JPEG compression - Why am I getting this now?

swag72

swag72

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Sara
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In a couple of threads people have commented that there is some JPEG compression in my pictures. I am unclear as to why people have only just started commenting on it. I am not doing anything different with my processing and resizing than I have always done. My only change is a new lappy, but not sure how that would do it.

The pictures where it have been commented on are below.

3356660927_204e466d04_o.jpg


3329940823_17b1056411_o.jpg


What am I looking for with regards to JPEG compression and any reasons why it has recently become an issue when my workflow hasn't changed?

Thanks for your help in advance.
 
Some time ago, I was going through a challenge, commenting on entries and it occurred to me that just about every photo exhibited severe compression artifacts. I then went and looked at mine on-line and they were the same. The same pics, viewed from the folder on my lapdog were fine. I was using a 3G internet dongle, which seemed to be zipping along nicely, so I imagine that the whole setup for it was compressing content to force it through more quickly.

May be the case for some of the commenters on your pics.

Maybe not. I haven't got my glasses or my thinking head on at the moment.
 
Zooming in yes you can see some artifacts. However I'm looking at the images you've posted and they are in fact fairly small, so any enlargement will show these up.

Now as you have changed your laptop, it means you've had to reinstall your imaging software. I wonder if you are using default settings that you weren't using before.

Ideally where possible the level of JPEG compression should be limited. The "rule of thumb" is not to compress beyond 10% of the original files size. So a 20Mb file should be around 2Mb. OK this will vary dependent on the image as some images compress better than others but it's a reasonable figure to start with.

Also opening and re-saving JPEG files will aggravate any artifacts you may be encountering. As will over sharpening, but your images don't look excessively over sharpened

Additionally are you saving the files as JPEG or RAW from your 50D. If JPEG then check you haven't for some reason gone to "small" file size

Hope this helps some
 
I don't actually save as JPEG - I shoot in RAW and convert to a TIFF when processed. I then upload the TIFF to Flickr and just cut and paste the link into the forum.

Am I doing something wrong? Should I be saving to JPEG and then loading onto Flickr?
 
The images on Flickr are JPGs right? SO if you uplod TIFs one can assume there is something on the Flickr server that then converts the TIF to a JPG. In which case you have no control over the compresion they might use.

If that's the case I would suggest you convert to TIF to do your final processing and then save as a JPG with the level of compression you choose. Then upload that.
 
swag72 said:
That makes sense - Will give that a go. Still can't understand why it is only something that has happened within the last 2 months or so.
Click to expand...

It doesn't have to be something that you changed at your end. There is 3rd partly involvement - namely Flickr - who are converting your tiffs to jpgs on upload and it could well be some recent setting change s/w update at their end which is causing the issue.
 
Could it be that Flickr does not want large files such as Tiffs.
 
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