question to resolution and interpolation

[marcush]

Hi,

I use Silverfast6 with a Nikon Coolscan IV.
Trying to avoid interpolation I use resolution of 2900 dpi ,offered as "real"
hardware resolution by Coolscan IV.
However as having read here in the forum,that only using the slider
should avoid interpolation .
So can anyone tell me folllowing :

Is there a difference,between :
a) using the slider to adjust the 2900 dpi hardware resolution
b) OR to manually enter value of 2900 dpi in the according field (frame-tab )

so will we have interpolation in point b),although using the hardware-resolution of 2900 dpi ?

To having made a test I can so far not see a quality difference with eyes,
when scanning the exact same shot both with slider (2900dpi) and
additionally entering the value 2900 dpi into the field .

HOwever I noticed an other srtange thing :
colors seem not to match 100% identical ,when using in one case
slider and entering the value in other case.
The difference is pretty small ,but it`s there.
( I took the two identical original Silverfast-test shots and layerd them into
photoshop to switch between the two shots and could notice a light
difference in colors in the gray background ... ??? )

Marcus

[LSI_Noack]

Dear marcush

there is no difference in selecting a dpi setting via the slider or entering the same value manually in the dpi resolution value field.

With

However as having read here in the forum,that only using the slider
should avoid interpolation .

I guess you are refering to Gregory C's forum entry under: viewtopic.php?t=2070 which reads:

use the resolution slider and select the second-highest resolution available on the slide. don't use the highest resolution because it is not a hardware resolution; it's an interpolated resolution which in my opinion should not be included in the slider's set of available hardware resolutions.

If you read this sentence closely, you will find that Gregory did not imply that the is any actual difference between selecting the dpi setting via the slider oder entering it manually.

If you use the same resolution as your scanning hardware does have, no interpolation will occur.

Actually, I doubt the difference in color you have experienced between the two scans which should be identical. There must be some other source of influence. Are you sure that you did not change any other settings, no automatic adjustments were made, no artifacts due to operations in Photoshop occured?
Could the bulb be the problem?

Yours sincerely
Sonny

[marcush]

Sonny,

Well - I was refering to several threads dealing with this subject ,but
that`s in deed good to hear ,there is no difference between
entering dpi value or going via slider.

Unfortunately the color as well as brightness are not exactly 100% identical,when making two scans from same prescan
(without changing anything) The difference is very little,but it would interest me,why it comes ???

I did not set any automatic adjustments ( switched them ALL off ) and took precisely notice of all the basic adjustments
between Photoshop and SilverFast.
I mainly scan negatives and create both own profiles and film-mask parameter ( by the way in my opinion many of your
profiles looking too contrasty, especially under studio-conditions )

Marcus

[LSI_Noack]

Dear marcush

I found I should add something to my statement above - what I said was for a given case: Entering a value in the dpi form manually that does exist on the slider.

However, you can enter values manually you cannot set by the slider: Please note that the slider set hardware resolutions. If you manually enter a value not supported by the hardware it will necessarily be an interpolated value.
Hold down the CTRL key to see the hardware res used by SilverFast.

[Gregory C]

hardware resolutions are preset by the hardware and usually increase geometrically; 30, 60, 120, 240, etc. 2900 doesn't sound like a likely hardware resolution. as Noack mentioned, the slider will only give you hardware resolution choices (except for the highest one). is 2900 available via the slider?

if the resolution you specify is not a hardware resolution, SF will select the next higher hardware resolution and down-sample to your specified resolution.