Jpeg Artifacts - caused by compression
What is best way to convert TIFFs to Jpeg for submission to BNP's forum?
I have noticed in my BNP submissions that a clean file on my computer will have accumulated serious bunch of artifacts when opened on the BNP's forum.
Could seriously use a better work flow than I am using now.
Rob.............
Rob- I (and many others at BPN) use Save for Web and Devices in Photoshop. This handy tool looks after colour space conversion (to sRGB), flattening layers, conversion from 16 to 8-bit, and will accurately produce a jpeg file of a certain size for BPN (200k). I find that at 1024 x 800 or less, Save for Web and Devices will produce an image <200k in size with only a small amount of jpeg compression (quality in the 80% range), and therefore with no noticeable artifacts.
Thanks John. I have used the - Save for web in Photoshop with less than great results. Some files work some do not. I quess that I was hopeing for a "Better Way," maybe there isn't one.
Rob..............
Rob,
Make sure that you don't re-open a jpg file after you are done processing it. The other thing is that sometimes it might be a good idea to post a slightly smaller image, maybe 800 pixels wide if there are jpg artifacts.
Rob- I have found that high-frequency images such as landscapes with lots of detail all over are difficult to save under 200k with a reasonable jpeg compression rate. Axel's suggestion to post a smaller image works in these situations. What works well are images with a detailed subject and smooth BG such as a bird portrait. Noise adds to the frequency of images so NR can help in cases where too much jpeg compression is needed to come in under 200k.Originally Posted by Rob Miner
Whether you use "Save as" or "Save for Web," you'll get jpeg artifacts if you use too much compression (too low a quality setting). Rather than work under the 200K (?) limit for uploading to BPN, use an outside host such as imageshack or photobucket, where you can save larger files and link to those on the forum
Jpeg compression - Reply
Many Thanks for the members that took the time to speak to the problem. For your help - I wish you a profitable New Year.
Rob...............
A "save as" jpeg file will include exif data so is larger.
A save for web strips the exif data to make it smaller.
Roger
In CS4, "Save for Web" has options for preserving part or all of the metadata.
Another advantage of Save for Web and Devices is that it actually produces the file size it says it's producing. Save as jpeg in Ps reports a file size which is under the actual size on the disk. I just did a test and saved a file as a jpeg- in the JPEG Options dialogue box a compression rate of 8 reported a file size of 190k. After saving, it actually takes up 274k of disk space! Not sure why the 84k discrepancy but there it is.
Axel, are you sure this is not a good idea, how else is Rob to view his image?:D
Last edited by Daniel Cadieux; 02-09-2010 at 10:47 AM.
I mean re-opening/re-saving in Photoshop. :)
Posting Permissions
Reply With Quote