XnView does'nt read properly Greyscale pictures

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floyer
Posts: 4
Joined: Tue Nov 27, 2012 7:52 am

XnView does'nt read properly Greyscale pictures

Post by floyer » Tue Nov 27, 2012 10:07 am

The Greyscale B&W pictures (8 bits) read by XnView are darker than those read by PhotoShop.
I tried to know why. My diagnosis is the following : XnView does'nt read properly Greyscale pictures.
Indeed, if I compare un greyscale chart read by PS and by XnView, I notice the following results :
read by PS / read by XnView
0 / 0
10 / 6
20 / 10
30 / 14
40 / 20
50 / 26
... / ...
100 / 65
... / ...
240 / 233
250 / 248
255 / 255

That explains the darkening !
The problem is the same with TIF or JPEG format

I located only one post about a similar problem but without solution to fix : http://newsgroup.xnview.com/viewtopic.php?f=36&t=25212

I'm using the last version (1.99.5) but the problem existed with the previous versions

Thanks a lot for your help

floyer
Posts: 4
Joined: Tue Nov 27, 2012 7:52 am

Re: XnView does'nt read properly Greyscale pictures

Post by floyer » Tue Nov 27, 2012 11:13 am

I forgot to mention that XnView is running under Windows XP SP3
Sorry

MaxSt
Posts: 133
Joined: Fri Apr 10, 2009 9:55 pm

Re: XnView does'nt read properly Greyscale pictures

Post by MaxSt » Wed Nov 28, 2012 4:07 am

PhotoShop would sometimes apply color profiles...

You should try opening your images in other programs, to be sure.

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XnTriq
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Re: XnView does'nt read properly Greyscale pictures

Post by XnTriq » Wed Nov 28, 2012 5:15 am


floyer
Posts: 4
Joined: Tue Nov 27, 2012 7:52 am

Re: XnView does'nt read properly Greyscale pictures

Post by floyer » Wed Nov 28, 2012 10:15 am

I've continued to investigate towards PS (thank to MaxSt for the idea!) and I noticed that the problem is only for the greyscale pictures resulted from a RGB to greyscale conversion done with PS. If the picture is originally a greyscale picture, PS and XnView read the picture in the same way!
Therefore, XNVIEW IS NOT RESPONSIBLE.
It's bother for me because I scan a lot of B&W negatives in RGB format and I convert in greyscale format with PS
(the conversion made by scanner is not satisfactory)
That means all my greyscale pictures converted with PS are not usable with other viewers.

Now, I must understand why PS applies such a profile when it converts, profile compensated when it reads the file.

Sorry to have you disturbed useless!

floyer
Posts: 4
Joined: Tue Nov 27, 2012 7:52 am

Re: XnView does'nt read properly Greyscale pictures

Post by floyer » Wed Nov 28, 2012 11:20 am

For those interested :
To avoid the above mentionned problem, you must modify the PS gray workspace : from "dot grain 15%" (default value) to "gray gamma 2.2"

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XnTriq
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Re: XnView does'nt read properly Greyscale pictures

Post by XnTriq » Wed Nov 28, 2012 10:00 pm

floyer wrote:For those interested :
To avoid the above mentionned problem, you must modify the PS gray workspace : from "dot grain 15%" (default value) to "gray gamma 2.2"
Thank you for reporting back, floyer (-:

FYI: Batch processing these samples
… with PngOptimizer gets rid of ICC profiles as well as gAMA chunks.

(Source files and output were inspected using TweakPNG.)

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