photoshop jpg vs nikon capture jpg

hello
i like to work out the images in photoshop, but i find out that,
when saving images as jpg, photoshop gives me almost half of
the quality of nikon capture, lets say, if photoshop gives me a file
of 5mb (at maximum quality) capture gives me a file of 10mb,

somebody knows if this is a big significance in loss of quality??

--

 

well i did tried, but at 20cmx25cm only
is kind of hard to see the diference, looks like i got better quality by
capture, but can be only my imagination, i have to wait until i can make
some proofs at 50cmx60cm, unless somebody knows by experience
regards
richard

 

Jpeg is a lossy compression format. In a nutshell it look's for pixels of
simpler hue and lightness. notes there position saves one and throws the
rest away. The setting you use dictates how close to similarity. At a low
setting and done once you can have a good image with a low file size for
posting or storing. But any further editing and saving will destroy more
detail.

Jpeg 2000 gives better results for same compression But is not as widely
supported as yet.

 

i like to work out the images in photoshop, but i find out that,

Photoshop gives you a choice of how much quality you want. What are you
choosing? How much quality are you instructing Photoshop to preserve?

More to the point: Why are you using JPEG in the first place, instead of, say,
TIFF?

 

i use jpg, because the photo lab were they print my photos they
only can make it from jpg, not with a tiff,
what i am saying is that capture can make me a better jpg rather photoshop,
and i was surprised about (i am talking of course of top qualities from both
programs)

 

Does this mean that you are getting jpegs from a Nikon camera that when
opened in PS have a file size of 10 mb
You are Then compressing them again by saving as jpeg giving a file size of
5 mb. Is that 5 mb in explorer or 5mb when opened in PS.

 

no, i use a raw file, (nef)
that file if i save it in nikon capture editor makes me
a much bigger jpg file than photoshop at maximum quality,
almost double in the "excellent" option of capture.

 

And are you opening the Nikon raw image in PS or the jpeg that you have
already saved

 

Bigger is not necessarily better. A JPEG file can contain all kinds of stuff
besides the image.

 

A common approach to compare compressed versions with the original ist
to put them into layers and stack them above each other, then setting
layer modes appropriately.

The original goes to the bottom, its layer mode is set to 'normal'.

Above the original you stack the compressed (e.g. JPEG) copies, their
layer mode each set to 'difference'.

Now you switch of every layer but the original and one of the compressed
copies. The more non-black features you see, the less fidelity in the
compressed image compared to the original.

(Two originals stacked abobe each other - topmost in difference mode -
would give you a completely black image).

Do this with each of the compressed versions. The brighter the resulting
image, the worse the compression in terms of quality.

I must note though that this method does not take into account how our
psychovisual system works, where some differences are more visible than
other differences (e.g. brightness vs. hue, hue vs. saturation). But
overall it can be helpful.

HTH,
Fred