What you're calling FastStone's assessment of the image quality is
actually a measure of the JPEG compression level. There doesn't really
appear to be any standard by which JPEG compression is measured. Some,
like FastStone, appear to be using a percentage from 1-100 but exactly
what that means I don't think is defined. Photoshop uses a range of
quality levels specified as integers between 1 and 12 but it then groups
those values into quality ranges.
So, whatever value FastStone is using has nothing to do with what you or
the camera or the lens produced. It has everything to do with the
degree of image compression used when the image was created or saved as
a JPEG after editing. You would probably have a hard time
distinguishing between two copies of the same image... saved with
different compression levels such that FastStone reports one of them as
80% and the other as 90%. Unless a lossless compression method is
chosen (possible) the quality level of a JPEG will always be reported as
less than 100.
Chuck Norcutt
On 5/19/2016 6:54 AM, bj@xxxxxxxxxxxxxxx wrote:
Chuck wrote;
What I think it that you worry too much. Your images
look just fine to
me. Take the image with the sheep, for example (an
E-M5 image). There
are thousands and thousands of blades of grass in
the foreground. Even
though they can only be a pixel or two wide
they're well resolved at
100%. What more do you want?
And I have no
idea what you're talking about when you say FastStone
gives you an
image quality rating. Stepping through the menus I can't
find any such
thing in FastStone and it certainly isn't mentioned in the
(incomplete)
help manual.
Chuck Norcutt
Re: Image quality rating. When you are
looking at an image in FastStone and for whatever reason - maybe you
gave manipulated the image - you wish to save the file in another
directory; with the cursor somewhere within the image, do <right-click>.
This brings up a menu.
Choose <save as> (In the same menu is the
colors option which includes sharpen/blur).
This brings up another
menu which shows at the top, the current directory location, and you can
from there choose another location.
It also shows the file name, and
you have the opportunity to change that to whatever you want.
Lower
down it shows the FastStone assessment of file quality as a percentage -
usually lower than 100 !
You are also given options. Click on OPTIONS
and you can reduce the file size using a slider AND if you give it a
little time it will tell you the new file 'quality %' assessment along
with the size of the chosen new file. When you are happy with your
choice (which you can reverse and go back at this point in time), you
can save in the previously chosen location.
Re: what more do I want?
Now that I have found I had the image quality set at less than optimum
(my fault - not that of the camera-lens combo), if the weather is not
too unkind tomorrow, I will try and demonstrate, using better
techniques. I will not be able to repeat those M5 images because in the
few days since I took them we have had windy wet weather which has
defoliated those particular trees. I will search for examples as similar
as I can find, in respect of colour, illumination and size. The weather
forecast for tomorrow is for more crap weather with wind and rain for
about 4 hours (after today being fine and sunny).
Cheers, Brian
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