Image detail lost after uploading to the web!

[GSDlover4ever]

I can edit an image and it can be sharp.... and look good and even when it is printed it still looks good...

However if i resize that image to 72dpi and reduce it to about 600-800 for the web and upload to flickr or photobucket a lot of the detail... is lost.

I do sharpen my images and usually once they are resized i sharpen them slightly again before uploading to the web.

On some occations the image looks to be over sharpened, basically like it has been sharpened with a knife. lol
So i reduce the sharpening... and it still looses quality when uploaded.

Any ideas?

 

[Musicman]

What level of JPEG compression are you applying? It will tend to blur the detail a little if you're heavy handed with compression.

Where are you uploading to?

You may find that your web host re-compresses the file. Especially, if they're producing re-sized versions.


A simple test: If you're happy with an image, upload the file. Keep a copy.

Download the one you've uploaded. If the file sizes are different, then the file's been modified. (or do an overlay in Photoshop with the layer blend mode set to 'Difference' to see what's changed)

 

[GSDlover4ever]

I am uploading to: flickr, it seems to change the size of my image slightly and sharpen it also.
With regards to compression, i usually use medium compression of about 5/6.

I must be doing something wrong... when i resize an image as their is a drastic change from the edited image that has been flattened and saved as jpeg to a resized image, a lot of the detail.... is lost.

 

[Musicman]

I just had a quick peek at your Flickr photostream. TBH, they don't look too bad to me, but I can see what you mean about the sharpening.

However, I notice you're uploading at 650 pixels or thereabouts, which is a curious choice and delicately close to 640, but not exactly 640 pixels.

When Flickr resizes to the new 640 pixel standard from an original that's 650 pixels wide, it's going to produce a lot of rounding errors in the scaling and exaggerate any breakdown of detail due to the JPEG compression. Bear in mind that this is a file that's already been resized once from a much larger master.

I think they also apply some sharpening when doing the downsize - in the same way that Photoshop recommends when you resize due to the rounding errors and indeed you do as you mention in your OP.

I suspect the combination of the two is why your images at 640 px look over sharpened - there's false detail being created in the resize and then that's being sharpened.

For the original size, the files you see on Flickr are exactly the ones you upload - at least in my tests they are identical byte-for-byte.

You may be better of by either:

a) uploading at 640 px so that Flickr displays your original file as uploaded on its photo page or on your front page

b) uploading at a larger size (I use 1024 px for Flickr) with a simple scale ratio vs 640 pixels to minimise resizing errors in down-scaling.

At 800 px, the scaling ratio is 0.8:1, at 1024 it's 1:0.625.

At 650 px it's 1:0.984615384615385.

You can see where the errors creep in.​

or

c) reducing the sharpening you apply to your original images.​

 

[Matt]

weve got a tutorial on resizing and saving for web use in the tutorial section, might be worth a look?