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Old Apr 8, 2004, 11:15 PM   #1
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Default Resizing for web sharing

Well I thought it was a good idea but apparently not.
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Old Apr 9, 2004, 7:18 AM   #2
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I've recently changed the image size that I post. That has helped some, just because I have less data. Makes my image a bit less impressive some times.... but that is the trade off for making the dialup user happy. I still have nightmares of when I was stuck with 24k dialup for about 5 years (line sharing within that part of town.)

I also limit to about 120K for a picture size as well. Luckly PhotoShop CS has an option to automatically reduce an image to a specific size so it isn't hard to get there.

png is a good open fileformat with good compression. Its a good choice after jpg.

Eric
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Old Apr 9, 2004, 8:50 PM   #3
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Having moved to the country with a 26.4K bps connection (the old line through the swamp might be replaced this sumer), I just skip over most posts with an image much over 50Kbytes. Since the best dial-up is less than twice my speed, and about half the people connected are on dial up, you should figure that by putting up large images you have about half the people skipping your images.

Doesn't matter how few artifacts there are, lots of folks are not going to look at them if they are large.
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Old Apr 10, 2004, 10:46 PM   #4
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ImKayd1

I am sorry, but you are wrong.

Get properties of both those images and you will see that they are not the same number of bytes. That is the size that really matters... the amount of data actually sent.

The first one is 42,754 bytes.
The second one is 233,115 bytes.

On my cable modem this is easy to handle. For BillDrew, that would take about 10 seconds to load (compared to less than 2 seconds for the first picture.) 200K is a large file for dialup.

You can find special cases to break this rule, but I'd say about 80% of all pictures will compress MUCH more with jpg. It basically damages/alters the picture so it compresses better. I know of no algorithm that compresses better than it.... It wasn't designed for image quality, it was designed for minimum size.

Eric

ps. Nice pictures, BTW. Good use of multiple flowers, they complement each other very well.
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Old Apr 11, 2004, 8:32 AM   #5
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Default I use 50-80% jpg quality for posts. What do you think?

Here's your original 42K JPG:


Here's the same photo, compressed to 80% quality (26K):


And here's the same photo, compressed to 50% quality (15K):


For the digital camera forum, I'd recommend using the compression method that has the smallest filesize without any reduction in photo quality. You pick the one that works best for you...web posting gives you a much greater tolerance for compression than print photos.

For posting most of our scouting pics on our troop website, I used 50%. Please note, however, that the larger the picture the more noticeable the compression artifacts. Consider also the audience of your pics...posting 800x600 pics at 50% compression would not be acceptable here in the digicam forum, but I have had no complaints from those in the Scouting community- most appreciate being able to see full screen shots of their boys in action. Food for thought!
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Old Apr 11, 2004, 8:48 AM   #6
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Just timed the download: about 15 seconds for the JPEG and about 90 seconds for the PNG. That does include a bit of time for Netscape to open a new tab. Keep in mind that bps is Bits Per Second, not Bytes per second and that there are more than 8 bits per byte since there are various parity/stop/start/handshaking/... bits as well as the bits/bytes in the image.

I am connected at 24.0K bps this morning: a bit slower than my normal 26.4k bps.
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Old Apr 13, 2004, 4:45 PM   #7
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I too am in a rural area with dailup and maximum of around 26K. Reducing the file size depends on at least three processes - cropping, resizing and degree of compression (or format selection). It also depends on other things, but they begin to drift away from a general purpose answer to more specialized circumstances.

I've done a little experimenting, and found that for my need for quality in looking at web photos, for most purposes, I do the following, in this order: (1) crop - hopefully creatively to improve the composition; (2) make whatever adjustments are needed (brightness, contrast, gamma, color balance, etc.); (3) reducing the image size so that the larger dimension is 640 - maintain aspect so that he other dimension is proportional; (4) save to JPEG at 70% quality. This generally will get me images in the range of about 50-75 KB depending on the actual crop dimensions.

For example, if I crop square, 640x640, file size would be greater. I did a quick test on a dowloaded A1 picture from Steve's A1 Review sample pictures. Resizing from 2560x1920 (3.1MB JPEG file) to 640x480 and saving at 75% gave me a 53 KB file with good enough quality for most purposes. Cropping to square at 1920x1920, then resizing to 640x640 and saving at 75% gave a 56 KB file - maybe somebody who knows JPEG can comment on why it wasn't proportional to the 53 KB 640 x 480.

Also, unless I have a reason to do otherwise, I don't bother to save the metadata - the information saved in the JPEG header. Don't know how much that saves, but I think some of the JPEG size optimizers available as freeware do it by stripping the header data.

This, of course, only addresses size, not quality. The acceptable level of quality can only be set by you - "eye of the beholder thingy." I keep saying "for most purposes" above. For some purposes - for example, sample pctures for comparison among cameras - it is necessary to provide the best possible image, so the image, as downloaded from the camera may be the best solution and those who need the large file can afford to wait for it.

That said, most of my posted pictures are in a gallery on a server not generally available to the public, and intended only for the use of my family for posting snapshots. My son - with his DSL - posts his full resolution Canon S400 shots and the gallery software makes the usual thumbnail, mid-resolution and full resolution images available. I post my 640/75% images only, and had no complaints. Works for me,

Therefore, I guess the answer to the question of optimum processing for web pics is as with most questions...it depends!
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Old Apr 29, 2004, 3:30 AM   #8
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Being also on dial-up, I also appreciate those who keep images within reason...maybe 50-100K per pix...depending on usage...I use IrFanView to resize/downsize for my website, keeping originals for use when needed...a quick loading but slightly less clear image seems to be more desireable, especially to us dial-ups!
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Old Apr 29, 2004, 3:54 AM   #9
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Nothing stops you linking to a higher size (bit) image - so people can choose to download a better quality version.

Most ISP's give some webspace, and theres a veriaty of online picture sharing websites.

Even though I'm always connected at at least 512kbps I deplore wastefull websites and threads which dont at least warn non 56k friendly pics etc.
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Old Jul 7, 2004, 3:28 PM   #10
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oh oh..
I keep all my pictures I post at about 100 kb, now I know that you won't ever open a thread where I post pictures, BillDrew. And I thought almost everybody has at least 768kbit downstream.

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