Most Compelling B&W Scans on 4990 w/48 bit Scan and PS Conversion?

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Originally Posted by Kirk Gittings

I just did the tests scans on an Epson 750, 16 bit Grayscale, Silverfast AI Studio, white, red, green and blue channels. The differences, though subtle, are the same I would expect from separating the channels from an RGB scan. Similar to Tyler's examples but a bit subtler with slightly better sharpness, shadow detail and less noise in the green chanel.

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I conducted a similar test to compare.

Interesting, within Silverfast, I was/am able to "select" separate color filters for both RGB and Grayscale. However, for each RGB scan with a separate filter for white, red, green and blue--I just didn't see discernable differences. This leads me to wonder that while "selection" is possible--it may not be functionally operational in either Silverfast or may be the 4990 scanner. Hmmmmm!

Also, I compared 16 bit grayscale with filters (white, red, green, blue) and 48 bit scans with similar color separations in P'shop. With the 4990, there are subtle differences--the 48 bit scans with green channel isolation in P'shop generally appear better in terms of detail and noise.

As I said the differences were subtle. If you are right and if the selection does not really function, why would there be any difference between them on my machine at all?

VueScan also has this function, and it works in grayscale. It's called "Make gray from" in the Input tab. I scan a lot of PMK developed film, and it makes very little difference (if any) wether I choose Auto, or use the green or red channel. The most obvious difference is ususally slightly different contrast and/or density.
This is from the VueScan Help file:

This option specifies how to make the gray color from the scanner's red, green, blue and infrared sensors.

The default, "Auto", either uses the scanner hardware to convert from the color CCD to gray, or converts in VueScan, mostly from the green channel.

Otherwise, the gray color is taken from either the red, green, blue or infrared channels. Using the red or infrared channel can be useful when scanning older, degraded black/white negatives that are silver based.

Advanced Option: This option is displayed when scanning with 8-bit or 16-bit gray.

Quote:

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Originally Posted by Kirk Gittings

As I said the differences were subtle. If you are right and if the selection does not really function, why would there be any difference between them on my machine at all?

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Interesting Point! I'm using a 4990 and Ai--reaching similar conclusions to sanking's earlier in this forum. Not sure why the difference. Notwithstanding--I'm more convinced now that channel separation in P'shop is probably my preferred approach going forward.

I have also noticed that the green channel is the best with my Epson 4990 using Silverfast Ai and PS CS3. I have a simple question with respect to bit depth. When I open my 48->24 bit files in PS CS3 they open as an 8-bit file so the first thing I do is convert them to a 16 bit file to take advantage of the added bit depth. Now I'm wondering why CS3 can't tell the bit depth is greater than 8. Am I doing this correctly? Is there some way to configure CS3 to open a file in the correct bit depth?

Scott

it's simply a nomenclature difference between Silverfast and Photoshop. Photoshop is naming bit depth per channel, Silverfast is summing the channels, a bit misleading.
Your files Silverfast is calling 24 bit, are really 8 bit per channel, three channel (RGB) files, and that is how Photoshop opens them.
You are not getting the high bit advantage scanning in 48 to 24 bit, then converting back to hi bit in Photoshop. Scan in Silverfast's 48 color, or 16 gray, to maintain your hi bit info from the scan id desired.
Tyler

Hope that makes sense.

Thanks Tyler that makes perfect sense. So to keep the high bit depth and the sharpness of the green channel I should scan in 48 color. Time to buy more RAM for my computer.

Scott

or scan as 16 bit gray, selecting the green channel in the option setting discussed above in this thread.
At least then it's 1/3 the file size, easier on RAM and storage.
Another trick, convert to 8 bit in PS and do a "save as", leaving the 16 bit intact. Do all your adjustment layering and proofing from the lower bit version. When happy, drag all those layers and masks as a group over to your 16 bit, flatten and save as a final printer file.
My standard workflow here.
Tyler

Thats good advice Tyler, especially for people who have a marginally performing computer.

my epitaph- "had a marginally performing computer..."

the mother of invention eh?
Tyler