EPSON Scan settings: which Gamma setting is "normal" ?

[Ken Lee]

When comparing negatives, pull the end points out and have the middle slider set at the midpoint 128. In other words, ignore the contents of the histogram and let the negative drop in where it falls. The scanner should hold this each subsequent scan if you save it as a setting.

Can you specify a number in the range of 1-255 in the "gamma" input box of the EPSON Scan software's "Histogram Adjustment" tool ? (see screen shot in post # 1)

[Steve Wadlington]

Ken,

I have a Epson scanner and a test awhile back on Stouffer 4x5 step tablet (transparent). That density range is really pushing past the limits of the design of the scanner but I was suprised to find that 1.0G that I always scanned negs at wasn't the most linear range on the scanner. I'm away from home at the moment but best I remember it was about 1.5 to 1.6.
I graphed out on and Excel spreadsheet to include all the densities of the tablet, mind you it wasn't linear on the high or low end, but all values where on the scan.

[Ken Lee]

Thanks for that. I intend to do the same and plot the results. I think it's very helpful to know.

If we profile a scanner, does it automatically work in a linear fashion ?

if so, then how do we profile the scanner ?

[Greg Miller]

Can you specify a number in the range of 1-255 in the "gamma" input box of the EPSON Scan software's "Histogram Adjustment" tool ? (see screen shot in post # 1)

No. But if you do precisely as Henry suggests (leaving black and white points at far ends of the scale) then a gamma of 1.0 = 128.

I personally would rather move the black and white points just outside the data in the histogram to allow the tonal gradations to be mapped over a larger mathematical base, but there are 1,000 ways to scan a cat.

[Ken Lee]

No. But if you do precisely as Henry suggests (leaving black and white points at far ends of the scale) then a gamma of 1.0 = 128.

I personally would rather move the black and white points just outside the data in the histogram to allow the tonal gradations to be mapped over a larger mathematical base, but there are 1,000 ways to scan a cat.

Excellent - Thank you for the clarification.

I always adjust the bottom of the histogram to render the black film edge as 0. However, not every photograph has a 100% white value, so IMHO it's best to adjust the high end according to... taste.

[Steve Wadlington]

Ken,

"Thanks for that. I intend to do the same and plot the results. I think it's very helpful to know.

If we profile a scanner, does it automatically work in a linear fashion ?

if so, then how do we profile the scanner ?"

I was thinking of setting up a Photoshop curve to correct a scan to linear, but that may not necessarily be the best. I was trying to figure what the absolute limits of the scanner was. I have had problems rendering the very high values in clouds and such.

I shoot tmax and use pyrocat hd as I believe you do. Wish I had more time to shoot.

[Daniel Moore]

The instructions for setting up linear output from Epson Scan for Colorperfect may be of interest to you.

[Ken Lee]

The page to which you linked, gives instructions on using their product Color Perfect and Color Scan.

They point out that what comes out of the scanner software, is Gamma-encoded to Gamma 2.2 on Windows, and 1.8 on Mac - and that they have a product which will linearize the image. I presume they apply a complimentary curve.

As far as I could tell, their product operates "down-stream" from the EPSON driver. In other words it's doing post-processing to correct some limitations inherent in the EPSON driver.

This suggests that the EPSON Scan driver can not be configured with respect to Gamma.

When I scan on a Mac, my 16-bit grayscale images come out Gamma 1.8 encoded. I normally convert them a Gamma 2.2, since that's how my monitor is calibrated. The 1.8 standard is pretty much obsolete at this point.

[Daniel Moore]

Reading further on I see this about Vuescan: "The normal Tiff files however are images edited and gamma encoded by VueScan while those of the RAW output mode are of linear gamma and are always equivalent to the light intensities read in by the scanner."

[Ken Lee]

Reading further on I see this about Vuescan: "The normal Tiff files however are images edited and gamma encoded by VueScan while those of the RAW output mode are of linear gamma and are always equivalent to the light intensities read in by the scanner."

Now you're talkin' - Thank you !