impossible for me to translate except to say i've no the answer :).

I've made a quick test by myself. Here is the strange result :).
On the folowing picture :
http://fr.trekearth.com/viewphotos.php?l=3&p=1081196
the file on the site and on my pc is exactly the same . I mean same size. I've compared both files with beyondcompare tool which make binary comparison. exactly the same.

Then I made a test on one of my latest post :
http://fr.trekearth.com/viewphotos.php?l=3&p=1153220
And here file size change : 276638 bytes for the file downloaded from site and 266889 for my file which have been used to upload on the web site . beyoncompare tool confirm that files are different and the differences are spread all over the file!.
So in this case TE has ADDED information to the file?????.
First I that it could be in exif area but I'm not sure. So from step to step, answer to your question seems to go far and far away .

Bref j'ai plus d'ides pour le moent :(.

A+
Jmarc
Reply With Quote
  #24  
Old 12-08-2009, 11:10 AM
John_F_Kennedy's Avatar
John_F_Kennedy John_F_Kennedy is offline
TE Junior Member
 
Join Date: Aug 2006
Location: Weiterstadt
Posts: 329
Default Re: Deterioration of photos posted in TE

I do a test in the morning:
original picture has 306.080 bytes
on TE the picture has 290.816 bytes

The difference comes from removing the EXIF data. Removing the EXIF-data means storing the picture once more. Because the compression is done once more, the picture loose quality.
Reply With Quote
  #25  
Old 12-08-2009, 11:43 AM
feather's Avatar
feather feather is offline
TE Expert
 
Join Date: Jun 2005
Location: North Yorkshire, England, UK
Posts: 3,381
Default Re: Deterioration of photos posted in TE

I agree Achim; that is almost certainly the reason for the reduction in file weight. Donato also had the additional problem that some of his images were inadvertantly in the wrong colour profile which makes a big difference when showing on the web, which requires sRGB for the best results.

It also happens if you use other applications that only accept jpeg. When I started to use Lightroom, when you export back to your hard drive the default is ProphotoRGB which has even more colour tones than Adobe RGB. I hadn't noticed that and when I wanted to use the files to make a slideshow, the quality was atrocious. It was almost as if half the colours were missing. (they probably were)

Donato - If you don't already know, it's easy in PS to change the colour profile for the ones already in Adobe RGB. Our friend Henk told me how: Edit > Convert to profile.

Kath
Reply With Quote
  #26  
Old 12-08-2009, 01:37 PM
Longroute's Avatar
Longroute Longroute is offline
TE Expert
Thread Starter
 
Join Date: Jan 2008
Location: Cagliari, Italy
Posts: 2,000
Default Re: Deterioration of photos posted in TE

Hello Kath,

"easy in PS to change the colour profile"

yes, it's something I discovered for myself, thanks anyway for telling me.

By the way there is something I found very interesting (beside being amazing) which lead me on the right track: I sent the original reduced picture which I could see was deteriorated in Te to a friend by email (so that he could see the difference). After the shipping was done by chance I gave a glance to the photo attached and lo! it was faded like in TE!!! That convinced me that the colour profile was wrong and even sending it by email the aspect changed... curious eh?

I was wondering: how many photographers ignore this RGB stuff....

Thanks again,
Donato
Reply With Quote
  #27  
Old 12-08-2009, 01:57 PM
feather's Avatar
feather feather is offline
TE Expert
 
Join Date: Jun 2005
Location: North Yorkshire, England, UK
Posts: 3,381
Default Re: Deterioration of photos posted in TE

..'how many photographers ignore this RGB stuff....'
I think quite a lot. Many people use Adobe RGB because it has more colour tones, hence implied better quality. The web and some other applications aren't set up for it. I use two programs for other things eg printing albums (Photo Record) and making slideshows (Pictures2exe) and they need sRGB to show the images to the best advantage. The other thing is both Lightroom and Adobe Camera Raw attached to PS have other profiles set as their default and you have to consciously change to sRGB. Until you get to know the program well it's easy to miss.
Kath
Reply With Quote
  #28  
Old 12-08-2009, 03:46 PM
Muse's Avatar
Muse Muse is offline
TE Expert
 
Join Date: Jul 2006
Posts: 1,173
Default Re:

Je suis peu sur TE (lassitude ou le dpart de bon nombre d'habitus?)Je n'avais pas fait attention ce que fait remarquer Donato et en y regardant de plus prs, je m'aperois que c'est exact..
Je peux comprendre que le site sature mais qu'on prvienne les membres ne serait pas plus mal!
Reply With Quote
  #29  
Old 12-08-2009, 08:46 PM
guillaumejm's Avatar
guillaumejm guillaumejm is offline
TE Junior Member
 
Join Date: Nov 2005
Posts: 407
Default Re: Deterioration of photos posted in TE

Hello achim!.
I think there is something around exif . But one thing I don't explain is what has been done to INCREASE the file size of one picture i've posted??.

There is may be modification about exif depending on personnal setting (allowing or not to display them).

I thought : perhaps it could also come from file format for example windows versus unix. I know that on text file it removes the CR or LF (don't remember which one). But for binary files as pictures I've never heard about such modification between OS.

Second point is why sometimes size changes and somtimes not?

Why when looking at differences they are spread all over the file and not only in one part?. I guess that exif data are all stored in a dedicated area of the file?;

If some IB technical team read this forum perhaps they could explain?.

Best regards
JMarc
Reply With Quote
  #30  
Old 12-09-2009, 10:49 AM
John_F_Kennedy's Avatar
John_F_Kennedy John_F_Kennedy is offline
TE Junior Member
 
Join Date: Aug 2006
Location: Weiterstadt
Posts: 329
Default Re: Deterioration of photos posted in TE

Hello Jean Marc,
JPG is a algorithm based on the JFIF specification. A part of this algortihm is the Huffman compression algorithm. It could happen that you need more informations for the coding - I don't want to explain it because this would need some pages.
Best wishes,
Achim
Reply With Quote
Reply


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 01:29 PM.



Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.
explore TREKEARTH