What benefit .png over .jpg?

Fri Oct 5 01:54:11 MST 2012

Film vs Digital is a mixed bag.

Film has more dpi resolution -- more MP. Digital is a lot more flexible --
you can go from ISO 200 to ISO 16,000 and back without thinking twice. With
a 35mm camera, you shot the roll of film, and if you needed a low-light
shot and you had ISO 50, you were hosed. :)

Now that cameras like the D600 are starting to inch in on that territory (
http://kenrockwell.com/nikon/d600.htm), that may change. But film is not
going away. Photography is an artistic medium, and as such, it's
subjective. Meaning, people will always have personal opinions based on
their own preferences, and often having little to do with reality, other
than they find it fun.

(I say this as someone who owns a very-obsolete D40, and wouldn't mind
tinkering with a film one.)

People are still using pinhole cameras. Why? Because it's fun.

Note also that the professional photographer I linked to loves that camera,
because it's full-frame (a full 35mm-sized sensor, rather than a smaller
sensor with the same aspect ratio), but he still shoots it in 6MP mode.

MP are great if you're printing things that are flippin' huge and are meant
to be seen up-close. Or if you're doing work that is usually done by a
large-format camera -- the kind Ansel Adams used. For 99.999% of what
people use cameras for, 6MP is just fine.

The same website had an article for the D60 that came out and made my D40
'obsolete.' The only thing you got was 10 MP instead of 6, and a slower
sensor (100 ISO at the bottom instead of 200). But hey, it sold!

I'm guilty of falling for this fallacy to a point. I typically shoot in RAW
format. But whenever I have to send a picture to a friend, it usually goes
straight to jpeg-basic. And they're thrilled to pieces with it. I'm just
indulging in my own vices by keeping things in the 'nice' image format for
myself.

But, like Ken said. Best thing to do, if you are a shutterbug, is to not
fret over the stats, grab a camera (any camera), go out, and shoot. You
will become a much better photographer by doing that than worrying about
camera specs.

</tangent>

Adam

On 4 October 2012 21:47, Joseph Sinclair <plug-discussion at stcaz.net> wrote:

> PNG addressed two problems with GIF.
> 1) GIF is an 8-bit format with an indexed color palette.  It's possible to
> do 24-bit color by overlaying a red, green, and blue image mask, but it's
> not ideal.  PNG is true 24-bit color with better compression.
> 2) GIF was, for a time, covered by patents on it's LZW compression, held
> by UNISYS that limited it's use in many situations.  Those patents are
> expired in 2003/2004 and there is no longer any patent encumbrance for GIF
> or LZW compression.
>
> GIF has built-in support for animation, which PNG does not.  MNG provides
> animation of PNG images, and APNG provides a more recent alternative
> animation mechanism for PNG images that's easier to create but less
> efficient in compression.
>
> I definitely agree that resolution matters most when printing.  A 1080p
> screen displays a 2 megapixel image, so more than that is not usually
> helpful for onscreen display (4 megapixel is fine for the rare 4K display).
>
> I don't worry much about file size with 32G thumb drives and SD cards now
> common.  I figure 4,000 images (8 megapixel PNG) on a single thumb drive or
> SD card is more than enough storage for away-from-home use, and at home 2TB
> backup drives are pretty cheap these days.
>
> BTW, typically 48 megapixel at 32-bit color (24 bits plus 8 bit alpha) is
> considered the minimum to match 35mm film.
> The biggest remaining problem in digital is dynamic range (quality film is
> usually 3-5 stops, digital struggles to get 2).
> The resolution difference isn't considered a big deal in most print
> publications (AZ highways is an exception, for good reason), so almost all
> professional photography is currently digital capture and workflow.
>
>
> On 10/04/2012 05:29 PM, Derek Trotter wrote:
> > Higher resolution allows for printing large pictures while maintaining
> picture quality. A few years ago I saw an article in Arizona Highways
> showing why they don't accept pictures in digital format. The had two
> photos of the same tree. One taken on film and one taken with a digital
> camera at several megapixels. Both looked equally as good. Then they blew
> up a small portion of the image. The film version looked great. The digital
> version was obviously of poor quality. The article went on to say what
> resolution was needed to equal the quality of 35mm film. I forget the
> number, but it was way higher than what was commonly available at the time.
> >
> > Someone please correct me if I'm wrong, but wasn't png developed in part
> because of concerns about software patents relating to the gif format?
> >
> > On 10/4/2012 17:16, joe at actionline.com wrote:
> >> 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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