Thanks. Very helpful explanation. I've always used .jpg almost
exclusively and never noticed any degradation when editing.
Guess I'll have to re-learn everything I thought I knew ;)
Never did understand the need for 3, 5, 8, 10 or larger megapixel cameras.
I take all my snapshots at about 1/2 megapixel jpg and then crop and
further resize everything down to about 1/4th the original size, and I
can't tell any difference in image quality, even with a jeweler's loop.
I've sometimes printed an original and a resized smaller version at Costco
and asked people to tell me which is better, and I've never found anyone
who could tell any difference.
People send these 3-megapixel (and bigger) images to me all the time and
they are really slow to load. So, I've always used imagemagick 'convert'
to bulk resize everything to about 1-20th the original size and they all
look the same to me.
On a recent vacation, I took more than 1,000 snapshots and by resizing
them, they all fit on a single CD with lots of room to spare. I also
upload our travel pix to a web page for our family to view online and by
reducing the image size, all the images load and display very quickly and
beautifully online. With 3+meg image files it would take 20 times more
bandwidth and 20 times longer to load and display.
So, I just don't understand the benefit of keeping snapshots in gigantic
image file sizes.
-------
> TL;DR,
> If you just want to have an image you can view and you want a smaller
> file size, then use JPEG and don't edit it.
> If you want to edit the image or it's very small and speed of display is
> important, use PNG.
>
> The two file formats are quite different:
> PNG is *lossless* which means that you can edit, adjust, etc... the file
> without losing any image data. It stores all of the data in compressed
> form, so it's larger, but everything from the original image is still
> present.
> JPEG is *lossy* it actually discards around 90% of the image data, so you
> can't edit a JPEG without losing some of the image quality; by the third
> or fourth edit a JPEG gets pretty bad. It also uses some fairly complex
> math to store and reconstruct the image, so it's much more computationally
> intensive to view a JPEG compared to a PNG.
> The system (generally) uses PNG for thumbnails because (for small images)
> PNG is generally faster to create and faster to load due to less
> computation needed to compress/decompress data versus reconstructing an
> image from mathematical models.
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%0A>%20%0A>%20Never%20did%20understand%20the%20need%20for%203,%205,%208,%2010%20or%20larger%20megapixel%20cameras.%0A>%20%0A>%20I%20take%20all%20my%20snapshots%20at%20about%201/2%20megapixel%20jpg%20and%20then%20crop%20and%0A>%20further%20resize%20everything%20down%20to%20about%201/4th%20the%20original%20size,%20and%20I%0A>%20can't%20tell%20any%20difference%20in%20image%20quality,%20even%20with%20a%20jeweler's%20loop.%20%0A>%20I've%20sometimes%20printed%20an%20original%20and%20a%20resized%20smaller%20version%20at%20Costco%0A>%20and%20asked%20people%20to%20tell%20me%20which%20is%20better,%20and%20I've%20never%20found%20anyone%0A>%20who%20could%20tell%20any%20difference.%0A>%20%0A>%20People%20send%20these%203-megapixel%20(and%20bigger)%20images%20to%20me%20all%20the%20time%20and%0A>%20they%20are%20really%20slow%20to%20load.%20So,%20I've%20always%20used%20imagemagick%20'convert'%0A>%20to%20bulk%20resize%20everything%20to%20about%201-20th%20the%20original%20size%20and%20they%20all%0A>%20look%20the%20same%20to%20me.%0A>%20%0A>%20On%20a%20recent%20vacation,%20I%20took%20more%20than%201,000%20snapshots%20and%20by%20resizing%0A>%20them,%20they%20all%20fit%20on%20a%20single%20CD%20with%20lots%20of%20room%20to%20spare.%20I%20also%0A>%20upload%20our%20travel%20pix%20to%20a%20web%20page%20for%20our%20family%20to%20view%20online%20and%20by%0A>%20reducing%20the%20image%20size,%20all%20the%20images%20load%20and%20display%20very%20quickly%20and%0A>%20beautifully%20online.%20%20With%203+meg%20image%20files%20it%20would%20take%2020%20times%20more%0A>%20bandwidth%20and%2020%20times%20longer%20to%20load%20and%20display.%0A>%20%0A>%20So,%20I%20just%20don't%20understand%20the%20benefit%20of%20keeping%20snapshots%20in%20gigantic%0A>%20image%20file%20sizes.%0A>%20%0A>%20%0A>%20-------%0A>%20>%20TL;DR,%0A>%20>%20%20%20If%20you%20just%20want%20to%20have%20an%20image%20you%20can%20view%20and%20you%20want%20a%20smaller%0A>%20>%20file%20size,%20then%20use%20JPEG%20and%20don't%20edit%20it.%0A>%20>%20%20%20If%20you%20want%20to%20edit%20the%20image%20or%20it's%20very%20small%20and%20speed%20of%20display%20is%0A>%20>%20important,%20use%20PNG.%0A>%20>%0A>%20>%20The%20two%20file%20formats%20are%20quite%20different:%0A>%20>%20PNG%20is%20*lossless*%20which%20means%20that%20you%20can%20edit,%20adjust,%20etc...%20the%20file%0A>%20>%20without%20losing%20any%20image%20data.%20%20It%20stores%20all%20of%20the%20data%20in%20compressed%0A>%20>%20form,%20so%20it's%20larger,%20but%20everything%20from%20the%20original%20image%20is%20still%0A>%20>%20present.%0A>%20>%20JPEG%20is%20*lossy*%20it%20actually%20discards%20around%2090%%20of%20the%20image%20data,%20so%20you%0A>%20>%20can't%20edit%20a%20JPEG%20without%20losing%20some%20of%20the%20image%20quality;%20by%20the%20third%0A>%20>%20or%20fourth%20edit%20a%20JPEG%20gets%20pretty%20bad.%20%20It%20also%20uses%20some%20fairly%20complex%0A>%20>%20math%20to%20store%20and%20reconstruct%20the%20image,%20so%20it's%20much%20more%20computationally%0A>%20>%20intensive%20to%20view%20a%20JPEG%20compared%20to%20a%20PNG.%0A>%20>%20The%20system%20(generally)%20uses%20PNG%20for%20thumbnails%20because%20(for%20small%20images)%0A>%20>%20PNG%20is%20generally%20faster%20to%20create%20and%20faster%20to%20load%20due%20to%20less%0A>%20>%20computation%20needed%20to%20compress/decompress%20data%20versus%20reconstructing%20an%0A>%20>%20image%20from%20mathematical%20models.%0A>%20%0A>%20%0A>%20%0A>%20---------------------------------------------------%0A>%20PLUG-discuss%20mailing%20list%20-%20PLUG-discuss@lists.plug.phoenix.az.us%0A>%20To%20subscribe,%20unsubscribe,%20or%20to%20change%20your%20mail%20settings:%0A>%20http://lists.PLUG.phoenix.az.us/mailman/listinfo/plug-discuss%0A>%20%0A>%20 "Reply to this message")
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