PNG vs JPG

VeijoM · 03-07-2009, 08:36 AM

Hi!

Is PNG-format used widely, or not at all, or something between, in web? I usually always see JPG pics in the web, and don't remember seeing a PNG file. Some might argue that JPG is usually ok for web, but would I find much "resistance" if trying to use PNG. Does different discussion forums (like PF) or photo sites (flickr, pbase etc.) allow use of PNG? Are there still problems with browsers? I would most likely use the better format if both are possible to use?

-Veijo-

Wheatfield · 03-07-2009, 09:23 AM

PNGs just never seemed to catch on. In theory, they are better than jpegs, but they are also larger files. I don't know what sort of support they have in the browser industry either.
Best is to just stay with jpegs, it's not like as if it makes enough of a difference to the viewer to matter.

chiem · 03-07-2009, 12:55 PM

It's not really a matter of which one being better. PNG is sort of the replacement for GIF, it's non-lossy, while JPG is lossy. PNG's adoption has been slow because of poor support from Internet Explorer for a long time. Wikipedia has a good article on PNG (and comparison with JPG), but to summarize:

- if you're editing an image in multiple steps, you'd want to save it in a non-lossy format. Each time you load and save a JPG image, you're losing quality.

- JPG works well on images where the color change between pixels tends to be gradual--such as any real life photo.

- JPG compresses poorly on images with lots of high contrast between pixels, such as a picture of a white background with lots of black lines in it. Screenshots, comics, etc. tend to store better as PNG.

rpriedhorsky · 03-07-2009, 01:10 PM

PNGs are very widely supported. Any modern browser can display them and any halfway competent image program can read/write them.

The difference is the compression. PNG uses lossless compression (all data is preserved), while JPEG uses lossy compression (throws away data you hopefully won't notice is missing) designed for photographs. (The acronym, in fact, expands to Joint Photographic Experts Group.) The tradeoff is fidelity to the original image vs. file size.

Rule of thumb: if you have an image which is a photo or something similar, and all editing is complete, and you want a small file that is easily shared, JPEG is appropriate. Otherwise, JPEG is the wrong choice.

In particular, JPEG is inappropriate for images which aren't photos or similar. You'll get visible compression artifacts and look stupid.

PNGs are also easily shared, but the PNG compression algorithm doesn't work very well on photos, so the files are big. JPEGs are generally much smaller (5-10x) and the compression artifacts are rarely a problem. For web stuff, don't worry about it; if I were submitting a good photo for a good print, I might send it as a PNG.

PNG is more like TIFF than JPEG. However, TIFF is an extraordinarily complex format with all sorts of weird extensions, so it's not as portable. If two programs "support" TIFF, you never know what they really mean. No one fully supports TIFF.

Here's Wikipedia's take on the comparison. There's a good illustration.

HTH,

Reid

**RobA_Oz** · 03-07-2009, 02:42 PM

Originally posted by Wheatfield

PNGs just never seemed to catch on. In theory, they are better than jpegs, but they are also larger files. I don't know what sort of support they have in the browser industry either.
Best is to just stay with jpegs, it's not like as if it makes enough of a difference to the viewer to matter.

I wouldn't put it like that, myself. I think it's fair to say that it's taking a while to catch on (if it ever does, in the way that JPEGs have). As processor speed rises and memory and HDD capacities increase, with parallel falls in prices, the size advantage of JPEG will continue to decrease in importance for the bulk of users.

Admittedly, though, it takes a while to jog people out of old habits, particularly Microsoft, whose support for PNG is probably key to its widespread adoption. The only trouble with that scenario is that, if they're true to past form, they'll probably try to "improve" it so they can stop anyone else using it.

Emotive45 · 03-07-2009, 04:46 PM

jpeg or gif for web is better - the lower the res the faster it loads. No one wants to wait whilst a picture downloads so the largest image should always be no more than 500 pixels on the longest side, this also makes stealing your work a little pointless as blown up for any other purpose it pixelates and is useless. so the smaller the better. You need to save in a format that will work across all browsers and open on all clients machines for viewing when work is done on an image. Those two being fully compatible with all across both pc and mac systems.

jpeg or gif best for design with fewer colours in, preferaby gif which can also allow a translucent background better suited for web pages.

tif is something I generally use when still working on an image as their is no loss in resolution. I shoot in raw and if something like a composite is being made, you adjust each image to suit, and save as a tif for better quality. With tif you can either save the file with all the layers like a psd or flatten it. sometimes it's necessary to do that if you don't want to reduce to 8 bit whilst your working on something in 16 bit. don't know about any other pp program but in photoshop you cannot convert a 16 bit raw to a jpeg until you have reduced the file to 8bit, and generally the only time your going to want to have something in jpeg format is if you have completed everything on it and need to save it for either print or web etc.

SpecialK · 03-07-2009, 08:23 PM

Quote:

Is PNG-format used widely, or not at all, or something between, in web? I usually always see JPG pics in the web, and don't remember seeing a PNG file.

I think you answered your own question :-)

RioRico · 03-08-2009, 01:16 AM

Many websites have substituted PNGs for GIFs for their misc images - icons, frames, buttons, etc. This happened because GIF* is a proprietary format, and the 'owner' has made occasional noises about assessing royalties. PNG is open-source and thus 'forever' free. Many many Wikipedia images are PNGs.

If you use MSIE (Internet Explorer) you can search your "Temporary Internet Files" folder; you'll likely find a few BMPs, many PNGs, many GIFs, and many many JPGs. If you use any Mozilla browser, it's trickier, as the extensions aren't saved with the hashed temp filenames. The great XnView image browser can read MSIE and Mozilla caches, and find and display all graphic files, and tell you the formats. (I don't know if XnView works with Mac or *nix systems.)

As was mentioned, PNG and GIF* and TIFF are lossless formats, safe but fat. JPEG is lossy, no matter how little compression you specify - you do NOT want to do multiple edits on a JPG file, unless you like pixelation and noise.

Class A · 03-08-2009, 03:57 AM

PNG is an improvement over GIF. As the GIF format (and unlike JPEG) it supports transparent backgrounds but it supports much higher colour depths than GIF (which is 8 bit = 256 colours only).

VeijoM · 03-08-2009, 08:04 AM

Glad to hear that photographically enthusiastic people feel that JPGs are ok for web usage (showing pics to one another).

-Veijo-

Erik · 03-08-2009, 01:25 PM

PNG is not for photos, unless you need lossless compression on the web. PNG is for web graphics and replaces (in an ideal world) GIF completely. PNG has support for alpha channels -- i.e. not just transparency, but partial transparency, so you can do things like drop shadows.

GIF is a hopelessly dated 1980's proprietary format that has urgently needed to disappear for at least a decade now, but due to Internet Explorer having absolutely garbage support for PNG until the very latest versions, it has not been as widely adopted as hoped.

If you used PNG for hi-res photos on the web you would get files that are about ten times as large as they need to be. Don't.

Arpe · 03-08-2009, 04:21 PM

Originally posted by RobA_Oz

Admittedly, though, it takes a while to jog people out of old habits, particularly Microsoft, whose support for PNG is probably key to its widespread adoption. The only trouble with that scenario is that, if they're true to past form, they'll probably try to "improve" it so they can stop anyone else using it.

MS already have their own "HD" format. You can download a Photoshop plug-in from MS somewhere. It can be lossless or lossy, your choice.

03-07-2009, 08:36 AM	#1
VeijoM Inactive Account Join Date: Jul 2007 Location: Helsinki, Finland Posts: 21	PNG vs JPG Hi! Is PNG-format used widely, or not at all, or something between, in web? I usually always see JPG pics in the web, and don't remember seeing a PNG file. Some might argue that JPG is usually ok for web, but would I find much "resistance" if trying to use PNG. Does different discussion forums (like PF) or photo sites (flickr, pbase etc.) allow use of PNG? Are there still problems with browsers? I would most likely use the better format if both are possible to use? -Veijo-

03-08-2009, 08:04 AM	#10
VeijoM Inactive Account Join Date: Jul 2007 Location: Helsinki, Finland Posts: 21 Original Poster	Thanks everyone for commenting Glad to hear that photographically enthusiastic people feel that JPGs are ok for web usage (showing pics to one another). -Veijo-

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03-07-2009, 09:23 AM	#2
Wheatfield Moderator Join Date: Apr 2008 Location: The wheatfields of Canada Posts: 15,986	PNGs just never seemed to catch on. In theory, they are better than jpegs, but they are also larger files. I don't know what sort of support they have in the browser industry either. Best is to just stay with jpegs, it's not like as if it makes enough of a difference to the viewer to matter.

03-07-2009, 12:55 PM	#3
chiem Forum Member Join Date: Dec 2008 Location: Cupertino, CA Posts: 54	It's not really a matter of which one being better. PNG is sort of the replacement for GIF, it's non-lossy, while JPG is lossy. PNG's adoption has been slow because of poor support from Internet Explorer for a long time. Wikipedia has a good article on PNG (and comparison with JPG), but to summarize: - if you're editing an image in multiple steps, you'd want to save it in a non-lossy format. Each time you load and save a JPG image, you're losing quality. - JPG works well on images where the color change between pixels tends to be gradual--such as any real life photo. - JPG compresses poorly on images with lots of high contrast between pixels, such as a picture of a white background with lots of black lines in it. Screenshots, comics, etc. tend to store better as PNG.

03-07-2009, 01:10 PM	#4
rpriedhorsky Senior Member Join Date: Dec 2008 Location: Minneapolis Posts: 210	PNGs are very widely supported. Any modern browser can display them and any halfway competent image program can read/write them. The difference is the compression. PNG uses lossless compression (all data is preserved), while JPEG uses lossy compression (throws away data you hopefully won't notice is missing) designed for photographs. (The acronym, in fact, expands to Joint Photographic Experts Group.) The tradeoff is fidelity to the original image vs. file size. Rule of thumb: if you have an image which is a photo or something similar, and all editing is complete, and you want a small file that is easily shared, JPEG is appropriate. Otherwise, JPEG is the wrong choice. In particular, JPEG is inappropriate for images which aren't photos or similar. You'll get visible compression artifacts and look stupid. PNGs are also easily shared, but the PNG compression algorithm doesn't work very well on photos, so the files are big. JPEGs are generally much smaller (5-10x) and the compression artifacts are rarely a problem. For web stuff, don't worry about it; if I were submitting a good photo for a good print, I might send it as a PNG. PNG is more like TIFF than JPEG. However, TIFF is an extraordinarily complex format with all sorts of weird extensions, so it's not as portable. If two programs "support" TIFF, you never know what they really mean. No one fully supports TIFF. Here's Wikipedia's take on the comparison. There's a good illustration. HTH, Reid

03-07-2009, 02:42 PM	#5
RobA_Oz Site Supporter Join Date: Nov 2008 Location: Tasmania, Australia Photos: Gallery Posts: 8,200	Originally posted by Wheatfield PNGs just never seemed to catch on. In theory, they are better than jpegs, but they are also larger files. I don't know what sort of support they have in the browser industry either. Best is to just stay with jpegs, it's not like as if it makes enough of a difference to the viewer to matter. I wouldn't put it like that, myself. I think it's fair to say that it's taking a while to catch on (if it ever does, in the way that JPEGs have). As processor speed rises and memory and HDD capacities increase, with parallel falls in prices, the size advantage of JPEG will continue to decrease in importance for the bulk of users. Admittedly, though, it takes a while to jog people out of old habits, particularly Microsoft, whose support for PNG is probably key to its widespread adoption. The only trouble with that scenario is that, if they're true to past form, they'll probably try to "improve" it so they can stop anyone else using it.

03-07-2009, 04:46 PM	#6
Emotive45 Inactive Account Join Date: Feb 2009 Posts: 67	jpeg or gif for web is better - the lower the res the faster it loads. No one wants to wait whilst a picture downloads so the largest image should always be no more than 500 pixels on the longest side, this also makes stealing your work a little pointless as blown up for any other purpose it pixelates and is useless. so the smaller the better. You need to save in a format that will work across all browsers and open on all clients machines for viewing when work is done on an image. Those two being fully compatible with all across both pc and mac systems. jpeg or gif best for design with fewer colours in, preferaby gif which can also allow a translucent background better suited for web pages. tif is something I generally use when still working on an image as their is no loss in resolution. I shoot in raw and if something like a composite is being made, you adjust each image to suit, and save as a tif for better quality. With tif you can either save the file with all the layers like a psd or flatten it. sometimes it's necessary to do that if you don't want to reduce to 8 bit whilst your working on something in 16 bit. don't know about any other pp program but in photoshop you cannot convert a 16 bit raw to a jpeg until you have reduced the file to 8bit, and generally the only time your going to want to have something in jpeg format is if you have completed everything on it and need to save it for either print or web etc.

03-07-2009, 08:23 PM	#7
SpecialK Pentaxian Join Date: Dec 2006 Location: So California Photos: Gallery Posts: 16,481	Quote: Is PNG-format used widely, or not at all, or something between, in web? I usually always see JPG pics in the web, and don't remember seeing a PNG file. I think you answered your own question :-)

03-08-2009, 01:16 AM	#8
RioRico Veteran Member Join Date: Jun 2008 Location: Limbo, California Posts: 11,263	Many websites have substituted PNGs for GIFs for their misc images - icons, frames, buttons, etc. This happened because GIF* is a proprietary format, and the 'owner' has made occasional noises about assessing royalties. PNG is open-source and thus 'forever' free. Many many Wikipedia images are PNGs. If you use MSIE (Internet Explorer) you can search your "Temporary Internet Files" folder; you'll likely find a few BMPs, many PNGs, many GIFs, and many many JPGs. If you use any Mozilla browser, it's trickier, as the extensions aren't saved with the hashed temp filenames. The great XnView image browser can read MSIE and Mozilla caches, and find and display all graphic files, and tell you the formats. (I don't know if XnView works with Mac or nix systems.) As was mentioned, PNG and GIF and TIFF are lossless formats, safe but fat. JPEG is lossy, no matter how little compression you specify - you do NOT want to do multiple edits on a JPG file, unless you like pixelation and noise.

03-08-2009, 03:57 AM	#9
Class A Pentaxian Join Date: Aug 2008 Location: Wellington, New Zealand Posts: 11,251	PNG is an improvement over GIF. As the GIF format (and unlike JPEG) it supports transparent backgrounds but it supports much higher colour depths than GIF (which is 8 bit = 256 colours only).

03-08-2009, 01:25 PM	#11
Erik Veteran Member Join Date: Nov 2008 Location: Umeå, Sweden Posts: 755	PNG is not for photos, unless you need lossless compression on the web. PNG is for web graphics and replaces (in an ideal world) GIF completely. PNG has support for alpha channels -- i.e. not just transparency, but partial transparency, so you can do things like drop shadows. GIF is a hopelessly dated 1980's proprietary format that has urgently needed to disappear for at least a decade now, but due to Internet Explorer having absolutely garbage support for PNG until the very latest versions, it has not been as widely adopted as hoped. If you used PNG for hi-res photos on the web you would get files that are about ten times as large as they need to be. Don't.

03-08-2009, 04:21 PM	#12
Arpe Pentaxian Join Date: Sep 2006 Location: New Zealand Photos: Gallery \| Albums Posts: 4,452	Originally posted by RobA_Oz Admittedly, though, it takes a while to jog people out of old habits, particularly Microsoft, whose support for PNG is probably key to its widespread adoption. The only trouble with that scenario is that, if they're true to past form, they'll probably try to "improve" it so they can stop anyone else using it. MS already have their own "HD" format. You can download a Photoshop plug-in from MS somewhere. It can be lossless or lossy, your choice.