optimizing jpegs for web

[grayliner@adobeforums.com]

ok so i have a digital camera that takes fairly high resolution images. needless to say to post them on the web you have to knock the res. down to 72 dpi. and adjust quality to allow for quick download times.
i've never fully master the art of resampling jpegs for the web, and for some reason the quality always stinks. if anyone has a tried and true technique for this please share the wealth.

[Toby_Thain@adobeforums.com]

Resize with Image Size; sharpen (I usually use "Unsharp Mask" @ 150%, 0.5 radius, threshold 3, but just "Sharpen" or "Sharpen More" would be OK); Save for Web (usually JPEG High).

This sequence can be automated with an Action.

[jonf@adobeforums.com]

I've never had much problem with simply sizing it down with Image Size dialog. What do you mean by "quality stinks" and how exactly are you adjusting quality? (If you save your jpeg at any quality below Medium you'll probably notice banding, pixelating and halos.) How large do these images need to appear in the website? Is your file size ending up too large if you keep quality at Medium or High?

[grayliner@adobeforums.com]

More or less there is a lot of detail loss, but when i kick up above medium the file size is just too large for web. If only the rest of the world woud get on broadband, or cable, or dsl, or anything but dial-up. In either case my image sizes are typically around, 4.5 inches my 3.25 inches, but i would like to go larger in image size. I just know that dial up users (such as myself when i had one) that if the images taking too long to download i would give up.

I'll gladly take any opinions or advice on the matter.

[jonf@adobeforums.com]

Generally I wouldn't expect that you'd notice much loss of detail on screen at any size above 5. Your files sizes ought to be around 50-80K or so, which isn't bad even on dial-up, unless there are a lot of them.

You can use progressive jpegs on the Web, so they'll upload a little at a time on slower connections, gradually becoming more complete instead of simply holding up the user.

Or if you need more detail available, you can always create links to your higher-quality files. Or use a mouse-over function so that files get clearer whenever the cursor passes over them. You'd want them to pre-load. That way a slow connection will see the lower quality files but if they remain on the page for any length of time the higher quality image will load up in the background, and show up on mouse-over.

[Paul_Hokanson@adobeforums.com]

Sharpening is the key when downsampling images, especially when going from a 4-6MP file to a very low res file for web display. Over-sharpening can be a problem, however, so carefully examine the preview in the Unsharp Mask dialog and adjust your settings to reveal edges in detail that was lost in the downsample, but do not produce halos and other over sharpening artifacts. Web graphics require different sharpening settings than those for print work, so keep your sharpen radius small (below .6) and use your eye. Some images will need a bit more than others.

Also, avoid jpg settings below 8 when saving files that contain lots of fine detail. With a small overall image pixel size (ex: 400px by 200px) dialup visitors shouldn't have too many problems with these jpgs.

[J_Rindfuss@adobeforums.com]

How do you create or set your JPGs to be "progressive"?

[peanutpie@adobeforums.com]

When you do a save as, you'll see a dialogue box come up that will show the compression levels, as well as Format Options. Simply choose Progressive from the list to have your images load a little at a time. Or if you do a Save for Web, there should be a check box listed under settings for Progressive.

[JasonSmith@adobeforums.com]

What version of PS are you using?

CS has some new sampling algorithms, if you are down sampling try the "Bicubic Sharper" setting.

[Robert_Kwong@adobeforums.com]

I have a problem with automating PS 7 Web gallery photos in the dozens say 150 - 3000 x 2000 images. When I batch processed them a few months before they all would go into the destination folder with the thumbnails, html coding, etc. and I would end up with the total folder size being less than 10 mb in size.

Now I am doing the same thing with similar file folders and the folders' size are about 800 + mb in size (bigger than the original folder) and to much to upload via ftp program. The actual thumbnails I have gotten info on are are even 2.3 mb in size! as well as the images. They used to be 50k and thumnails 1 K.

I have tried reloading PS7, dumping preferences, etc., but to no avail. What's a Photographer to do? Did I disable some default button or action??