Ah-HA! Clipping on K-M B&W negative scans ... :)

[dmr]

Ok, here's something I just stumbled on. I was getting ready to repeat my postive vs. negative scan test on a fresh negative and I started to check over my settings when I noticed that the "exposure control for negatives" was set to "auto". I would have sworn that I had everything set to manual everything for the test, but maybe not ... Anyway ...

My first thought was along the line of {blush} oh {shoot} did I {foul} up and invalidate the test? so I set auto exposure control to off and began my B&W negative scan of the new test negative. I looked at the prescan and it was AWFUL! Contrasty as all get-out and yes, clipped!

Sanity check time, turn it back on, re-prescan - normal, good histogram. Turn it back off, prescan - ICK! Try playing with the single enabled exposure control slider, no real effect.

Below is the settings panel that has the control. For some reason they have negative exposure as buttons on the top and slide exposure as a checkbox on the side.

Also below are the two scans, the first with auto exposure off and this histogram, no level adjustment either on the scanner or in Photoshop, and then with auto exposure on, and the histogram. It looks to me like there is information missing (clipped) at both ends of the scale on the manual one, but very close to what I would consider normal.

I then did a quick scan (not hi res) as color positive both with the auto expose for slides on and off. There really didn't seem to be any difference on the positive, but for negative there sure was!

Oh well ... Learning more and more about the quirks of this thing all the time. 🙂

 

[ed1k]

Did you go to exposure control tab before final scan? You have to set exposure manually when autoexposure is off. I'm very pleased with B&W results from my K-M Dual IV, and yes I do everything manually (focus and exposure).
Eduard

 

[ed1k]

I'll add some more details:
Select image area - this affects histogramm on exposure tab;
Moving slider left or right you're changing exposure but in order to see the result of changes you did (histogram and preview) you have to click small button on right off the slider.
That's probably it.

I scan my b&w negs as colour positive (it gives me 4 sliders to play with exposure 🙂 and I don't care about colour balance here), 16 bit (gives much bigger latitude therefore forgiving for exposure errors), multiple scanns is OFF (I do have 3x sampling already because of RGB mode). Photoshop: 1) mode to Grayscale; 2) Invert; 3) Layers; 4) Saving for print archive (tiff); 5) Resize for web with bicubic sharpening; 6) mode to RGB; 7) mode to 8 bit per channel; 8) save jpeg for web archive.

My examples you can find here
http://wlad.kiev.ua/view/0/0/0/en/index.html

P.S. I mean last five b&w pics from URL above, I just bought my scanner so not many pics so far.

 

[dmr]

Did you go to exposure control tab before final scan? You have to set exposure manually when autoexposure is off. I'm very pleased with B&W results from my K-M Dual IV, and yes I do everything manually (focus and exposure).
Eduard

No, I just played with it briefly and realized it was clipping on both ends when it was at the default setting. The auto exposure gave me a sane histogram so I used it that way for the test. I will play with that some more when I get a chance, I do have quite a few more to look at and scan.

 

[ed1k]

The auto exposure gave me a sane histogram

Not really. You have to select (crop) image area _correctly_ before autoexposure. You have a dark strip on top of your examples/tests. That strip doesn't have any value but fools autoexposure algorithm into thinking you have enough black space in your image. Hence those comments there in separate thread about white and flat look of your scans. Doing layers in photoshop be aware you have two cut-off sliders and one slider in the middle - don't hesitate to move a middle slider also. Curves might lead to significant digital artefacts if you're novice in this area (you can get some effect known as "solarization" in traditional b&w darkroom).

Eduard.