how much quality is lost when i save in jpg rather than png format

[Duzzy]

An interesting experiment is to take an image, and save to a new name, and compare the quality of the images, (setting the compression to high will speed up the process).

To add to this, more compression equals lower quality and smaller files, less compression equals better quality and larger files.

@Barman

set the snipping tool JPEG settings to highest to retain as much detail as possible.

Can you do that with the snipping tool, how?

 

[jturk]

Saving a file from the snipping tool to JPEG, which you are not going to edit is OK as the JPEG compression process is only performed once, thogh it will degrade to some extent, set the snipping tool JPEG settings to highest to retain as much detail as possible.

it sounds like you have already answered this but i want to be clear. i dont plan to edit any images once ive saved them. that being said, how much will saving in a jpg rather than png "degrade" the image?

also, how do you set the snipping tool jpg settings to retain as much detail as possible?

thank you.

 

[Influx]

, every edit and save as a JPEG file will have a detrimental effect on image quality.

wow, thanks barman, that i never knew. any reason why this happens -- short explanation ? lol

a Jpeg image discards information that is deemed to be un-necessary for the human eye to "see the image", this reduces the size, but also removes subtle detail. As this process is repeated every time a file is saved, the image quality is reduced each time.

An interesting experiment is to take an image, and save to a new name, and compare the quality of the images, (setting the compression to high will speed up the process).

When the jpeg system was developed the web was young and image quality was low so this loss was not really an issue, but today with high bandwidth, and HD screens the compression can be noticeable with "artefacts", (stray pixels and blocky images).

If you wish to retain quality for the web, the PNG image which has a better lossless compression is the way to go.

I do keep Jpeg images from my own camera but the system I use keeps a master copy, and a list of changes and "publishes" a copy for upload as required. A lot of my original images are stored as digital negatives (Raw), format which creates huge files but can be edited continuously without detail loss.

Hope that's short & simple enough, unfortunately image compression is a complex subject

I agree. Interesting and Great Information. JPEG is still widely used on animations, gfxs though.

 

[ignatzatsonic]

it sounds like you have already answered this but i want to be clear. i dont plan to edit any images once ive saved them. that being said, how much will saving in a jpg rather than png "degrade" the image?

Take a few jpegs and play with them as a test.

Do some minor editing and save as jpeg. Reopen this edited jpeg, do more minor editing, and resave. Etc.

Go back to the original, do the same minor editing you did on the jpeg, and save as png. Reopen the edited png, do more minor editing like you did on the jpeg, and resave as png, Etc.

If you re-edit the jpeg a number of cycles, the defects will become visible, particularly under a zoom. Aging eyes or a small low resolution monitor are more forgiving.

It plays hell with wallpaper. If you are fussy about wallpaper and do a lot of cropping and editing to get them just right, make all saves in a lossless format--png, tiff, bmp.

 

[Qdos]

In photo editing programs you can choose the amount of compression on JPG images.

By default it's often set at 30%, you can adjust it to nil however.

That way editing is effectively lossless

 

[Barman58]

An interesting experiment is to take an image, and save to a new name, and compare the quality of the images, (setting the compression to high will speed up the process).

To add to this, more compression equals lower quality and smaller files, less compression equals better quality and larger files.

@Barman

set the snipping tool JPEG settings to highest to retain as much detail as possible.

Can you do that with the snipping tool, how?

Sorry my bad , this is not an option in the snipping tool, though I can remember setting this so must be available in alternative applications

 

[Barman58]

Saving a file from the snipping tool to JPEG, which you are not going to edit is OK as the JPEG compression process is only performed once, thogh it will degrade to some extent, set the snipping tool JPEG settings to highest to retain as much detail as possible.

it sounds like you have already answered this but i want to be clear. i dont plan to edit any images once ive saved them. that being said, how much will saving in a jpg rather than png "degrade" the image?

also, how do you set the snipping tool jpg settings to retain as much detail as possible?

thank you.

Sorry for confusion, looks like snipping tool is fixed, One way would be to save as PNG and then use an editor to create any JPGs as required.

As for losses an example file I've just checked is 4912 x 3264 pixels and the digital negative file is 16.15MB in size, which is just over 16MB for the image (16032768 bytes), plus a little for overheads. The jpeg is only 8.5MB so almost half of the original data is missing, though of course the actual method used for compression would mean that the JPG version is not simply half as detailed but is considerably degraded. this export was done at 100 which is for maximum detail a setting of 50 gives a file just over 1MB but with visible degredation.

A useful comparison with some example images is at http://www.wfu.edu/~matthews/misc/graphics/formats/formats.html

 

[DeaconFrost]

You can't add quality to a photo, so when saving images from the web, why not just leave them in the format they are already in?

 

[FliGi7]

i want to save in png rather than jpg so that i dont lose any of the quality.

also, how much of the quality is lost by saving in jpg instead of png?

im saving pics directly from websites btw.

Why exactly are you trying to preserve the utmost quality on the downloaded images?

As an aside, if you're trying to save jpg's from the web as png's, you might want to stop and think if/how that makes sense to save an image that's already been compressed and image quality lost into a lossless format. It may make sense for you since we have no clue the reasoning behind this, but that's something to think about.

 

[gigagiggles]

"i want to save in png rather than jpg so that i dont lose any of the quality.
im saving pics directly from websites btw."

It can't be done. You're after fool's gold.

The websites' authors have already done the compression prior to placing the images onto the webpages before uploading. They took into consideration the bandwidth, traffic and browsing experience to have some loss in quality of images. If the authors decided on png's, you're in luck. If it's jpg's, then that is the format of the pictures you're saving.

 

[rraod]

Barman,

If I resave a JPG with save quality as 100% instead of standard value of 80%, will I retain the quality of image?

 

[manhunter2826]

^^thanks for that too buzzy

 

[jturk]

a few questions about jpg & png images & loss of quality......

heres what im doing....

sometimes i will save an image directly off a website or i will use the snipping tool to copy an image from a youtube video.

i am only saving them once & i am NOT editing these images & dont plan to.

here are my questions...

1. will i lose picture quality if i save in jpg format rather than png if all im doing is saving pics directly from websites or snipping images from youtube videos?

a) if i will lose picture quality, will it be noticeable?

2. is this quote accurate...
"You can't add quality to a photo, so when saving images from the web, why not just leave them in the format they are already in?"


thank you.

 

[logicearth]

It doesn't matter in the slightest. To all questions. You'll never notice any difference.

 

[Cancerous]

If the image has a transparent background, saving as .jpg will make it lose its transparency and give it a solid white background.

Quality loss is only noticeable in large images, but even then the difference isn't noticeable to an untrained eye.