Chuck,
I appreciate your explanation of the details of this process. I see what
you are saying, and it helps me to understand what is involved. Thanks a
lot!
Jim Nichols
Tullahoma, TN USA
----- Original Message -----
From: "Chuck Norcutt" <chucknorcutt@xxxxxxxxxxxxxxxx>
To: "Olympus Camera Discussion" <olympus@xxxxxxxxxxxxxxxxx>
Sent: Saturday, March 26, 2011 11:04 PM
Subject: Re: [OM] IMG: Friday Tulip - Jim N.
>A good monitor will display 8 bits. But prints are limited to about 5-6
> bits. And, regardless of what you might have thought, 16 bits can't
> actually be seen on any device. In fact, if you feed a 16 bit image to
> your monitor it's probably being converted to 8 bits on the fly.
>
> The reason to have 16 bits is only for editing binary integers.
> Whenever you reduce the brightness of a pixel its value is divided by
> something. If the brightness range is only 8 bits and runs from 0-255
> dividing 128 by, say, 3 yields 42.667 which (since it's integer
> arithmetic) gets rounded to 43. But in 16 bit parlance the same
> brightness value is 128 x 16 = 2048. Dividing 2048 by 3 yields 682.667
> which (since it's still integer arithmetic) gets rounded to 683.
> Although both numbers got rounded to an integer the amount of precision
> lost by rounding to the nearest integer value is much smaller in the 16
> bit value.
>
> If I were to now convert 683 down to 8 bits I'd get 683/16 = 43. We end
> up with exactly that same value as if we had used 8 bits to start with.
> So, for a single adjustment there is no difference. However multiple
> brightness, contrast, saturation, etc, etc, adjustments gradually
> introduce more and more rounding errors into the 8 bit calculations.
> Using 16 bit values reduces the cumulative effects of those rounding
> errors which has a tendency to introduce spikes and the jaggies into
> histograms.
>
> So, forget 16 bits on the final, processed output. No one can see it...
> even if you think you can. :-)
>
> Chuck Norcutt
>
>
> On 3/26/2011 12:59 PM, Jim Nichols wrote:
>> Thanks for the clarification, C.H. When I save jpegs, I normally use
>> level
>> 12 in PS Elements unless the destination places a limit on file size.
>>
>> So, it appears that I can convert to 8-bit and do a final cleanup of my
>> images without losing any quality in the displayed image. That helps me
>> in
>> my decision making.
>>
>> Jim Nichols
>> Tullahoma, TN USA
>> ----- Original Message -----
>> From: "C.H.Ling"<ch_photo@xxxxxxxxxxxxx>
>> To: "Olympus Camera Discussion"<olympus@xxxxxxxxxxxxxxxxx>
>> Sent: Saturday, March 26, 2011 11:51 AM
>> Subject: Re: [OM] IMG: Friday Tulip - Jim N.
>>
>>
>>> Our monitor can only display 8 bit information (24 bit RGB). TIFFs are
>>> mostly non compressed (and not compress very well), JPEG is compressed
>>> image, some informations are lost during the compression. In many cases
>>> the
>>> quality loss is very little unless you use very high compression rate. I
>>> use
>>> level 11 in PS, I cannot distinguish its quality from TIFF.
>>>
>>> C.H.Ling
>>>
>>> ----- Original Message -----
>>> From: "Jim Nichols"<jhnichols@xxxxxxxxxxxxx>
>>>
>>>
>>>> Hi Chuck and C.H.,
>>>>
>>>> The images that I post are placed in the Leica Users Group (LUG)
>>>> gallery,
>>>> which will accept either tiff or jpeg images. The tiff image files are
>>>> much
>>>> larger than the jpegs, hence I concluded that they contained more
>>>> details,
>>>> etc. In looking at the images that I have posted recently, the tiff
>>>> images
>>>> "appear to me" to be of better quality. Perhaps this is just a
>>>> perception
>>>> that I have. For that reason, I have sometimes resisted changing them
>>>> to
>>>> 8-bit for final touch up.
>>>>
>>>> Am I mistaken? Do our monitors and prints show only what would exist
>>>> in
>>>> an
>>>> 8-bit image? I'm not enough of a techie to know how to evaluate this.
>>>>
>>>> I also save all of my RAW files, so I can, and sometimes do start over
>>>> when
>>>> I don't like my work in post-processing.
>>>>
>>>> Jim Nichols
>>>> Tullahoma, TN USA
>>> touch pixel brightness levels
>>>>>>> except for final sharpening at print resolution.
>>>>>>>
>>>>>>> If neither your display nor prints can show the 16-bit
>>>>>>> color/luminosity
>>>>>>> detail why keep it?
>>>>>>>
>>>>>>> Chuck Norcutt
>>>>>>>
>>>>>>>
>>>>>>> On 3/25/2011 6:04 PM, Jim Nichols wrote:
>>>>>>>> Thanks, Chuck. I have had a busy day, but saw that after I put it
>>>>>>>> up.
>>>>>>>> I'm
>>>>>>>> torn, at times, between the need to edit, which, in my case means
>>>>>>>> going
>>>>>>>> to
>>>>>>>> an 8-bit image, or the desire to retain more detail in a 16-bit
>>>>>>>> tiff
>>>>>>>> image.
>>>>>>>> Lately, when I can, I have been going with the tiff.
>>>>>>>>
>>>>>>>> Jim Nichols
>>>>>>>> Tullahoma, TN USA
>>>
>>> --
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>>>
>>
>>
> --
> _________________________________________________________________
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>
>
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